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Researchers have noticed a stream of gaseous particles being spewed from the Sun, which is heading straight to Earth. Experts believe the stream of particles, which are currently making their way across 150 million kilometre journey from the Sun to Earth across space, will arrive on Saturday, April 4. This could trigger northern lights above the Arctic circle for the entire weekend.
Cosmic forecasting site Space Weather stated: “A minor stream of solar wind is heading toward Earth. Estimated time of arrival: April 4-5.
“Geomagnetic unrest and Arctic auroras are possible when the gaseous material arrives.”
Auroras, which include northern lights – aurora borealis – and southern lights – aurora australis, are caused when solar particles hit the atmosphere.
As the magnetosphere gets bombarded by solar winds, stunning blue lights can appear as that layer of the atmosphere deflects the particles.
However, researchers also note the consequences of a solar storm and space weather can extend beyond northern or southern lights.
For the most part, the Earth’s magnetic field protects humans from the barrage of radiation which comes from sunspots, but solar storms can affect satellite-based technology.
Solar winds can heat the Earth’s outer atmosphere, causing it to expand.
This can affect satellites in orbit, potentially leading to a lack of GPS navigation, mobile phone signal and satellite TV such as Sky.
Additionally, a surge of particles can lead to high currents in the magnetosphere, which can lead to higher than normal electricity in power lines, resulting in electrical transformers and power stations blowouts and a loss of power.
Rarely does an event such as this happen, with the biggest technology-crippling solar storm coming in 1859, when a surge in electricity during what is now known as the Carrington Event, was so strong that telegraph systems went down across Europe.
There are also reports that some buildings set on fire as a result of the electrical surge.
However, a recent study has found these solar storms should happen every 25 years on average, meaning we are well overdue.
Research from the University of Warwick and the British Antarctic Survey analysed the last 14 solar cycles, dating back 150 years.
Alien news: ET base discovered on asteroid – shock claim
Comet ATLAS burning bright with atmosphere HALF the size of the Sun
NASA: Space agency releases images of astronauts in space
The analysis showed that ‘severe’ magnetic storms occurred in 42 out of the last 150 years, and ‘great’ super-storms occurred in 6 years out of 150.
The researchers said if it had hit Earth, it could have downed technology on our planet.
Lead author Professor Sandra Chapman, from the University of Warwick’s Centre for Fusion, Space and Astrophysics, said: “These super-storms are rare events.
“But estimating their chance of occurrence is an important part of planning the level of mitigation needed to protect critical national infrastructure.
“This research proposes a new method to approach historical data, to provide a better picture of the chance of occurrence of super-storms and what super-storm activity we are likely to see in the future.”
Source: Read Full Article | 0.846205 | 3.358328 |
In a lecture in October of 2015, Dr. Carolyn Porco, Imaging Team Leader for the Cassini Mission to Saturn, said, regarding the chance of life on Enceladus:
Should we ever make such a discovery, if we ever, anywhere, find that there has been a second, independent genesis in our Solar System, then I think that at that point the spell is broken. The existence theorem has been proven. And we could safely infer from that, that life is commonplace; that it is not a bug but a feature of the universe in which we live and that it has occurred a staggering number of times throughout the 13.7 billion years of the history of the cosmos. And I think that that might be the kind of discovery that could change a great many things.
Maybe I'm just curmudgeonly contrarian, but the discovery of extraterrestrial life would not impress me.
Keep in mind that I'm talking about bacteria in the seas of Enceladus; or even little fishes. Leave aside, for the moment, those greymen in their saucers.
It is wrong to say that life on Enceladus would necessarily
be independent of life on Earth. Despite the self-assurance of our scientists, no one knows
how life arose. Clearly this Solar System began with the ingredients for life. Earth and Enceladus, however they formed, formed from the same stuff
. Strictly speaking, Enceladus is but a distant continent; and especially if its life uses familiar DNA, Occam's razor — that fave principle! — would suggest that life on both worlds had a single
If, on the other hand, Enceladan life uses an unfamiliar DNA, with unprecedented nucleobases or a triple helix or the like, then one could speak more soundly of an independent
genesis. Still, it is a leap to say that one
System disposed to life — even multiple threads of life — implies life has occurred a "staggering" number of times elsewhere
To be sure, on what grounds do I set a special boundary on our System? If I am unwilling to grant a fundamental separation of Earth and Enceladus, what right have I to separate this System from the Milky Way? Clearly, by my standards, this Galaxy
began with the ingredients for life. Yes? Indeed this Universe
began with the ingredients for life!
Life here implies life everywhere.
But that conclusion doesn't sit right with anyone. Why do you suppose we keep looking for proof
of life far from Earth?
Just as we know that the abundance of life on Earth does not
imply an abundance in the Universe, another instance of life in our System would not
imply another instance anywhere else in the Universe.
Life on Enceladus would, at most, make life not unique to Earth. But why does that matter? Why does that prospect excite Dr. Porco?
It excites her because she thinks we — not she; but you and I — are under a spell.
We think Earth is special. That we are special.
To Porco, this is a delusion. A spell that must be broken
. To her, there is — or rather, must be
— nothing special about our world. More to the point, nothing special about us
. Thinking ourselves special smacks of... ugh... religion
... and other icky, unscientific things. Porco is literally a disciple of none other than Carl Sagan; and if anything thrilled Carl Sagan, it was smothering the significance of mankind under billions and billions of stars.
Sagan's deepest hope was that the greymen are indeed out there. I suspect Porco's deepest hope is the same. I'm not saying she's a UFO enthusiast. I'm saying she's a Darwinian. To a Darwinian a man is just an especially complicated bacterium. If we find extraterrestrial bacteria, we will surely find extraterrestrial men; for between the two is a Darwinian straight line.
is the true goal. When E.T. is found, religion will be humiliated. Science will win, once and for all.
You may think I am (unfairly) imputing a lot to Dr. Porco. But she is a type
. When I hear about spells being broken, I know the type is present. She has also said:
All the atoms of our bodies will be blown into space in the disintegration of the solar system, to live on forever as mass or energy. That's what we should be teaching our children, not fairy tales about angels and seeing Grandma in Heaven.
That's Dr. Porco for you: a conventional secular nihilist; and a woman you should never employ as a babysitter.
But I didn't come here to bury Dr. Porco. My point is only that the discovery of extraterrestrial life will break no spell. Life, in some ways, is trivial. Whether it exists under the ice of Enceladus or in the fumes of the Marianas Trench, it's just life. You can certainly marvel at its variety and dispersion. I'd never deny the wonder of it all. Indeed, be excited by the vitality of Creation! But life is already
commonplace. And whenever was it dogma that only Earth possessed any life? It has in fact been a naive presumption, among God-fearing and godless alike, that where there is ground to walk on, there will be creatures. And even if turns out that terrestrial life does not encompass all life, that would not mean mankind is not a special case. God would still favor us.
I am not under a spell. I am not misled. There is nothing in the Creed or the Magisterium that says, "There can be no life on Enceladus." Should fishes be revealed in the environs of Saturn, my worldview will not shift.
Ah. But what if the greymen
were revealed? Well, that is a category difference. The discovery of greymen would
impress me. The hype would be justified.
You see, I am not
a Darwinian. I know it is not
possible for rational minds to arise from material processes. I would surely be jarred by the existence of fully rational aliens.
Would Sagan and Porco therefore have their victory? Would my spell be broken? Hardly. The Faith does not preclude non-human rational beings — think of angels, after all. What would
jar me, what would give me pause, would be the novel mystery:
Where do aliens fit in the economy of salvation?
Aliens, being rational, would by definition be made in the image of God. They would presumably be free-willed. They would likely be sinners. So did our Christ die for them, too? Or are there two Christs in Heaven? The human Christ — fully divine; fully human — and the alien Christ — fully divine; fully alien?
Well, mysterious as that situation might be, it is perhaps no more mysterious than the Trinity or the one Incarnation we know about. And in any event, pace
Dr. Porco, I would remain just as stupidly deluded about the existence of God and the significance of mankind.
We religious folk are obstinate, sometimes. Metaphysical truths can steel a person, that way.P.S.
At the risk of being one of those authors who tactlessly plugs his books at the end of every article, blog post, and tweet, I will mention that my excellent novel The Giant's Walk
wonders about the salvation of rational non-humans... | 0.805777 | 3.563623 |
Currently, there are stringent regulations and rules in place to protect interstellar objects from contamination by earth-based organisms, either single or multi-cellular. The scientists studying the water of Mars do not wish to contaminate the sample that might contain evidence of life with life. At some point, though, we do know what needs to happen: Colonization. The universe is a laboratory of wonder and amazement, and there comes time to start fiddling with things. You see, all known and verified life forms in the entire universe are located on one floating rock, and, more specifically, upon the smear of soil and air that skims across the surface along with the sloshing jostle of sea that slips around the top of massive tectonic plates. We are one giant volcano away, one nuclear winter, one asteroid, one broken Paris Accord away from potentially ending all life in the universe, period. Not just our own, but all life. This is the only place we know there is life.
For this reason, I question the decision to focus on interplanetary exploration without the notion of any terraforming, at all. There was serious discussion of how to terraform Venus, for example, by Carl Sagan, who suggested releasing genetically-modified bacteria into the upper atmosphere of the planet to eat through and shift the atmosphere into something more habitable to life, to permit terraforming to happen. Mars, a rock devoid of surface water, seems a poor candidate for life as we know it in our forested, grassy, suburbs. But, life is pernicious and takes root at the base of deep sea vents and at the top of the Himalayan range. The sort of life that is possible in a Martian atmosphere will emerge or not, if enough seed life is planted. I say, start throwing the life forms – the tiny ones – all over our stellar town. See what we can get moving. See what terraforming we can make happen on Venus and Mars. The multi-cellular, complex organic life that could be the legacy of earth is currently limited to just one little blue ball. Our situation on earth has never been more precarious. It’s time to make sure that life has a better chance of continuing, even if it isn’t us continuing.
Spread life. Terraform to support life. If it is human life, that’s great for us, but the first step is getting a massive, complex eco-system of single-cellular life forms to pave the way for the massive, complex eco-system of some sort of multi-cellular, complex organisms. We cannot guarantee that they will eventually form cities, become anthropologists, and recreate our marvelous, mysterious, nihilistic dance with creation. But, where there’s life, there’s hope. That’s what they say, anyway.
Make more life. There are planets near us that are indifferent to their status as sterile labs, and form a naked canvas for the organic fingerpainting smears of Darwin’s God.
Posted By Blogger to Dogslandia at 1/31/2017 12:45:00 AM | 0.817044 | 3.384897 |
Objects in the orbital debris environment are detected and monitored by a combination of remote and in situ measurements, and ground tests are used to help interpret those measurements. Calibration and analysis are required to interpret the measurements of the MMOD environment in terms of common parameters, usually impact flux (number per area per unit time) as a function of mass or diameter in various regions of space. Although parts of the NASA MMOD programs rely on measurements used to maintain the U.S. Strategic Command (USSTRATCOM) satellite catalog, NASA’s primary program for measurement of debris uses sensors that sample only a portion of the debris environment, and the program performs a statistical analysis of the data to estimate the number of objects. That is, the sensors measure the number of objects per unit of time passing through a relatively small, but defined, volume of space. Orbital telemetry elements of objects in the catalog are converted to flux,1 and this calculated flux can then be compared to the measured flux to test sensor calibration.
Orbital debris and meteoroids less than 10 cm in size in low Earth orbit (LEO) are measured with ground-based telescopes and radar and by examining the surfaces of returned spacecraft. Each type of sensor is capable of detecting debris of increasingly smaller sizes. Figure 2.1 compares the current measured orbital debris flux with the meteoroid flux for altitudes below 600 km. Both radar and optical measurements show an orbital debris flux increasing with altitude, up to 900 km, where the flux of 1-cm debris is measured by Haystack as being about 10 times larger than that indicated by optical measurements. At geosynchronous Earth orbit (GEO) altitudes, ground radar and telescopes are used to track the orbital debris environment, where the cataloged sizes are larger than 1 meter. Figure 2.2 illustrates the number of uncataloged objects detected near GEO by the Michigan Orbital Debris Survey Telescope (MODEST), a telescope located in Chile and configured to look for uncataloged objects.2 Although the cataloged population in LEO contains all debris above 10 cm in size, in GEO the detection threshold for the satellite catalog is about 1 m.
The flux of orbital debris of the smallest sizes (less than about 1 mm) is obtained by analyzing the surfaces of satellites returned to Earth. The major uncertainty with these measurements lies in relating the damage measured on a particular returned surface to the damage measured on other types of surfaces or structures. This uncertainty is reduced through hypervelocity testing of various types of surfaces and structures. However, data of this type has been limited to impacts at altitudes below 600 km, the upper limit of space shuttle operations. For debris of larger
1 Kessler, D.J., Derivation of the collision probability between orbiting objects: The lifetimes of Jupiter’s outer moons, Icarus 48:39-48, 1981.
2 NASA Orbital Debris Program Office, Orbital Debris Mitigation and Reentry Risk Management Course, NASA Johnson Space Center, Houston, Tex., 2010.
FIGURE 2.1 Measurements of orbital debris below 600 km are compared to the meteoroid flux at altitudes below 600 km. The orbital debris measurements (in some cases, averaged over several altitudes below 600 km) reflect use of the cataloged objects (99165 two-line elements), Haystack Auxiliary (HAX) radar, Haystack Long Range Imaging Radar, Goldstone radar, and returned spacecraft surfaces. At higher altitudes, the orbital debris flux increases with altitude, up to 900 km, where HAX has measured the flux of 1-cm objects as being about 10 times larger. The meteoroid flux remains nearly constant over this region. SOURCE: Courtesy of NASA-JSC, from Orbital Debris Program Office, “APPEL Orbital Debris Mitigation & Reentry Risk Management Course,” CD, NASA Johnson Space Center, Houston, Tex., 2010, Part 1B, pp. 18 and 27.
sizes (between 2 mm and 10 cm in LEO), an exposed surface larger than that of a typical satellite is required to obtain a meaningful sample of “impacts,” so ground telescopes and short-wavelength radars are used. However, neither telescopes nor radars actually track the objects that are detected; rather, they stay in a “staring mode” that essentially counts the number of objects passing through their relatively small field of view. While the debris is in the field of view, its direction of motion, signal strength, and range (for radar) or angular velocity (for telescopes) are measured. The largest source of uncertainty with these sensors exists in interpreting the signal strength in terms of the size or mass of the object passing through the field of view.
Signal strength is reported by telescopes in units of stellar magnitude, and by radar as radar cross section (RCS). Stellar magnitude is related to RCS statistically by using a sample of small fragments in which both RCS and magnitude are measured for each object.3 An advantage of detecting uncataloged debris with both radars and telescopes is finding debris that may not be seen by one or the other alone. In 1995, NASA began operations of the NASA-built and NASA-designed 3-meter Liquid Mirror Telescope (LMT). However, as a result of budget cuts, the LMT was shut down in 2001. Although the LMT was providing useful data on uncataloged debris, the amount of debris found was less than predicted as a result of its lower than expected albedo. The decision to discontinue opera-
3 D.J. Kessler and K.S. Jarvis, Obtaining the properly weighted average albedo of orbital debris from optical and radar data, Advances in Space Research 34(5):1006-1012, 2004.
FIGURE 2.2 Uncataloged objects detected by MODEST compared to a total detected population near geosynchronous Earth orbit (GEO) altitude, indicating a significant population of objects in GEO that are uncataloged, possibly as a result of explosions near GEO. The diagonal line represents what the size of the population might be as the result of an explosion in GEO and suggests that such an event may be the source of this smaller debris; however, further analysis and observation will have to be performed to determine the source of these uncataloged objects and whether the size distribution will continue along this line for absolute magnitudes larger than 16. SOURCE: Adapted, courtesy of NASA-JSC, from Orbital Debris Program Office, “APPEL Orbital Debris Mitigation & Reentry Risk Management Course,” CD, NASA Johnson Space Center, Houston, Tex., 2010, Part 1B, pp. 18 and 27.
tions of the LMT left only the remote observations using radar, which continue today and have become the most important technique for monitoring the debris environment for debris ranging in size between 2 mm and 10 cm.
NASA’s orbital debris monitoring efforts currently receive data from three radars: Haystack (debris to 6 mm) and Haystack Auxiliary (HAX) (to 2 cm) in Westford, Massachusetts, and Goldstone (to 2 mm) in California’s Mojave Desert. Following a significant debris-producing event, these radars are oriented to measure the flux of small debris produced in the stream of fragments generated by the event in order to test the debris source models. The most important limitation of these radars is their location; their higher latitude limits to orbital inclinations greater than about 28 degrees any observations of uncataloged debris; in addition, debris from objects in a Molniya-type orbit (which is highly elliptical, with an apogee near geosynchronous altitude and a perigee in the Southern Hemisphere) cannot be detected, because most of the U.S. ground-based sensor systems are in the Northern Hemisphere. Some of the limitations with respect to observational inclination will be resolved with remote operations by NASA of the Meter-Class Autonomous Telescope (MCAT) at Kwajalein Atoll in the Pacific Ocean beginning in 2012. This low-latitude location will permit detection of uncataloged debris at low inclinations, although not to sizes as small as can be detected by current radar capabilities. MCAT will also detect GEO debris as small as 10 cm.
The major uncertainty in these measurements is in relating RCS to the physical characteristics of the debris.
Ground tests combined with radar calibrations have been used to address this issue. Between 1991 and 1992, DOD conducted a series of hypervelocity tests to simulate the hypervelocity breakup of a payload, known as the Satellite Orbital Debris Characterization Impact Test (SOCIT) series. In the fourth and final test, a flight-ready, 35-kg transit payload was hit with a 150-g projectile at 6 km/s.4 The results of that test not only helped shape future debris breakup models for the LEGEND (LEO-to-GEO Environment Debris) model, but also supplied a number of fragments that could be used to measure RCS on a radar range, under the assumption that the fragments had physical characteristics similar to those of fragments in orbit. The results were a distribution of possible RCS returns from objects having a particular size, mass, and shape. From these distributions, an orbital debris size estimation algorithm (also known as the Size Estimation Model, or SEM) was developed to relate RCS to size.5
Limitations of the SEM became obvious when the Haystack radar begin to discover new sources of debris. The most-verified new source of debris was droplets of sodium potassium (NaK) from Russian radar ocean reconnaissance satellites. Using the SEM, it was concluded that 60 kg of NaK were in orbit.6 Since these droplets are simply liquid-metal spheres, they each have a well-understood RCS that depends only on their size. When an algorithm was applied to the measured RCS distribution of NaK objects, their total mass was calculated at 150 kg.7 The reason for the difference in total mass is that the RCS is larger for objects with certain orientations than for any metal sphere of the same size. Consequently, the SEM includes biases toward smaller objects when a large number of smaller-size objects are known to exist.
The Haystack radar also discovered objects with orbital characteristics expected for aluminum oxide slag from solid-rocket-motor exhaust8—particles that would likely be nearly spherical but non-metallic. Little data exists on the amount of slag that solid-rocket motors are likely to produce or on their expected RCS. Other sources of debris, such as fragments from upper-stage rockets and satellites made of a larger range of materials, were not included in the sample of objects used to establish the SEM. Obtaining samples of these fragments requires a ground test program similar to the 1991 to 1992 series of SOCIT tests, and such a test program does not currently exist.
The SEM is important to both the Orbital Debris Environment Model (ORDEM), which must correctly convert RCS to size of debris and hazard, and to the LEGEND model, which must properly capture the relative contributions of various sources of debris to help NASA “lead the continued development and adoption of international and industry standards and policies to minimize debris, such as the United Nations Space Debris Mitigation Guidelines” (p. 7) as required in the 2010 National Space Policy.
Finding: The current lack of radar cross-section calibrations for fragments from a larger range of materials used in modern satellites and rocket bodies, as well as non-fragmentation debris, represents a significant source of uncertainty in interpreting key measurements of the orbital debris environment.
Figure 2.3 summarizes the capabilities of the sensors on which the NASA orbital debris programs depend to define the orbital debris environment and summarizes the types of damage that debris of different sizes can cause. Missing from the orbital debris monitoring program is a capability to monitor the flux of debris smaller than 2 mm in size as a function of both time and altitude. Lessons can be learned by reflecting on the early research done during the 1960s to understand the meteoroid hazard.
Like the flux for orbital debris, the flux for meteoroids larger than a few millimeters has been determined using
4 D.M. Hogg, T.M Cunningham, and W.M. Isbell, Final Report on the SOCIT Series of Hypervelocity Impact Tests, Report No. WL-TR-93-7025, Wright Laboratory, Armament Directorate, Wright-Patterson Air Force Base, Ohio, July 1993.
5 E.G. Stansbery, C.C. Pitts, G. Bohannon, et al., Size and Orbit Analysis of Orbital Debris Data Collected Using the Haystack Radar, NASA JSC-25245, NASA Johnson Space Center, Houston, Tex., 1991.
6 D.J. Kessler, M.J. Matney, R.C. Reynolds, R.P. Bernhard, E.G. Stansbery, N.L. Johnson, A.E. Potter, and P.D. Anz-Meador, “A Search for a Previously Unknown Source of Orbital Debris: The Possibility of a Coolant Leak in Radar Ocean Reconnaissance Satellites,” IAA-97IAA.6.3.03, presented at the 48th International Astronautical Conference, Turin, Italy, October 6-10, 1997 (also pp. 129-150 in Space Safety and Rescue 1997 (G.W. Heath, ed.), Science and Technology Series, Volume 96, American Astronautical Society, Springfield, Va.).
7 P. Krisko, NASA’s sodium potassium generation and propagation model, Orbital Debris Quarterly News 8(1):6-7, 2004, available at http://orbitaldebris.jsc.nasa.gov/newsletter/pdfs/ODQNv8i1.pdf, accessed July 7, 2011.
8 D.J. Kessler, N. Johnson, E. Stansbery, R. Reynolds, K. Siebold, M. Matney, and A. Jackson, The importance of non-fragmentation sources of debris to the environment, Advances in Space Research 23(1):149-159, 1999.
FIGURE 2.3 Orbital debris program sensor capabilities for low Earth orbit orbital debris measurements. The capabilities for characterization of small debris are a function of returned samples and a variety of remote measurement capabilities. The importance of these size ranges is highlighted by their associated potential effects on space shuttle subsystem reliability. SOURCE: Adapted, courtesy of NASA, from Lyver, J., “NASA Micrometeoroid and Orbital Debris Program Overview to National Research Council,” presentation to the Committee for the Assessment of NASA’s Orbital Debris Programs, December 13, 2010, National Research Council, Washington, D.C., p. 10.
remote observations, in the case of meteoroids by measuring the meteor ion trail in Earth’s atmosphere. Smaller-size meteoroids have been measured using a multitude of in situ sensors on satellites. Similar to the situation with measurements of orbital debris, there has been more uncertainty in the remote sensing data for meteoroids than in the in situ data. The in situ data from satellites such as the three Pegasus satellites launched in 1965 has turned out to be critical in helping to resolve uncertainties in the remotely sensed data and was a major component in defining the parameters in meteoroid environment models used today. Given uncertainty in the current RCS calibrations, in situ data are also likely to be a major component in defining parameters in models of the orbital debris environment.
Although no major changes from 1960s in situ measurements of the background meteoroid flux have been detected, that is not the expectation for the orbital debris environment, which is predicted to be, and has been measured to be, much more dynamic than the meteoroid environment. Ironically, dynamic changes in the orbital debris environment were measured as a result of an experiment on the Long Duration Exposure Facility, which was intended to detect meteoroid streams. Instead of meteoroid steams, most of the 15,000 impacts detected were interpreted as being the result of Earth-orbiting debris streams.9 The source of those debris streams is still uncertain, although some streams have been associated with solid rocket motors. In addition to helping to confirm RCS calibrations, the much higher flux measured with in situ instrumentation will translate to more quickly monitoring
9 J.P. Oliver, S.F. Singer, J.L. Weinberg, C.G. Simon, W.J. Cooke, P.C. Kassel, W.H. Kinard, J.D. Mulholland, and J.J. Wortman, LDEF Interplanetary Dust Experiment (IDE) results, pp. 353-360 in LDEF—69 Months in Space, Proceedings of the Third Post-Retrieval Symposium, November 8-12, NASA Langley Research Center, Hampton, Va., 1993; W.J. Cooke, J.P. Oliver, and C.G. Simon, The orbital characteristics of debris particle rings as derived from the IDE observations of multiple orbit intersections with LDEF, pp. 361-371 in LDEF—69 Months in Space, Proceedings of the Third Post-Retrieval Symposium, November 8-12, NASA Langley Research Center, Hampton, Va., 1993.
changes in the environment, and possibly to identifying the sources of those changes. Such in situ sensors are also likely to contribute to understanding spacecraft anomalies, as discussed in Chapter 10, “Spacecraft Anomalies.”
Given the potential for rapid growth in the debris population, it is necessary to have a robust measurement program in place for detecting changes in the orbital debris environment quickly, and to increase the number of mitigation and remediation options available for use. If such a measurement program had been in place at the beginning of the space program, the consequences of explosions in orbit would likely have been detected, and mitigation guidelines put in place, much earlier. Similarly, early detection of the consequences of collisions in orbit might prompt a quicker recognition of the need for remediation actions.
Finding: NASA’s orbital debris programs do not include the capability to monitor with in situ instrumentation the penetrating flux of objects smaller than a few millimeters. Data collected by in situ monitoring could be used to resolve uncertainties in measurements made remotely, to help identify new sources of debris, and to provide clues to the causes of spacecraft anomalies. | 0.836648 | 3.699933 |
The article argues about Sagittarius A*, the supermassive black hole in our Milky Way, and is inspired by the revolutionary pic due to the Event Horizon Telescope activity. We define the outlines of our theory, which describes Sgr A* as a holostar, as well as we give a proper model in order to frame the inertial equivalence in space-rotating systems.
As anticipated in my previous article, we succeeded in getting the direct observation, for the first time, of what we can define the “shadow” of the event horizon of a black hole, to be exact of the gigantic and supermassive black hole M87*, which is located in the center of the namesake galaxy M87 (or Virgo A) . The relative pic was shared around the world and was rightly named “the pic of the century”. The team of scientists of the EHT (Event Horizon Telescope) project, announced this epochal novelty on April 10, 2019, together with the release of the pic and the publication of a series of highly detailed scientific articles.
Let’s recap: the VLBI technology is the networking of the largest radio telescopes, located in various parts of the globe, so as to form the equivalent of a single radio telescope (Event Horizon Telescope or EHT) with a radius equal to that of the Earth. This technology has lead us to the result, the pic of the century.
We will better discuss the results released by EHT team to the world on April 10th 19 in the next article.
However EHT had already provided a public result, relative to what seemed to be the main object of its efforts, i.e. Sagittarius A*, the supermassive black hole in our galaxy. Honestly, everyone expected the event of April 10th to deal with it even more, given that the discussion started with that early result is still pending.
The difference, which in all likelihood has orientated the choice of the EHT team, with M87* is that Sagittarius A* hasn’t shown any signs of an accretion disk during this period.
An accretion disk is made up of matter that, whirling and at extreme speed, falls into a black hole: while doing this matter produces light radiation in the form, for us remote observers, of radio waves. It is precisely this light, which rings it, that allows us to see the shadow of a black hole, by contrast, as a background.
Now, if we start from the assumption that every black hole is surrounded by an event horizon that prevents even light escaping, only this boundary light, the last sign of life of matter before disappearing beyond the horizon itself, can give us an image that, like a shadow or a background, allows us to glimpse the black hole. Without an accretion disk, any black hole, being surrounded by that insuperable horizon, remains totally invisible.
In this regard I used the comparison of the Sun and its corona (an area which surrounds our star and is much warmer than the solar surface). If I take an x-ray picture, the Sun appears black and the corona bright; so, if having only x-rays available, I could see the surface of the star only by contrast with its corona. Therefore, using only x-ray detectors while I were looking for stars to photograph, I would prefer those stars with a corona, like the Sun.
But what happens if I’d have not only x-rays, but also visible light available? If I use the latter, it happens that I see the Sun, i.e. its surface, without being dazzled by the corona.
Something like this has happened, and I suppose it’s still happening on EHT’s computers, about Sagittarius A*. With very unexpected results.
The EHT team, as I said, before the recent silence, had already provided a result (with relative pic of Sagittarius A*). More exactly, so far it has observed that “Its (Sgr A*’s) emission region is so small that the source may actually have to point directly at the direction of the Earth” and “it could be that the radio jet is pointing almost at us” so “we are looking at this beast from a very special vantage point”.
Here the links:
So, as you can see from the wonderful images shown in the articles, there is a substantial difference between what we expected to see (jets of matter, accelerated almost to the speed of light, would have allowed us to see, as their background, the gigantic black silhouette, the shadow, of the horizon of Sgr A*) and what, at least at the moment (i.e. without a true accretion disk), we have seen: an uniform emission zone.
Hence: either there is matter that is falling on Sgr A* in a symmetrical and uniform way, like dew, something quite incredible, or what we are seeing is rather a jet. Jets of matter may occur as a result of a funnel effect: in other words, when there is an excess of matter that is falling, swirling too much into a too small area, a funnel effect is produced, until a part is expelled. Now a jet, to be seen so small and symmetrical, has to point directly to the Earth, with a really remarkable precision.
Obviously, such a symmetrical emission should have a polar origin, which would imply that the supermassive black hole is spinning “lying” with respect to the galactic plane of rotation (as Uranus does with respect to the plane of rotation of planets in the solar system). The fact that one of its poles could point with extreme precision towards us has the same probability of occurring than the one of winning in the national lottery with the first ticket which we decide to bet on. It would appear as if Galileo, after having ingeniously created an adequate telescope, had pointed it at the Moon for the first time and, first of any other thing, had observed that on the lunar soil there was a telescope pointed exactly towards him. Not to mention that a jet of matter “shot” towards us at a speed close to that of light should show a considerable blueshift effect.
So, the conclusion I consider more probable, the one that, in my opinion, will be corroborated by the results of new observations, once they will be provided, is that we are looking simply at what it seems to be, i.e. at an image of that winking superstar, not at an event horizon (see Footnote 1).
(Image still enlarged, but I suppose that this could depend on the radio wavelength chosen for each single round of observations: if the next one chosen will be smaller – or the frequency higher – I think we will see a smaller zoom effect).
As I wrote in my main article, the EGR (the extension of General Relativity from uniformly accelerated systems to space-rotating systems) predicts the theoretical impossibility of any gravitational singularity, and therefore the non-existence of any event horizon. The reason is largely intuitive, since EGR is a theory that implies a new (and more relativistic) conception of inertia: just as the inertia of a massive body prevents it from reaching a speed equal to that of light, in the same way its inertia prevents it from reaching a zone of space wherein escape velocity is greater than or equal to that of light, because, to get there, the body would have to reach a speed greater than or equal to that of light. Whatever the condition, free fall, as in the example of the first article, or high density as in the common case of collapsing of a neutron star, the single particle P, approaching the most extreme state of curvature, observes a corresponding increase of the remote inertia, in particular of the relativistic mass, of all other particles, together with their relative temporal slowing down: therefore their motion looks as lagging behind the one of particle P, and as balancing its growing proper inertia in delay. The outward push, which is experienced by the P particle, due to extreme relativistic conditions of other ones, gets at some point to an equilibrium with the gravitational pressure on P.
Relativistic inertial mass is relative, in contrast to gravitational one ,which is not. Therefore the relative times, for this inertial component (which is increasingly significant in the neighbourhood of the Schwarzschild radius – see Fn 2) have to be treated as in Restricted Relativity, since relativistic inertial mass does nothing but progressively replace the velocity component, when acceleration acts in conditions close to the speed of light. In particular, relativistic inertial mass is always remote for any single particle, as concerning all the others, and it is not increasing the particle gravitational mass, but its proper inertia, or reverse acceleration, which is a centrifugal component. All this has the consequence that the motion of all the particles finally lies on the spheroidal surface about which we argued in the first article, whose smallest or polar radius is equal to the Schwarzschild radius.
From the point of view of the fast-ticking observer (see Fn 3), he/she sees the situation as that relative to the rotating astronaut hanging on to a handle (see as before “Einstein is asked etc.”). That is, he/she sees a constant centrifugal inertial component undergone by the particle P (increasing proper inertia: if we could use the comparison of a proton in an accelerator, he/she sees the proton acquiring more and more inertial mass and therefore pressuring towards the outer edge of the accelerator, tending to describe a longer circumference as a result of its greater inertia).
From the point of view of the single particle P, it sees the situation as if it were the remote inertia, that of all the other particles, to grow; but, due to consequent relativistic dilation of their time, their pressure acts ever more delayed, letting an increasing part of P’s acceleration balance gravitational pressure (using the previous comparison, our proton, from its own point of view, sees the accelerator acquiring greater relativistic mass and consequently time dilation, that is, it sees the latter describing a circumference with radius ever greater, which leaves our proton free to put more pressure on the edge, on equal proper inertia).
From the most “remote” point of view, i.e. the ideal center of rotation, the situation is shown better in this way: it’s as if a retrograde precession (with respect to astronaut’s rotation) of space is implying for all the particles, as a consequence, to be describing circumferences that lag behind, or end geometrically first, on equal radius, with respect to the euclidean ones (the ones we all know, related to a flat space). Gravitational curvature causes the opposite effect, to make particles describe circumferences that move forward, or end geometrically later, on equal radius (well effect.. imagine you are going down a spiral staircase: to find yourself on equal than starting coordinates, for example on the y-axis, you tread a path longer than a flat circumference, on equal radius, but if the y-axis is rotated in the opposite direction to yours, you end the path by treading a distance shorter than a flat circumference, on equal radius).
We can represent the same with better words by saying that, seen from the remote point of view, or center of rotation, gravitational curvature tends to make particles move following a tangent-to-the-radius angle that is smaller than the right one, while relativistic inertial mass due to relativistic speed tends to make particles move following a tangent-to-the-radius angle that is greater than the right one. Equilibrium is reached just along right angle, at a speed really close to that of light; however no particle ever exceeds it.
All this is nothing other than the result of discovering, through the hypothesis of space rotation, the role of remote inertia, and the relative nature of its relationship and opposition to proper inertia.
Since we talked about spiral staircases and tangent angles, it is appropriate to introduce now the logarithmic spiral model (or “spira mirabilis” model) as the descriptive model that is proper for space-rotating systems.
After defining a generic logarithmic spiral as the locus of the points traced by a body P in a rectilinear and uniformly accelerated motion on a growing segment OP, while the segment OP is rotating (at a constant angular velocity ω) around the origin O of a system of polar coordinates (therefore the fast-ticking point is at a distant and polar position), we have that the distance r of P from the origin is developed in this way (here and below, “e” is Euler’s number, while “^” indicates the beginning of the exponent):
(Note that from the point of view in O, or origin or remote point, P always moves in a rectilinear and uniformly accelerated motion – or free fall – whilst it is the x,y coordinate system that is rotating in the opposite direction; instead the fast-ticking point of view, as already shown in the first article, sees the movement of the astronaut as having completely absorbed the movement of the wheel). Among the many notable features of a logarithmic spiral, it is to mention that its tangent is constant at every point.
By adapting the generic function to the motion of galaxies, we have:
r= S e^pαθ
where S is the Schwarzschild radius of the galaxy, p is a dimensionless constant, α=dτ/dT=1⁄γ is the inverse of the Lorentz factor (see Fn 4). (Interesting, in my opinion, and perhaps in the one of some passionate about mathematics and symmetry mind, to note that p≅1⁄e if we take the crude average of the results of these two studies:
average giving us a “pitch” angle (the complement of the tangent angle) equal to 20.38° – it’s to remark that for a pitch close to 20.20° we have exactly p=1⁄e). In order to complete: θ is the cumulative measurement of the angle between the rotating OP segment and the abscissa axis, so θ=ω∆T , with ω=f(Tc) function of the cosmological time or “age” of the Universe Tc (dimensionless quantity, in our context).
The function r= S e^pαθ so describes the isoequivalence curve for any massive body in a flat gravitational field, or, better, in a field characterized by an absolutely constant (spread in a constant way) mass density, and wherein dτ/dT=constant≅1 ; that’s to say our curve being the locus of the points where proper inertia and remote inertia are opposite and equal, so that the curve can be trod indifferently in both directions, in free fall. This is the real meaning of the aforementioned emergency of the principle of equivalence; as well as the misunderstanding of its emergency (i.e. about real nature of inertia) causes the apparent need for dark matter about which everyone is talking till now.
The difference with the actual motion of a star is obviously due to gravity, namely local and overall density differences, as well as the collapse of density at the edge of the disk, with the passage to galactic halo zone. It is gravity also to make not indifferent the two directions of free fall, as well as to make all stars tread less “pitched” curves, so causing density waves and well-known spiral arms.
The relatively little density differences in close-to-collapse line of stellar matter, suggest us that a similar logarithmic spiral can describe the pre-collapsing particles movement in a star.
In fact a collapsing neutron star is just coming from a state characterized by ERDM, extremely relativistic degenerate matter, in which the speed of particles is already close to the speed of light; so, if the star is isolated, while it is going to collapse, the equation of the combined spiral covered by deconfined particles (basically quarks), still in polar coordinates, is seen, from the fast-ticking point of view (while the astronaut, i.e. the candidate black hole, has absorbed upon him/herself, in the opposite sense, all the space rotation between him/herself and the f.t. point) to be:
r= s e^(δ/D)pαθ
with s Schwarzschild radius of the neutron star (which also describes the polar radius of the maximum pressure spheroidal surface inside the star – i.e. what we called center of mass so far); δ is the maximum density allowed by the Pauli exclusion principle, and D the actual stellar density in close-to-collapse line; increasing gravitational pressure is involving that δ/D is going to be close to 1, so that deconfined particles find ever less dispersive, in terms of energy, follow in a combined way the spiral; θ (see also below) is a cumulative quantity in the opposite sense outside or inside the s radius, so that collapsing toward s is, from a certain point on, the less expensive solution for particles; p is small as a consequence of density differences at different radii of the star (gravitational curvature).
When collapse starts, for r→s in both senses (from outside and from inside) we have that the ratio between proper time and f.t. observer’s time approaches zero,
so that the combined spiral trod by the particles under pressure degenerates into a circumference of radius s (polar projection of the real spheroidal surface) in which matter remains captured indefinitely.
We can describe the situation according to the famous example of running dogs, example which has always been reported as one of the intuitive way to understand logarithmic spirals: a few dogs, starting at the same time from various points on the edge of a huge circular room, and running because each of them has as objective getting to reach the one on its right, are describing, in a fairly intuitive way, each a logarithmic spiral. But if when approaching the center of the large room, each of them sees the dog on its own right becoming progressively bigger, heavier and slower, everyone will tend, in order to reach the other, more and more to maintain a right angle with respect to the radius that connects it to the center, describing, to the end, just a circumference.
I add, as regards neutron stars, that the characteristic, according to which points with maximum density, and therefore where the star is also maximally neutral and compact, lie on a spheroid at some km from the geometric center of the star, is a hypothesis by itself sufficient to explain very strong magnetic fields, otherwise incomprehensible. In fact, not only components different from neutrons would concentrate both on the surface and in the inside, but they, own to the very high spin and compactness of the star, would be trapped and forced to rotate at different radial speeds, with constant and huge consequent flows, generated in the hottest central zone.
In the case regarding our friend Sgr A* (I like to think to this superstar as a female entity, for the decisive matriarchal role played towards the entire galaxy) the situation is different, in the sense that it stands beyond S, the galactic Schwarzschild radius.
It can be shown that the logarithmic spiral we have formulated (r= S e^pαθ) proceeds, also in this case, in its development with close continuity; however its tangent begins to change very slowly (but constantly), and its pitch begins to become gradually smaller, as the spiral winds, gaining proximity to the superstar, that is, the closer that dτ/dT becomes smaller than 1 and nearer to zero. Moreover, we note that θ becomes θ=-ω∆T, i.e. geometrically the segment OP (from origin to body P) appears to rotate in an inverse sense (time-verse rotation vs previous space-verse one); so, geometrically, θ becomes a cumulative quantity in the opposite sense. All this indicates that, from S on, matter can thicken in a single sense, and only following the path that leads to the superstar, as we wrote in the main article. The fact that there is only one central area of density and the related and progressive temporal distortion put an end to the relative isoequivalence of the two directions of the path, preserving it only for a single sense, the one of the arrow of time, i.e. the one which proceeds towards the center; in parallel, it disappears every motion difference due to gravity, i.e. relative to the mass the body P in free fall.
In other respects, as in stellar case, for r→s (s Schwarzschild radius of the superstar) the ratio between proper time and f.t. observer’s time approaches zero,
so that the spiral degenerates, in the same way, in a circumference of radius s where matter remains captured – if we consider its development on the entire spheroidal surface – as in an almost perfectly two-dimensional and gigantic hologram, which emits energy almost uniformly, in the form of photons with large gravitational redshift (radio waves). The density of this holostar, in the case of Sgr A*, is consistent with the existence of hadrons and free electrons.
It is interesting to see the spiral inside the galactic center of mass, while developing by gathering its radial component in the opposite and time-verse direction, to be, except for the final stretch (heavily influenced by the relativistic dilation of time), the exact scale reproduction of the outer spiral (see Fn 5). This is one of the properties of the “spira mirabilis“, but in the case of our galaxy it gives rise to a particular harmony or resonance.
We know that the galactic Schwarzschild radius is about 0.25 light years, 2.4 × 10 ^ 15 meters. That of Sgr A*, like its mass, is a part in 200,000, that is 1.2 × 10 ^ 10 meters. If we keep the proportion 1.2 × 10 ^ 10 : 2.4 × 10 ^ 15 = 2.4 × 10 ^ 15 : x, we have x = 4.8 × 10 ^ 20 meters, equal to 50.700 light years, which strangely is the radius of the galaxy. In fact, multiplied by two it gives us the diameter we all know, about 100,000 light years.
with regard to the two Schwarzschild radii, while the scale derivation of the radius of the entire galactic disk, as far as I know, is mine.
This shows, at least for the Milky Way, that r= S e^pαθ and r= s e^pαθ are the same identical curve, as in geometric theory of logarithmic spirals (so called self-similarity, which is so important in fractal geometry), and that switching the two Schwarzschild radii is an uniform scaling transformation of the same object, as changing the zoom on Google Maps.
I believe that all this could be due to the fortunate position of the Milky Way, located in a very very peripheral cluster with respect to the reference super cluster (Virgo), and furthermore in a cluster, ever the local one, with a “handlebar” distribution of the mass, where the Milky Way represents the center of one of the two polarities. I think it is the best position to detect such a perfect “spira mirabilis“.
The center of the other pole of the local cluster handlebar, i.e. the Andromeda galaxy, was recently (meant on a scale of millions of years, of course) disturbed by the transit of the Triangulum galaxy (which, obviously, being smaller, suffered much more). However: the central superstar of Andromeda seems to have a mass 40 times that of ours, whilst the radius of the entire galaxy is 2.2 times that of ours. If the previous proportion has a certain value also for Andromeda, therefore the Andromeda mass should be √88 times that of ours, i.e. about 9.4 times. Having read estimations ranging from 1 time to 20 times, I would say that the result lies in a fairly middle position.
I apologize for the absolutely bad quality of equation rendering, unfortunately if I want to change it I will have to upgrade my subscription to the site, and then to insert necessary plugins.
It was not possible writing subscripts, whilst I remind you that “^” indicates that what you read next is the exponent.
I thank Maurizio Bernardi for his contribution about logarithmic spiral geometry.
Patamu register #102963 2019/04/06;
Patamu register #102820 2019/04/04.
1) Scientist of EHT team, in their first article dated 19/04/10, state that their result is absolutely consistent with the Kerr relativistic metric (the GR metric relative to a spinning black hole), but that there are at least two other solutions, beyond that which foresees an event horizon; these comply with expectations of the Kerr metric, however without foreseeing a horizon; solutions which the result of April 10th cannot therefore exclude. As we will see in my next article, my suggestion, describing black holes as holostars, is the fourth hypothesis, and it is the one that requires coherence with the Kerr relativistic metric par excellence.
2) The Schwarzschild radius is the theoretical minimum radius of the sphere within which all the mass of a body should be compressed in order to have an escape velocity on body’s surface equal to or greater than the speed of light; if the body proceeds in its collapse, the Schwarzschild radius remains the radius of the sphere that delimits the event horizon, since no information can come out from within that sphere.
3) The fast-ticking observer is, in General Relativity, the inertial observer, the one not subject to any acceleration, located very far from the gravitational field, and, in the case of the EGR, placed in polar position, that is, not rotating; his/her clock, as noticing the relative slowness of all other clocks, is fast-ticking, i.e. with the faster ticking; consequently, his/hers is the clock that records the longest duration relatively to an event.
4) The Lorentz factor γ is here defined simply as the ratio between the time marked by the fast-ticking clock of a non-accelerated observer in measuring the duration of an event, and proper time, that is the time marked by a clock joined with the event whose duration is measured: dT/dτ=γ. The factor is derived from the simple observation that the two clocks must measure the same speed, c, in the case of light. Here we assume the notation α used for its inverse, so α=1⁄γ=dτ/dT, that is α is the ratio between the proper time and the non-accelerated observer time.
5) Actually, inner spiral, including final stretch, is the perfect scale reproduction of outer one, but in a four-dimensional scale, since we have to take into account space-time curvature. The path followed by P is exactly in scale, but it is trod along a spiral staircase, thus, in order to keep the scale, ends before if compared to a flat spiral: it is trod up to s instead than up to the geometric center, as the difference is trod through time. | 0.905042 | 3.894865 |
As I’ve mentioned previously, my career is based around looking for alien life in the universe. Naturally, this brings up the very pertinent question of “Where exactly does one look for aliens?”
The answer, surprisingly, is “pretty much all over the place.” And with good reason – here on Earth, living organisms have been found in some of the most seemingly inhospitable places, which suggests that life is, above all, tenacious in the extreme.
Where to begin, then? Why not in our own backyard? As it turns out, there are more than a few places in our own Solar System that might harbor life. So, without further adieu, let’s take a guided tour of the Solar System’s hottest real estate, moving from the inner planets outwards.
Venus may seem like a surprising candidate – the surface is hot enough to melt lead, the atmospheric pressure is crushing, and it rains sulfuric acid. But Venus was not always so grim. It is thought that it may have had oceans for the first two billion years of its history, before the growing intensity of the young sun triggered a runaway greenhouse effect that boiled them off. Life may have been able to get a toehold in these early seas, as it did on Earth.
But where could such life have fled to under the onslaught of rising temperatures? Curiously, it turns out that while the surface may be utterly inhabitable, at ~50km above the ground, the atmosphere of Venus is remarkably Earth-like in temperature and pressure. It’s still fairly acidic, there’s no oxygen, and it’s still on the warm side, but there are organisms on Earth that will quite happily live in similar conditions. UV radiation would be a problem – however, interestingly enough, cylcooctasulfate – a sulfur compound that absorbs UV rays and re-emits them as visible light, and that’s used by terrestrial microbes as “sun screen” – is found in the Venusian atmosphere at an altitude of 50km.
No, I’m not suggesting Earth’s been invaded – I’m instead referring to the idea of the shadow biosphere. The basic premise of the shadow biosphere is that we assume that all life on Earth is biochemically similar to us (e.g., it uses the same types of proteins and DNA, same chemical reactions, and so forth), and therefore we would fail to detect microbes that used radically different biochemistry. The microbes wouldn’t be “aliens”, per se, as it’s assumed that they would’ve evolved here on Earth – but such a finding would still be incredibly significant, as it would suggest that life may developed independently on Earth, multiple times.
Supporters of the shadow biosphere hypothesis point to the fact that the vast majority of microbes can’t actually be cultured in a laboratory, and as a result, we know very little about them. There have been searches for “weird life”, including, most notoriously, GFAJ-1. GFAJ-1 was initially reported to use arsenic in the construction of its DNA (as opposed to phosphorus, which is what all known life uses instead). However, after its discovery was announced, further experimentation couldn’t detect the presence of arsenic in its DNA, and biochemical modeling suggested that DNA using arsenic wouldn’t actually be chemically stable. The search goes on.
This list obviously wouldn’t be complete without everyone’s favorite red planet, Mars. Mars has long held a fascination, in part due to early observations of channels or canals on the surface (these were later revealed to be the result of an optical illusion). As it turns out, such a reputation might be warranted – Mars is the most Earth-like planet in our Solar System, and shows evidence of being a much warmer, wetter planet in its past (most notably, the presence of dry river networks and lake beds). In the present day, there also appears to be seasonal flows of liquid brine or extremely salty water, most likely the result of salts absorbing water vapor from the atmosphere.
As I mentioned in my previous essay, methane has also been detected in the Martian atmosphere. Since methane isn’t chemically stable under Martian conditions, something must actively producing it. Stranger yet, the production appears to be sporadic, suggesting that this is the result of an active process. While there are purely geological processes that can produce methane, here on Earth, the vast majority of methane is produced by microbes, which obviously raises suspicions.
It’s unlikely the Martian microbes – if they exist – are living on the surface, due to the high flux of radiation. Instead, they’ll most likely be found in deep subsurface habitats or aquifers, or potentially underneath the polar ice caps. Future missions to Mars (notably the ESA’s ExoMars and NASA’s Mars 2020 Rover) will hopefully give us better answers to the age old question of life on Mars.
Moving into the outer Solar System, Europa is one of the four major moons of Jupiter, and is covered entirely by a thick layer of ice. It’s been a target of great interest to astrobiologists since the data from the Voyager missions suggested the presence of a vast ocean underneath the ice layer. The thickness of the ice shell and the depth of the ocean is subject to debate, but it’s thought that it could be as much as 100 miles deep, and encompass a volume of water twice the size of all of Earth’s oceans. Given the importance of liquid water to life as we know it, this obviously makes it a potential candidate for habitability.
Due to the complete absence of sunlight underneath the ice shell, if there’s life on Europa, it’s probably clustered around hydrothermal vents, much like the vent ecosystems seen on ocean floors here on Earth. These vents are driven by volcanic heating driven by the intense tidal forces of Jupiter, which also keeps the ocean from freezing, and is also most likely responsible for the alleged plumes of water erupting from the surface.
Several missions are planned to study Europa – ESA’s Jupiter Icy Moons Explorer and NASA’s Europa Multi-Flyby Mission, which will hopefully be able to measure the thickness of the ice shell, gather more data on the chemical composition of the surface, and sample the surface plumes (if they exist). Proposals have been circulating to actually drill down and explore the ocean, but such a mission is a while off.
Similar to Europa, Enceladus is an ice covered moon orbiting Saturn. It features extensive plumes of water erupting from its southern hemisphere, thought to originate in a subsurface ocean. The exact mechanisms driving the plumes hasn’t been determined, but there’s likely hydrothermal activity in play. Since the plumes are so extensive, the Cassini mission in orbit around Saturn has been able to conveniently sample some of the erupted material, and discovered that it has a high salt content (suggesting hydrothermal activity) and traces of simple organic compounds. Given the presence of organics, liquid water, and a likely energy source, Enceladus has become a hot topic amongst astrobiologists, and will hopefully be the target of future exploration
Another moon of Saturn, Titan is the second largest moon in the Solar System, and the only one with a dense atmosphere. The atmosphere is made up of a mixture of nitrogen, methane, and a mixture of organic compounds. Titan is a chilly -355 degrees Fahrenheit, so cold that methane is liquid at the surface. In fact, the most interesting thing about Titan is that liquid methane takes the place of water – there are rivers and lakes of the stuff.
Consequently, unlike the other worlds we’ve looked at, if there’s life on Titan, it’s very different from the water-based life we’re familiar with. Potential biochemical pathways have been identified for the Titanian atmosphere, and, interestingly enough, some of the features in Titan’s atmospheric composition would be consistent with presence of metabolizing organisms. Nonetheless, life on Titan remains a much more speculative topic, and will require further exploration of this mysterious, haze shrouded moon.
While Earth may be the most habitable world in our Solar System, it isn’t the only place life might have evolved. No alien life has been conclusively detected, but the hunt is on. The most exciting aspect of this search is that if life evolved independently, multiple times within the same solar system, it suggests that the emergence of life is a common event.
In other words, if we discover that our Solar System is teeming with life, it’s likely that so is the rest of the galaxy.
Tessa is a 28 year old PhD student, and perhaps the world’s only queer trans astrobiologist. A nerd going way back, her interests include science fiction, space exploration, sustainability, science communication, and feminism and gender. Her hobbies also include horseback riding, playing the flute, social dancing, knitting, and occasional attempts at writing fiction. She currently resides in Tempe, AZ with her even nerdier fiancee and a mastiff mix who thinks he’s a lapdog. She tweets occasionally @spacermase. | 0.843246 | 3.702557 |
Saturn’s distinctive rings were observed in unprecedented detail by NASA’s Cassini spacecraft, and scientists have now used those observations to probe the interior of the giant planet and obtain the first precise determination of its rotation rate.
The length of a day on Saturn, according to their calculations, is 10 hours 33 minutes and 38 seconds.
The researchers studied wave patterns created within Saturn’s rings by the planet’s internal vibrations. In effect, the rings act as an extremely sensitive seismograph by responding to vibrations within the planet itself.
Similar to Earth’s vibrations from an earthquake, Saturn responds to perturbations by vibrating at frequencies determined by its internal structure. Heat-driven convection in the interior is the most likely source of the vibrations. These internal oscillations cause the density at any particular place within the planet to fluctuate, which makes the gravitational field outside the planet oscillate at the same frequencies.
“Particles in the rings feel this oscillation in the gravitational field. At places where this oscillation resonates with ring orbits, energy builds up and gets carried away as a wave,” explained Christopher Mankovich, a graduate student in astronomy and astrophysics at UC Santa Cruz.
Mankovich is lead author of a paper, published January 17 in the Astrophysical Journal, comparing the wave patterns in the rings with models of Saturn’s interior structure.
Most of the waves observed in Saturn’s rings are due to the gravitational effects of the moons orbiting outside the rings, said co-author Jonathan Fortney, professor of astronomy and astrophysics at UC Santa Cruz. “But some of the features in the rings are due to the oscillations of the planet itself, and we can use those to understand the planet’s internal oscillations and internal structure,” he said.
Mankovich developed a set of models of the internal structure of Saturn, used them to predict the frequency spectrum of Saturn’s internal vibrations, and compared those predictions with the waves observed by Cassini in Saturn’s C ring. One of the main results of his analysis is the new calculation of Saturn’s rotation rate, which has been surprisingly difficult to measure.
As a gas giant planet, Saturn has no solid surface with landmarks that could be tracked as it rotates. Saturn is also unusual in having its magnetic axis nearly perfectly aligned with its rotational axis. Jupiter’s magnetic axis, like Earth’s, is not aligned with its rotational axis, which means the magnetic pole swings around as the planet rotates, enabling astronomers to measure a periodic signal in radio waves and calculate the rotation rate.
The rotation rate of 10:33:38 determined by Mankovich’s analysis is several minutes faster than previous estimates based on radiometry from the Voyager and Cassini spacecraft.
“We now have the length of Saturn’s day, when we thought we wouldn’t be able to find it,” said Cassini Project Scientist Linda Spilker. “They used the rings to peer into Saturn’s interior, and out popped this long-sought, fundamental quality of the planet. And it’s a really solid result. The rings held the answer.”
The idea that Saturn’s rings could be used to study the seismology of the planet was first suggested in 1982, long before the necessary observations were possible. Coauthor Mark Marley, now at NASA’s Ames Research Center in Silicon Valley, subsequently fleshed out the idea for his Ph.D. thesis in 1990, showed how the calculations could be done, and predicted where features in Saturn’s rings would be. He also noted that the Cassini mission, then in the planning stages, would be able to make the observations needed to test the idea.
“Two decades later, people looked at the Cassini data and found ring features at the locations of Mark’s predictions,” Fortney said.
We are now accepting pre-orders for our healthy and delicious storable food. Stock up today! | 0.892364 | 4.056067 |
What makes Saturn’s atmosphere so hot
New mapping of the giant planet’s upper atmosphere reveals likely reason why it’s so hot
The upper layers in the atmospheres of gas giants — Saturn, Jupiter, Uranus and Neptune — are hot, just like Earth’s. But unlike Earth, the Sun is too far from these outer planets to account for the high temperatures. Their heat source has been one of the great mysteries of planetary science.
New analysis of data from NASA’s Cassini spacecraft finds a viable explanation for what’s keeping the upper layers of Saturn, and possibly the other gas giants, so hot: auroras at the planet’s north and south poles. Electric currents, triggered by interactions between solar winds and charged particles from Saturn’s moons, spark the auroras and heat the upper atmosphere. (As with Earth’s northern lights, studying auroras tells scientists what’s going on in the planet’s atmosphere.)
The work, published today in Nature Astronomy, is the most complete mapping yet of both temperature and density of a gas giant’s upper atmosphere – a region that has been poorly understood.
“Understanding the dynamics really requires a global view. This dataset is the first time we’ve been able to look at the upper atmosphere from pole to pole while also seeing how temperature changes with depth,” said Zarah Brown, lead author of the study and a graduate student in the University of Arizona Lunar and Planetary Laboratory.
By building a complete picture of how heat circulates in the atmosphere, scientists are better able to understand how auroral electric currents heat the upper layers of Saturn’s atmosphere and drive winds. The global wind system can distribute this energy, which is initially deposited near the poles toward the equatorial regions, heating them to twice the temperatures expected from the sun’s heating alone.
“The results are vital to our general understanding of planetary upper atmospheres and are an important part of Cassini’s legacy,” said study co-author Tommi Koskinen, a member of Cassini’s Ultraviolet Imaging Spectograph team. “They help address the question of why the uppermost part of the atmosphere is so hot, while the rest of the atmosphere – due to the large distance from the Sun – is cold.”
Managed by NASA’s Jet Propulsion Laboratory in Southern California, Cassini was an orbiter that observed Saturn for more than 13 years before exhausting its fuel supply. The mission plunged it into the planet’s atmosphere in September 2017, in part to protect its moon Enceladus, which Cassini discovered might hold conditions suitable for life. But before its plunge, Cassini performed 22 ultra-close orbits of Saturn, a final tour called the Grand Finale.
It was during the Grand Finale that the key data was collected for the new temperature map of Saturn’s atmosphere. For six weeks, Cassini targeted several bright stars in the constellations of Orion and Canis Major as they passed behind Saturn. As the spacecraft observed the stars rise and set behind the giant planet, scientists analyzed how the starlight changed as it passed through the atmosphere.
Measuring how dense the atmosphere is gave scientists the information they needed to find the temperatures. Density decreases with altitude, and the rate of decrease depends on temperature. They found that temperatures peak near the auroras, indicating that auroral electric currents heat the upper atmosphere.
Density and temperature measurements together helped scientists figure out wind speeds. Understanding Saturn’s upper atmosphere, where planet meets space, is key to understanding space weather and its impact on other planets in our solar system and exoplanets around other stars.
“Even though thousands of exoplanets have been found, only the planets in our solar system can be studied in this kind of detail. Thanks to Cassini, we have a more detailed picture of Saturn’s upper atmosphere right now than any other giant planet in the universe,” Brown said.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA’s Jet Propulsion Laboratory, or JPL, a division of Caltech in Pasadena, manages the mission for NASA’s Science Mission Directorate in Washington. JPL designed, developed and assembled the Cassini orbiter.
Related Journal Article | 0.852217 | 4.024287 |
In the News
On Jan. 30, 2020, the venerable Spitzer Space Telescope mission will officially come to an end as NASA makes way for a next-generation observatory. For more than 16 years, Spitzer has served as one of NASA’s four Great Observatories, surveying the sky in infrared. During its lifetime, Spitzer detected planets and signs of habitability beyond our solar system, returned stunning images of regions where stars are born, spied light from distant galaxies formed when the universe was young, and discovered a huge, previously-unseen ring around Saturn. Read on to learn more about this amazing mission and gather tools to teach your students that there truly is more than meets the eye in the infrared universe!
How It Worked
Human eyes can see only the portion of the electromagnetic spectrum known as visible light. This is because the human retina can detect only certain wavelengths of light through special photoreceptors called rods and cones. Everything we see with our eyes either emits or reflects visible light. But visible light is just a small portion of the electromagnetic spectrum. To "see" things that emit or reflect other wavelengths of light, we must rely on technology designed to sense those portions of the electromagnetic spectrum. Using this specialized technology allows us to peer into space and observe objects and processes we wouldn’t otherwise be able to see.
Infrared is one of the wavelengths of light that cannot be seen by human eyes. (It can sometimes be felt by our skin as heat if we are close enough to a strong source.) All objects that have temperature emit many wavelengths of light. The warmer they are, the more light they emit. Most things in the universe are warm enough to emit infrared radiation, and that light can be seen by an infrared-detecting telescope. Because Earth’s atmosphere absorbs most infrared radiation, infrared observations of space are best conducted from outside the planet's atmosphere.
So, to get a look at space objects that were otherwise hidden from view, NASA launched the Spitzer Space Telescope in 2003. Cooled by liquid helium and capable of viewing the sky in infrared, Spitzer launched into an Earth-trailing orbit around the Sun, where it became part of the agency's Great Observatory program along with the visible-light and near-infrared-detecting Hubble Space Telescope, Compton Gamma-Ray Observatory and Chandra X-ray Observatory. (Keeping the telescope cold reduces the chances of heat, or infrared light, from the spacecraft interfering with its astronomical observations.)
Over its lifetime, Spitzer has been used to detect light from objects and regions in space where the human eye and optical, or visible-light-sensing, telescopes may see nothing.
Why It's Important
NASA's Spitzer Space Telescope has returned volumes of data, yielding numerous scientific discoveries.
Vast, dense clouds of dust and gas block our view of many regions of the universe. Infrared light can penetrate these clouds, enabling Spitzer to peer into otherwise hidden regions of star formation, newly forming planetary systems and the centers of galaxies.
Infrared astronomy also reveals information about cooler objects in space, such as smaller stars too dim to be detected by their visible light, planets beyond our solar system (called exoplanets) and giant molecular clouds where new stars are born. Additionally, many molecules in space, including organic molecules thought to be key to life's formation, have unique spectral signatures in the infrared. Spitzer has been able to detect those molecules when other instruments have not.
Stars are born from condensing clouds of dust and gas. These newly formed stars are optically visible only once they have blown away the cocoon of dust and gas in which they were born. But Spitzer has been able to see infant stars as they form within their gas and dust clouds, helping us learn more about the life cycles of stars and the formation of solar systems.
Infrared emissions from most galaxies come primarily from stars as well as interstellar gas and dust. With Spitzer, astronomers have been able to see which galaxies are furiously forming stars, locate the regions within them where stars are born and pinpoint the cause of the stellar baby boom. Spitzer has given astronomers valuable insights into the structure of our own Milky Way galaxy by revealing where all the new stars are forming.
Spitzer marked a new age in the study of planets outside our solar system by being the first telescope to directly detect light emitted by these so-called exoplanets. This has made it possible for us to directly study and compare these exoplanets. Using Spitzer, astronomers have been able to measure temperatures, winds and the atmospheric composition of exoplanets – and to better understand their potential habitability. The discoveries have even inspired artists at NASA to envision what it might be like to visit these planets.
Data collected by Spitzer will continue to be analyzed for decades to come and is sure to yield even more scientific findings. It's certainly not the end of NASA's quest to get an infrared window into our stellar surroundings. In the coming years, the agency plans to launch its James Webb Space Telescope, with a mirror more than seven times the diameter of Spitzer's, to see the universe in even more detail. And NASA's Wide Field Infrared Survey Telescope, or WFIRST, will continue infrared observations in space with improved technology. Stay tuned for even more exciting infrared imagery, discoveries and learning!
Use these lessons, videos and online interactive features to teach students how we use various wavelengths of light, including infrared, to learn about our universe:
Using Light to Study Planets
Students build a spectrometer using basic materials as a model for how NASA uses spectroscopy to determine the nature of elements found on Earth and other planets.
Time > 2 hrs
- Lessons: Cool Cosmos Infrared Lessons
- Website: Cool Cosmos Infrared Primer
- Materials: Infrared Posters and Printouts
- Article: NASA Celebrates the Legacy of the Spitzer Space Telescope
- Website: Spitzer Space Telescope Mission
- Video: Spitzer Final Voyage VR 360
- Video: Science in a Minute: The Art of Spitzer Space Telescope
- Images: Spitzer Zoomable Images
- Participate: NASA/IPAC Teacher Archive Research Program
Also, check out these related resources for kids from NASA’s Space Place:
TAGS: Teachable Moments, science, astronomy, K-12 education, teachers, educators, parents, STEM, lessons, activities, Spitzer, Space Telescope, Missions, Spacecraft, Stars, Galaxies, Universe, Infrared, Wavelengths, Spectrum, Light
In the News
It only happens about 13 times a century and won’t happen again until 2032, so don’t miss the transit of Mercury on Monday, Nov. 11! A transit happens when a planet crosses in front of a star. From our perspective on Earth, we only ever see two planets transit the Sun: Mercury and Venus. This is because these are the only planets between us and the Sun. (Transits of Venus are especially rare. The next one won’t happen until 2117.) During the upcoming transit of Mercury, viewers around Earth (using the proper safety equipment) will be able to see a tiny dark spot moving slowly across the disk of the Sun.
Read on to learn how transits contributed to past scientific discoveries and for a look at how scientists use them today. Plus, find resources for engaging students in this rare celestial event!
Why It's Important
Then and Now
In the early 1600s, Johannes Kepler discovered that both Mercury and Venus would transit the Sun in 1631. It was fortunate timing: The telescope had been invented just 23 years earlier, and the transits of both planets wouldn’t happen in the same year again until 13425. Kepler didn’t survive to see the transits, but French astronomer Pierre Gassendi became the first person to see the transit of Mercury. Poor weather kept other astronomers in Europe from seeing it. (Gassendi attempted to view the transit of Venus the following month, but inaccurate astronomical data led him to mistakenly believe it would be visible from his location.) It was soon understood that transits could be used as an opportunity to measure apparent diameter – how large a planet appears from Earth – with great accuracy.
STEM Lessons for Educators
Bring the wonder of space to your students. Explore our collection of standards-aligned lessons featuring NASA missions and science.
After observing the transit of Mercury in 1677, Edmond Halley predicted that transits could be used to accurately measure the distance between the Sun and Earth, which wasn’t known at the time. This could be done by having observers at distant points on Earth look at the variation in a planet’s apparent position against the disk of the Sun – a phenomenon known as parallax shift. This phenomenon is what makes nearby objects appear to shift more than distant objects when you look out the window of a car, for example.
Today, radar is used to measure the distance between Earth and the Sun with greater precision than transit observations. But the transits of Mercury and Venus still provide scientists with opportunities for scientific investigation in two important areas: exospheres and exoplanets.
Some objects, like the Moon and Mercury, were originally thought to have no atmosphere. But scientists have discovered that these bodies are actually surrounded by an ultrathin atmosphere of gases called an exosphere. Scientists want to better understand the composition and density of the gases in Mercury’s exosphere, and transits make that possible.
“When Mercury is in front of the Sun, we can study the exosphere close to the planet,” said NASA scientist Rosemary Killen. “Sodium in the exosphere absorbs and re-emits a yellow-orange color from sunlight, and by measuring that absorption, we can learn about the density of gas there.”
When Mercury transits the Sun, it causes a slight dip in the Sun’s brightness as it blocks a tiny portion of the Sun’s light. Scientists discovered they could use that phenomenon to search for planets orbiting distant stars. These planets, called exoplanets, are otherwise obscured from view by the light of their star. When measuring the brightness of far-off stars, a slight recurring dip in the light curve (a graph of light intensity) could indicate an exoplanet orbiting and transiting its star. NASA’s Kepler space telescope found more than 2,700 exoplanets by looking for this telltale drop in brightness. NASA’s TESS mission is surveying 200,000 of the brightest stars near our solar system and is expected to potentially discover more than 10,000 transiting exoplanets.
Additionally, scientists have been exploring the atmospheres of exoplanets. Similarly to how we study Mercury’s exosphere, scientists can observe the spectra – a measure of light intensity and wavelength – that passes through an exoplanet’s atmosphere. As a result, they’re beginning to understand the evolution and composition of exoplanet atmospheres, as well as the influence of stellar wind and magnetic fields.
During the transit of Mercury, the planet will appear as a tiny dot on the Sun’s surface. To see it, you’ll need a telescope or binoculars outfitted with a special solar filter.
WARNING! Looking at the Sun directly or through a telescope without proper protection can lead to serious and permanent vision damage. Do not look directly at the Sun without a certified solar filter.
The transit of Mercury will be partly or fully visible across much of the globe. However, it won’t be visible from Australia or most of Asia and Alaska.
Mercury’s trek across the Sun begins at 4:35 a.m. PST (7:35 a.m. EST), meaning viewers on the East Coast of the U.S. can experience the entire event, as the Sun will have already risen before the transit begins. By the time the Sun rises on the West Coast, Mercury will have been transiting the Sun for nearly two hours. Fortunately, the planet will take almost 5.5 hours to completely cross the face of the Sun, so there will be plenty of time for West Coast viewers to witness this event. See the transit map below to learn when and where the transit will be visible.
Don’t have access to a telescope or binoculars with a solar filter? Visit the Night Sky Network website to find events near you where amateur astronomers will have viewing opportunities available.
During the transit, NASA will share near-real-time images of the Sun directly from the Solar Dynamics Observatory. Beginning at 4:41 a.m. PST (7:41 a.m. EST) you can see images of Mercury passing in front of the Sun at NASA’s 2019 Mercury Transit page, with updates through the end of the transit at 10:04 a.m. PST (1:04 p.m. EST).
If you’re in the U.S., don’t miss the show, as this is the last time a transit will be visible from the continental United States until 2049!
Use these lessons and activities to engage students in the transit of Mercury and the hunt for planets beyond our solar system:
Exploring Exoplanets with Kepler
Students use math concepts related to transits to discover real-world data about Mercury, Venus and planets outside our solar system.
Time 30 mins - 1 hr
Sun Screen: A 'Pi in the Sky' Math Challenge
When Mercury passes in front of the Sun, how much sunlight is lost on Earth? Students use the mathematical constant pi to find the solution in this illustrated math challenge.
Time < 30 mins
Solar Sleuth: A 'Pi in the Sky' Math Challenge
In this illustrated math problem, students use pi and data from the Kepler space telescope to find the size of a planet outside our solar system.
Time < 30 mins
Can You Spot Mercury?
Play science sleuth and see if you can spot Mercury passing in front of – or transiting – the sun in these images from NASA.
Oh, the Places We Go: 18 Ways NASA Uses Pi
Whether it's sending spacecraft to other planets, driving rovers on Mars, finding out what planets are made of or how deep alien oceans are, pi takes us far at NASA. Find out how pi helps us explore space.
- NASA near-real-time transit images
- Video: What’s Up – November 2019
- 2019 Mercury Transit Map
- Night Sky Network Events
- NASA Museum Alliance Resources
- Exoplanet Exploration Website
- Interactive: 5 Ways to Find a Planet
- Interactive: Eyes on Exoplanets
- Posters: Exoplanet Travel Bureau
- Video: What’s in an Exoplanet Name?
- Video: The Search for Another Earth
- Kepler Mission Website
- Kepler Education Activities
Check out these related resources for kids from NASA’s Space Place:
In the News
Looking up at the Moon can create a sense of awe at any time, but those who do so on the evening of January 20 will be treated to the only total lunar eclipse of 2019. Visible for its entirety in North and South America, this eclipse is being referred to by some as a super blood moon – “super” because the Moon will be closest to Earth in its orbit during the full moon (more on supermoons here) and “blood" because the total lunar eclipse will turn the Moon a reddish hue (more on that below). This is a great opportunity for students to observe the Moon – and for teachers to make connections to in-class science content.
How It Works
Eclipses can occur when the Sun, the Moon and Earth align. Lunar eclipses can happen only during a full moon, when the Moon and the Sun are on opposite sides of Earth. At that point, the Moon can move into the shadow cast by Earth, resulting in a lunar eclipse. However, most of the time, the Moon’s slightly tilted orbit brings it above or below Earth’s shadow.
The time period when the Moon, Earth and the Sun are lined up and on the same plane – allowing for the Moon to pass through Earth’s shadow – is called an eclipse season. Eclipse seasons last about 34 days and occur just shy of every six months. When a full moon occurs during an eclipse season, the Moon travels through Earth’s shadow, creating a lunar eclipse.
Unlike solar eclipses, which require special glasses to view and can be seen only for a few short minutes in a very limited area, a total lunar eclipse can be seen for about an hour by anyone on the nighttime side of Earth – as long as skies are clear.
What to Expect
The Moon passes through two distinct parts of Earth’s shadow during a lunar eclipse. The outer part of the cone-shaped shadow is called the penumbra. The penumbra is less dark than the inner part of the shadow because it’s penetrated by some sunlight. (You have probably noticed that some shadows on the ground are darker than others, depending on how much outside light enters the shadow; the same is true for the outer part of Earth’s shadow.) The inner part of the shadow, known as the umbra, is much darker because Earth blocks additional sunlight from entering the umbra.
At 6:36 p.m. PST (9:36 p.m. EST) on January 20, the edge of the Moon will begin entering the penumbra. The Moon will dim very slightly for the next 57 minutes as it moves deeper into the penumbra. Because this part of Earth’s shadow is not fully dark, you may notice only some dim shading (if anything at all) on the Moon near the end of this part of the eclipse.
At 7:33 p.m. PST (10:33 p.m. EST), the edge of the Moon will begin entering the umbra. As the Moon moves into the darker shadow, significant darkening of the Moon will be noticeable. Some say that during this part of the eclipse, the Moon looks as if it has had a bite taken out of it. That “bite” gets bigger and bigger as the Moon moves deeper into the shadow.
At 8:41 p.m. PST (11:41 p.m. EST), the Moon will be completely inside the umbra, marking the beginning of the total lunar eclipse. The moment of greatest eclipse, when the Moon is halfway through the umbra, occurs at 9:12 p.m. PST (12:12 a.m. EST).
As the Moon moves completely into the umbra, something interesting happens: The Moon begins to turn reddish-orange. The reason for this phenomenon? Earth’s atmosphere. As sunlight passes through it, the small molecules that make up our atmosphere scatter blue light, which is why the sky appears blue. This leaves behind mostly red light that bends, or refracts, into Earth’s shadow. We can see the red light during an eclipse as it falls onto the Moon in Earth’s shadow. This same effect is what gives sunrises and sunsets a reddish-orange color.
A variety of factors affect the appearance of the Moon during a total lunar eclipse. Clouds, dust, ash, photochemical droplets and organic material in the atmosphere can change how much light is refracted into the umbra. Additionally, the January 2019 lunar eclipse takes place when the full moon is at or near the closest point in its orbit to Earth – a time popularly known as a supermoon. This means the Moon is deeper inside the umbra shadow and therefore may appear darker. The potential for variation provides a great opportunity for students to observe and classify the lunar eclipse based on its brightness. Details can be found in the “Teach It” section below.
At 9:43 p.m. PST (12:43 a.m. EST), the edge of the Moon will begin exiting the umbra and moving into the opposite side of the penumbra. This marks the end of the total lunar eclipse.
At 10:50 p.m. PST (1:50 a.m. EST), the Moon will be completely outside the umbra. It will continue moving out of the penumbra until the eclipse ends at 11:48 p.m (2:48 a.m. EST).
What if it’s cloudy where you live? Winter eclipses always bring with them the risk of poor viewing conditions. If your view of the Moon is obscured by the weather, explore options for watching the eclipse online, such as the Time and Date live stream.
Why It’s Important
Lunar eclipses have long played an important role in understanding Earth and its motions in space.
In ancient Greece, Aristotle noted that the shadows on the Moon during lunar eclipses were round, regardless of where an observer saw them. He realized that only if Earth were a spheroid would its shadows be round – a revelation that he and others had many centuries before the first ships sailed around the world.
Earth wobbles on its axis like a spinning top that’s about to fall over, a phenomenon called precession. Earth completes one wobble, or precession cycle, over the course of 26,000 years. Greek astronomer Hipparchus made this discovery by comparing the position of stars relative to the Sun during a lunar eclipse to those recorded hundreds of years earlier. A lunar eclipse allowed him to see the stars and know exactly where the Sun was for comparison – directly opposite the Moon. If Earth didn’t wobble, the stars would appear to be in the same place they were hundreds of years earlier. When Hipparchus saw that the stars’ positions had indeed moved, he knew that Earth must wobble on its axis!
Lunar eclipses are also used for modern-day science investigations. Astronomers have used ancient eclipse records and compared them with computer simulations. These comparisons helped scientists determine the rate at which Earth’s rotation is slowing.
Ask students to observe the lunar eclipse and evaluate the Moon’s brightness using the Danjon Scale of Lunar Eclipse Brightness. The Danjon scale illustrates the range of colors and brightness the Moon can take on during a total lunar eclipse, and it’s a tool observers can use to characterize the appearance of an eclipse. View the lesson guide below. After the eclipse, have students compare and justify their evaluations of the eclipse.
Evaluating a Lunar Eclipse
Students use the Danjon Scale of Lunar Eclipse Brightness to illustrate the range of colors and brightness the Moon can take on during a total lunar eclipse.
Time 30 mins - 1 hr
Use these standards-aligned lessons and related activities to get your students excited about the eclipse, Moon phases and Moon observations:
Observing the Moon
Students identify the Moon’s location in the sky and record their observations over the course of the moon-phase cycle in a journal.
Time 30 mins - 1 hr
Students learn about the phases of the moon by acting them out.
Time 30 mins - 1 hr
Whip Up a Moon-Like Crater
Whip up a moon-like crater with baking ingredients as a demonstration for students.
Time 30 mins - 1 hr
Teachable Moment: What’s a Supermoon and Just How Super Is It?
Are supermoons as super as they're made out to be? Learn what causes them and explore related activities for teachers and students.
Measuring the Supermoon
Students use analog and digital tools to measure the Moon’s apparent size and brightness.
Time 30 mins - 1 hr
Modeling the Earth-Moon System
Students learn about scale models and distance by creating a classroom-size Earth-Moon system.
Time 30 mins - 1 hr
Make a Moon Phases Calendar and Calculator
Like a decoder wheel for the Moon, this calendar will show you where and when to see the Moon and every moon phase throughout the year!
- Try these related resources for students from NASA’s Space Place:
- Lunar Eclipses and Solar Eclipses – This guide for kids provides an overview of lunar and solar eclipses.
- Why Does the Moon Have Craters? – Check out NASA’s Space Place for the answer, written just for kids.
- NASA Moon Website – Find out more about the Moon along with the NASA robots and humans who have visited it.
When Lean Teodoro was growing up on the remote island of Saipan in the middle of the Pacific Ocean, her dream of one day working for NASA always seemed a bit far-fetched to those around her. Now, a geophysics student on the premed track at the University of Hawaii and a summer 2018 intern at NASA’s Jet Propulsion Laboratory, Teodoro is making her dream a reality. This summer, she took a short break from her internship searching for asteroids with NASA’s NEOWISE team to tell us about her career journey so far, what inspired her to study STEM and how she hopes to play a role in human space exploration of the future.
What are you working on at JPL?
I work with the NEOWISE team, the Near-Earth Object Wide-field Infrared Survey Explorer. My focus is on near-Earth asteroids. I do a lot of image analysis and processing. Not all of the time do asteroids get detected through our automated system, so my job is to look at archives to find previously undetected asteroids.
What is a near-Earth object and how do you look for them?
Near-Earth objects are objects [such as asteroids and comets] that are very near to Earth's orbit. There are other asteroids that are located roughly between the orbits of Mars and Jupiter, but my focus is on those that are closer to Earth. The way that we detect them is we have this [space telescope called NEOWISE] that surveys the sky in two wavelengths. It senses the heat of asteroids. So I look at images from NEOWISE and, if I see a red dot that is bright, then that's usually an asteroid. But I go through several search techniques to see if the signal-to-noise ratio is good. So there are several processes that work.
What is the ultimate goal of the project?
My ultimate goal is to try to increase the number of known near-Earth objects so that, in the future, we can get more precise measurements for their positions and movements -- just in case they pose a risk to Earth.
What's an average day like for you?
I go through, I'd say, hundreds of images per day. I also took part in a side project where I had to get the measurements of an asteroid that was observed 39 years before it was officially discovered. We looked at this astronomical plate from the 1950s. You can see a very small arrow pointing to an asteroid. Positions for the asteroid hadn’t been discovered yet, so my job was also to find those. It had a lot to do with coding and I had very little experience with coding, so it was nice.
What other skills have you been able to pick up at JPL?
My major is geophysics, so I had little knowledge about astronomy. My whole research team exposed me to an exciting world of astronomy, so that was really nice. They were very encouraging. I've learned so much more about astronomy this summer than I did throughout my whole undergrad career. I mean, there is some connection between geophysics and astronomy, in a way, but this summer, I really learned so much.
Meet JPL Interns
Read stories from interns pushing the boundaries of space exploration and science at the leading center for robotic exploration of the solar system.
You grew up on the remote island of Saipan in the Northern Mariana Islands. How did you get exposed to STEM and what got interested in pursuing it as a career?
When I was young, my dad would always make us go fly kites at night on the beach. There was this one night where I was just looking at the Moon. I was like, "Oh my god, I really want to learn more about astronomy.” I think since then, I've been interested in STEM. But when you're coming from a really small island, you feel very limited. So I didn't have that strong foundation in STEM. And that's the reason why I wanted to move off the island -- because I knew that I couldn't get the opportunities if I stayed. That's the reason I moved to the University of Hawaii. They have a strong geology and geophysics program, and it's a great research university. Since I started there, I've been doing research related to NASA -- like the NASA Hawaii Space Grant Consortium. I feel like if I didn't move to the University of Hawaii, I wouldn't be where I am today, interning at JPL.
So you moved from one island to another?
[Laughs.] Yeah, I couldn't leave the island vibe, I guess. I think it's just a little closer to home. I feel more at home when I'm in Hawaii. Not only that, but also they have a great program, so that was a plus, too. And they have close affiliations with NASA, so that was really great, because my goal was to work for NASA.
Was it a challenge to move away from the island where you grew up?
It was definitely a challenge leaving family and friends behind. I was there on my own. The reason why I chose the University of Hawaii is because of their program. I had a really hard time choosing my major because I was interested in health, but I was interested in geology as well. I'm doing premed as well [as geology and geophysics]. I'm really interested in how humans or organisms can adapt to extreme environments and in learning about geology – for example on Mars – and health, and seeing how we can combine those two fields to contribute to future human space exploration.
What do your family and people back home think of your career path?
It's so funny because I remember, in middle school, I would always tell my friends and family how I wanted to work for NASA, and they would laugh about it because I don't think anyone back home has ever done something big like that. Having them see me working here -- it just kind of opened their eyes, like, “Wow, it's possible,” you know? Most of the time, people back home just stay for financial reasons. It was really expensive moving to Hawaii. But I really wanted to do it. So here I am, and I'm so happy.
Did you know that we have a group of student teachers from the Northern Mariana Islands that has come to NASA’s MUREP Educator Institute at JPL the past couple summers?
Yeah! So three weeks ago, I was walking to my office, and I saw a few friends from back home. I was like, “Oh my god, what are you guys doing here?” We all went to the same high school and everything! They were telling me about that whole program. I was like, “Oh my god, I feel so happy. That's so great.” The chances -- it was mind-blowing. I'm so happy for them. I'm really excited for the future of Saipan and the whole Northern Mariana Islands.
What's the most JPL- or NASA-unique experience you've had so far?
Of all the internships I've had in the past, JPL is really unique because everyone is just so passionate about the work that they do, so it really rubs off on you. Not only that, but also the intern community here is just amazing. And not only the interns, but also my mentors and the other scientists and engineers I've met. I've made so many friends throughout my summer here from all over the nation and all over the world, which is nice because I'm from this small island, and it just makes me realize how big the world is.
I feel like interning at JPL builds a foundation for me. And with my mentors here at JPL and in Hawaii, I do feel more confident in being a minority and a woman in STEM. I feel more driven to be successful and to inspire people from back home to go and pursue what they want to do. Don't let the confinements of your environment stop you from what you want to do.
What’s your ultimate career goal?
My ultimate goal is to try and contribute to future human space exploration. That's what I really want to do. I'm still trying to figure out how I can pave my path by combining health and geosciences. We'll see how it goes.
Explore JPL’s summer and year-round internship programs and apply at: https://www.jpl.nasa.gov/edu/intern
The laboratory’s STEM internship and fellowship programs are managed by the JPL Education Office. Extending the NASA Office of Education’s reach, JPL Education seeks to create the next generation of scientists, engineers, technologists and space explorers by supporting educators and bringing the excitement of NASA missions and science to learners of all ages.
Looking for a stellar 2018 calendar? Try this new Moon Phases Calendar and Calculator DIY from the Education Office at NASA’s Jet Propulsion Laboratory!
Download the free, decoder-ring style calendar and assemble it to see when and where to view the Moon every day of the year. The calendar features daily moon phases, moonrise, moonset and overhead viewing times, a listing of Moon events including supermoons and lunar eclipses, plus graphics depicting the relative positions of Earth and the Moon during various moon phases. Use it to teach students about the phases of the Moon, for sky-gazing or simply as a unique wall calendar.
In the classroom, it makes a great addition to this Teachable Moment and related lessons about supermoons – two of which will ring in the new year in January 2018.
Explore these and more Moon-related lessons and activities from NASA/JPL Edu at the links below:
The term “supermoon” has been popping up a lot in the news and on social media over the past few years. But what are supermoons, why do they occur and how can they be used as an educational tool. Plus, are they really that super?
How it Works
As the Moon orbits Earth, it goes through phases, which are determined by its position relative to Earth and the Sun. When the Moon lines up on the opposite side of Earth from the Sun, we see a full moon. The new moon phase occurs when the Moon and the Sun are lined up on the same side of Earth.
The Moon doesn’t orbit in a perfect circle. Instead, it travels in an ellipse that brings the Moon closer to and farther from Earth in its orbit. The farthest point in this ellipse is called the apogee and is about 405,500 kilometers from Earth on average. Its closest point is the perigee, which is an average distance of about 363,300 kilometers from Earth. During every 27-day orbit around Earth, the Moon reaches both its apogee and perigee.
Full moons can occur at any point along the Moon’s elliptical path, but when a full moon occurs at or near the perigee, it looks slightly larger and brighter than a typical full moon. That’s what the term “supermoon" refers to.
Because supermoon is not an official astronomical term, there is no definition about just how close to perigee the full moon has to be in order to be called “super." Generally, supermoon is used to refer to a full moon 90 percent or closer to perigee. (When the term supermoon was originally coined, it was also used to describe a new moon in the same position, but since the new moon isn’t easily visible from Earth, it’s rarely used in that context anymore.)
A more accurate and scientific term is “perigee syzygy.” Syzygy is the alignment of three celestial bodies, in this case the Sun, Moon and Earth. But that doesn’t quite roll off the tongue as easily as supermoon.
Why It’s Important
Make a Moon Phases Calendar
Use this Moon "decoder wheel" to see where and where to view the Moon all year!
As the largest and brightest object in the night sky, the Moon is a popular focal point for many amateur and professional astronomers pointing their telescopes to the sky, and the source of inspiration for everyone from aspiring space scientists to engineers to artists.
The supermoon is a great opportunity for teachers to connect concepts being taught in the classroom to something students will undoubtedly be hearing about. Students can practice writing skills in a Moon journal, study Moon phases and apply their math skills to observing the supermoon. (Click here for related activities from JPL’s Education Office.)
Incorrect and misleading information about the Moon (and supermoons) can lead to confusion and frustration. It’s important to help students understand what to expect and be able to identify inaccurate info.
What to Expect
As with anything that moves closer to the person viewing it, the supermoon will appear bigger than an average full moon. At its largest, it can appear 14% larger in diameter than the smallest full moon. Keep in mind that a 14% increase in the apparent size of something that can be covered with a fingernail on an outstretched arm won’t seem significantly bigger. Unlike side-by-side comparisons made in science and everyday life, students will not have seen the full moon for at least 30 days, and won’t see another for at least 30 more days. Comparing a supermoon with a typical full moon from memory is very difficult.
Leading up to a supermoon, there are often misleading images on popular media. A technique that involves using a long telephoto lens to take photographs of the Moon next to buildings or other objects makes the Moon look huge compared with its surroundings. This effect can make for great photographs, but it has nothing to do with the supermoon. In fact, these photos can be taken during any Moon phase, but they will likely be used in stories promoting the supermoon.
There are also images that have been edited to inaccurately dramatize the size of the supermoon. Both of these can lead students, and adults, taking pictures with their cell phone to think that they’ve done something wrong or just aren’t cut out for observing the sky, which isn’t true!
Your students may have noticed that when they see a full moon low on the horizon, it appears huge and then seems to shrink as it rises into the night sky. This can happen during any full moon. Known as the Moon Illusion, it has nothing to do with a supermoon. In fact, scientists still aren’t sure what causes the Moon Illusion.
The full moon is bright and the supermoon is even brighter! Sunlight reflecting off the Moon during its full phase is bright enough to cast shadows on the ground. During a supermoon, that brightness can increase up to 30 percent as a result of the Moon being closer to Earth, a phenomenon explained by the inverse square law. (Introduce students to the inverse square law with this space-related math lesson for 6th- through 8th-graders.) As with the size of the Moon, students may not remember just how bright the last full moon was or easily be able to compare it. Powerful city lights can also diminish how bright a supermoon seems. Viewing it away from bright overhead street lights or outside the city can help viewers appreciate the increase in brightness.
What Not to Expect
A supermoon will not cause extreme flooding, earthquakes, fires, volcanic eruptions, severe weather, nor tsunamis, despite what incorrect and non-scientific speculators might suggest. Encourage your students to be good scientists and research this for themselves.
The excitement and buzz surrounding a supermoon is a great opportunity to teach a variety of Moon topics with these lessons from JPL’s Education Office:
- *NEW* Observing the Moon (Grades K-6) – Students identify the Moon’s location in the sky and record their observations over the course of the moon-phase cycle in a journal.
- *NEW* Measuring the Supermoon (Grades 5-12) – Students take measurements of the Moon during its full phase over multiple Moon cycles to compare and contrast results.
- *NEW* Moon Phases Calendar and Calculator – Like a decoder wheel for the Moon, this calendar will show you where and when to see the Moon and every moon phase throughout the year!
- *NEW* Look at the Moon! Journaling Project – Draw what you see in a Moon Journal and see if you can predict the moon phase that comes next.
- Moon Phases (Grades 1-6) – Students learn about the phases of the Moon by acting them out. In 30 minutes, they will act out one complete Moon cycle.
- Whip Up a Moon-Like Crater (Grades 1-6) – Whip up a Moon-like crater with baking ingredients as a demonstration for students.
- Modeling the Earth-Moon System (Grades 6-8) – Using an assortment of playground and toy balls, students will measure diameter, calculate distance and scale, and build a model of the Earth-Moon system.
- Learn more about the Moon on NASA's Moon website.
- See where NASA is heading next on NASA's Moon to Mars website.
- Imagine a future in space with NASA's Moon to Mars posters.
For the record: This story originally stated a supermoon would be visible in January and February 2018. The two supermoons of 2018 are both in January.
Find out how one student's far-fetched dream landed her an internship at JPL. Astronomy intern Alyx Stevens shares what it's like to work at the leading center for robotic exploration of the solar system.
Today, successful women in science all contribute to a "little piece of the puzzle." Farisa Morales makes her contribution as an astronomer at NASA's Jet Propulsion Laboratory studying other planetary systems, observing the sky through the Spitzer Space Telescope and analyzing the dust around distant stars outside our solar system in search of new planets. But she didn't discover this passion until she was in college.
At the start of her college experience, Morales was majoring in mathematics and decided on taking an internship at JPL for engineering. She was later introduced to Spitzer Project Scientist Michael Werner, who asked her to take on huge task far from her comport zone: help take in data from the giant space telescope. This would range from searching for baby star formations to discovering distant galaxies at the edges of the universe. Farisa found her calling and she wanted to be exposed to even more. She switched her major to astrophysics and now has her PhD. "Life just takes you places and you are the main force pushing through," said Morales.
As part of the University of Southern California's Organization of Women in Physics, Morales takes an active role in encouraging women to be a part of the science field. Over the years she's juggled raising two kids, working and studies, but she says, "If I can do it, why can't others?" hoping to see a rise in the number of women in science.
days, she spends her time writing proposals, programming downloaded
images from Spitzer, learning about a specific telescope or publishing a
recent finding. Even teaching astronomy at Cerritos College, Los
Angeles Mission College, Pierce College and California State University,
Northridge adds to her busy schedule. In five to ten years she sees
herself at a full-time job teaching at a university while still
maintaining her research activities at JPL. She's earned a few awards
including an American Astronomical Society Chambliss award. To Morales,
the work itself is satisfying. "My life has not been in vain because I'm
providing the answers to one little tiny piece of the cosmic puzzle,"
she said. "I came into this world, and I worked and solved a little tiny
piece of the puzzle. And when I leave, that is my legacy. The
realization of knowing you're a productive human being and you're
leaving something positive for humanity to continue to build upon is | 0.911063 | 3.919201 |
A six year study by NASA’s Far Ultraviolet Spectroscopic Explorer, or FUSE, satellite has turned up previously hidden quantities of deuterium – a heavier isotope of hydrogen. Astronomers have wondered for years why the levels of deuterium in the Milky Way vary across the galaxy. FUSE has found that deuterium tends to bind to interstellar grains of dust, hiding it from view. Extreme events, like supernovae shockwaves, can vapourize the grains of dust, freeing the deuterium, and making it visible.
A heavy form of hydrogen created just moments after the Big Bang has been found to exist in larger quantities than expected in the Milky Way, a finding that could radically alter theories about star and galaxy formation, says a new international study led by the University of Colorado at Boulder.
CU-Boulder astrophysicist Jeffrey Linsky said new data gathered by NASA’s Far Ultraviolet Spectroscopic Explorer, or FUSE, satellite, shows why deuterium appears to be distributed unevenly in the Milky Way Galaxy. It apparently has been binding to interstellar dust grains, changing from an easily detectable gaseous form to an unobservable solid form, said Linsky, a fellow of JILA, a joint institute of CU-Boulder and the National Institute of Standards and Technology.
The FUSE deuterium study, six years in the making, solves a 35-year-old mystery concerning the distribution of deuterium in the Milky Way while posing new questions about how stars and galaxies are made, according to the research team. A paper on the subject by a team of international researchers led by Linsky is being published in the Aug. 20 issue of The Astrophysical Journal.
“Since the 1970s, we have been unable to explain why deuterium levels vary all over the place,” said Linsky. “The answer we found is as unsettling as it is exciting.”
Since deuterium — a hydrogen isotope containing a proton and a neutron — is believed burned and lost forever during star formation, scientists think the amount of deuterium present in the universe is “pure” and serves as a tracer for star creation and galaxy building over billions of years, said Linsky. While primordial deuterium in the distant, early universe has been measured at concentrations of about 27 parts per million parts hydrogen atoms, measurements by FUSE and NASA’s Copernicus satellite have shown a “patchy” distribution of the element in the Milky Way galaxy, often at far lower levels.
In 2003, Princeton University’s Bruce Draine, a co-author on the new study, developed a model showing that deuterium, when compared to hydrogen, might preferentially bind to interstellar dust grains. The observations by FUSE — which can detect the telltale spectral fingerprints of deuterium in the ultraviolet energy range — strongly support the theory, according to The Astrophysical Journal paper authors.
“Where there are high concentrations of interstellar dust in the galaxy, we see lower concentrations of deuterium gas with FUSE,” said Linsky. “And where there is less interstellar dust, we are measuring higher levels of deuterium gas.”
In relatively undisturbed areas of the universe — like regions around Earth’s sun, for example — deuterium atoms systematically “leave” the gas phase and replace normal hydrogen atoms in dust grains, said Linsky. When a pocket of the universe is disturbed by events like a supernova shock wave or violent activity triggered by nearby hot stars, the dust grains are vaporized, releasing deuterium atoms back into a gas, which has been measured by FUSE, the researchers said.
Scientists assumed from astrophysical theories that at least one-third of the primordial deuterium present in the Milky Way was destroyed over time as it cycled through the stars, said Linsky. But according to the new FUSE findings, the present-day deuterium abundance is less than 15 percent below the primordial values.
“This implies that either significantly less material has been converted to helium and heavier elements in stars or that much more primordial gas has rained down onto the galaxy over its lifetime than had been thought,” said Linsky. “In either case, our models of the chemical evolution of the Milky Way will have to be revised significantly to explain this important new result.”
Launched in 1999, FUSE is a NASA Explorer mission developed in cooperation with the French and Canadian Space Agencies and by Johns Hopkins University, CU-Boulder and the University of California, Berkeley. CU-Boulder’s Center for Astrophysics and Space Astronomy designed and built the mission’s $9 million spectrograph, which collects and funnels UV light from the satellite’s four telescopes.
The paper was co-authored by scientists from Princeton, Johns Hopkins and Northwestern universities, the Space Telescope Science Institute, CU-Boulder, the University of Wisconsin-Madison, the University of Texas-Austin, NASA-Goddard, the Laboratoire d’Astrophysique in Marseille, France, and the Observatoire de Paris-Meudon in Meudon, France. Other CU-Boulder co-authors include JILA’s Brian Wood, CASA’s Michael Shull and CASA doctoral graduate Seth Redfield.
Original Source: UCB News Release | 0.869249 | 4.009775 |
We are closer to being able to build a Dyson Sphere than we think. By enveloping the sun in a massive sphere of artificial habitats and solar panels, a Dyson Sphere would provide us with more energy than we would ever know what to do with while dramatically increasing our living space. Implausible you say? Something for our distant descendants to consider? Think again. We could conceivably get going on the project in about 25 to 50 years, with completion of the first phase requiring only a few decades.
Given that our resources here on Earth are starting to dwindle, and combined with the problem of increasing demand for more energy and living space, this would seem to a good long-term plan for our species.
Now, before I tell you how we could do such a thing, it's worth doing a quick review of what is meant by a "Dyson sphere".
Dyson Spheres, Swarms, and Bubbles
The Dyson sphere, also referred to as a Dyson shell, is the brainchild of the physicist and astronomer Freeman Dyson. In 1959 he put out a two page paper titled, "Search for Artificial Stellar Sources of Infrared Radiation" in which he described a way for an advanced civilization to utilize all of the energy radiated by their sun. This hypothetical megastructure, as envisaged by Dyson, would be the size of a planetary orbit and consist of a shell of solar collectors (or habitats) around the star. With this model, all (or at least a significant amount) of the energy would hit a receiving surface where it can be used. He speculated that such structures would be the logical consequence of the long-term survival and escalating energy needs of a technological civilization.
Needless to say, the amount of energy that could be extracted in this way is mind-boggling. According to Anders Sandberg, an expert on exploratory engineering, a Dyson sphere in our solar system with a radius of one AU would have a surface area of at least 2.72x10^17 km2, which is around 600 million times the surface area of the Earth. The sun has an energy output of around 4x10^26 W, of which most would be available to do useful work.
I should note at this point that a Dyson sphere may not be what you think it is. Science fiction often portrays it as a solid shell enclosing the sun, usually with an inhabitable surface on the inside. Such a structure would be a physical impossibility as the tensile strength would be far too immense and it would be susceptible to severe drift.
Dyson's original proposal simply assumed there would be enough solar collectors around the sun to absorb the starlight, not that they would form a continuous shell. Rather, the shell would consist of independently orbiting structures, around a million kilometres thick and containing more than 1x10^5 objects. Consequently, a "Dyson sphere" could consist of solar captors in any number of possible configurations. In a Dyson swarm model, there would be a myriad of solar panels situated in various orbits. It's generally agreed that this would be the best approach. Another plausible idea is that of the Dyson bubble in which solar sails, as well as solar panels, would be put into place and balanced by gravity and the solar wind pushing against it.
For the purposes of this discussion, I'm going to propose that we build a Dyson swarm (sometimes referred to as a type I Dyson sphere), which will consist of a large number of independent constructs orbiting in a dense formation around the sun. The advantage of this approach is that such a structure could be built incrementally. Moreover, various forms of wireless energy transfer could be used to transmit energy between its components and the Earth.
So, how would we go about the largest construction project ever undertaken by humanity?
As noted, a Dyson swarm can be built gradually. And in fact, this is the approach we should take. The primary challenges of this approach, however, is that we will need advanced materials (which we still do not possess, but will likely develop in the coming decades thanks to nanotechnology), and autonomous robots to mine for materials and build the panels in space.
Now, assuming that we will be able to overcome these challenges in the next half-decade or so-which is not too implausible- how could we start the construction of a Dyson sphere?
Oxford University physicist Stuart Armstrong has devised a rather ingenious and startling simple plan for doing so-one which he claims is almost within humanity's collective skill-set. Armstrong's plan sees five primary stages of construction, which when used in a cyclical manner, would result in increasingly efficient, and even exponentially growing, construction rates such that the entire project could be completed within a few decades.
Broken down into five basic steps, the construction cycle looks like this:
1. Get energy
2. Mine Mercury
3. Get materials into orbit
4. Make solar collectors
5. Extract energy
The idea is to build the entire swarm in iterative steps and not all at once. We would only need to build a small section of the Dyson sphere to provide the energy requirements for the rest of the project. Thus, construction efficiency will increase over time as the project progresses. "We could do it now," says Armstrong. It's just a question of materials and automation.
And yes, you read that right: we're going to have to mine materials from Mercury. Actually, we'll likely have to take the whole planet apart. The Dyson sphere will require a horrendous amount of material-so much so, in fact, that, should we want to completely envelope the sun, we are going to have to disassemble not just Mercury, but Venus, some of the outer planets, and any nearby asteroids as well.
Why Mercury first? According to Armstrong, we need a convenient source of material close to the sun. Moreover, it has a good base of elements for our needs. Mercury has a mass of 3.3x10^23 kg. Slightly more than half of its mass is usable, namely iron and oxygen, which can be used as a reasonable construction material (i.e. hematite). So, the useful mass of Mercury is 1.7x10^23 kg, which, once mined, transported into space, and converted into solar captors, would create a total surface area of 245g/m2. This Phase 1 swarm would be placed in orbit around Mercury and would provide a reasonable amount of reflective surface area for energy extraction.
There are five fundamental, but fairly conservative, assumptions that Armstrong relies upon for this plan. First, he assumes it will take ten years to process and position the extracted material. Second, that 51.9% of Mercury's mass is in fact usable. Third, that there will be 1/10 efficiency for moving material off planet (with the remainder going into breaking chemical bonds and mining). Fourth, that we'll get about 1/3 efficiency out of the solar panels. And lastly, that the first section of the Dyson sphere will consist of a modest 1 km2 surface area.
And here's where it gets interesting: Construction efficiency will at this point start to improve at an exponential rate.
Consequently, Armstrong suggests that we break the project down into what he calls "ten year surges." Basically, we should take the first ten years to build the first array, and then, using the energy from that initial swarm, fuel the rest of the project. Using such a schema, Mercury could be completely dismantled in about four ten-year cycles. In other words, we could create a Dyson swarm that consists of more than half of the mass of Mercury in forty years! And should we wish to continue, if would only take about a year to disassemble Venus.
And assuming we go all the way and envelope the entire sun, we would eventually have access to 3.8x10^26 Watts of energy.
Once Phase 1 construction is complete (i.e. the Mercury phase), we could use this energy for other purposes, like megascale supercomputing, building mass drivers for interstellar exploration, or for continuing to build and maintain the Dyson sphere.
Interestingly, Armstrong would seem to suggest that this might be enough energy to serve us. But other thinkers, like Sandberg, suggest that we should keep going. But in order for us to do so we would have to deconstruct more planets. Sandberg contends that both the inner and outer solar system contains enough usable material for various forms of Dyson spheres with a complete 1 AU radius (which would be around 42 kg/m2 of the sphere). Clearly, should we wish to truly attain Kardashev II status, this would be the way to go.
And why go all the way? Well, it's very possible that our appetite for computational power will become quite insatiable. It's hard to predict what a post-Singularity or post-biological civilization would do with so much computation power. Some ideas include ancestor simulations, or even creating virtual universes within universes. In addition, an advanced civilization may simply want to create as many positive individual experiences as possible (a kind of utilitarian imperative). Regardless, digital existence appears to be in our future, so computation will eventually become our most valuable and sought after resource.
That said, whether we build a small array or one that envelopes the entire sun, it seems clear that the idea of constructing a Dyson sphere should no longer be relegated to science fiction or our dreams of the deep future. Like other speculative projects, like the space elevator or terraforming Mars, we should seriously consider putting this alongside our other near-term plans for space exploration and work.
And given the progressively worsening condition of Earth and our ever-growing demand for living space and resources, we may have no other choice.
This post originally appeared on Sentient Developments.
Top illustration by Oh Jihoon. | 0.810554 | 3.227733 |
The first ever film of the Universe is to be created using the world’s largest digital camera.
British astronomers are involved in the Large Synoptic Survey Telescope (LSST) project to be built in the Chilean Andes.
The telescope will achieve first light in 2020 and its main sky survey will begin in 2022.
It will be able to take images of the sky that each cover over 40 times the area of the moon, building up a survey of the entire visible sky in just three nights.
The film, which scientists say could feature dangerous asteroids and uncover some of the mysteries of dark matter and dark energy, will be recorded on a giant digital camera comprising 3.2 billion pixels.
That means billions of galaxies, stars and solar system objects will be seen for the first time and monitored over 10 years.
British astronomers will now play a key part after funding from the Science and Technology Facilities Council confirmed the UK’s participation.
Professor Isobel Hook, of Lancaster University, said: “This telescope will completely revolutionise astronomical surveys.
“By imaging the entire visible sky every few nights it will be particularly powerful for finding and studying astronomical objects that change or move.
“For me one of the most exciting prospects is the vast quantity of supernovae it will find – many tens of thousands per year.
“We will be able to use these to better understand the mysterious Dark Energy that appears to be pushing the Universe apart.”
Steven Kahn, the LSST Director, said: “It is great to see UK astronomers engaging in preparation for LSST, and we look forward to seeing our collaboration develop over the coming years.
“LSST will be one of the foremost astronomy projects in the next decades and the UK astronomical community will contribute strongly to its success.
“The telescope is being built in the Chilean Andes. Conditions there are some of the driest on Earth, making it the ideal position for observing.”
The LSST is a ‘synoptic’ survey because it will form an overall view of the Universe: billions of objects will be imaged in six colours, spanning a volume of the Universe that is larger than any previously explored.
Manchester University Professor Sarah Bridle, the LSST:UK Project Scientist, said: “”What is unique about LSST is that each of its images covers a large area of sky to a depth that captures faint objects, and that it takes these images really quickly.
“That combination of area, depth and speed means that we can do lots of different science with the same dataset.”
She added: “LSST will build up a very detailed map of billions of galaxies, with approximate distances to each, from which we will learn about the mysterious dark energy that seems to be accelerating the expansion of the Universe.
“But, equally, it will look for changes in the sky from night to night; both moving objects, like asteroids, and new ones, like supernovae, that appear where nothing had been seen before.
“Covering each patch of sky over 800 times during its decade of operations, it will construct our first motion picture of the Universe.”
Show Comments (0) | 0.80345 | 3.446998 |
Ion Propulsion System
Dawn's futuristic, hyper-efficient ion propulsion system allows Dawn to go into orbit around two different solar system bodies, a first for any spacecraft. Meeting the ambitious mission objectives would be impossible without the ion engines.
Ion propulsion was proved on NASA's Deep Space 1 mission, which tested it and11 other technologies while journeying to an asteroid and a comet.
Each of Dawn's three 30-centimeter-diameter (12- inch) ion thrust units is movable in two axes to allow for migration of the spacecraft's center of mass during the mission. This also allows the attitude control system to use the ion thrusters to help control spacecraft attitude.
Two ion propulsion engines are required to provide enough thruster lifetime to complete the mission, and the third engine serves as a spare. Since launch the spacecraft has used each of the three ion engines, operating them one at a time. Dawn will use ion propulsion with interruptions of only a few hours each week to turn to point the spacecraft's antenna to Earth. Total thrust time to reach the first science orbit will be 979 days, with more than 2,000 days of thrust through entire the mission. This surpasses Deep Space 1's 678 days of ion propulsion operation by a long shot.
The thrusters work by using an electrical charge to accelerate ions from xenon fuel to a speed 7-10 times that of chemical engines. The electrical power level and xenon fuel feed can be adjusted to throttle each engine up or down in thrust. The engines are thrifty with fuel, using only about 3.25 milligrams of xenon per second (about 10 ounces over 24 hours) at maximum thrust. The Dawn spacecraft carried 425 kilograms (937 pounds) of xenon propellant at launch. Xenon was chosen because it is chemically inert, easily stored in a compact form, and the atoms are relatively heavy so they provide a relatively large thrust compared to other candidate propellants. At launch, the gaseous xenon stored in the fuel tank was 1.5 times the density of water. At maximum thrust, each engine produces a total of 91 millinewtons—about the amount of force involved in holding a single piece of notebook paper in your hand.
You would not want to use ion propulsion to get on a freeway — at maximum throttle, it would take Dawn's system four days to accelerate from 0 to 60 MPH. As slight as that might seem, over the course of the mission the total change in velocity from ion propulsion will be comparable to the push provided by the Delta II rocket that carried it into space — all nine solid-fuel boosters, plus the Delta's first, second and third stages. This is because the ion propulsion system will operate for thousands of days, instead of the minutes during which the Delta performs.
The electrical power system provides power for all onboard systems, including the ion propulsion system when thrusting. Each of the two solar arrays is 27 feet (8.3 meters) long by 7.4 feet (2.3 meters) wide. On the front side, 18 square meters (21.5 square yards) of each array is covered with 5,740 individual photovoltaic cells. The cells can convert about 28 percent of the solar energy that hits them into electricity. On Earth, the two wings combined could generate over 10,000 watts. The arrays are mounted on opposite sides of the spacecraft, with a gimbaled connection that allows them to be turned at any angle to face the sun.
A nickel-hydrogen battery and associated charging electronics provided power during launch and continues to provide power at any time the solar arrays are directed away from the sun. | 0.851926 | 3.559336 |
COLLEGE PARK, Md. — Don’t adjust your telescope: If you feel like the moon seems smaller, you’re actually right. A new study, following up on earlier research that found the moon has shriveled as it’s cooled over time, shows that it’s still shrinking and experiencing so-called “moonquakes” in the process.
Scientists believe the moon was created some 4.5 billion years ago as the result of collisions from asteroids and meteors, but the collisions made its interior hot. As it eventually cooled off, it also shriveled — similar to how a grape shrivels when it becomes a raisin. The wrinkles we see on raisins are likened to stair-shaped cliffs that consequently formed on the moon’s surface, which experts say are called thrust faults.
Now researchers at the University of Maryland say quakes occurring from those faults have continued as the moon continues to shrink. The researchers, led by Nicholas Schmerr, an assistant professor of geology, analyzed massive quantities of seismic data from instruments placed on the moon’s surface by NASA’s Apollo missions in the 1960s and ’70s. The team created a new algorithm that gave the scientists more accurate epicenter locations for 28 moonquakes recorded between 1969 and 1977.
The research team superimposed the Apollo location data onto imagery taken by NASA’s Lunar Reconnaissance Orbiter (LRO), which revealed many thrust faults. Based on the moonquakes’ proximity to the thrust faults, the researchers found that at least eight of the quakes recorded were caused by tectonic activity, rather than asteroid impacts and quakes from the moon’s interior.
“We found that a number of the quakes recorded in the Apollo data happened very close to the faults seen in the LRO imagery,” Schmerr explains in a statement, adding that the LRO imagery also reveals physical evidence of recent fault movement, such as landslides and tumbled boulders. “It’s quite likely that the faults are still active today. You don’t often get to see active tectonics anywhere but Earth, so it’s very exciting to think these faults may still be producing moonquakes.”
The scientists say the moonquakes would be similar to an earthquake with a magnitude of 2 to 5.
Images taken by the LRO show more than 3,500 cliffs, or fault scarps, since 2009. Fresh tracks from boulder falls also support the theory of moonquakes, as do bright patches along the fault scraps where landslides appear to have occurred.
“For me, these findings emphasize that we need to go back to the moon,” adds Schmerr said. “We learned a lot from the Apollo missions, but they really only scratched the surface. With a larger network of modern seismometers, we could make huge strides in our understanding of the moon’s geology. This provides some very promising low-hanging fruit for science on a future mission to the moon.”
The study was published in the journal Nature Geoscience. | 0.849083 | 3.742916 |
5 astronomy facts that will change your perspective of time & space
Sure, we’ve sent satellites to a number of different planets and had a man walk on the moon. But to be honest, there’s still a whole lot that we Earthlings don’t know about the world beyond our planet.
However, many of the things we do know are pretty mind-boggling. These five astronomy facts might just change your perspective of time and space.
Space isn’t completely silent
You’ve heard it before: space isn’t just quiet, it’s totally silent. And that’s true ... sort of.
No, you won’t be hearing the “pew-pew” laser sound you hear in just about every outer space movie. Since space exists in a vacuum and has no atmosphere, sound can’t get in as humans hear it. However, radio transmissions have been able to pick up some spooky space object sounds that would otherwise be undetectable by the human ear.
That’s not true of planets with air pressure and atmospheres, though. These things do permit for the type of sound you can hear. So while you’re here on Earth, you’re going to keep on hearing the sound of car horns, barking dogs, and sirens.
Boiling ice is a thing
Need some ice for that burn? Located about 33 light-years away, exoplanet Gliese 436 b is composed of a variety of different water elements, including ice that burns.
While the pressure on the planet keeps ice elements solid, surface temperatures reaching upwards of 570 degrees F (or 300 degrees C) heat the top surface of the water to the point where it turns into a vapor. That’s right: hot ice!
Strange days on Venus
If you’ve ever felt like your work day is dragging on, count your lucky stars that you don’t live on Venus.
The axis rotation on Venus is slow like molasses: it takes about 243 Earth days to go through a single cycle. And yet its orbit takes only 225 days, meaning a day is longer than a year on Venus.
In terms of sunrises, you’ll get only two per Earth year on Venus — one every 117 days. But since it takes 243 earth days to complete an axis, both sunrises technically occur on the same day. Oh, and since Venus rotates in a different direction than Earth, the direction of sunrise and sunset are reversed. The sun rises in the west and sets in the east.
There’s a ton of booze in space
Care to party in outer space? Head about 10,000 light-years away to constellation Aquila, where there’s a gaseous cloud called G34.3 that’s made of alcohol.
To get an idea of the size of this cloud, go ahead and multiply our solar system’s diameter by a thousand. As for the amount of alcohol contained in that cloud? It’s said to contain enough alcohol to supply every single person on Earth with 300,000 pints of beer each and every single day for the next billion years.
Saturn’s moon is like a Yin-Yang
Saturn’s moon Iapetus has a very unique look. One of its hemispheres is very dark, and one is very light. Not only is this unlike any other moon in the solar system, but it looks suspiciously like the Yin-Yang.
What’s responsible for this unique contrast? Some scientists say particles from another moon have fallen on what is now the dark side of the moon; others say it’s due to volcanic eruptions. Either way, Iapetus is one of the more striking moons in the solar system.
Curious about the next frontier?
No doubt about it, outer space is a weird and wacky place. From clouds straight out of a psychedelic dream to ice that sizzles and endless days on Venus, these facts are truly out of this world. | 0.896102 | 3.291033 |
The 0.7 m GROWTH-India telescope at the Indian Astronomical Observatory located in Hanle, Ladakh, has made its first science observation which is a follow-up study of a nova explosion. Novae are explosive events involving violent eruptions on the surface of white dwarf stars, leading to a temporary increase in brightness of the star. Unlike a supernova, the star does not go on to die but returns to its earlier state after the explosion. A report on this published in The Astronomer’s Telegram notes the magnitude of the nova explosion first identified by Darnley et al as it varies, from November 8 to November 10.
The GROWTH-India telescope is part of a multi-country collaborative initiative – known as the Global Relay of Observatories Watching Transients Happen (GROWTH) – to observe transient events in the universe.
The fully robotic telescope is designed to capture cosmic events occurring over relatively shorter periods of the cosmological timescale: years, days and even hours.
Universities and research institutes from the US, the UK, Japan, India, Germany, Taiwan, and Israel are part of the initiative.
Their primary research objective is time-domain astronomy, which entails the study of explosive transients and variable sources (of light and other radiation) in the universe.
Its goals are threefold:
- Search for explosions in the optical regime whenever LIGO group detects a Binary Neutron Star merger
- Study nearby young supernova explosions
- Study nearby asteroids.
Novae are explosive events involving violent eruptions on the surface of white dwarf stars, leading to a temporary increase in brightness of the star. Unlike a supernova, the star does not go on to die but returns to its earlier state after the explosion.
The recurrent nova, named M31N-2008, has been observed to erupt several times, the most recent eruption happening in November 2018. | 0.903022 | 3.719614 |
Chandra X-ray Observatory
NASA's Chandra X-ray Observatory was launched and deployed by Space Shuttle Columbia on July 23, 1999, is the most sophisticated X-ray observatory built to date. The observatory was first proposed to NASA in 1976, they began funding in 1977, and after twenty years it was launched into space. Chandra was created to observe X-rays from high-energy regions of the universe, such as the remnants of exploded stars.
The Observatory has three major parts, the first is the X-ray telescope, whose mirrors focus X-rays from celestial objects; second is the science instruments which record the X-rays so that X-ray images can be produced and analyzed; and third is the spacecraft, which provides the environment necessary for the telescope and the instruments to work.
Chandra's unusual orbit was achieved after deployment by a built-in propulsion system which boosted the observatory to a high Earth orbit. This orbit, which has the shape of an ellipse, takes the spacecraft more than a third of the way to the moon before returning to its closest approach to the Earth of 16,000 kilometers (9,942 miles). The time to complete an orbit is 64 hours and 18 minutes. The spacecraft spends 85% of its orbit above the belts of charged particles that surround the Earth. Uninterrupted observations as long as 55 hours are possible and the overall percentage of useful observing time is much greater than for the low Earth orbit of a few hundred kilometers used by most satellites.
Extraordinary commitment and precision is required to plan and build telescopes that will be placed in space where they are operated by remote control in a hostile environment of wild temperature swings and hard vacuum, after withstanding the controlled fury of launch. The entire process typically takes many years and creativity is demanded when unexpected changes are imposed. The Chandra observatory was first proposed to NASA in 1976 and funding began in 1977 when NASA's Marshall Space Flight Center started the definition studies of the telescope. In 1992, there was a major restructuring of the observatory. NASA decided that in order to reduce cost, the number of mirrors would be decreased from twelve to eight and only four of the six scientific instruments would be used. At this point the planned orbit was changed from low to high Earth orbit to preserve the scientific capability of Chandra. Teams of scientists, engineers, technicians and managers who work at numerous government centers, Universities and corporations have been building and assembling Chandra over the past twenty years. Many of these dedicated men and women have been involved in the project from its inception.
Originally, it was called the Advanced X-ray Astrophysics Facility, but in 1998 it was changed to Chandra after Subrahmanyan Chandrasekhar. Chandra immigrated in 1937 from India to the United States, where he joined the faculty of the University of Chicago, a position he remained at until his death. He and his wife became American citizens in 1953.
Trained as a physicist at Presidency College, in Madras, India and at the University of Cambridge, in England, he was one of the first scientists to combine the disciplines of physics and astronomy. Early in his career he demonstrated that there is an upper limit to the mass of a white dwarf star, which is now called the Chandrasekhar limit. A white dwarf is the last stage in the evolution of a star such as the Sun. When the nuclear energy source in the center of a star such as the Sun is exhausted, it collapses to form a white dwarf. This discovery is basic to much of modern astrophysics, since it shows that stars much more massive than the Sun must either explode or form black holes.
Chandra was a popular teacher who guided over fifty students to their Ph.D.’s. His research explored nearly all branches of theoretical astrophysics and he published ten books, each covering a different topic, including one on the relationship between art and science. For 19 years, he served as editor of the Astrophysical Journal and turned it into a world-class publication. In 1983, Chandra was awarded the Nobel prize for his theoretical studies of the physical processes important to the structure and evolution of stars.
Cassiopeia A is a well-known supernova remnant located about 11,000 light years from Earth. Chandra's sharp X-ray vision allows scientists to determine both the amount and location of these crucial elements objects like Cas A produce. Due to its unique evolutionary status, Cassiopeia A (Cas A) is one of the most intensely studied of these supernova remnants. A new image from NASA's Chandra X-ray Observatory shows the location of different elements in the remains of the explosion: silicon (red), sulfur (yellow), calcium (green) and iron (purple). Each of these elements produces X-rays within narrow energy ranges, allowing maps of their location to be created. The blast wave from the explosion is seen as the blue outer ring.
X-ray telescopes such as Chandra are important to study supernova remnants and the elements they produce because these events generate extremely high temperatures — millions of degrees — even thousands of years after the explosion. This means that many supernova remnants, including Cas A, glow most strongly at X-ray wavelengths that are undetectable with other types of telescopes.
Chandra's sharp X-ray vision allows astronomers to gather detailed information about the elements that objects like Cas A produce. For example, they are not only able to identify many of the elements that are present, but how much of each are being expelled into interstellar space.
The Chandra data indicate that the supernova that produced Cas A has churned out prodigious amounts of key cosmic ingredients. Cas A has dispersed about 10,000 Earth masses worth of sulfur alone, and about 20,000 Earth masses of silicon. The iron in Cas A has the mass of about 70,000 times that of the Earth, and astronomers detect a whopping one million Earth masses worth of oxygen being ejected into space from Cas A, equivalent to about three times the mass of the Sun. (Even though oxygen is the most abundant element in Cas A, its X-ray emission is spread across a wide range of energies and cannot be isolated in this image, unlike with the other elements that are shown.)
Astronomers have found other elements in Cas A in addition to the ones shown in this new Chandra image. Carbon, nitrogen, phosphorus and hydrogen have also been detected using various telescopes that observe different parts of the electromagnetic spectrum. Combined with the detection of oxygen, this means all of the elements needed to make DNA, the molecule that carries genetic information, are found in Cas A.
Oxygen is the most abundant element in the human body (about 65% by mass), calcium helps form and maintain healthy bones and teeth, and iron is a vital part of red blood cells that carry oxygen through the body. All of the oxygen in the Solar System comes from exploding massive stars. About half of the calcium and about 40% of the iron also come from these explosions, with the balance of these elements being supplied by explosions of smaller mass, white dwarf stars.
While the exact date is not confirmed, many experts think that the stellar explosion that created Cas A occurred around the year 1680 in Earth's timeframe. Astronomers estimate that the doomed star was about five times the mass of the Sun just before it exploded. The star is estimated to have started its life with a mass about 16 times that of the Sun, and lost roughly two-thirds of this mass in a vigorous wind blowing off the star several hundred thousand years before the explosion.
Earlier in its lifetime, the star began fusing hydrogen and helium in its core into heavier elements through the process known as "nucleosynthesis." The energy made by the fusion of heavier and heavier elements balanced the star against the force of gravity. These reactions continued until they formed iron in the core of the star. At this point, further nucleosynthesis would consume rather than produce energy, so gravity then caused the star to implode and form a dense stellar core known as a neutron star. The exact means by which a massive explosion is produced after the implosion is complicated, and a subject of intense study, but eventually the infalling material outside the neutron star was transformed by further nuclear reactions as it was expelled outward by the supernova explosion. Chandra has repeatedly observed Cas A since the telescope was launched into space in 1999. The different datasets have revealed new information about the neutron star in Cas A, the details of the explosion, and specifics of how the debris is ejected into space.
...(download the rest of the essay above) | 0.916968 | 3.458456 |
A PhD student from The International Centre for Radio Astronomy Research (ICRAR) in Perth has produced one of the most accurate measurements ever made of how fast the Universe is expanding. Florian Beutler, a PhD candidate with ICRAR at the University of Western Australia, has calculated how fast the Universe is growing by measuring the Hubble constant.
“The Hubble constant is a key number in astronomy because it’s used to calculate the size and age of the Universe,” said Mr Beutler.
As the Universe swells, it carries other galaxies away from ours. The Hubble constant links how fast galaxies are moving with how far they are from us.
By analysing light coming from a distant galaxy, the speed and direction of that galaxy can be easily measured. Determining the galaxy’s distance from Earth is much more difficult. Until now, this has been done by observing the brightness of individual objects within the galaxy and using what we know about the object to calculate how far away the galaxy must be.
This approach to measuring a galaxy’s distance from Earth is based on some well-established assumptions but is prone to systematic errors, leading Mr Beutler to tackle the problem using a completely different method.
Published today in the Monthly Notices of the Royal Astronomical Society, Mr Beutler‘s work draws on data from a survey of more than 125,000 galaxies carried out with the UK Schmidt Telescope in eastern Australia. Called the 6dF Galaxy Survey, this is the biggest survey to date of relatively nearby galaxies, covering almost half the sky.
Galaxies are not spread evenly through space, but are clustered. Using a measurement of the clustering of the galaxies surveyed, plus other information derived from observations of the early Universe, Mr Beutler has measured the Hubble constant with an uncertainly of less than 5%.*
“This way of determining the Hubble constant is as direct and precise as other methods, and provides an independent verification of them,” says Professor Matthew Colless, Director of the Australian Astronomical Observatory and one of Mr Beutler‘s co-authors. “The new measurement agrees well with previous ones, and provides a strong check on previous work.”
The measurement can be refined even further by using data from larger galaxy surveys.
“Big surveys, like the one used for this work, generate numerous scientific outcomes for astronomers internationally,” says Professor Lister Staveley-Smith, ICRAR‘s Deputy Director of Science. | 0.838605 | 3.762675 |
In 2015, a stellar-mass black hole in a binary star system underwent an accretion event causing it to erupt brightly across the electromagnetic spectrum. Slurping down the plasma from its stellar partner — an unfortunate sun-like star — the eruption became a valuable observation for astronomers and, in a recent study, researchers have used the event to better understand the magnetic environment surrounding the black hole.
The binary system in question is V404 Cygni, located 7,795 light-years from Earth, and that 2015 outburst was an X-ray nova, an eruption that previously occurred in 1989. Detected by NASA’s Swift space observatory and the Japanese Monitor of All-sky X-ray Image (MAXI) on board the International Space Station, the event quickly dimmed, a sign that the black hole had consumed its stellar meal.
Combining these X-ray data with observations by radio, infrared and optical telescopes, an international team of astronomers were able to measure emissions from the plasma close to the black hole’s event horizon as it cooled.
The black hole was formed after a massive star ran out of fuel and exploded as a supernova. Much of the magnetism of the progenitor star would have been retained post-supernova, so by measuring the emissions from the highly charged plasma, astronomers have a tool to probe deep inside the black hole’s “corona.” Like the sun’s corona — which is a magnetically-dominated region where solar plasma interacts with our star’s magnetic field (producing the solar wind and solar flares, for example) — it’s predicted that there should be a powerful interplay between the accreting plasma and the black hole’s coronal magnetism.
As charged particles interact magnetic fields, they experience acceleration radially (i.e. they spin around the magnetic field lines that guide their direction of propagation) and, should the magnetism be extreme (in a solar or, indeed, black hole’s corona), this plasma can be accelerated to relativistic speeds. In this case, synchrotron radiation may be generated. By measuring the radiation across all wavelengths, astronomers can thereby probe the magnetic environment close to a black hole as this radiation is directly related to how powerful a magnetic field is generating it.
According to the study, published in the journal Science on Dec. 8, V404 Cygni’s hungry black hole has a much weaker magnetic field than theory would suggest. And that’s a bit of a problem.
The researchers write: “Using simultaneous infrared, optical, x-ray, and radio observations of the Galactic black hole system V404 Cygni, showing a rapid synchrotron cooling event in its 2015 outburst, we present a precise 461 ± 12 gauss magnetic field measurement in the corona. This measurement is substantially lower than previous estimates for such systems, providing constraints on physical models of accretion physics in black hole and neutron star binary systems.”
Black holes are poorly understood, but with the advent of gravitational wave (and “multimessenger”) astronomy and the excitement surrounding the Event Horizon Telescope, in the next few years we’re going to get a lot more intimate with these gravitational enigmas. Why this particular black hole’s magnetic environment is weaker than what would be expected, however, suggests that our theories surrounding black hole evolution are incomplete, so there will likely be some surprises in store.
“We need to understand black holes in general,” said collaborator Chris Packham, associate professor of physics and astronomy at The University of Texas at San Antonio (UTSA), in a statement. “If we go back to the very earliest point in our universe, just after the Big Bang, there seems to have always been a strong correlation between black holes and galaxies. It seems that the birth and evolution of black holes and galaxies, our cosmic island, are intimately linked. Our results are surprising and one that we’re still trying to puzzle out.” | 0.902898 | 4.117557 |
A team of scientists behind a telescope located in BC’s Okanagan Valley have found the second repeating fast radio burst (FRB) ever recorded, which they said provides new clues about the puzzling pulses of radio energy from far outside our own galaxy.
The repeating FRB was one of 13 new bursts detected in just two weeks by the Canadian Hydrogen Intensity Mapping Experiment (CHIME), a radio telescope designed and built by scientists at the University of British Columbia, McGill University, the University of Toronto, the Perimeter Institute for Theoretical Physics and the National Research Council of Canada.
The discoveries, described in two papers in Nature, were presented at the American Astronomical Society meeting in Seattle.
“Until now, there was only one known repeating FRB,” said Ingrid Stairs, a member of the CHIME team and an astrophysicist at UBC. “Knowing that there is another suggests that there could be more out there. ”
Stairs said that with CHIME, “mapping the entire northern hemisphere every day, we’re bound to find more repeaters over time.”
Knowing where they are, she furthered, “will enable scientists to point their telescopes at them, creating an opportunity to study these mysterious signals in detail.”
While scientists said that studying fast radio bursts is challenging because they’re rarely spotted and “mostly one-offs,” the repeating burst was one of a total of 13 bursts detected during a pre-commissioning run in the summer of 2018.
The discoveries are particularly noteworthy for the fact that the telescope was running at a fraction of its full capacity when they were made.
“We’re very excited to see what CHIME can do when it’s running at full capacity,” said Deborah Good, a PhD student in physics and astronomy at UBC who is part of CHIME’s FRB team. “At the end of a year we may have found 1,000 more bursts. Our data will break open some of the mysteries of FRBs.”
While most FRBs have been spotted at wavelengths of a few centimetres, the latest FRBs were detected at wavelengths of nearly a metre, which opens up new lines of inquiry, according to the CHIME team.
“The environment of the FRB has a much larger effect on the shape of the signals at long wavelengths,” said Good.
“Seeing these bursts with CHIME will give us a good idea about what FRBs are like and where they come from, by showing us more about how their brightness changes at different frequencies and what’s happening to the signal on its way to Earth,” she added.
Tom Landecker, a CHIME team member from the National Research Council, said the findings provide rich information about the sources and environments that generate fast radio bursts.
“[We now know] the sources can produce low-frequency radio waves and those low-frequency waves can escape their environment, and are not too scattered to be detected by the time they reach the Earth,” he said. “That tells us something about the environments and the sources.”
“The findings are just the beginning of CHIME’s discoveries,” said Stairs.“In the next phase, we plan to capture the full high-resolution data stream from the brightest bursts, which will let us better understand their positions, characteristics and magnetic environments. The next few years will be very exciting.”
Added Landecker: “We haven’t solved the problem, but it’s several more pieces in the puzzle.” | 0.809486 | 3.890528 |
Dual degree courses in which astrophysics plays a prominent role are
becoming more and more popular. And the students making this choice seem
to be at least as talented in physics and mathematics as the students opting
for single subjects. It is much more than a vote against specialisation.
Astrophysics adds spice to the study of physics, mathematics, chemistry
and geology. The subject contains all the records, the hottest, densest,
oldest, most violent and most tenuous phenomena lying in and between the
galaxies. And it also forces the students to apply their Earthbound, laboratory-based
thoughts to the far-flung realms of space and time.
Moons, planets, stars, galaxies and the Universe are not only remote
but they also have a strong fascination for scientific amateurs. So the
students can augment their course texts by turning to a huge selection of
books written for a much wider audience.
Let us begin with three first-class examples of the general textbook.
These are all revised editions of previous publications. In astrophysics
this is a good sign because the vast majority of books in this field never
endure beyond the first edition.
Astronomy: The Evolving Universe by Michael Zeilik is as near perfect
an introductory astronomy textbook as you could hope to find. Zeilik has
devided the subject evenly into four sections. The first uses historical
examples to introduce the movement of celestial objects, our view of the
Galaxy and Universe, the birth of astrophysics and the design of telescopes.
The other sections are devoted to the structure of planets, stars and galaxies
and a review of cosmology.
You can approach Zeilik’s text in two ways. The student looking for
an easy time can bypass the mathematics (which has been placed in boxes
labelled ‘enrichment focus’), the observations (boxes labelled ‘activity
focus’), the study exercises and the problems. The more dedicated students
can revel in these joys and will find their minds being stimulated whether
they like it or not. The book is lavishly illustrated and an enormous amount
of effort has been put into ensuring that the figures and tables are clear
Introductory Astronomy and Astrophysics by Michael Zeilik and Elske
Smith is a revised edition of the 1973 Elske Smith and Kenneth Jacobs
classic. This book is aimed at the serious science student, the level being
for the first-year undergraduate. It makes an excellent textbook for this
group. Maths and physics are well to the fore. The authors seem to enjoy
sorting out such things as the basis of the relationship between stellar
mass and luminosity, the standard big-bang model, the accretion rates in
pre-planetary nebulae and the pressure gradients in atmospheres. It follows
the traditional ‘Earth-out’ approach, going from ‘the familiar to the fantastic’.
In line with the poverty of most students, all the illustrations in
Introductory Astronomy and Astrophysics are in black and white.
The New Cosmos was first published in 1967 but this is the completely
revised fourth edition. I have always found the book to be a superb foundation
for my third year students’ further reading. I tell them that if they know
and understand what is in the book, they are guaranteed an honours degree.
Written by Ulbrecht Unsold and Bodo Baschek, New Cosmos gets down to the
core of the matter and gives you the bare bones of the whole of final year
university astrophysics without any frills. It is indispensable.
Staying briefly with students in their final year, Introduction to Stellar
Astrophysics, Volume 3: Stellar Structure and Evolution by Erika Bohm-Vitense
joins Basic Stellar Observation and Data and Stellar Atmosphere in this
three-volume set. The new book reviews in detail the physical process that
govern the pressure, density, opacity, composition, energy generation and
transportation inside stars and it discusses how these vary as a function
of stellar mass and age. Bohm-Vitense emphasises the observational evidence
for stellar evolution.
Nuclei in the Cosmos contains 10 contributed essays on the rather young
subject of nucleosynthesis. Here, nuclear physicists, particle physicists
and astrophysicists get together to study the way in which thermo-nuclear
processes create elements in the early universe, interstellar matter and
stars. They combine theory and observation skilfully and much is made of
the way in which the cosmic composition varies from galaxy to galaxy and
as a function of time.
The highly acclaimed first edition of Malcolm Longair’s High Energy
Astrophysics has been completely revised and expanded into two volumes.
The first volume, Particles, Photons and Their Detection concentrates on
cosmic rays, the interactions between high-energy particles and electrons,
the radiation they emit, Compton scattering, X-ray, gamma-ray and neutrino
telescopes, the solar wind, solar flares and the dynamics of the particles
in magnetic fields. Longair stresses the observational limitations which
exist in each waveband. He exhorts the astrophysicists who are interested
in the particles that come from the vicinity of active galactic nuclei and
black holes not to overlook the analogies that exist in the interactions
between particle streams and the Earth’s magnetosphere. The excitement of
this contemporary area of astrophysics leaps from every page.
Students of astronomy and astrophysics usually have to spend at least
three hours a week in the laboratory or at the observatory. The easiest
way to engender a love for the subject, and a feeling of awe and wonder
when in the company of the animals of the celestial zoo, is simply to stand
outside on a clear dark night and gaze at your own particular sky. David
H. Levy refers to his book The Sky: A User’s Guide as an ‘owner’s manual’.
It is designed to provide a sense of what observing is all about. It suggests
what to look at and how to record what is seen. It challenges observers
and gently leads them through the first steps to the more complex. The inquisitiveness,
depth, humour and humanity of Levy’s approach to the subject makes this
a gem of a book.
The Trained Eye: An Introduction to Astronomical Observing by Leon
Palmer is a laboratory manual for American students who are embarking on
introductory college astronomy. The suggested projects divide equally between
indoor ones for cloudy nights and outdoor ones that use binoculars and small
telescopes. Much thought has been given to guiding the student carefully
through each step of the exercises. Challenges of Astronomy: Hands-on Experiments
for the Sky and Laboratory by W. Schlosser, T. Schmidt-Kaler and E. F. Milone
contains another extended series of laboratory exercises but here the students
have to do much more thinking for themselves and the wealth of equations
and references makes it a perfect starting point for the more extended projects
that students can expect in their second and third years. This book is full
of bright ideas and continually stresses the interplay between observational
and theoretical astrophysics.
I feel a pang of sadness as I relegate my much used copy of Errors of
Observation and Their Treatment (1955) by J. Topping to my ‘historical’
bookcase but it has at last been overtaken. Louis Lyons’s A Practical Guide
to Data Analysis for Physical Science Students is exactly what the title
implies. Students often regard the estimation of the accuracy of their results
as an obscure and tedious chore. Lyons not only provides them with the necessary
formulae, but also explains in detail what they are supposed to be doing,
and why, and how they can recognise if the errors that they calculate are
reasonable. He even provides detailed worked examples.
David Hughes is the reader in astronomy at the University of Sheffield.
* * *
Astronomy: The Evolving Universe (sixth edition) by Michael Zeilik,
Wiley, pp 568, £27.50
Introductory Astronomy and Astrophysics (second edition) by Michael
Zeilik and Elske V. P. Smith, Saunders, pp 503, £15.95
The New Cosmos (completely revised fourth edition) by Albrecht Unsold
and Bodo Baschek, Springer-Verlag, pp 438, $59
Introduction to Stellar Astrophysics, Volume 3: Stellar Structure and
Evolution by Erika Bohm-Vitense, Cambridge University Press, pp 285, £40
hbk/ £13.95 pbk
Nuclei in the Cosmos edited by Heinz Oberhummer, Springer-Verlag, pp
High Energy Astrophysics (second edition), Volume 1: Particles, Photons
and Their Detection by Malcolm S. Longair, Cambridge University Press, pp
418, £45 hbk/ £15.95 pbk
The Sky: A User’s Guide by David H. Levy, Cambridge University Press,
pp 295, £16.95
The Trained Eye: An Introduction to Astronomical Observing by Leon Palmer,
Saunders, pp 274, £7.00
Challenges of Astronomy: Hands-on Experiments for the Sky and Laboratory
by W. Schlosser, T. Schmidt-Kaler and EF Milone, Springer-Verlag, pp 236,
A Practical Guide to Data Analysis for Physical Science Students by
Louis Lyons, Cambridge, pp 95, £9.95 hbk/ £7.95 pbk | 0.836147 | 3.170207 |
MIT scientists are designing a satellite-based observatory that they say could for the first time provide a sensitive survey of the entire sky to search for planets outside the solar system that appear to cross in front of bright stars. The system could rapidly discover hundreds of planets similar to the Earth.
Google, the Internet search powerhouse that in recent years has expanded to include mapping of the stars as well as the surfaces of the moon and Mars and which has an ongoing collaboration with NASA's Ames Research Center, provided a small seed grant to fund development of the wide-field digital cameras needed for the satellite. Because of the huge amount of data that will be generated by the satellite, Google has an interest in working on the development of ways of sifting through that data to find useful information.
Dubbed the Transiting Exoplanet Survey Satellite (TESS), the satellite could potentially be launched in 2012. "Decades, or even centuries after the TESS survey is completed, the new planetary systems it discovers will continue to be studied because they are both nearby and bright," says George R. Ricker, senior research scientist at the Kavli Institute for Astrophysics and Space Research at MIT and leader of the project. "In fact, when starships transporting colonists first depart the solar system, they may well be headed toward a TESS-discovered planet as their new home."
Most of the more than 200 extrasolar planets discovered so far have been much larger than Earth, similar in size to the solar system's giant planets (ranging from Jupiter to Neptune), or even larger. But to search for planets where there's a possibility of finding signs of living organisms, astronomers are much more interested in those that are similar to our own world.
Most searches so far depend on the gravitational attraction that planets exert on their stars in order to detect them, and therefore are best at finding large planets that orbit close to their stars. TESS, however, would search for stars whose orbits as seen from Earth carry them directly in front of the star, obscuring a tiny amount of starlight. Some ground-based searches have used this method and found about 20 planets so far, but a space-based search could detect much smaller, Earth-sized planets, as well as those with larger orbits.
This transit-detection method, by measuring the exact amount of light obscured by the planet, can pinpoint the planet's size. When combined with spectroscopic follow-up observations, it can determine the planet's temperature, probe the chemistry of its atmosphere, and perhaps even find signs of life, such as the presence of oxygen in the air.
The satellite will be equipped with six high-resolution, wide-field digital cameras, which are now under development. Two years after launch, the cameras--which have a total resolution of 192 megapixels--will cover the whole sky, getting precise brightness measurements of about two million stars in total.
Statistically, since the orientation of orbits is random, about one star out of a thousand will have its planets' orbits oriented perpendicular to Earth so that the planets will regularly cross in front of it, which is called a planetary transit. So, out of the two million stars observed, the new observatory should be able to find more than a thousand planetary systems within two years.
In fact, if a new estimate based on recent observations of dusty disks is confirmed, there might even be up to 10 times as many such planets.
Because the satellite will be repeatedly taking detailed pictures of the entire sky, the amount of data collected will be enormous. As a result, only selected portions will actually be transmitted back to Earth. But the remaining data will be stored on the satellite for about three months, so if astronomers want to check images in response to an unexpected event, such as a gamma-ray burst or supernova explosion, "they can send us the coordinates [of that event] and we could send them the information," Ricker says.
The team is still trying to secure the full funding to build, launch and operate the satellite, once the design work is completed this year. The Harvard-Smithsonian Center for Astrophysics and the Origins of Life Initiative, NASA Goddard and NASA Ames as well as the privately funded Las Cumbres Observatory Global Telescope Network are already scientific participants with MIT on the TESS program.
The NASA Ames Research Center is a full partner in the TESS program. Their Small Spacecraft Division, formed in 2006, specializes in low-cost, rapid development of spacecraft and missions. Â Further, NASA Ames is partnering with universities and industry to support privately financed space missions and related activities.
Regardless of the funding for the satellite, the same wide-field cameras being developed for TESS could also be used for a planned ground-based search for dark matter in the universe--the invisible, unknown material that astronomers believe is more prevalent in space than the ordinary matter that we can see. Some of the unknown dark-matter particles must constantly be striking the Earth, and the plan is to train a bank of cameras inside tanks of fluid deep underground, to detect flashes of light produced by the impacts of these dark particles. Ricker's Kavli group is participating with MIT physics professor Peter Fisher's team in this new physics research initiative.
The electronic detectors for the new cameras are being developed in collaboration with MIT's Lincoln Laboratory. The lab's expertise in building large, highly sensitive detectors is a significant factor in making possible these unique cameras, which have no moving parts at all. If all goes well and funding is secured, the satellite could be launched in 2012 with NASA support, or even earlier with a private sponsor.
Ricker's MIT colleagues on the TESS project include Kavli Institute research scientist Roland Vanderspek, professors Sara Seager, Josh Winn, Adam Burgasser, Jim Elliot, Jacqueline Hewitt and several others. | 0.852186 | 3.953921 |
An Australian-led team of galactic archaeologists is on a quest to find stars born at the same time and place as the Sun, and have mapped the chemical make-up of almost 350,000 stars, with the ultimate goal of shining a light on the Milky Way's history.
Stars formed together in clusters share the same chemical composition — which scientists liken to DNA — but a family reunion remains unlikely as the stars usually drift light years apart after their formation.
The team has been surveying the skies with a spectrograph, analysing what elements stars are made from.
The project, dubbed the GALAH survey when it was created in 2013, released its first major data set today.
"This is a tremendously large number of stars that we're able to collect information for," GALAH project scientist and UNSW senior lecturer Sarah Martell said.
"That really helps us in understanding both the history of what's going on there … but also because when you're looking for unusual things, the only way to find them is to look at a lot of things.
"The question is where are the stars that formed around the Sun? It should have formed with a bunch of other stars, it should have siblings — and where are they?"
The survey makes use of the HERMES spectrograph at the Australian National University's Siding Spring observatory, which allowed researchers to analyse starlight across the spectrum to determine the chemical composition of stars.
Martin Asplund of the ANU, who leads the analysis of the survey, said chemical tagging of stars was key to finding the Sun's long-lost siblings.
"[HERMES] spreads out the starlight into different wavelengths, different frequencies. and from that we can then identify each star's chemical fingerprint," he said.
Analysis of the data is still ongoing, so no sibling stars for our Sun have been found yet — but the data set of 342,000 stars will assist scientists looking to deduce the history of the Milky Way.
"By looking at a lot of stars, we're able to get a really clear picture of the historical development of the galaxy: When did stars form, how did they make new elements, how does that form into new generations of stars?" Dr Martell said.
Galactic archaeologists look back in time for answers
Galactic archaeology studies the Milky Way for clues about its history, but Professor Asplund said it presented some unique challenges.
"The problem we have is that stars move around, so not like archaeologists, they look for relics in the ground," he said.
"The problem that we have, we look for stars that were born at a certain time, but they are moved around in the galaxy in the billions of years since they were formed."
Analysis of such a large and complex data set has also thrown up challenges for researchers, who have had to adapt with novel methods to deal with the data, writing new computer programs to keep up with the vast amounts of information.
"One of the real challenges of moving into big data for astronomy is figuring out how to deal with it all," Dr Martell said.
"When you have 342,682 stars, you need a computer program that doesn't think too hard."
The GALAH survey will continue to analyse the data collected so far, but ultimately researchers want to collect data on 1 million stars.
The team hopes to resume its data collection in August, and Professor Asplund said he hoped the Sun's siblings would be found within a few years. | 0.839224 | 3.856814 |
Artist’s impression of ESA’s Hildalgo spacecraft. Image credit: ESA.Click to enlarge
Telescope facilities across the world are watching the skies for rocky remnants from outer space on a collision course with planet Earth. Currently one or two of these so called ‘Near Earth Objects’ [NEOs] are being recorded each day but fortunately for humankind the vast majority are the size of a human fist and pose no threat. Nevertheless, the presence of large impact craters on Earth provides dramatic evidence of past collisions, some of which have been catastrophic for the planet’s species, as was the case with the dinosaurs. This week, experts from across Europe and the US met in London to consider current and future efforts to monitor NEOs in order to better predict those with Earth impacting trajectories, since it is inevitable that a catastrophic collision will happen again in the future.
Professor Monica Grady, a leading expert on meteorites from the Open University explains, “It’s simply a question of when, not if, a NEO collides with the Earth. Many of the smaller objects break up when they reach Earth’s atmosphere and have no impact. However, a NEO larger than 1 km will collide with Earth every few hundred thousand years and an NEO larger than 6 km, which could cause a mass extinction, will collide with Earth every hundred million years. And we are overdue for a big one!”
NEO’s, remnants from the formation of the inner planets, range in size from 10 metre objects to those in excess of 1 km. It is estimated that 100 fist sized meteorites, fragments of NEO’s, fall to Earth on a daily basis but larger objects impact with Earth on a much less regular basis.
Professor Alan Fitzsimmons from Queens University Belfast is a UK astronomer (supported by the Particle Physics and Astronomy Research Council) involved in the study of NEO’s, using telescope facilities such as the European Southern Observatory’s Very Large telescope in Chile, the Isaac Newton Telescope in La Palma and the Faulkes Telescope in Hawaii. He said, “By the end of the decade as new dedicated facilities, such as the Pan-STARR project in Hawaii, come on line there will be a quantum leap in the discovery of NEO’s – with rates anticipated to increase to hundreds per day. This will provide us with a greater ability to determine which ones are on a potential Earth colliding trajectory.”
Studies of one such asteroid (Apophis), which was discovered in June2004, have shown that there is a low probability that this object will impact the Earth in 2036. This has raised a whole series of issues about the prospect of deflecting the asteroid before a very close approach in 2029. Government’s across the world are looking at the issue and in particular at the technologies and methods required to carry out an asteroid deflection manoeuvre in space.
The European Space Agency’s NEO Mission Advisory Panel (NEOMAP), of which Professor Fitzsimmons is a member, has selected “Don Quixote” as their preferred option for an asteroid deflecting test mission. Don Quixote would comprise two spacecraft – one of them (Hildalgo) would impact the asteroid at a very high relative speed while the second spacecraft (Sancho) would arrive earlier to monitor the effect of the impact to measure the variation of the asteroid’s orbital parameters. This attempt to deflect an incoming NEO would act as a precursor mission with the primary objective of modifying the trajectory of a “non-threatening” asteroid.
Richard Tremayne-Smith, from the British National Space Centre, heads up the coordination of UK NEO activity and helps provide an international lead on NEO efforts on the issue. He said, “NEO collisions are the only known natural disaster that can be avoided by applying appropriate technology – and so it is the interest of Governments across the World to take interest in this global issue. Here in the UK we take the matter very seriously and progress is being made in taking forward the recommendations of the UK NEO Task Force Report in an international arena.”
The current method of studying NEOs is achieved through a combination of 3 different methods:- the study of meteorites to understand their structure and composition; earth based astronomical observations of asteroids; and space based observations and encounters with asteroids.
Much can be understood about the nature of asteroids from the study of meteorites which are fragments of asteroids that have broken up and fallen to Earth. Professor Grady explains how the ground based study of meteorites is crucial to future plans for dealing with asteroids.
“In order to define successful strategies for deflecting asteroids that might collide with Earth, it is essential to understand the material properties such as the composition, strength and porosity of asteroids. By putting together such information with data from both ground based and space based studies we can begin to build an accurate picture of these diverse phenomena.”
UK scientists are involved in a number of other missions which will also be investigating the properties of asteroids and comets. This includes NASA’s Stardust mission which collected samples from Comet Wild 2 in January 2004. These samples are set to return to Earth in January 2006 and scientists from the Open University will be involved in their analysis. The European Space Agency’s Rosetta mission which is currently on route to Comet Churyumov-Gerasimenko will pass by two asteroids, Steins and Lutetia, before reaching its target in 2014, gathering data about their properties as it flies past.
Original Source: PPARC News Release | 0.86287 | 3.717162 |
The effect of the new telescope.
No, it is not the gold that can be seen on the first materials that come from the said telescope. The photo and video below show the surface of the Sun, and this in as detailed as no other photographs so far.
each "cell"that can be seen on the materials is the Sun. area larger than Poland. It measures about 1,100 kilometers in diameter. The whole frame covers a region whose diameter is 1.5 times the diameter of the Earth.
The sun in 4K
Although the film from the telescope (which can be viewed in 4K) lasts only 14 seconds, in fact it presents on record of 10-minute activity on the surface of the Sun. During these 10 minutes, the hottest plasma (the bright part of each "cell") rises, then sinks and cools (creating dark "cell rings"). Interestingly, among these dark "borders" you can notice very strong shines, which are markers of the magnetic field penetrating the Sun's surface.
Although the Sun is the star closest to Earth, we still don't know everything about it. We still don't completely understand his behavior, such as those that lead to solar storms. Projects like the Solar Telescope Daniela K. Inouye do Solar Orbiter probe are implemented to change this.
These photos are just the beginning
Solar Telescope Daniela K. Inouye is a telescope that can observe the Sun as closely as any other observatory built so far. It was equipped with a mirror with a diameter of 4 meters (which makes it the largest solar telescope in the world) and an advanced cooling system that prevents overheating when concentrating a huge amount of sunlight. His apparatus allows him to see on the surface of the sun extremely small structures – up to 20 km in diameter.
Since the Solar Telescope Daniela K. Inouye has just started his work, in the future we will see even more such or even more detailed materials. I can't wait for them.
"These first photos are just the beginning.", said David Boboltz from the US National Science Foundation (NSF), which oversees the construction of the facility and its operations. "Over the next six months, a team of scientists, engineers and technicians will continue to test the telescope to prepare it for use by the international solar research community." | 0.804362 | 3.435119 |
Comets and meteors have fascinated the human race since they were first spotted in the night sky. But without science and space exploration to aid understanding of what these chunks of rock and ice are, ancient cultures often turned to myth and legend to explain them.
The Greeks and Romans believed that the appearance of comets, meteors and meteor showers were portentous. They were signs that something good or bad had happened or was about to happen. The arrival of a comet could herald the birth of a great figure, and some people have even argued that the star in the sky which the Persian Magi followed to Bethlehem to see the newborn Jesus was actually a comet.
In the spring of 44BC, a comet that appeared was interpreted as a sign of the deification of Julius Caesar, following his murder. Caesar’s adopted son Octavian (soon to be the Emperor Augustus) made much of the comet, which burned in the sky during the funerary games held for Caesar. This portentous event was frequently celebrated in the ancient sources. In his epic poem, the Aeneid, Virgil describes how “a star appeared in the daytime, and Augustus persuaded people to believe it was Caesar”.
Augustus celebrated the comet and the deification of his father on coins (it did help to be the son of a god when trying to rule the Roman Empire), and many examples survive today.
The Roman historian Cassius Dio referred to “comet stars” occurring in August 30BC. These are mentioned as among the portents witnessed after the death of the Egyptian queen Cleopatra. Experts are not entirely sure what it means when Dio uses the plural term “comet stars”, but some have connected this recorded event to the annual Perseid meteor shower.
Though it retains an ancient Greek name, we now know that the arrival of the Perseid meteor shower every August is actually the Earth’s orbit passing through debris from the Swift-Tuttle comet.
The meteor shower is named for the Perseidai (Περσείδαι), who were the sons of the ancient Greek hero Perseus. Perseus was a legendary figure with a fine family pedigree – he was the mythical son of Zeus and Argive princess Danaë (she of the golden rain). Perseus earned himself a constellation after a number of epic adventures across the Mediterranean and Near East that included the frequently illustrated murder of the Gorgon sister, Medusa.
Another of Perseus’s celebrated acts was the rescue of the princess Andromeda. Abandoned by her parents to placate a sea monster, the princess was found by Perseus on a rock by the ocean. He married her and they went on to have seven sons and two daughters. Sky watchers believed that the constellation Perseus, located just beside Andromeda in the night sky, was the origin of the shooting stars they could see every summer, and so the name Perseid stuck.
Tears and other traditions
In Christian tradition the Perseid meteor shower has long been connected to the martyrdom of St Lawrence. Laurentius was a deacon in the early church at Rome, martyred in the year 258AD, during the persecutions of the Emperor Valerian. The martyrdom supposedly took place on August 10, when the meteor shower was at its height, and so the shooting stars are equated to the saint’s tears.
Detailed records of astronomical events and sky watching can be found in historical texts from the Far East too. Ancient and medieval records from China, Korea and Japan have all been found to contain detailed accounts of meteor showers. Sometimes these different sources can be correlated, which has allowed astronomers to track, for example, the impact of Halley’s comet on ancient societies both east and west. These sources have also been used to find the first recorded observation of the Perseid meteor shower as a specific event, in Han Chinese records of 36AD.
Though the myths and legends may make one think that ancient civilisations had little scientific understanding of what meteors, comets and asteroids could be, this couldn’t be farther from the truth. The early astronomers of the Near East, those who created the Babylonian and Egyptian calendars, and astronomical data were – by far – the most advanced in antiquity. And a recent study of ancient cuneiform texts has proven that the Babylonian ability to track comets, planetary movements and sky events as far back as the first millennium BC involved a much more complex geometry than had been previously believed. | 0.823551 | 3.33606 |
Fast rotating white dwarf drags its space-time in a cosmic dance
How astronomers used Einstein’s theory of general relativity to estimate the rotation of a white dwarf in a binary star system
January 30, 2020
The results are published in this week’s issue of „Science“.
The white dwarf-pulsar binary system PSR J1141-6545 discovered by the CSIRO’s Parkes radio telescope. The pulsar orbits its white dwarf companion every 4.8 hours. The white dwarf’s rapid rotation drags space-time around it, causing the entire orbit to change its orientation.[less]
The white dwarf-pulsar binary system PSR J1141-6545 discovered by the CSIRO’s Parkes radio telescope. The pulsar orbits its white dwarf companion every 4.8 hours. The white dwarf’s rapid rotation drags space-time around it, causing the entire orbit to change its orientation.
In 1999, a unique binary system was discovered with the Australian Parkes Radio Telescope in the constellation Musca (the Fly), close to the famous Southern Cross constellation. In this system, the radio pulsar PSR J1141-6545 and a relatively massive white dwarf star orbit each other, with a ‘year’ lasting less than 5 hours. A radio pulsar is a fast-rotating neutron star, which emits radio waves along its magnetic poles. “This pulsar’s orbit is very special. It hurtles through space with a maximum speed of almost a million km/h in its orbit as the maximum separation between the stars is barely larger than the size of our Sun.’’, says Dr. Vivek Venkataraman Krishnan, the first author of the paper and a scientist at the Max Planck Institute for Radio Astronomy, who performed the data analysis and parts of the observations of PSR J1141-6545 when he was a PhD student at Swinburne University of Technology in Australia.
Unlike other binary systems that consist of a pulsar and a white dwarf, theoretical models indicate that the white dwarf companion to PSR J1141-6545 formed before the pulsar. An important prediction of these models is that, before the supernova explosion that formed the pulsar, there was significant mass transfer from the progenitor of the pulsar to the white dwarf. This resulted in an enormous acceleration of the white dwarf's rotation. “Measuring this rotation is an important test of our models of the evolution of binary systems’’, says Prof. Thomas Tauris, a co-author of the study and expert in neutron stars and white dwarfs at the University of Aarhus in Denmark.
The standard means for measuring the rotation of a star is by studying its spectral lines. However, the white dwarf companion to PSR J1141-6545 is too faint for that. So how can one measure its rotation? The answer came from an unexpected direction and leads back over 100 years in the development of theoretical physics.
Even before the completion of general relativity in November 1915, Albert Einstein had already realized that in a theory where gravitation is the result of curved space-time, the rotation of a mass will in general - unlike in Newton's theory of gravity - contribute directly to the gravitational field. To put it simply, the rotation of a mass swirls the space-time in its vicinity, an effect commonly known as “frame-dragging”. Later in 1918, Josef Lense and Hans Thirring - with substantial support from Albert Einstein - calculated this effect for our Solar System using general relativity. In particular, they calculated how the dragging of space-time caused by the rotation of the Sun influences the movement of planets. They concluded that these effects were impossibly small to measure at that time.
Meanwhile, technology progressed and the frame-dragging effect caused by the Earth's rotation was eventually detected by satellite experiments such as Gravity Probe B, and the combination of the laser-ranging satellites LAGEOS 1 & 2 and LARES. While Gravity Probe B used a set of four precision gyroscopes to measure this effect, the latter experiments measured a slow precession of the orbital plane of the satellites in the direction of Earth's rotation, the so-called “Lense-Thirring precession”. This precession of the satellites has, in the meantime, been confirmed to an accuracy of about 2%, in agreement with the prediction by general relativity. The effect is extremely small: LAGEOS-1, for example, is in a circular orbit with a radius of approximately 12,300 km. Its orbital plane precesses only by 0.0000086 degrees per year, which corresponds to a full rotation in about 40 million years.
The situation in the vicinity of the white dwarf companion to PSR J1141-6545, according to the stellar evolution models, should be quite different: although it is a bit smaller than the Earth, its mass is 340,000 times larger, similar to the mass of the Sun. It is expected to rotate around its own axis within a few minutes. “If LAGEOS-1 was hypothetically orbiting this white dwarf, its orbit would precess by several degrees a day, as the dragging of space-time is about 100 million times stronger’’, says Dr. Norbert Wex, co-author and specialist in general relativity at the MPIfR.
It is impossible to send satellites to this white dwarf as it is several thousand light-years away (a few hundred quadrillion kilometres), but fortunately, there is a pulsar in orbit. The radio signals from this pulsar provide a precise measurement of its motion, similar to the laser ranging measurements of the LARES and LAGEOS-1 & 2 satellites. “With the help of atomic clocks, we were able to perform highly accurate measurements of the arrival times of the pulsar signals at the Parkes and UTMOST radio telescopes. We could track the pulsar in its orbit with an average ranging precision of 30 km per measurement, over a period of almost twenty years. This led to a precise determination of the size and orientation of the orbit”, explains Dr. Vivek Venkatraman Krishnan.
At the distance of the pulsar from the white dwarf, the dragging of space-time is about a million times weaker than at the distance of a LAGEOS-1-like orbit. However, the Lense-Thirring precession should still cause, over these 20 years, precession of the pulsar's path of about 150 km. “Observations of pulsar J1141-6545 indeed show such a deviation which, after detailed calculations and ruling out a range of potential experimental errors, were confirmed to be caused by a change in its orbital orientation”, explained Dr. Willem van Straten, co-author and scientist at Auckland University of Technology in New Zealand.
A careful analysis of this measurement which took into account the Lense-Thirring effect allowed the estimation of the rotational period of the white dwarf: it was found to be about 100 seconds. This is a beautiful confirmation of the idea that, before the supernova explosion that formed the pulsar 1.5 million years ago, there was a significant mass transfer from the progenitor of the pulsar to the white dwarf. “Here Albert Einstein gave us a tool, which we can now use to find out more about pulsars and their companions in the future’’, said Prof. Matthew Bailes, co-author and scientist at Swinburne University, Australia.
New and upcoming radio telescopes such as MeerKAT and the Square Kilometre Array (SKA) will play a central role in understanding how Einstein’s theory is at play in such natural laboratories. “With the SKA expected to detect more exotic binary systems like this one, we’ll be able to investigate many more effects predicted by general relativity” concluded Dr. Evan Keane, co-author and scientist at the SKA Organisation in the UK.
Video sequence, showing the pulsar- white dwarf binary system PSR J1141-6545.
Copyright: Mark Myers, ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav).
The research team consists of V. Venkatraman Krishnan, M. Bailes, W. van Straten, N. Wex, P. C. C. Freire, E. F. Keane, T. M. Tauris, P. A. Rosado, N.D.R. Bhat, C. Flynn, A. Jameson and S. Osłowski. Authors with MPIfR affiliation include Vivek Venkataraman Krishnan, the first author, and also Norbert Wex, Paulo Freire and Thomas Tauris. | 0.85018 | 3.843111 |
“If the Universe Is Teeming with Aliens… Where Is Everybody?” -Stephen Webb
It's one of the biggest conundrums in the Universe, known as the Fermi Paradox: if the Universe is so conducive to life, and if there are so many opportunities for it within our galaxy alone, why isn't there any evidence (outside of the History Channel) of extraterrestrial life?
Moreover, why haven't we been visited by some extraterrestrial intelligence? After all, given the fact that our Universe is nearly 14 billion years old, while our galaxy itself is only a hundred-thousand light years from end-to-end, shouldn't all of the potentially habitable planets have been visited, and colonized, by now?
A couple of years ago, I went through the estimates -- both conservatively and liberally -- of how rare or common intelligent life in the Universe is. But what I wanted to focus on, today, are the difficulties in even intelligently speaking about this question. First off, let's start with the good news.
The good news is, we're here. That means we have at least one example in the Universe where things worked out in favor of intelligent life. As far as we can tell, this means the following things have happened:
- A star was born with a planet that orbits it at the right distance for it to be potentially habitable.
- That planet had the right mix of elements on it -- particularly carbon, nitrogen, oxygen, hydrogen and phosphorus -- in order to create life-as-we-know-it.
- Life actually begun, at some point. This means, at the very least, a self-replicating complex molecule encoded with information that isn't necessarily fixed from one iteration to the next, found a way to replicate itself. (The "information-encoded" clause distinguishes DNA/RNA-based life from, say, a non-living crystal.)
- Life succeeded for a long enough time that it evolved not only beyond this simple, primitive state, but into complex, multi-cellular, highly differentiated organisms.
- At least one of these organisms developed what we consider "intelligence" to be, and used it to learn about -- and in some ways, master and manipulate -- their environment.
- Eventually, before going extinct, these organisms -- and it's the great hope our our civilization -- managed to leave their own world, and set out to explore, and possibly colonize and/or inhabit some of the other ones in our galaxy.
Now, there's no doubt that all but the last step, above, has already happened here on Earth. And there are huge contingents of our society striving to achieve that last one, which -- despite everything -- I'm still extremely optimistic about our chances of successfully accomplishing.
But the big question is this: how common should this occurrence actually be? Should there really be tens-of-thousands of civilizations just like (or even more advanced than) us out there right now, in our galaxy alone? Or are we the only ones like us, in the entire history of the observable Universe, who've ever existed?
Of course, we don't know. But the fact of the matter is this: we have no right to expect that just because it happened once, here, that any of these steps are at all common!
Thankfully, we do have some evidence to tell us that some of the things that happened are, in fact, common.
The stars, for example. We know there are somewhere between about 200 billion and 400 billion stars in our galaxy. The vast majority of them -- about 95% -- live as long or longer than our Sun, meaning that they do have, at least potentially, plenty of time for evolution to take place.
We've also measured the metallicity of these stars, or how abundant heavy elements (i.e., not Hydrogen or Helium) are, and we find that our Sun is pretty run-of-the-mill. In other words, the heavy elements that we need for life on Earth are common and abundant all throughout our galaxy. In fact, the largest star thus far discovered in our galaxy, VY Canis Majoris (below), was found to have all the atoms and molecules -- including phosphorous -- in the outermost layers of its atmosphere!
And we've also learned, through our exoplanet hunts, that perhaps as many as 20% of the stars in our galaxy have planets within their habitable zones.
In other words, we're quite confident that, within our galaxy alone, there are literally billions of stars with rocky planets orbiting at the right distance for life to exist, and they're loaded up with the right kinds and amounts of elements to possibly give rise to life.
Which is amazing! But, it's not everything. For example, we don't know how hard it is for life to actually begin. We'd like to think that it's easy -- after all, the laws of physics and chemistry are the same everywhere in the Universe -- so that life would exist in many different places. But it's possible that to take that leap -- from non-life to life -- is actually an extraordinarily rare process.
The fact that life appeared at least 3.8 billion years ago on Earth is the only evidence we have, at this point, of life existing anywhere in the Universe. While we don't think the conditions on Earth were all that rare or special, it is possible that the emergence of life here was rare and special. We'll continue to search for life on Earth that doesn't share a universal common ancestor with other known forms of life (because evidence that it happened here twice independently would be amazing), and for life -- both past and present -- on other worlds, as well as continuing to make life-from-non-life in the lab. But until we succeed somewhere, we won't have any real quantitative idea of how rare or common life in the Universe actually is.
The development part is another great unknown. For nearly 3 billion years, life on Earth was no more complex than single-celled, asexually reproducing organisms. Yes, this includes some extraordinary one-celled creatures, like corals and sponges, but still single-celled organisms, nonetheless. But at some point, evolution permitted complex, highly differentiated, multicellular animals to arise.
Is that a commonplace occurrence in the Universe? Or is that an extraordinary rarity? Again, we have no quantitative information except this one instance here on Earth. Until we do, we're really just playing a guess-timation game.
Finally, here we are! The most intelligent species -- as far as we know -- ever to exist! Even given the existence of life and the evolution of highly complex, highly differentiated creatures, how likely or rare is the evolution of a human-level of intelligence? Our brain-to-body-size ratio dwarfs that of our nearest competitor, the dolphin, by nearly a factor of two, and the next-nearest great ape by a factor of about three. A chimpanzee society might not have the intelligence to understand or explore the Universe, but we certainly are capable!
How rare is this level of intelligence? As far as we know, we're the only species to attain it in the history of Earth, and we have no idea how common this is in the Universe. It could be extremely common, or we could be the only ones.
And finally, what about spacefaring civilizations? What about the colonization of other worlds? The fact that we haven't either contacted or been contacted by another species very likely tells us that all of these things haven't happened abundantly in our galaxy, but how rare or common is it?
The evidence, at this point, points to, at best, not that common. (And, at worst, we might be the first-and-only, and even that's only if we can get our act together!)
But the fact of the matter is, I've never thought of the Fermi paradox as very much of a paradox. It's not at all hard to imagine that the answer to, "Where is everybody?" is that there isn't anybody else.
But there could be, and so we have to look. Either way, what is here is remarkable, and I want to know everything I can about it.
I really enjoy reading your posts. You are a very good teacher and I frequently find your writings nicely thought-provoking. Thanks for the work.
Two steps of life as we are seem highly unprobable to me, judging purely from the inordinate amount of time it took to get there - the first is the arising of multicellular life, the second being the evolution of a species that has developed sufficient intelligence to kickstart a process where cultural evolution outpaces biological evolution.
less likely but so long was allowed it was bound to happen.
One idea that I never see discussed is that there may certain particular conditions which highly support the chance of abiogenesis elsewhere, but are not present here. We may be extremely lucky that it eventually happened on this planet. Imagine other advanced civilizations looking at Earth and deciding it's not very likely life would ever start here..
My guess (and its just a guess), is that the two bottleneck points are:
- Evolution of high intelligence
- Interstellar travel
IMO, the last one is the biggie.
I really can't see why a species would set out to "colonize the galaxy". They might want to leave their planetary system if the star is in danger of dying, but that happens only very rarely.
Seems to me one of the lessons of science is we are not special. Other than that to many unquantified variables. But you have narrowed it down to between 1 and a few million possible intelligent life forms.
Interesting issue, there are three main possibilities that are had to distinguish from at the moment, but firstly I want to point out that usually the "paradox" is phrased wrongly that gets people on the wrong foot before they even start. The correct question is "why has evolution been allowed to proceed without outside interference for a billion+ years on an ordinary planet on an ordinary star. If aliens were going to have visited earth it would probabilistically have been hundreds of millions of years ago, and we wouldn't be here.
A potentially strong argument against space faring life isn't to do with difficulty, but works in reverse, just one space faring race could have colonized the entire galaxy by now, arguing against it being likely.
Even so, here are the three main possibilities
1. Intelligent space faring life is incredibly rare
2. Once life gets the capability to explore, it loses the desire (e.g. cyberheaven etc)
3. Enforced non-interference, e.g.
http://en.wikipedia.org/wiki/Zoo_hypothesis like things where advanced life stops less advanced life from interfering with other advanced life.
Purely statistically 2,3 seem more likely than 1, however its hard to take that too seriously
(4. oh yes we live in a simulation, not sure that helps ...)
Going forward, measuring atmospheres of exoplanets will help a bit, if say we measure atmospheres of 10,000 potentially habitable planets and find no oxygen, then we know that is definitely a sticking point. If we find oxygen e.g. at least simple life, but not necessarily space faring, then the only way to distinguish between 2,3 is to actually explore.
There are lots of other possible explanations put forward, ones that aren't similar to these however are illogical or wrong because of statistical/ civilization expansion speed arguments.
There are of course two longstanding observations...one has been mentioned already. This one, for any of a myriad set of reasons, the people out there are withholding their presence on purpose. This presupposes a pretty good singular civilizing structure in the galaxy or cosmos though.
The second observation is actually Carl Sagan's. The difficulty is not with life but with the self destructive tendencies of highly advanced civilizations because a balanced climb to the necessary sophistication is very difficult and civilizations tend to disappear rather quickly. The jury is certainly still out with us, but we have been in a series of brinksmanships since the nineteen-forties. In this regard the civilizations rise and fall rather quickly and can be many but still only a few at a time anywhere in the galaxy and rare elsewhere too.
But I rather like the speculation that by the time you could actually range far afield and visit elsewhere you also outgrow all need and desire to do so. As some of our SF speculators explain, these people may be so self contained that rather like black holes, very little leaks out that indicates coherence as we might recognize it.
Still as Seti searches, where's all the radio?
Or maybe it really is a conspiracy of silence by our own that keeps us struggling with this question.
I don't know that life is common (of course) but even if it is common given the distances involved I think it quite likely that we just can't detect it.
So there is no paradox. There is irony perhaps...it's everywhere but we can't ever detect it :)
I can't buy into the idea that there are alien civilizations out there but they don't want to explore the galaxy, or they have laws that don't allow contact with us. In billions of years, statistically someone would have said hello.
The most plausible conclusion seems to be that we are unique or very rare. In that case, there must be something that prevents space-faring civilizations coming into existence. Either it's something in our future or in our past.
It could be that we are likely to self-destruct before we colonize space, but again that doesn't seem statistically plausible. The most likely explanation for me is that the sticking point is in our past and that we have already overcome it. Looking at the evolution diagram above, it looks like life got started pretty early in Earth's history, so that bit was easy, but then the move to complex multi-cellular life took billions of years. Perhaps that's the step that is really difficult.
This solar system alone has one life supporting planet and one near miss that once had water in abundance and vulcanism to add a dynamic to the atmosphere.
Using our solar system as a typical example, rather than as an extreme outlier, I would guess that at least 80% of F, G and K class stars could have Earth or Mars type planets with abundant water and atmospheres that could support life, even if they're Mars or Earth sized Ganymedes tidally locked to supersized Jupiters in the life optimum zone.
The only logical conclusion, therefore, that the really clever could permit themselves to reach within the framework of the currently accepted scientific paradigm, while at the same time avoiding what Professor Michio Kaku has described as the ‘third rail’ of science, is that:
Interstellar travel (in a practical sense) is not now and never will be possible;
And that, therefore:
There is no point in speculating on other possibilities.
Alan L, in 73,000 years, Voyager 1 will have travelled a distance of 4.2 light years - enough to reach the nearest star (if it was pointed in the right direction). So your conclusion that interstellar travel will never be possible is disproved by empirical evidence.
" In billions of years, statistically someone would have said hello."
If you travelled to a new star every day of your life and travelled there within the same day as you left, how many stars would you visit in 1 billion years?
And 1 billion years ago, what evidence would exist? Cyanobacteria don't have webcams.
In reality, to the external world, any traveller would take some years to move between the stars even if from their POV it took no time at all.
That puts a huge crimp on how far someone can explore the universe.
"That puts a huge crimp on how far someone can explore the universe."
unless you're Q :)
There are other areas of the galaxy where stars are much closer together than our region.
If it is more common for advanced civilizations to die out than to survive, perhaps we should be looking for that rather than for an existing civilization.
In other words, if a civilization had destroyed itself technologically, by means of nuclear radiation or some other method, wouldn't that be an observable phenomenon from a distance? I mean, what would we need to do to see a planet or system with a radiation signature that is clearly not natural?
But what if they didn't destroy themselves by nuclear weapons. Also, nuclear radiation coming from a planet hundreds of lightyears IMO is just lost in background noise.
next gen optical telescopes might be able to "zoom" in on planets. And second way which costs little but can maybe provide clues, again IMO is what SETI used to do.
There's something else also to note. Intelligent life, even highly intelligent life doesn't mean industrial revolution and all that follows it. We can see examples of that in our history. Industrial revolution had all the elements to happen cca. 2000 years ago. We have records of steam machines from Alexandria. But they remained just curiosities. There just wasn't that "eureka" moment. There are still parts of the world today that live more or less like they did 5000 - 10000 years ago. So in principal I argue that it's very much possible to have alien civilizations that could just function fine without ever thinking of leaving their planet.
Also very much possible, and this is much more worrying, it might as well turn out that there can't be space exploration as we imagine it today. Am talking about relativity of course. Maybe there is no way around it. Maybe all you get is one way tripm if even that. I hope that isn't the case, but is just as valid argument.
after all, the laws of physics and chemistry are the same everywhere in the Universe- this statement is ridiculous. Our laws a of physics and chemistry are based upon "our" observations. We have no concept of how physics and chemistry may have been developed on other planets, or their true properties. We can only "assume" that these laws are universal based upon our experts. To blanket the entire "universe" with these rules is ridiculous and vain. If intelligent life exists out there then who are we to say that "our" science is the most complete model of the universe. We have no idea how other advanced "species" might percieve their findings and that they are the same as ours. Scientific observations are objective. We must accept this idea and not presume that we are the " highest authority" on the subject of how the entire universe works. We are but one small entity in the universe. To assume that we are the end all, be all of science is ridiculous
"We have no concept of how physics and chemistry may have been developed on other planets"
Yes we do.
They are exactly the same laws of physics as ours.
If we assume that they are different, then why the hell do stars still form and blow up like they do with the physics we know from our locality?
If the physics can change arbitrarily, then why aren't distant galaxies made of custard?
The distant universe acts exactly like they obey the same laws.
Do you have any evidence to show what the physics is like elsewhere that demonstrates it is not?
"That puts a huge crimp on how far someone can explore the universe."
I'm not talking about someone. I'm talking about a Type III civilization.
"I’m talking about a Type III civilization."
even so, everyone is governed by same laws of nature.
If every planet in the universe (except the others in our solar system) currently had life as intelligent as those lifeforms on Earth are we sure that we would be able to detect it using current technology?
If they were 500 light years away, they'd not be sending anything we'd be detecting for maybe another 400 years...
"I’m not talking about someone. I’m talking about a Type III civilization."
So they'd use Donner and Blitzen to give them a lift, right?
@ Steve Morris
You missed the part that I've bolded for your benefit below:
Interstellar travel (in a practical sense) is not now and never will be possible;
if a civilization had destroyed itself technologically, by means of nuclear radiation or some other method, wouldn’t that be an observable phenomenon from a distance?"
Maybe we have seen it but not recognized it. I do recall reading, writing now this blog, about unexplained flash(es) in space
Sorry for the auto-correct :(
I do recall reading, in this blog, about unexplained flash(es) in space
Re. Cosmonut @ #5: "I really can’t see why a species would set out to “colonize the galaxy”. They might want to leave their planetary system if the star is in danger of dying, but that happens only very rarely."
Rarely? Surely you jest! 100% of stars die, thus 100% of scientifically-capable intelligent land-dwelling species will realize that their stars will also die.
The prospect of the extinction of all life on one's home planet is a powerful and sufficient incentive for interstellar travel. If you don't think so, go kill yourself right now. If you got offended at that suggestion, you've proved my point. Sorry to guinea-pig you without asking first, but the point needs to be made unequivocally, that any land-dwelling and scientifically-capable intelligent species with an individual and collective survival instinct will eventually reach the point where it desires to spread to other star systems before its home star explodes or otherwise dies.
The bottom-line question on the cosmic Darwin test is, who actually makes it? I originally called this issue "cosmic selection" but found that term was already used by Eric Chaisson at Tufts, so I'm calling it "natural selection on the cosmic scale."
There is nothing about interstellar travel that violates our present scientific understandings. In theory it is not impossible to construct a colony ship sufficient to support a genetically viable population of Earth life over a many-generational voyage at relatively slow speeds, e.g. a small single-digit percentage of c.
The problems are technical: 1) Reliable means of propulsion that will function for perhaps thousands of years. 2) Reliable means of life-support that will do likewise. 3) Accurate means of assessing the likelihood of deadly microbes on any planet found suitable for colonization. 4) Means of constructing habitats and life-support infrastructure on a new planet. Assuming we don't darwinize ourselves via climate change or a missed meteorite or biological warfare (nukes are passe: bugs are the real deal), we have more than sufficient time to experiment until we have solutions to all four of those issues.
There is another critical issue, 5) whether we can curb our instinctual drives toward reckless reproduction, conspicuous consumption, domination of others, and desire for emotional drama, sufficiently for the colony ship to survive the journey. This is the issue of social evolution. Bluntly, we must evolve socially or we will become one more of many failed species.
As for why we haven't run into the mythical Grays as they take the inevitable similar steps out of their home system and to other stars: how easy would it be for us to detect objects of the type I just described, as they streak through our galaxy? Not so easy, no, not at all. And who says the Grays, or the Greens, Blues, and Purples, use the same means of communication that we use? For while science is uniform throughout the universe, technology is most likely diverse. And we don't have the last word on the science either, as new developments in physics may lead to new means of communication.
Re. Jesters at #18: I see that Wow put that nonsense to rest in the subsequent post, but I'll stick my neck out and give the nonsense a name: pseudoscientific post-modernist bullsh--. And I'll go just a little further:
Envision this. The children of every scientifically-capable and land-dwelling intelligent species throughout our galaxy, and throughout the entire universe, learn the very same laws of classical physics as Earthlings learn. When you sat in that classroom in secondary school and learned that material, you participated in a ritual that is truly universal. Every similar species must necessarily discover the laws of classical physics in order to make technological progress beyond a crude level. Whether they go on from there in the same sequence that we have, with Einsteinian relativity coming next, and the quantum theory coming thereafter, is anybody's guess. Perhaps some civilizations go straight from their Newton to their equivalent of someone who has yet to be born on Earth, whose theories may substantially change our own paradigms.
But they all had their Newton, singular or plural.
And personally, I find that deeply meaningful, aesthetically beautiful, and very much exciting.
"Rarely? Surely you jest! 100% of stars die, thus 100% of scientifically-capable intelligent land-dwelling species will realize that their stars will also die."
About every 10 billion years.
I'd call that a rare event, seeing as something I do less than once a year would be called "rare".
The need to colonise expands with the rate of population needs and the rate of a species once it reaches a high level of self determination is not much more than replacement, except for very new colonists.
Taking 100 years to get to a nearby useful planet without genocide of its current inhabitants means the expansion doesn't go very fast.
Unless what you want to do IS basically expand and use up every resource as Agent Smith attributed to a virus. And humans.
But if they were to do that, then the War of the Worlds type invasion is inevitable and we can't do a damn thing.
Which would work for them until they found a race with the same idea and goals and the technology to act on them.
Re. Wow at #29: If I'm not mistaken, we have about 2-1/2 billion years to go, not ten billion, before our Sun goes red giant, and between now and then it will expand to the point where the oceans boil.
Eventually each of us will die (and the "upload your mind to a computer" meme is just another form of reincarnation belief, personally I'd rather come back as a cat).
If you expected to die within the year, would you call that "a rare event" or would you seek to prolong your life? "Later" is "now," just a little further away on the time dimension. Every "later" inevitably becomes a "now."
If the Sun were going to blow next week, and the mythical Grays landed a spaceship in your back yard tomorrow, would you ask them to take you as a passenger, or would you stick around and endure a death that was probably horrifically cruel?
There is no escaping this, not at all: every land-dwelling species that is scientifically capable and has an individual and collective survival instinct, will eventually confront this issue and seek to go to the stars as an alternative to extinction.
This also leads to the moral imperative that we, here and now, take such steps as are needed to preserve the right of our distant descendants to choose their outcome for themselves. We do not have a right to squander resources and crash ecosystems and revert humanity to a state from which space travel becomes impossible due to lack of concentrated energy sources or raw materials. We are obligated to give our distant descendants the capacity to pass the cosmic Darwin test. Operationally this translates to living sustainably, supporting progress in science and technology, supporting universal science education, and supporting space exploration.
Re. Wow at #30: Yes, population growth could theoretically drive the need to colonize other planets in one's own star system, colonize interplanetary space, and eventually go to the stars. Except for one problem. Any _rate_ of growth is exponential growth. And exponential growth eventually goes into overshoot and collapse.
Sustainability, which necessarily includes zero population growth beyond a sustainable level, is a mandatory pre-requisite for having the resource surpluses needed to muster the technology to go interplanetary and interstellar.
The other two prerequisites for going interplanetary and eventually interstellar are b) an absence of regional and global warfare for the length of time needed to complete the task, and c) a society that recognizes and protects the right to freedom of scientific inquiry.
Those three things will also prove to be universal. Any civilization that manages to go interstellar will necessarily have achieved sustainability, peace, and freedom of scientific inquiry, as the prerequisites for that stage of development. This does not mean that the mythic Grays or Blues or Purples will be benign, only that they cannot be malevolent in ways that preclude those three conditions.
Know what I find really frustrating? All the "no we can't, no we won't, no we shouldn't" arguements against space exploration and migration, that typically come from the obscurantist anti-science crowd. I can't help but envision them sitting around the campfire in ancient Africa, telling their fellow tribemates that it really isn't worthwhile, good, or necessary for any of them to migrate beyond the mountains and the seas. You can see where that would have gotten us by now, and, plus one decent sized meteorite, where it could have gotten us.
BTW, in case it wasn't clear, I'm on your side re. Jesters. 'Twas Jesters who was engaged in "pseudoscientific postmodernist BS", not yourself. You did a good job shooting down his hot-air balloon.
"If I’m not mistaken, we have about 2-1/2 billion years to go"
Yeah, but that's still pretty infrequent. There's no huge rush to invent space travel for quite a long time. Its far more likely we'd get smacked out of existence with a space rock and end that way than the sun goes boom.
In deep time, evolution is liable to kill us all off. Just like it did for the Allosaur.
"Any _rate_ of growth is exponential growth."
Replacement isn't. And much of the world is trying to stop exponential growth. And it's likely not to change either, if we'd managed to produce space colonies. There's better things to do than bring up babies continuously.
Re. Wow at #32:
A spacefaring civilization can take steps to protect itself from space rocks: this problem can be solved entirely from within present science and technology, all it takes is the will to devote the needed resources. What we can't protect against are supervolcanos and caldera events. (Though presumably we could maintain stored food supplies sufficient to get over the global impact on agriculture; this is a "resilience" strategy rather than a "prevention" strategy.) Beyond that, are gamma ray bursters and nearby supernovae and possibly wandering black holes, also wholly beyond our control. I take all of those as further incentives for "Mars and the stars."
I think your "frequent/infrequent" arguement is fundamentally mistaken. Consider a natural human death at older age, for example 70 years: that's a 1-in-70-year event. Now consider a death during childhood, example at 7 years: that's a 1-in-7-year event. Yet which of those two deaths do we consider the more tragic, and make the more heroic efforts against? Infant and child mortality used to be so common (more-frequent) that a high birth rate was needed to ensure replacement.
In any case, death is a singular event for each individual, and extinction is a singular event for each species, which is the basis of my arguement that "frequency" is irrelevant. All other factors equal, you will seek to preserve your own life as long as you are conscious, and the honors accorded to altruistic self-sacrifice further make the point. Multiply that by the scale of humanity, and the drive for space migration is an inevitable conclusion. The fact that the vast majority of humans give this no thought today, is not surprising. But now that we know that space travel of any kind is possible, and we have numerous such narratives in the culture via fiction, any truly existential threat to our species will bring it back to mind each time.
Re. #33: "Replacement isn't" what? Isn't exponential growth?
That's obvious enough, and of course any given space colony will also have sustainable population limits. There will be times and places where high birth rates are viable (e.g. in the growth phase of a colony on a new planet), and times and places where ZPG is essential (e.g. as a new planet reaches carrying capacity).
For any given human, it's more or less a matter of "luck" (subjective outlook on events beyond one's control) whether they live at a time when high birth rates or low birth rates are needed. That "luck" works in both directions, as the individual preferences for having many, few, one, or no children, interact with the needs of the society on their planet during their life. And for those who wish more or fewer children than their local norms encourage, absent new methods of propulsion beyond current physics, it won't be possible to hop a flight to a planet in another star system where one's own preference matches the present local need.
Though, the idea of desired family size as incentive for individuals to choose to migrate among star systems, could be interesting to work out in fiction (we can assume FTL travel as a plot device;-). Hmm...
"A spacefaring civilization can take steps to protect itself from space rocks"
irrelevant, G, to my point.
I was defending the extinction times. Solar extinction is a rare event to anyone who needs to survive it, even species.
Asteroid hit is something a species may have to worry about removing them. I.e. something we ourselves have to worry about far more than the sun going boom.
A much less rare event.
When it comes to getting off this planet, the asteroid strike is a much more urgent reason.
"Re. #33: “Replacement isn’t” what? Isn’t exponential growth? "
"That’s obvious enough"
Then you shouldn't have claimed any replacement was exponential growth.
Why won't you talk to me?
Talk to me!
Sorry, this conversation never happened.
I think the Drake formula is a great starting point, but there MUST be variables that are not included. For example, using the earth as a model, you can add a sufficiently sized moon, a large Jupiter-sized planet with a strong electromagneto-sphere, presence of an asteroid belt, etc. Plus, any life must not have been destroyed by a cataclysmic event. So, yes, there are BILLION of stars, but the funnel narrows quickly.
Additionally, the goal is to find life that is functionally useful. For example, life beyond a certain distance (say 100+ light years) would likely be impossible to communicate with. Imagine how much civilization would change in the 200+ years it would take to send and receive a message! It just would not be useful.
So, the real question is "Is there life in the universe that is close enough to have an impact on society?" The answer, unfortunately, sounds like a resounding "no" (but we should keep looking!)
Based on our own experience, maybe we already have the answer to why other intelligent species have not gotten into contact. To reach the point where contact is possible, an advanced technology is required. Advanced technology requires an efficient energy source. Efficient energy sources have negative environmental impacts. Perhaps other civilizations either rendered their environments uninhabitable through their use of energy or they had the wisdom to realize that continued use of these energy sources would lead to their own extinction and reverted to a pre-technological existence. Either way, they would be unable to contact us.
@ Sean T
"Efficient energy sources have negative environmental impacts"
- what would be the negative impact of cold fusion on the enviroment?
Well, apart from not being possible...
Seriously, it didn't work. Sean is talking about the venues of power production we currently have that get most attention at the moment.
Nuclear, obvious problem, known right from the start.
Coal, Gas and Oil have a problem we've really only recently (last fifty years or so) known about.
In my opinion, the weakness is somewhere in the advanced-technology-to-space-travel-to-colonizing transitions. I think we have good reasons to believe that this represents an escalation of increasingly unlikely events.
I can imagine, say, intelligent life arising and achieving space-faring technology once every twenty-thousand years somewhere in our galaxy, on average. But only a few of those will even dabble in interstellar travel. And, of those, only a few will attempt to colonize. And, of those, surely we can't expect almost any of them to succeed over a long enough term to be noticed by another such civilization? That is, I don't have too much trouble imaging that the Earth has been visited by aliens sometime in the last 250 million years. I do have trouble believing that there'd be any evidence of such a visit.
I was under the impression that Sean was talking about technologically advanced civilization (not only us). Surely we are not talking about coal powered space ships or diesel for that matter.
And I wouldn't call us advanced in the first place, as far as space exploration goes. I mean we invented stick and rope airplane 100 years ago.
If we can't even imagine other means of energy production other than fossil fuel burning then ok.. that's our problem. But I wouldn't call that a rule for all other planets and possible species.
p.s. it might very well be that cold fusion is a dud.. it was just a first thing to pop in my head. But in general I can't agree that an efficient energy source is by default negative on enviroment.
"I was under the impression that Sean was talking about technologically advanced civilization (not only us)."
You missed this bit, SL:
"Based on our own experience,..."
It still applies to the rest of his statements in that post.
Wow and SL,
Precisely. We haven't yet found any energy source that doesn't have negative environmental impact. Maybe someday we will. However, even more generally, the hallmark of an intelligent, technologically advanced civilization is its ability to modify its environment. Perhaps such environmental modifications lead inexorably to extinction of the species unless they are able to forsee this and revert to a pre-technological state. In either case, they cannot contact us.
@ Sean and Wow,
sorry if I misunderstood you. Here is my dilemma. If we are talking about interstellar travel, there are 2 different things to address. One is power source, second is propulsion source. Those 2 needn't be same thing. And more than likely won't be. Even today there are many ideas on propulsion.. some theoretical, some practical.. on non thermo-chemical propulsion.
If we are talking about power source for the planet, this again needn't be negative for the planet. Solar power isn't, geo-thermal, wind, tidal.. etc. Yes, most of them today are in infancy, but even today, the means are there. Now what's wrong with an earth like planet that has strong winds i.e. Life could evolve, civilizations could evolve, but due to high winds all their power is wind based. They regard fossil fuels as inefficient. They can cause their breeze is 200km/h wind.
Even if we stick to "today's" means. Personally, I don't think it will be that long (50-100 years) before we start mining asteroids. Yes, it is negative impact on asteroid field, but not for any planet or ecosystem (granted if there's no ecosystem on asteroids).
I of course agree that fossil fuels have negative impact, even nuclear power because of radioactivity. But those are not the only ones.
And if we try to think what might be out there, we need to be rooted in physics, biology etc.. but we can't be too much rooted in what exists on earth as far as fuel and how much or little there is of it.
None of those solutions for travel mean that we drop the speed limit of light, though, so rather moot with respect to the question of the thread "where is everybody?". We have no reason to believe that they ought to be here by now.
But the dirtiest nuclear power for interstellar travel doesn't impact on the earth after it leaves close orbit, so the distinction isn't germane to Sean's contention.
We have to have enough power to make the society independent of the necessity of work for long enough to develop interstellar travel. And we aren't showing up intelligence as being of any damn use in making that switch without screwing things up and causing an (effective, from the Drake equation perspective) end of civilisation.
We can hope that other intelligence won't bollix things up so bad, but they will almost definitely go through the "burn things for energy" state and most of our improvements have been finding more efficient ways to burn things.
Whether the institutional demand to remain on pre-stone-age technology ideas is parochial for intelligence able to civilise or whether it's just a failing of the specific evolution of the hominid brain can be questioned.
"None of those solutions for travel mean that we drop the speed limit of light"
of course not. My only comment to Sean was in regard to energy source.
As for practical means of travel, unless we discover some new physics i.e. mach effects, negative mass (exotic particles etc.) we are looking at generation ships at best (I leave earth, my grand grand children reach the destination).
It might well be this is the way of Universe. In that case, I see rather violent colonizations for any species. Imagine spending 4 generations in order to reach a suitable planet for colonization only to discover it's already populated. If the species on the ship is of similar mindset as us, and they notice that the species on the planet is inferior, they won't just say...ok we'll move along for 4 generations more. More likely they will put them in a zoo or keep as pets and colonize the planet. From this perspective, I wouldn't like to meet any E.T's close to earth for a good while.
From the POV of the rest of the world, even near-light-speed travel is light speed only travel, and even though YOU get there in your lifetime, it was a one-way trip.
It would reduce the anger a bit.
But maybe that's why the ID4 aliens were so cheesed off?
It would be really expensive to lift war gear up out of your gravity well and drop it (safely) in another, so any colonists would be poorly armed and left with mostly throwing rocks as a recourse, and one that would either be ineffective at conquest or ruin the planet for use, so I'd still say that a hostile take over would require some plotnium to make happen.
This does mean that the most likely colonisation will be to something no more than a few hundred years away by travel, few thousand tops, so that the destination will have no moral quandry living on the surface by the time you get there.
If we do meet others, it will likely be when either we colonise other planets near someone's home or planets near us get colonised and we are looking at mostly unlived but liveable by us planets.
I doubt an alien civilisation will do any different. Space invaders is really expensive for the invaders and there's a lot more utility in just not trying and moving on to the next.
For nearly 3 billion years, life on Earth was no more complex than single-celled, asexually reproducing organisms. Yes, this includes some extraordinary one-celled creatures, like corals and sponges, but still single-celled organisms, nonetheless.
Not that it affects your story, but for accuracies sake, neither corals nor sponges are single-celled.
The supposed paradox is easy to resolve for yourself using an excel spreadsheet. Put in the age of the universe, the number of stars. a reasonable fraction of stars that contain planets, a reasonable fraction of those that contain single celled life, a reasonable fraction that produce multicelled life, a reasonable fraction that contain complex life, a reasonable fraction that produce intelligent life etc, etc. You get a reasonable density of intelligent civilizations in the galaxy. THEN, comes the kicker. You put in a lifetime for a civilization. Considering the age of the universe, this lifetime dominates everything else in determining the average distance between civilizations. You can vary any other paramater all you want but this "civilization lifetime" dominates everything.
The interesting question is what this "civilization lifetime" means.
I might be wasting my time if Ethan doesn't read this, but here goes...
Why would an alien civilization, thousands or even millions more advanced use radio waves for communication? Transmitting in that way might be great for planetary use or to make a call to the moon... but for interplanetary communications, radio waves suck. It's apparent they suck even now, to us, though it's the best way we got to communicate.
Why not Quantum Entanglement used for communications? If you can find a way to transmit FASTER than the speed of light, wouldn't it be a no-brainer to capitalize on that benefit?
If this is the case... we're going to be listening to quasars and other cosmic static forever...
We should be worshiping our oversized Moon and our asteroid belt with Jupiter's closeness. I think these bodies at just the right distances fueled the fast erosion required to produce a primordal soup and periodic mass and minor extinctions allowing us to evolve. This may be why intelligent life might be a singularity in the universe.
Great topic. A few added perspectives:
My understanding is SETI has investigated an area within a radius of a mere 100 light years, leaving the vast balance of hundreds of thousands of light years in the Milky Way still to be explored. Just because we developed radio communications first is also no reason to expect other intelligences will do the same or still be using it. Or even that they would be remotely interested in us.
So for all we know, there may even be many civilizations in the galaxy within their own 100 - 200 light year bubbles, just waiting to discover each other. There also may have been many such civilizations that are already in the dustbin of the galaxy's eons, and many such in the future centuries of our galaxy.
Our sun's mundane location in the relative backwater of the galaxy, combined with humanity's rather recent development is a perfectly logical reason why no else one has found us yet. If we want to be found that is...
Most likely any other intelligence out there is at least thousands if not millions of years ahead of us in technology as well as their own evolution. Their unimaginably sophisticated technology paired with that unknown ET evolutionary history means there is no reason not to expect that they will be much longer lived than the puny century a human gets to live. Why expect then that this incredibly advanced alien species that lives for who knows how much longer than us would have any issue with dealing with the vast interstellar distances necessary for colonizing small sectors of the galaxy?
The same thoughts for their AI technology, which is a very likely way for even ourselves to explore. Humans will send AI to the stars first, just like we are doing now on Mars.
For all we know, the other side of our galaxy is literally teeming with ET's, but our side of the Milky Way is much quieter for some unknown reason. If that were the case, we would most likely think we are the lone form of intelligence in the galaxy. Not to mention the billions of other galaxies. Intelligence could be common throughout our universe.
Or not and we are alone, but I think we need to think long and hard before ruling other intelligence out.
I think one of the big variables that I never see discussed is whether life, given enough time, invariably arises out of a particular, fixed set of circumstances, or whether it instead requires specific changes to those conditions to occur in a specific order. The primordial soup argument seems to be that making life is like making toast - if you have the right materials (bread, toaster) push the button and wait long enough, voila, you have toast. But maybe life is more like chocolate cake - you need the right ingredients and conditions, added in the right order. You can't bake and then add the eggs, or put the frosting on first. So life might require more than just a planet with conditions like earth 3.5 billion years ago; it might require a planet that had a similar history and sequence of geologic, climatic and environmental change. So while Earth-like planets may be common, Earth-like planets that have similar things happen to them in a similar order (eg, collisions with other objects, atmospheric changes, volcanic eruptions, development of a moon, etc.). If life is like chocolate cake, it might be way, way more rare than if it is like toast.
Our technological civilization in the cosmological timescale is in its infancy. We as humans just started to get a sense of understanding of our solar neighborhood and the vastness of our universe. At this time any statements about intelligent life in other realms of the universe and our effort to communicate with them are speculative with our limited technology and may be even dangerous.
The evolution of our species and all species in this planet earth has been based on the survival of the fittest. If life in other areas of the universe have followed the same path to intelligence, and are still around, most probably they developed a very unique civilization to survive and set colonies beyond their own planet.
I hope that our own species which developed by trial and error based on the survival of the fittest develops the intelligence required to survive for a long time in this planet of ours and learns on how to travel and prosper in other worlds and under different environmental conditions.
#46 Sean T - You wrote "Perhaps such environmental modifications lead inexorably to extinction of the species unless they are able to forsee this and revert to a pre-technological state." Setting aside the irony of you typing that thought on a computer, consider that a "pre-technological state" has not averted the extinction of 99% of the species ever lived on this planet, and such a state would not save us or any other intelligent species from extinction. Technology possibly will be our undoing, but on the other hand it is our only possible means of avoiding extinction - by world hopping, at least until the entire universe dies its cold death. Without it, our time here on Earth is limited; either we will perish as the sun ages, or sooner due to some other climactic extinction event.
I've been tempted to quickly rule out intelligence on Earth on numerous occasions...
You are misinformed, as I understand it, you can't use quantum entanglement to send faster than light messages. Entanglement just means that there is a correlation between two sets of measurements done at different and potentially widely separated locations. This correlations cannot be detected without ordinary communciation of the measurement results, so ordinary communication must still be involved to use quantum entanglement as a means of communication.
You determine the state of a particle by measuring, but you don't control the outcome of that measurement. That is, assuming that a message code exists, for example, in a sequence of photon helicities, it's still not possible to send a message that way. The helicity of a photon is determined when it's measured, but an experimenter has no control over whether a particular photon will be measured as having a left or right helicity. Thus, a non-random string of helicities is impossible. Entanglement just means that the random string of helicities measured at one location will be reproduced at another location. To see that entanglement has occurred, it is necessary to compare random strings to see that they are identical. This requires ordinary, c or slower, communication.
You started out this post with the quote...
“If the Universe Is Teeming with Aliens… Where Is Everybody?” -Stephen Webb
But I don't think you mention that that is the title of an excellent book by Webb. In the book Webb discusses 50 possible explanations for the question. They range from "We are alone in the universe" to "They are already here among us"
I highly recommend this book. It is on my top 10 list.
"Why would an alien civilization, thousands or even millions more advanced use radio waves for communication?"
For the same reason we do: it travels a long way.
"If you can find a way to transmit FASTER than the speed of light, wouldn’t it be a no-brainer to capitalize on that benefit?"
Entangled particles, even if it could transfer FTL messages would still require that one of the particles be moved at less-than-light-speed to the place where you want to talk to.
And once you'd used it once, for one single bit of information (whether binary or analogue), it would no longer be entangled, requiring a new particle be moved over.
Even if it worked, it wouldn't!
Finally, the answers I was looking for. Thanks!
It's a problem with woo-like treatments of "cutting edge" science (as in "not part of the school curriculum") that got you, Ted.
I.e. the way all these healing crystals use "quantum" to "explain" how they make you feel better.
So some barnpot with some buzzword bingo list gave you a poor idea of what the science was and left you with a silly idea.
Unfortunately, it is an idea that looks a lot like the woomancer ideas and they aren't really here to find out science, but to promote their Google Gallileo credentials (and complain that they're being oppressed because nobody thinks their ideas are worth a plugged nickel).
Hence responses will tend to be abrupt and short, since effort is not rewarded.
If you ask questions and get blunt answers that you (because you live in your own head and know why you asked, whereas everyone else has to guess) think are unwarranted, ignore the tone and look to the content.
It saves everyone time and effort this way.
Of course there is life on other planets. HOW DO YOU THINK WE GOT HERE? That's the only way life got onto this planet - it CAME FROM ANOTHER PLANET. Your notion of "life arising from non-organic matter" was the alchemy of last century. Once you realize that life on earth came from another planet, you'll be a step farther down the road.
So if life here came from another planet because that's the only way, how did life get on that planet to get here?
wait for it.. he's checking ufo/ancient aliens forums for an answer to that particular question :D
Actually, I think it's just another "All the scientists are wrong" blabbler.
Reasonable assumption 1: There are many planets in the galaxy capable of supporting life, in principle.
Reasonable assumption 2: We actually have no idea how hard it is for intelligent life to evolve on a planet.
Reasonable assumption 3: If intelligent life evolves, it will either leave its host planet and colonize the galaxy or it will become extinct.
Deduction: Since no galactic civilizations are observed, I conclude that either A) it is incredibly difficult for intelligent life to evolve, or B) intelligent life becomes extinct very easily.
In other words, the Great Filter, but in case A optimistic and in case B pessimistic.
"If intelligent life evolves, it will either leave its host planet and colonize the galaxy or it will become extinct."
The period between "life evolves" and "leaves the planet" can be pretty damn big. The gap between leaving the planet and colonising the galaxy is even bigger.
We have at least three divergent evolution paths to intelligence here on earth. It seems intelligence is a valid path to survival as a species.
We have evidence of some life-like forms on the earth only some million years after its formation, therefore it seems some form of life is pretty easy to manage.
It took 4 billion years, near enough, to evolve complex macro scale life capable of supporting a species where intelligence would be a survival trait.
So from the evidence of one, it seems all you really need is billions of years to get intelligent life. Whether any planet remains stable enough for billions of years is most likely the limiting factor for the abundance of intelligent life.
wow , if your sample size is one, the error bars in how long it takes to evolve intelligent life is pretty large. If it took 4 billion years on Earth, it might take ten billion typically. Or it might take 1 billion.
On the other hand, once intelligent life has evolved, things move much more quickly. From Stone Age to Space Age - a few thousand years. From Space Age to colonising a galaxy 100,000 light years in diameter - perhaps 100 million years at most. The migration across the galaxy is orders of magnitude faster than evolving intelligent life.
"wow , if your sample size is one, the error bars in how long it takes to evolve intelligent life is pretty large."
Yup, indeed it does.
Problem for your statement is that I've already told you we have a sample of three.
"If it took 4 billion years on Earth, it might take ten billion typically. Or it might take 1 billion."
Again, true. However, how does this support your assertion before: "A) it is incredibly difficult for intelligent life to evolve"?
It may take a long time for it to become a viable strategy to spend so much biological effort in carting round an intelligence with the rest of the vitally necessary meatsack, but we have three examples now of high intelligence from three different branches of evolution, one of which isn't a chordate, not even bilaterally symmetrical (which is even earlier in evolutionary history)!
"From Stone Age to Space Age – a few thousand years."
"From Space Age to colonising a galaxy 100,000 light years in diameter – perhaps 100 million years at most."
Nope, we have ZERO evidence for that and a huge amount of evidence that this would be impossible without FTL travel, likewise nowhere in evidence.
Assuming "strong" AI supersedes organic intelligence the long travel time of interstellar travel becomes tractable.
And since we have seen no evidence of self-replicating von Neumann machines, I must reluctantly assume we are the first technological civilisation in the Local Group, at least.
"Assuming “strong” AI supersedes organic intelligence the long travel time of interstellar travel becomes tractable."
Well, rather mooting the "where is everybody?" query, since the answer is "they're traveling".
wow, we really don't have 3 independent examples of the evolution of intelligent life.
My estimate of 100 million years to colonize a galaxy assumes that FTL travel is impossible. 100 million years is a long time to travel 100,000 light years, especially if you're a super-advanced von neumann machine.
Yes we do.
Three very different branches of evolution with a hell of a long way to go back before they have a common ancestor, each having worked their niche with extremely high intelligence.
"100 million years is a long time to travel 100,000 light years"
So that gets you between two stars. Not much of a colonisation.
You have to travel to one star. Colonise. Travel to a second. Colonise. Travel to a third... Travel to the 104,203,221,004th star. Colonise.
Each traverse requiring ~10 years at light speed.
Though it isn't necessary to go linearly, unless your intent is to colonise every planet, there's no damn reason to do so.
These are not 3 independent data points. And who would colonise a galaxy one star at a time?
Yes, they are three independent data points.
Unless you're a YEC and all three were created a few thousand years ago with their intelligence as-is.
And who would colonise a galaxy one star at a time? Anyone who had to colonise the stars.
The octopus, dolphin and humans all evolved on the same planet from a common ancestor. That ancestor was already a highly evolved organism. It was multi-cellular, it was an animal not a plant, it had sense organs, etc, etc.
wow, how do you do your weekly shopping? Travel to the supermarket, buy bread, return home. Travel to the supermarket, buy milk, return home. Travel to the supermarket, buy cheese, return home.
"The octopus, dolphin and humans all evolved on the same planet from a common ancestor. "
Steve, look up genetics and evolution, your complaint here is meaningless.
Three very different clades achieved an intelligent version.
You have to go back 600million years to find the common-est ancestor possible and evolution had 600 million years to explore the changes possible in an evolving system.
They are definitely three independent examples.
You are refusing them because you want your assertions to be correct.
PS note that we have no evidence against intelligence from intermediates from the 600mya ancestor to these three today, nor any that may turn up in the next 600 million years.
Intelligence seems to be a viable survival strategy.
"For instance, on the planet Earth, man had always assumed that he was more intelligent than dolphins because he had achieved so much — the wheel, New York, wars and so on — whilst all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man — for precisely the same reasons."
D.A. - THGG
Of course, the mice were really in charge, so we weren't free to play about in the oceans.
Indeed the whole idea of coming out of the trees was a bad idea all along.
Until we invented digital watches...
There's the answer to "where's everybody?". The highway got canceled, and now nobody wants to play with us anymore :)
That, and being "mostly" harmless :D
wow, please don't patronise me by telling me to "look up evolution".
Steve, you are deserving of condescension when you claim as you did.
Our brain-to-body-size ratio dwarfs that of our nearest competitor, the dolphin, by nearly a factor of two, and the next-nearest great ape by a factor of about three.
If we're talking about the bottlenose dolphin, it's my information that it's about 7/5. The bottlenose dolphin has an encephalization factor of about 5 while the average human has an encephalization factor of about 7. The bottlenose dolphin encephalization factor lies somewhere between Homo Ergaster and Homo Erectus.
I have posted the following on Panda's Thumb several years ago but it, perhaps, is worth repeating here. There is a good case to be made that larger brain size may have a selection advantage. The Cretaceous dinosaurs had higher encephalization factors then did their Jurassic ancestors while today's mammals have a higher encephalization factor then the mammals of 50 million years ago. Encephalization is a necessary condition for intelligence. It is, however, not a sufficient condition as Homo Neanderthalis had about the same encephalization factor as modern humans and Homo Heidelbergensis wasn't far behind. Organization of the brain is also important. The Sapiens and Neanderthals had different brain organization.
Dolphins don't have to use a huge amount of brain matter to work out how to stand up on two feet.
Estimating the likelihood of intelligent life seems a statisticians game and I'm not a statistician. However, I feel intuitively that two important factors were left out of the post.
1. what is the relative age of life (variable L) relative to the age of earth (variable E)? It seems to me that the larger the result of L/E the larger the probability that earth like planets have tendency to produce life. The Earth is 4.6 billion and life started 3.6 billion. It seems life started very quickly.
2. What is the likelihood that life came into existence multiple times on earth? It seems much more likely that life started and failed multiple times on earth rather the it being the result of one unimaginably fortuitous event that managed to, even more fortuitously, survive a precarious environment. If this is true, doesn't this virtually prove that the earth (and planets like it) are much more likely to produce life then not?
I completely agree with Bill that life started and failed many times on Earth and it took this long to reach where we are now. So in my opinion a civilization as advanced as us may be less than a dozen. The dinosaurs were wiped out by asteroids and we been lucky enough to not have been hit by any as devastating as before.
The issue of space exploration is always dependent on the economy of said nation. A country struggling with it's economy is less likely to fund space exploration and to make breakthroughs in space exploration, we need to allocate the funds to invent new and more efficient technology. However, o reach the point where contact is possible, we need advanced technology. Advanced technology requires an efficient energy source and there is only so much on a planet. Maybe other civilizations realized their impending doom and reverted back to a pre-technology era. Or when a society reaches this point, people would fight against each other as their survival instincts kick in, leading to the civilization's self-destruction. Either way, the civilization will fall and be unable to contact us.
Can we make a thought experiment please?
I have checked thoroughly in the Encyclopedia universal laxative Universalactica and the following items are known.
The Milky Way galaxy has 1 planet with intelligent life which is called Earth.
This galaxy also has 11 other planets with worms and germs.
No mention of any other planets with more complex animals.
There are 3 listed with only mossy or plant like life.
Looking at what is listed for the closest one million galaxies to the Milky Way, the following items are known.
This group of one million galaxies has 11 planets with rats.
5 million planets with worms and germs.
No new intelligent life.
Looking at the closest one Billion galaxies to the Milky Way, the following items are known.
There are 650 planets with intelligent life.
There are 12,000 planets with rats.
5 Billion planets with worms and germs
The encyclopedia was able to only make an estimate on total number of planets in the universe with intelligent life, and that was “...probably less than 140,000, and looks like there is at least 600 million Light Years distance between a pair.”
Another interesting fact shown is that metal is present in all known galaxies all the way out to the vacuum pump. Also, the average distance between planets with intelligent life works out to be close to a Billion Light Years. The modern intergalactic ship will not engage warp speed/inflation drive until well away from a galaxy. This is the reason for the 21 or more Earth years to leave any galaxy or to slow down before entering another galaxy.
"Can we make a thought experiment please?"
Go ahead, start thinking.
"I have checked thoroughly in the Encyclopedia universal laxative Universalactica "
Go ahead, start thinking.
"Also, the average distance between planets with intelligent life works out to be close to a Billion Light Years"
Feel free to start thinking any time you like.
"before entering another galaxy."
Well? Go ahead. Start thinking. | 0.838529 | 3.182085 |
Orange you glad you've just seen the first-ever image of a black hole?
Today (April 10), a global collaboration of more than 200 astronomers presented the first image of a directly-observed black hole. The picture of a glowing orange-yellow ring around a dark core, was compiled from observations by eight ground-based radio telescopes known collectively as the Event Horizon Telescope (EHT).
Researchers' data showed the black hole at the heart of Messier 87 (M87), a galaxy within the Virgo cluster located about 55 million light-years from Earth. But what exactly is the image showing, and why is the irregular ring orange? [IT'S HERE: The First-Ever Close-Up of a Black Hole]
Though black holes are compact objects, they are exceptionally massive — the mass of M87's black hole is about 6.5 billion times that of our sun, the National Science Foundation (NSF) said in a statement. Because of this enormous mass, black holes warp spacetime, heating the dust and gas around them to extreme temperatures, according to NSF.
By definition, black holes are invisible, because no light escapes from them. But a prediction made by Albert Einstein in his theory of general relativity stated that under certain circumstances, an outline of a black hole and its light-swallowing event horizon could be seen, according to representatives of the Haystack Observatory at MIT, which houses one of the EHT telescopes.
"If immersed in a bright region, like a disc of glowing gas, we expect a black hole to create a dark region similar to a shadow," EHT Science Council chair Heino Falcke, a professor of radio astronomy and astroparticle physics at Radboud University in the Netherlands, said in the NSF statement.
The black hole in M87 isn't the closest to Earth, but it's among the biggest, which made it a very promising target for the EHT, Derek Fox, an associate professor in the Department of Astronomy and Astrophysics at Penn State University, told Live Science (Fox was not affiliated with the EHT discovery).
In the image, the dark circle represents the "shadow" of the black hole and its boundary, created by the glowing material that surrounds it. However, the colors of the bright ring in the image aren't the actual hues of the gas; rather, they represent a color map chosen by EHT researchers to depict the brightness of the emissions, Fox explained.
"The yellow is the most intense emission, the red is less intense, and then black is little or no emission at all," Fox said. In the optical range, the ring around the black hole would likely appear white, perhaps tinged with blue or red, according to Fox.
"I'd expect it to be more of a whitish glow that is brighter along the crescent, dimmer at the other points, and then black where the black hole is casting its shadow," he said.
- 9 Facts About Black Holes That Will Blow Your Mind
- The 12 Strangest Objects in the Universe
- Stephen Hawking's Most Far-Out Ideas About Black Holes
Originally published on Live Science. | 0.824822 | 3.866212 |
These Ancient Stars May Be the Oldest Ever Seen in the Milky Way
Astronomers have found what may be the oldest stars in the Milky Way. The stars, discovered in the galaxy’s bulge, reveal that extraordinarily powerful explosions known as hypernovas might have dominated the Milky Way during its youth, researchers say.
The oldest stars in the universe are poor in what astronomers call “metals” — elements heavier than helium. When these stars died in giant outbursts known as supernovas, they released these metals into the cosmos, and each succeeding generation of stars is generally more metal-rich than the last.
Previous research suggested the first stars formed about 13.6 billion years ago, within 200 million years of the Big Bang, initiating what scientists call the cosmic dawn. Astronomers have not yet discovered a first star, but extremely metal-poor stars that were probably immediate successors of the first stars have been seen in the outer regions, or “halo,” of the Milky Way. [Watch: The Universe’s Oldest Stars May Be Close to Us]
Still, prior studies indicated that extremely metal-poor stars should mostly be found not in the halos of galaxies, but in their central regions, or “bulges.” Galactic bulges are loaded with gas and dust — the building blocks from which stars are born.
Stars from the cosmic dawn
Until now, astronomers had not detected any extremely metal-poor stars in the Milky Way’s bulge, in part because Earth is located in the Milky Way’s halo, and the bulge is very far away, with a lot of intervening dust obscuring Earth’s view of the bulge.
In addition, the vast majority of the stars in the Milky Way’s bulge are metal-rich. Because the bulge is dense with gas and dust, star formation happened quickly there, and when the galaxy’s early stars died, they enriched their surroundings with heavier elements within the first 1 billion to 2 billion years of the universe. This makes finding extremely metal-poor stars in the Milky Way’s bulge “like searching for a needle in a haystack,” said study lead author Louise Howes, an astronomer now at Lund University in Sweden, who carried out this research while at Australian National University in Canberra.
Now, Howes and her colleagues have, for the first time, identified stars from the cosmic dawn in the Milky Way’s bulge.
“These are the oldest stars that have ever been found in the Milky Way,” Howes told Space.com.
The researchers used the Australian National University’s SkyMapper telescope to scan about 5 million stars in the Milky Way’s bulge. They focused on the fingerprints of elements in the stars, which appear as distinct lines in the spectrum of their light.
A starry sleuth job
After using SkyMapper to discover more than 14,000 potential extremely metal-poor stars, the scientists used the Australian Astronomical Observatory’s Anglo-Australian Telescope to confirm that more than 500 of these stars were extremely metal-poor, each possessing less than one-hundredth the amount of iron seen in the sun. As expected, most of the extremely metal-poor stars that astronomers now know about are found in the galaxy’s bulge instead of its center.
Using the Magellan Clay telescope at the Las Campanas Observatory in Chile, the astronomers closely analyzed 23 of the most metal-poor bulge stars to determine their chemical composition. Oddly, the researchers found that these bulge stars were as poor in carbon as they were in iron. In contrast, metal-poor stars in the galaxy’s halo are often rich in carbon, possessing as much as the sun does.
“That’s surprising — it’s goes against what was predicted,” Howes said.
These findings suggest that the earliest stars might not have died in normal supernovas, but in titanic explosions known as hypernovas, which are 10 times more powerful than regular supernovas.
“This work really changes our ideas of what the first stars would have looked like, and how they would have developed and died, and how the galaxy would have evolved, and also sheds light on the formation of all the elements in the universe,” Howes said.
This research analyzed only one-third of the part of the sky that the Milky Way’s bulge covers. Future research could analyze the rest of the bulge that astronomers can see, so they can learn more about the metal-poor stars there, Howes said.
The scientists detailed their findings online Nov. 11 in the journal Nature. | 0.875177 | 3.807477 |
Dawn has been cruising toward Ceres, the largest object in the main asteroid belt between Mars and Jupiter, since September 2012. That's when it departed from its first dance partner, Vesta.
Ceres presents an icy -- possibly watery -- counterpoint to the dry Vesta, where Dawn spent almost 14 months. Vesta and Ceres are two of the largest surviving protoplanets -- bodies that almost became planets -- and will give scientists clues about the planet-forming conditions at the dawn of our solar system.
When Dawn enters orbit around Ceres, it will be the first spacecraft to see a dwarf planet up-close and the first spacecraft to orbit two solar system destinations beyond Earth.
"Our flight plan around Ceres will be choreographed to be very similar to the strategy that we successfully used around Vesta," said Bob Mase, Dawn's project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "This approach will build on that and enable scientists to make direct comparisons between these two giants of the asteroid belt."
As a prelude, the team will begin approach operations in late January 2015. The next month, Ceres will be big enough in Dawn's view to be imaged and used for navigation purposes. Dawn will arrive at Ceres -- or, more accurately, it will be captured by Ceres' gravity -- in late March or the beginning of April 2015.
Dawn will make its first full characterization of Ceres later in April, at an altitude of about 8,400 miles (13,500 kilometers) above the icy surface. Then, it will spiral down to an altitude of about 2,750 miles (4,430 kilometers), and obtain more science data in its survey science orbit. This phase will last for 22 days, and is designed to obtain a global view of Ceres with Dawn's framing camera, and global maps with the visible and infrared mapping spectrometer (VIR).
Dawn will then continue to spiral its way down to an altitude of about 920 miles (1,480 kilometers), and in August 2015 will begin a two-month phase known as the high-altitude mapping orbit. During this phase, the spacecraft will continue to acquire near-global maps with the VIR and framing camera at higher resolution than in the survey phase. The spacecraft will also image in "stereo" to resolve the surface in 3-D.
Then, after spiraling down for two months, Dawn will begin its closest orbit around Ceres in late November, at a distance of about 233 miles (375 kilometers). The dance at low-altitude mapping orbit will be a long waltz -- three months -- and is specifically designed to acquire data with Dawn's gamma ray and neutron detector (GRaND) and gravity investigation. GRaND will reveal the signatures of the elements on and near the surface. The gravity experiment will measure the tug of the dwarf planet, as monitored by changes in the high-precision radio link to NASA's Deep Space Network on Earth.
At this low-altitude mapping orbit, Dawn will begin using a method of pointing control that engineers have dubbed "hybrid" mode because it utilizes a combination of reaction wheels and thrusters to point the spacecraft. Up until this final mission phase, Dawn will have used just the small thruster jets, which use a fuel called hydrazine, to control its orientation and pointing. While it is possible to explore Ceres completely using only these jets, mission managers want to conserve precious fuel. At this lowest orbit, using two of the reaction wheels to help with pointing will provide the biggest hydrazine savings. So Dawn will be spinning up two of the gyroscope-like devices to aid the thrusters.
In 2011, the Dawn team prepared the capability to operate in a hybrid mode, but it wasn't needed during the Vesta mission. It was only when a second (of four) reaction wheels developed excessive friction while Dawn was leaving Vesta in 2012 that mission managers decided to use the hybrid mode at Ceres. To prove the technique works, Dawn engineers completed a 27-hour in-flight test of the hybrid mode, ending on Nov. 13. It operated just as expected.
"The successful test of this new way to control our orientation gives us great confidence that we'll have a steady hand at Ceres, which will enable us to get really close to a world that we only know now as a fuzzy dot amidst the stars," said Marc Rayman, Dawn's chief engineer and mission director, based at JPL.
Of course, mission planners have built some extra days into the schedule to account for the small uncertainty in the efficiency of the solar arrays at such a large distance from the sun, where sunlight will be very faint. The solar arrays provide power to the ion propulsion system, in addition to operating power for the spacecraft and instruments. Mission planners also account for potential variations in the gravity field of Ceres, which will not be known precisely until Dawn measures them.
"We are expecting changes when we get to Ceres and, fortunately, we built a very capable spacecraft and developed flexible plans to accommodate the unknowns," said Rayman. "There's great excitement in the unexpected -- that's part of the thrill of exploration."
Starting on Dec. 27, Dawn will be closer to Ceres than it will be to Vesta.
"This transition makes us eager to see what secrets Ceres will reveal to us when we get up close to this ancient, giant, icy body," said Christopher Russell, Dawn's principal investigator, based at UCLA. "While Ceres is a lot bigger than the candidate asteroids that NASA is working on sending humans to, many of these smaller bodies are produced by collisions with larger asteroids such as Ceres and Vesta. It is of much interest to determine the nature of small asteroids produced in collisions with Ceres. These might be quite different from the small rocky asteroids associated with Vesta collisions."
Dawn's mission is managed by JPL for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Ala. UCLA is responsible for overall Dawn mission science. Orbital Sciences Corp. in Dulles, Va., designed and built the spacecraft. The German Aerospace Center, the Max Planck Institute for Solar System Research, the Italian Space Agency and the Italian National Astrophysical Institute are international partners on the mission team. The California Institute of Technology in Pasadena manages JPL for NASA.
To learn more about hybrid mode at Ceres, read Rayman's Dawn Journal [link].
For more information about Dawn, visit: http://www.nasa.gov/dawn and http://dawn.jpl.nasa.gov .
To learn more about hybrid mode at Ceres, read Rayman's Dawn Journal .
News Media ContactJia-Rui Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif. | 0.844061 | 3.873502 |
(click to enlarge)
Five billion years from now, our Milky Way galaxy will collide with the Andromeda galaxy. This will mark a moment of both destruction and creation. The galaxies will lose their separate identities as they merge into one. At the same time, cosmic clouds of gas and dust will smash together, triggering the birth of new stars. To understand our past and imagine our future, we must understand what happens when galaxies collide. But since galaxy collisions take place over millions to billions of years, we can’t watch a single collision from start to finish. Instead, we must study a variety of colliding galaxies at different stages. By combining recent data from two space telescopes, astronomers are gaining fresh insights into the collision process.
“We’ve assembled an atlas of galactic ‘train wrecks’ from start to finish. This atlas is the first step in reading the story of how galaxies form, grow, and evolve,” said lead author Lauranne Lanz of the Harvard-Smithsonian Center for Astrophysics (CfA).
Lanz presented her findings today in a press conference at the 218th meeting of the American Astronomical Society.
The new images combine observations from NASA‘s Spitzer Space Telescope, which observes infrared light, and NASA‘s Galaxy Evolution Explorer (GALEX) spacecraft, which observes ultraviolet light. By analyzing information from different parts of the light spectrum, scientists can learn much more than from a single wavelength alone, because different components of a galaxy are highlighted.
GALEX‘s ultraviolet data captures the emission from hot young stars. Spitzer sees the infrared emission from warm dust heated by those stars, as well as from stellar surfaces. Therefore, GALEX‘s ultraviolet data and Spitzer’s infrared data highlight areas where stars are forming most rapidly, and together permit a more complete census of the new stars.
In general, galaxy collisions spark star formation. However, some interacting galaxies produce fewer new stars than others. Lanz and her colleagues want to figure out what differences in physical processes cause these varying outcomes. Their findings will also help guide computer simulations of galaxy collisions.
“We’re working with the theorists to give our understanding a reality check,” said Lanz. “Our understanding will really be tested in five billion years, when the Milky Way experiences its own collision.” | 0.837055 | 3.740508 |
Earlier this week, skywatchers in the southern U.S. got to see the crescent moon cover or “occult” the star Zeta Tauri. Friday night (May 10) the moon will be at it again but this time will pass in front of the Beehive, a bright star cluster in Cancer. Good news. Occultations will be visible over a much wider area — across the eastern two-thirds of the U.S. and Canada, Central America and eastern South America.
On a dark night, the Beehive looks like a fuzzy spot with the naked eye and a beautiful splash of stars in a pair of binoculars. Friday evening, the 6-day-old moon will slowly glide over the cluster from west to east, covering and uncovering stars as it goes. About a dozen brighter stars — between magnitude 6 and 7.5 — lie in its path. All of these should be easy to watch disappear through a small telescope.
The entire show lasts between 2 and 3 hours. East Coast viewers will see it happen in a dark sky starting around 9:30 p.m. local time and ending around midnight. If you live in the Midwest you can start watching as soon as mid-twilight or about 9 p.m. By the time darkness falls in the mountain states, the moon will have already made it halfway through the cluster. Observers there should begin their watch around 8:30 p.m. to make the best of the remaining occultations. Only those living in the Pacific time zone won’t see the event — by the time it’s dark enough, the moon will have departed the Beehive.
During an occultation, the dark edge of the moon (called the “limb”) slowly approaches a star. Before it’s occulted, the star seems to hover over the limb for an eternity, and then just like that, it’s gone in a split second. The slow approach vs. the sudden disappearance makes for exciting viewing. Although the moon’s phase is approaching half, there will still be enough earthshine to make the dark limb of the moon stand out against the sky, the better to anticipate when a star will be covered. One tip. When observing occultations, place the bright part of the moon out of the field of view to better see the earth-lit limb without the glare.
Depending on your location the moon will take a slightly different path across the Beehive. From the northern U.S., it passes a little south of the cluster’s core; from the Caribbean, it passes directly over the center, and from the northern half of South America, north of center. Each of us has a unique perspective! That’s because the moon is close enough to Earth that its position shifts relative to the background stars when seen from different places across the planet.
A star disappears so suddenly when it’s occulted because the moon has very little atmosphere. If an astronaut on the moon were watching Earth occult a star, it would slowly fade before it disappeared, filtered by the air, water and dust that comprise our planet’s atmosphere.
Watching occultations also allows us to see the moon move in real time. It orbits the Earth with an average speed of 2,288 mph (3,680 kph), but we’re normally not aware of how fast that is because the moon is so far away. We only detect its slow eastward creep over the hours. But when the moon covers a star you see that rapid motion in real time, with the star covered in an instant! That said, remember it will take time for the moon to crawl toward each star, so the whole show will last a long time.
Cross your fingers for clear skies Friday, May 10. If you don’t have a scope you can still see a bunch of stars near the moon, but if you do have a telescope, take some time and see if you can watch a stellar bee or two disappear. | 0.805045 | 3.351191 |
Ancient cultures around the world believed that consciousness and history move in a vast cycle of time with alternating Dark and Golden Ages – Plato called it the Great Year.
Today we know it as one “precession of the equinox,” an obscure astronomical motion, and most consider the Golden Age to be just a myth.
But are we correct? An increasing amount of scientific evidence suggests that long before the Dark Ages, mankind had a deep understanding of astronomy, mathematics, holistic healing, and a profound ability to live in tune with nature.”
I hope that by calling attention to new research more people will become aware that the ancient teachings of the Yugas, cycles of time that affect our earth and human history, are increasingly supported by scientific discovery.
Restructuring the Solar System
One recent discovery of interest is 2012VP113, nicknamed Biden, a dwarf planet about 450 km in diameter found to be orbiting our sun in a pattern quite similar to Sedna, one
of the largest dwarfs, discovered in 2002. Mike Brown, an astrophysicist at Caltech, famed for killing Pluto by his discovery of so many of these minor planets, was the first to note that Sedna cannot exist in its current position without the gravitational help of some unseen body.
The discovery of Biden only underlines this point and heightens the quest for a large mass affecting our solar system. But where and how big?
Two Spanish astronomers, Carlos and Raul de la Fuente Marcos, at the Complutense University of Madrid in Spain, have examined these distant dwarfs and noticed some unusual patterns.
They have concluded that because Biden and Sedna are not large enough to exert much influence on each other, they must be kept in their place by not one but two large undiscovered planets that each has a mass of at least ten times that of the earth.
Furthermore, these mega planets are required to be at least 200 to 250 AU away from the sun (one AU or astronomical unit is equivalent to the distance between the sun and the earth).
The Binary Research Institute has long hypothesized that there must be another large mass, most likely a companion star, that affects our solar system.
In BRI’s view, such a mass is required not only to explain the incline of these outer dwarf planet orbits to the plane of the major planets (for example Pluto’s orbit is inclined about 17 degrees) but also as a way to explain the changing orientation of the entire solar system to the fixed stars by about 50 arc seconds per year, a.k.a. precession.
In such a model the orbits of these dwarfs are not unexpected. While the Spanish astronomers are not saying the mass affecting our solar system is a companion star, their assumptions concerning the large mass and great distance of their hypothetical planets, are clearly moving us in BRI’s direction.
Year by year mainstream astronomy is getting closer to the idea there must be something big out there, and it is influencing our solar system in ways heretofore unknown.
But it is not just the position of these orbits that is so interesting. The most confirming fact from a Great Year perspective is that the orbital periods of these new dwarf planets are in resonance with known Great Year periodicities. And the Spanish astronomers are indeed talking about these resonances.
Planets or moons moving in resonance with one another are a sign of gravitational influences and an indication that these bodies have been dancing together for very long periods of time – and not just due to some random star passing by disturbing a planet out of its orbit.
As stated, the resonances of the newly discovered dwarfs are quite confirming to anyone studying the 24,000-year precessional cycle.
For example, Sedna orbits the sun in 12,000 years, once per Yuga or twice per Yuga cycle (one complete precessional cycle after applying Kepler’s laws to the current observed rate of about 25,770 years).
And Biden’s orbit is in a 3:1 ratio to Sedna, meaning it orbits the sun three times per Yuga, and six times in a complete Yuga cycle.
For those that study planetary resonances and understand the Great Year cycle, this supports the 24,000-year precession cycle to a tee!
Commenting in NewScientist on the dwarf planets that are raising all this attention, Scott Shepard of the Carnegie Institution for Science, and one of the discoverers of Biden, said,
“As there are only a few of these extremely distant objects known, it’s hard to say anything definitive about the number or location of any distant planets, however, in the near future we should have more objects to work with to help us determine the structure of the outer solar system.”
From the point of view of this Yuga observer that “structure” will eventually be found to contain a mass equivalent to a companion star. This mass, which along with our sun, appears to complete one revolution through the constellations of the zodiac in about 24,000 years.
Please note, we mention the zodiac here only because it serves as a way to measure the observed motion of the sun as it moves through the sky. The sun, observed at the same time each year, can be seen to move through these twelve constellations at the rate of about 2000 years each. The pieces are coming together!
If it is realized that our solar system is being influenced by a large mass, such as a companion star, then we have the necessary ingredients for a vast cycle of time as described by so many ancient civilizations.
Just as the celestial driven cycles of day and night, every 24 hours, and of the seasons, every year, cause an ebb and flow that affects all life, so too would there finally be a known celestial cause for the heretofore mythical Great Year.
Known to the Indians as the Yuga cycle with its distinct periods of rising and falling ages, and to the Greeks that broke these epochs into the Iron, Bronze, Silver and Golden Ages, ancient cultures around the world seemed to accept this cycle as a way of life.
If we find the solar system is not quite as we had thought we just might find that history too will be recast in a different light. Perhaps then our old myths of a long lost higher age won’t be so easily discarded. Small planets do matter.
By Walter Cruttenden, Ancient Origins;
To learn more about this topic please join us at the 9th annual Conference on Precession and Ancient Knowledge this October 17-19 in Rancho Mirage, California. Our speakers include: Dr. Dean Radin, Walter Cruttenden, Dr. Robert Schoch, Laird Scranton, Marie D. Jones, Dr. Amit Goswami and many more! www.CPAKonline.com or phone Sandy at 949-399-9000.
This article is published with the permission of Ancient-Origins.net. They release the most up to date news and articles relating to ancient human origins, archaeology, anthropology, lost civilizations, scientific mysteries, sacred writings, ancient places and more. | 0.898038 | 3.474331 |
If intelligent life is out there, it probably resides in a solar system with many planets. The more planets a star has, a recent study found, the more circular the orbits tend to be. Because planets on circular orbits do not move toward or away from their star, their climates may be stable enough to foster advanced life.
Our own solar system fits that pattern. The sun has eight or nine planets (depending on how you count), and most of them have fairly circular paths. Earth's orbit, for example, has an eccentricity of just 1.7 percent. (Eccentricity ranges from 0 percent for a perfect circle to nearly 100 percent for extreme ellipses.) Mercury and Pluto pursue oval-shaped orbits, with eccentricities of 21 and 25 percent, respectively, but even Pluto—whose planetary status is controversial—seems tame when compared with many of the planets orbiting other stars, where eccentricities can exceed 60, 70, even 80 percent.
As far as we know, such wild worlds exist only in solar systems with one or two planets, say astronomers Mary Anne Limbach and Edwin L. Turner of Princeton University, who conducted the study. In contrast, solar systems with four or more planets feature moderately round orbits. The conclusions, based on 403 planets with previously measured orbital eccentricities in hundreds of solar systems, appeared in January in the Proceedings of the National Academy of Sciences USA.
Jack Lissauer, a planetary scientist at the nasa Ames Research Center, notes that the newfound correlation makes sense because planets on circular orbits do not interfere much with one another. A planet on an elongated path, on the other hand, can “mess up the orbits of the other planets and kick them out [of the system],” Limbach says.
These planetary road hogs do not make good abodes themselves. When near their sun, they fry; when far away, they freeze. Thus, intelligent beings are more likely to prosper on planets with circular orbits. Such beings would see many other worlds orbiting their star, just as we do—and may even bicker over which ones are truly planets. | 0.838212 | 3.535986 |
Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at the globular cluster known as Messier 30. Enjoy!
During the 18th century, famed French astronomer Charles Messier noted the presence of several “nebulous objects” in the night sky. Having originally mistaken them for comets, he began compiling a list of them so that others would not make the same mistake he did. In time, this list (known as the Messier Catalog) would come to include 100 of the most fabulous objects in the night sky.
One of these objects is Messier 30, a globular cluster located in the southern constellation of Capricornus. Owing to its retrograde orbit through the inner galactic halo, it is believed that this cluster was acquired from a satellite galaxy in the past. Though it is invisible to the naked eye, this cluster can be viewed using little more than binoculars, and is most visible during the summer months.
Messier measures about 93 light years across and lies at a distance of about 26,000 light years from Earth, and approaching us at a speed of about 182 kilometers per second. While it looks harmless enough, its tidal influence covers an enormous 139 light years – far greater than its apparent size.
Half of its mass is so concentrated that literally thousands of stars could be compressed in an area that spans no further than the distance between our solar system and Sirius! However, inside this density only 12 variable stars have been found and very little evidence of any stellar collisions, although a dwarf nova has been recorded!
So what’s so special about this little globular? Try a collapsed core – and one that’s even been resolved by Earth-bound telescopes. According to Bruce Jones Sams III, an astrophysicists at Harvard University:
“The globular cluster NGC 7099 is a prototypical collapsed core cluster. Through a series of instrumental, observational, and theoretical observations, I have resolved its core structure using a ground based telescope. The core has a radius of 2.15 arcsec when imaged with a V band spatial resolution of 0.35 arcsec. Initial attempts at speckle imaging produced images of inadequate signal to noise and resolution. To explain these results, a new, fully general signal-to-noise model has been developed. It properly accounts for all sources of noise in a speckle observation, including aliasing of high spatial frequencies by inadequate sampling of the image plane. The model, called Full Speckle Noise (FSN), can be used to predict the outcome of any speckle imaging experiment. A new high resolution imaging technique called ACT (Atmospheric Correlation with a Template) was developed to create sharper astronomical images. ACT compensates for image motion due to atmospheric turbulence.”
Photography is an important tool for astronomers to work with – both land and space-based. By combining results, we can learn far more than just from the results of one telescope observation alone. As Justin H. Howell wrote in a 1999 study:
“It has long been known that the post-core-collapse globular cluster M30 (NGC 7099) has a bluer-inward color gradient, and recent work suggests that the central deficiency of bright red giant stars does not fully account for this gradient. This study uses Hubble Space Telescope Wide Field Planetary Camera 2 images in the F439W and F555W bands, along with ground-based CCD images with a wider field of view for normalization of the noncluster background contribution. The quoted uncertainty accounts for Poisson fluctuations in the small number of bright evolved stars that dominate the cluster light. We explore various algorithms for artificially redistributing the light of bright red giants and horizontal-branch stars uniformly across the cluster. The traditional method of redistribution in proportion to the cluster brightness profile is shown to be inaccurate. There is no significant residual color gradient in M30 after proper uniform redistribution of all bright evolved stars; thus, the color gradient in M30’s central region appears to be caused entirely by post-main-sequence stars.”
So what happens when you dig even deeper with a different type of photography? Just ask the folks from Chandra – like Phyllis M. Lugger, who wrote in her study, “Chandra X-ray Sources in the Collapsed-Core Globular Cluster M30 (NGC 7099)“:
“We report the detection of six discrete, low-luminosity X-ray sources, located within 12” of the center of the collapsed-core globular cluster M30 (NGC 7099), and a total of 13 sources within the half-mass radius, from a 50 ks Chandra ACIS-S exposure. Three sources lie within the very small upper limit of 1.9” on the core radius. The brightest of the three core sources has a blackbody-like soft X-ray spectrum, which is consistent with it being a quiescent low-mass X-ray binary (qLMXB). We have identified optical counterparts to four of the six central sources and a number of the outlying sources, using deep Hubble Space Telescope and ground-based imaging. While the two proposed counterparts that lie within the core may represent chance superpositions, the two identified central sources that lie outside of the core have X-ray and optical properties consistent with being cataclysmic variables (CVs). Two additional sources outside of the core have possible active binary counterparts.”
History of Observation:
When Charles Messier first encountered this globular cluster in 1764, he was unable to resolve individual stars, and mistakenly believed it to be a nebula. As he wrote in his notes at the time:
“In the night of August 3 to 4, 1764, I have discovered a nebula below the great tail of Capricornus, and very near the star of sixth magnitude, the 41st of that constellation, according to Flamsteed: one sees that nebula with difficulty in an ordinary [non-achromatic] refractor of 3 feet; it is round, and I have not seen any star: having examined it with a good Gregorian telescope which magnifies 104 times, it could have a diameter of 2 minutes of arc. I have compared the center with the star Zeta Capricorni, and I have determined its position in right ascension as 321d 46′ 18″, and its declination as 24d 19′ 4″ south. This nebula is marked in the chart of the famous Comet of Halley which I observed at its return in 1759.”
However, we cannot fault Messier, for his job was to hunt comets and we thank him for logging this object for further study. Perhaps the first clue to M30’s underlying potential came from Sir William Herschel, who often studied Messier’s objects, but did not report his findings formally. In his personal notes he wrote:
“A brilliant cluster, the stars of which are gradually more compressed in the middle. It is insulated, that is, none of the stars in the neighborhood are likely to be connected with it. Its diameter is from 2’40” to 3’30”. The figure is irregularly round. The stars about the centre are so much compressed as to appear to run together. Towards the north, are two rows of bright stars 4 or 5 in a line. In this accumulation of stars, we plainly see the exertion of a central clustering power, which may reside in a central mass, or, what is more probable, in the compound energy of the stars about the centre. The lines of bright stars, although by a drawing made at the time of observation, one of them seems to pass through the cluster, are probably not connected with it.”
So, as telescopes progressed and resolution improved, so did our way of thinking about what we were seeing… By Admiral Smyth’s time, things had improved even more and so had the art of understanding more:
“A fine pale white cluster, under the creature’s caudal fin, and about 20 deg west-north-west of Fomalhaut, where it precedes 41 Capricorni, a star of 5th magnitude, within a degree. This object is bright, and from the straggling streams of stars on its northern verge, has an elliptical aspect, with a central blaze; and there are but few other stars, or outliers, in the field.
“When Messier discovered this, in 1764, he remarked that it was easily seen with a 3 1/2-foot telescope, that it was a nebula, unaccompanied by any star, and that its form was circular. But in 1783 it was attacked by WH [William Herschel] with both his 20-foot Newtonians, and forthwith resolved into a brilliant cluster, with two rows pf stars, four or five in a line, which probably belong to it; and therefore he deemed it insulated. Independently of this opinion, it is situated in a blankish space, one of those chasmata which Lalande termed d’espaces vuides, wherein he could not perceive a star of the 9th magnitude in the achromatic telescope of sixty-seven millimetres aperture. By a modification of his very ingenious gauging process, Sir William considered the profundity of this cluster to be of the 344th order.
“Here are materials for thinking! What an immensity of space is indicated! Can such an arrangement be intended, as a bungling spouter of the hour insists, for a mere appendage to the speck of a world on which we dwell, to soften the darkness of its petty midnight? This is impeaching the intelligence of Infinite Wisdom and Power, in adapting such grand means to so disproportionate an end. No imagination can fill up the picture of which the visual organs afford the dim outline; and he who confidently probes the Eternal Design cannot be many removes from lunacy. It was such a consideration that made the inspired writer claim, “How unsearchable are His operations, and His ways past finding out!”
Throughout all historic observing notes, you’ll find notations like “remarkable” and even Dreyer’s famous exclamation points. Even though M30 may not be the easiest to find, nor the brightest of the Messier objects, it is still quite worthy of your time and attention!
Locating Messier 30:
Finding M30 is not an easy task, unless you’re using a GoTo telescope. In any other case, it’s a starhop process, which must begin with identifying the the big grin-shape of the constellation of Capricornus. Once you’ve separated out this constellation, you’ll begin to notice that many of its primary asterism stars are paired – which is a good thing! The northeastern most pair are Gamma and Delta, which is where binocular-users should start.
As you move slowly south and slightly west, you’ll encounter your next wide pair – Chi and Epsilon. The next southwestern set is 36 Cap and Zeta. Now, from here you have two options! You can find Messier 30 a little more than a finger width east(ish) of Zeta (about half a binocular field)… or, you can return to Epsilon and look about one binocular field south (about 3 degrees) for star 41 which will appear just east of Messier 30 in the same field of view.
For the finderscope, star 41 is a critical giveaway to the globular cluster’s position! It won’t be visible to the unaided eye, but even a little magnification will reveal its presence. Using binoculars or a very small telescope, Messier 30 will appear as only a small, faded gray ball of light with a small star beside it. However, with telescope apertures as small as 4″ you’ll begin some resolution on this overlooked globular cluster and larger apertures will resolve it nicely.
And here are the quick facts on Messier 30 to help you get started:
Object Name: Messier 30
Alternative Designations: M30, NGC 7099
Object Type: Class V Globular Cluster
Right Ascension: 21 : 40.4 (h:m)
Declination: -23 : 11 (deg:m
Distance: 26.1 (kly)
Visual Brightness: 7.2 (mag)
Apparent Dimension: 12.0 (arc min)
We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects, , M1 – The Crab Nebula, M8 – The Lagoon Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons. | 0.908492 | 3.858063 |
Early this morning, at 09:12 UTC, the cloudy pre-dawn sky above the coastal town of Kourou, French Guiana was brilliantly sliced by the fiery exhaust of a Soyuz VS06, which ferried ESA’s “billion-star surveyor” Gaia into space to begin its five-year mission to map the Milky Way.
Ten minutes after launch, after separation of the first three stages, the Fregat upper stage ignited, successfully delivering Gaia into a temporary parking orbit at an altitude of 175 km (108 miles). A second firing of the Fregat 11 minutes later took Gaia into its transfer orbit, followed by separation from the upper stage 42 minutes after liftoff. 46 minutes later Gaia’s sunshield was deployed, and the spacecraft is now cruising towards its target orbit around L2, a gravitationally-stable point in space located 1.5 million km (932,000 miles) away in the “shadow” of the Earth.
The launch itself was really quite beautiful, due in no small part to the large puffy clouds over the launch site. Watch the video below:
A global space astrometry mission, Gaia will make the largest, most precise three-dimensional map of our galaxy by surveying more than a billion stars over a five-year period.
“Gaia promises to build on the legacy of ESA’s first star-mapping mission, Hipparcos, launched in 1989, to reveal the history of the galaxy in which we live,” says Jean-Jacques Dordain, ESA’s Director General.
Repeatedly scanning the sky, Gaia will observe each of the billion stars an average of 70 times each over the five years. (That’s 40 million observations every day!) It will measure the position and key physical properties of each star, including its brightness, temperature and chemical composition.
By taking advantage of the slight change in perspective that occurs as Gaia orbits the Sun during a year, it will measure the stars’ distances and, by watching them patiently over the whole mission, their motions across the sky.
The motions of the stars can be put into “rewind” to learn more about where they came from and how the Milky Way was assembled over billions of years from the merging of smaller galaxies, and into “fast forward” to learn more about its ultimate fate.
“Gaia represents a dream of astronomers throughout history, right back to the pioneering observations of the ancient Greek astronomer Hipparchus, who catalogued the relative positions of around a thousand stars with only naked-eye observations and simple geometry. Over 2,000 years later, Gaia will not only produce an unrivaled stellar census, but along the way has the potential to uncover new asteroids, planets and dying stars.”
– Alvaro Giménez, ESA’s Director of Science and Robotic Exploration
Of the one billion stars Gaia will observe, 99% have never had their distances measured accurately. The mission will also study 500,000 distant quasars, search for exoplanets and brown dwarfs, and will conduct tests of Einstein’s General Theory of Relativity.
“Along with tens of thousands of other celestial and planetary objects,” said ESA’s Gaia project scientist Timo Prusti, “this vast treasure trove will give us a new view of our cosmic neighbourhood and its history, allowing us to explore the fundamental properties of our Solar System and the Milky Way, and our place in the wider Universe.”
Follow the status of Gaia on the mission blog here. | 0.926362 | 3.779224 |
It wouldn't need to turn as fast to stay focused, maybe increasing the lifetime of its reaction wheels.
On Earth when you "turn" a telescope, you are really keeping it pointed in one direction! It's the Earth that's turning, and you have to turn the telescope mount to keep the legs pointed at the ground.
It's the same thing as having to move the antenna to keep it pointed at the ground!
As an aside, how do space telescopes handle pointing antennas at earth?
GAIA uses a phased array that can always beam towards earth as the telescope rotates (see this answer), and TESS stores, compresses and processes almost two weeks of data while measuring near apoapsis, then zooms past Earth and sends it in an 8 hour burst during periapsis. (See this answer and this answer).
In space you don't turn a telescope, you leave it mostly alone and it nearly keeps pointing in one direction. There are small tidal forces especially in LEO (see this answer), and other torques like solar pressure (see this answer) that will very slowly tilt a telescope, so the reaction wheels have to handle that.
But there is no major space-telescope-turning necessary to compensate for Earth's rotation. That's strictly an "Earth thing".
Why aren't space telescopes put in GEO?
It's a crowded place, and there's a lot of "space citizenship" necessary to stay there. You have to worry very much about station-keeping in order not to drift near any of your ultra-expensive hardware neighbors, and that can interfere with science scheduling.
A communications satellite can do stationkeeping at the same time it serves its primary function because its antennas don't need to be pointed with arc-second stability like an optical telescope would.
It took a lot of work to boost Hubble up to 540 kilometers above much of the atmosphere so that it wouldn't have to do station-keeping burns. Putting it in GEO could actually force it to do more station keeping, exactly opposite of what you want.
The chance that a future big-science optical or radio space telescope for Astronomy will be put in LEO or GEO as the best place for it is very small. These days spacecraft reliability is very high, on-board computing and image processing can sort and pre-process data somewhat, and X-band links even in deep space can do data-dumps during short periods of time. See this answer and this answer.
While MEO could avoid station-keeping that would be necessary in LEO or GEO, I think most telescopes will be much farther from Earth's reflected light and radiated heat, either like TESS which spends most of it's time almost as far from Earth as the Moon, or JWST out near Sun-Earth L2.
The moon is another option. Without any atmosphere so a UV telescope (like those on the Chang'e landers) or IR telescope could work there without needing to be attached to a spacecraft. A radio telescope on the far side would also be shielded from artificial electromagnetic radiation from the Earth, as well as light and heat from the Sun during the two week long lunar night.
There are so many places to put future telescopes, I don't think we'll see any major ones in LEO or GEO. The only reason for GEO would be a low-budget, like a cubesat or nanosatellite project where one uses a low-cost multi-satellite release (see this answer or this question or this question (not everyone can see it, you can also get an idea by looking at this question). | 0.820445 | 3.531983 |
Up for a challenge? Some of the toughest targets for a backyard observer involve little or no equipment at all. Northern hemisphere Spring brings with it one of our favorite astronomical pursuits: the first sighting of the extremely thin, waxing crescent Moon. This unique feat of visual athletics may be fairly straight forward, requiring nothing more than a working pair of Mk-1 eyeballs… but it’s tougher than you think. The angle of the evening ecliptic in the Spring is still fairly high for mid-northern latitudes, taking the Moon up and out of the weeds when it reaches waxing crescent phase.Continue reading “Astro-Challenge: Spotting Slender Moons”
Earlier this week, Universe Today challenged North American readers to spot the slender, exceptionally “young” crescent Moon on the evening of New Year’s Day.
Three visual athletes based in Arizona took up the challenge on Wednesday evening, with amazing results. Mike Weasner, Rob Sparks and Jim Cadien managed to spot the razor thin crescent Moon just 13 hours and 48 minutes after it passed New phase earlier on January 1st. The sighting was made using binoculars, and they even managed to image the wisp of a crescent hanging against the desert sky.
This is a difficult feat, even under the best of conditions. Weasner and Sparks observed from Mike’s Cassiopeia observatory based just outside of Oracle, Arizona.
Concerning the feat, Weasner wrote on his observing blog:
“At 1800 Mountain Standard Time (MST), Rob reported that he had located the young Moon using his 8×42 binoculars. At 18:02 MST, I picked it up in the 12×70 binoculars. With the New Moon occurring at 11:14 Universal Time (UT), my observation occurred with the Moon only 13 hours and 48 minutes old. A new record for me (and Rob and Jim as well). Our DSLRs were clicking away!”
We can personally attest to just how hard it is to pick out the uber-thin crescent Moon against the twilight sky. Low contrast is your enemy, making it tough to spot and even tougher to photograph. Add to that a changing twilight sky that alters hue from moment to moment.
Though this isn’t a world record, its close to within about two hours. The youngest confirmed Moon spotting using binoculars stands at 11 hours and 40 minutes accomplished by Mohsen G. Mirsaeed in Iran back in September 7th, 2002, and the youngest Moon sighted with the unaided eye goes to Steven James O’Meara in May 1990, who spotted a 15 hour 32 minute old crescent.
And of course, you can see the Moon at the moment of New during a a solar eclipse. Unfortunately, no total solar eclipses occur in 2014, just an usual non-central annular eclipse brushing Australia and Antarctica on April 29th and a deep 81% partial eclipse crossing North America on October 23rd.
Weasner also noted that a bright Venus aided them in their quest. It’s strange to think that Venus, though visually tiny, is actually intrinsically brighter than the limb of the Moon, owing to its higher albedo. In fact, some great pictures have also been pouring in to Universe Today of Venus as it heads towards inferior conjunction this month on January 11th. And don’t forget, that quoted magnitude of the lunar crescent (about magnitude -3.4) was also scattered along the lunar disk which was only 0.4% illuminated, and subject to atmospheric extinction to boot!
And yes, it is possible to catch the Moon photographically during a non-eclipse at the moment of New phase. The Moon can wander up to 5 degrees – about ten times its average apparent diameter as seen from the Earth – above or below the ecliptic and appear a corresponding distance from the limb of the Sun. Unlike many moons in the solar system, Earth’s moon has a fixed inclination to our orbit (as traced out by the ecliptic,) not our rotational axis. Thierry Legault accomplished this challenging photographic feat last year. Of course, this should only be attempted by seasoned astrophotographers, as aiming a camera near the Sun is not advised.
Why attempt to spot the razor thin New Moon? What’s the benefit? Well, several lunar based dating systems, such as the Islamic calendar, rely on the spotting of the new crescent Moon to mark the beginning of a new month. Being strictly lunar-based, the Islamic calendar moves an average of -11 days out of sync each year versus the modern day Gregorian calendar. On some years, there can even be a bit of ambiguity as to exactly when key months such as Ramadan will begin based on when the Moon is first sighted.
Also, such a feat demonstrates what the human eye is capable of when pushed to its physiological limits. In fact, French astrophysicist Andre Danjon theorized that the lunar crescent is formed at about 5 degrees elongation from the Sun, a point beyond which a lunar crescent can be sighted — usually quoted at about 7 degrees elongation from the Sun — and has become known as the Danjon Limit. Danjon also gave his namesake to the characterization of total lunar eclipses by color and hue, known as the Danjon Number. Accounting for the motion of the Moon, this places the theoretical limit that the forming crescent can be sighted with optical assistance at just over 11 hours.
And you don’t have to wait until the Moon passes New… a similar attempt can be made in the dawn skies as the waning crescent Moon slides towards the Sun at the end of each lunation.
But perhaps the true reward is simply catching a glimpse of the ethereal for yourself, a delicate and airy Moon clinging briefly on the horizon. Kudos to Mike and Rob on a great catch!
The South African Astronomical Observatory also maintains a site with predictions worldwide. | 0.819006 | 3.232172 |
Update: On the morning of October 5, 2017, Conjunction Morning!
The Venus-Mars Conjunction of November 3, 2015.
The Venus-Mars Encounter, February 3, 2017. (There was no conjunction. Venus approached Mars and then moved away. This was the closest approach)
Mars and Venus were last in conjunction on November 3, 2015 when they were about 3/4 degree apart. As with the last conjunction the 2017 conjunction occurs in a sky full of planets as noted here. Also note that these conjunctions occur farther east along the solar system’s (ecliptic) plane.
As Venus heads toward its solar superior conjunction, it passes Mars on the morning of October 5. Conjunctions of Venus and the visible outer planets (Mars. Jupiter, and Saturn) can occur when Venus is within 47 degrees of the sun, its greatest angular separation from the sun. Because Mars is small and its brightness greatly varies depending on its distance from Earth, Mars is dim when it appears near Venus. (Note this in the two images at the top of this article.) A Venus-Mars conjunction cannot occur when Mars is near opposition and at its brightest. For more about the Mars appearance and its opposition, see 2017-2019: Mars Observing Year with a Perihelic Opposition, July 27, 2018 and 2018: Mars Perihelic Opposition.
Mars’ separation from the sun has grown to 23 degrees after its solar conjunction on July 27, 2017. Earth is slowly catching Mars, yet opposition is months away. From this scale drawing notice that Venus’ orbit is closer to Earth than Mars.
On conjunction morning the separation of the pair is about one-fourth of a degree. This would be spectacular conjunction if Mars were brighter. The planets are close for a few mornings before and after this close passing.
Future Venus-Mars Conjunctions
The next six conjunctions are summarized below:
|August 24, 2019||0.31 degree (d)||Venus and Mars are 3 degrees east of the sun, setting just minutes after sunset. This conjunction is not visible.|
|July 13, 2021||0.49 d||The pair is in the evening sky, setting about 90 minutes after sunset. Look low in the western sky. Regulus is about 10 degrees to the upper left of the Venus and a four-day-old waxing crescent moon is 20 degrees to upper left of Venus. Just 2 nights before the closest conjunction look for the moon near Venus (6 degrees)|
|February 13, 2022||6.58 d||This widely spaced conjunction occurs in the morning with the pair rising 2.5 hours before the sun. Feb 13 is the date the of the conjunction, although the pair is closest on February 19, 5.8 degrees. (Conjunctions are defined in at least 3 ways.)|
|March 12, 2022||3.99 d||This conjunction is a continuation of the close approach that starts in early 2022 in the morning sky. The first conjunction is noted above and the planets continue to be close together for many mornings. The pair is close again on March 16, 3.8 degrees|
|February 22, 2024||0.63 d||Venus and Mars rise about 35 minutes before the sun during bright twilight. To see this conjunction, optical assistance, binoculars or telescope, is needed.|
|January 8, 2026||0.17 d||This conjunction is closer than the 2017 conjunction, but the planets are 1 degree from the sun, hidden in the sun’s brilliance.|
From this list, the 2021 conjunction and the widely spaced conjunctions in 2022, with an extended period when the two planets appear together, are the best times to see Venus and Mars close together during the next decade. | 0.82667 | 3.578339 |
NASA's Osiris-Rex spacecraft has beenfor several weeks now, and its latest batch of data shows a tiny world that's not quite what scientists expected.
Analysis of the surface shows Bennu is between 100 million and a billion years old, making it a significantly more senior celestial body than predicted. It may have formed out of the debris from some ancient cosmic collision involving a larger object in the main asteroid belt eons ago.
But the biggest and most confounding discovery from the first-ever close-up views of Bennu is that it's kind of a mess. Based on earlier observations from telescopes, scientists had expected the asteroid to have some relatively wide, smooth spots ideal for swiping a sample to bring back to Earth. Instead, its surface looks to be strewn with all kinds of large boulders, including at least one the size of a supermarket at 58 meters (190 feet) in diameter that could be an asteroid in its own right.
"Bennu does not contain the extensive patches of fine-grained regolith according to which we designed the mission," the Osiris-Rex team said in a research letter published in the journal Nature on Tuesday.
Measurements from the Osiris-Rex cameras confirm previous estimations that Bennu is one of the darkest known objects in the solar system, which is another factor that's not exactly helpful for navigation. As if that weren't enough to worry about, there seem to be some floating particles around the asteroid to watch out for.
The particles seem to be ejected from the surface of the asteroid itself, something that surprised scientists.
"The discovery of plumes is one of the biggest surprises of my scientific career," said Dante Lauretta, Osiris-Rex principal investigator, in a statement.
During a call with media Tuesday, Osiris-Rex project manager Rich Burns said that analysis performed after the particles were first spotted helped determine that they didn't pose an immediate threat to the spacecraft.
The team will still move forward and select two possible sample sites in areas that are relatively free of any hazards to the spacecraft, though it doesn't look like the sites will be the nice, open parking lot-size spaces it'd originally planned for.
"That task looks more challenging than we expected," the team said in the letter. "Regardless of the final site selected, the requirements for guidance, navigation and control accuracy need to be tightened."
Ingredients for life?
Overall, the emerging picture of Bennu is of a large, black asteroid littered with boulders of all sizes, pocked with craters and sprinkled with a layer of dust and other small particles.
But analyzing what lies within the small world reveals the presence of some exciting things that scientists were hoping to find.
Another new paper examines the mineral composition of Bennu and finds a number of elements that make up the building blocks of life, including molecules of water and its components. A popular theory holds that water and other key molecules that make Earth habitable may have been originally delivered to the surface of our planet by primordial asteroid and comet impacts.
"Osiris-Rex spectroscopic observations ... show that the pristine sample that will be returned from Bennu has the potential to inform our understanding of water in the early Solar System and its origins on Earth," said Victoria Hamilton and other co-authors from the Osiris-Rex science team in a paper published Tuesday in Nature Astronomy.
Rather than being one big hunk of solid monolithic rock, Bennu's interior also appears to be made up of a literal pile of rubble that clumped together to form a larger object.
A different study takes a look at Bennu's shape, which is often described as similar to a spinning top. It finds the asteroid has a volume that is about one-sixth that of the asteroid Ryugu, currently being visited by.
Bennu and Ryugu are both classified as Apollo-type asteroids, which are a type of near-Earth asteroid that hang out between the sun and the orbit of Mars. Both space rocks have elliptical orbits that cross the orbital paths of both Earth and Mars.
In a separate series of papers published Tuesday in the journal Science, the Hayabusa2 team confirms that Ryugu also has a spinning-top shape formed from similarly dark cosmic rubble.
"Thanks to the parallel missions of Hayabusa2 and Osiris-Rex, we can finally address the question of how these two asteroids came to be," said professor Seiji Sugita of the University of Tokyo, a co-author of one of the papers, in a release. "That Bennu and Ryugu may be siblings yet exhibit some strikingly different traits implies there must be many exciting and mysterious astronomical processes we have yet to explore."
The most striking difference so far between the two asteroids is that Ryugu is far drier. While this may seem to be a disappointing finding at first, Sugita says the discoveries from Ryugu and Bennu, including the subtle contrasts between the two, could actually have implications for finding life beyond Earth.
"There are uncountably many solar systems out there and the search for life beyond ours needs direction," Sugita said. "Our findings can refine models that could help limit which kinds of solar systems the search for life should target."
But for now, both missions are focused on bringing samples home. Hayabusa2 has already collected one sample and has plans to gather another, while Osiris-Rex prepares for its own sample swipe in 2020.
Update, 11:20 a.m. PT: Added new images and Osiris-Rex team comments from a NASA press call. | 0.87807 | 3.564429 |
The morning of the last day of this week’s July 22-26, 2013, Pluto Science Conference opened up the discussion with outer atmosphere (far out) and magnetosphere (really far out) talks.
Fran Bagenal (University of Colorado) started the session with a talk on “The Solar Wind Interaction with Pluto’s Escaping Atmosphere.” Pluto’s interaction with the solar wind was first suggested in 1981 by Larry Trafton. There are two generally predicted regimes of what this interaction might look like: (1) Venus-like (small escape rate) and (2) Comet-Like (high escape rate). A key parameter distinguishing the two is what the atmospheric escape rate might be, that is, how many atmospheric molecules (assumed to be nitrogen) are escaping from Pluto, no longer being bound by gravity. Current estimates for the escape rate, based on a number of approaches, notably a recent one by Darrell Strobel (2012), have this number at 2-5×1027 molecules/sec. This is large enough to suggest Pluto will appear to be “comet-like” in its interaction with the solar wind. However, we need to wait until 2015 for the New Horizons fly-by with their in-situ particle instruments SWAP & PEPSSI to make the interaction measurements.
When describing the Pluto System in terms of solar wind interaction, Fran Bagenal showed this image, which superimposed one of Darrell Strobel’s atmospheres (characterized with an exobase at 12 Pluto radii). Pluto becomes a “large object” for interaction with the solar wind.
When solar wind particles (protons) interact with the Pluto atmosphere, their path through space is bent along the magnetic field lines, and to convert momentum, pickup ions (neutral hydrogen atoms from the heliosphere that undergo a collisional charge-exchange interaction with solar wind protons, get ionized, are “picked up” by the solar magnetic field) get tossed onto new trajectories. Those ions are charged and will begin to rotate and follow electrical field lines. Where do the ionized particles go? A weak magnetic field will create large gyro-radii of pick-up ions which can extend millions of kilometers upstream of Pluto. This is best modeled with a kinetic interaction.
Peter Delamere (University of Alaska, Fairbanks) spoke in greater detail about “The Atmosphere-Plasma Interaction: Hybrid Simulations.” Plasma interaction is an atmospheric diagnostic tool. Neutral gases are not easily picked up, but ions and how they interact with the solar wind can be detected with in-situ instruments such Hew Horizons’ SWAP and PEPSSI. He discussed his model plasma interaction mode, which was validated using Comet 19P/Borrelly that had been visited by Deep Space 1 on Sept 22, 2001.
Example of Comet 19B/Borelly environment time vs. energy reveals the structure of the interaction between a comet and the solar wind. The X-axis is time from closes approach, with the Y-axis energy. The color code is the number of particles counted by the PEPE instrument aboard Deep Space 1. This is similar to what the data is expected to look at for Pluto when New Horizons reaches it in 2015, however, the solar wind at 33 AU may be more extended and more diffuse and therefore the signal strength (in terms of counts) will be much less.
If we can understand where the bow shock forms, this becomes a diagnostic of the atmosphere, and if indeed the exosphere extends out to 10 Pluto radii as suggested by recent work by Darrell Strobel (2012) and other models, then this is a sizable ‘obstacle.’ But is it inflated enough to form a bow shock? Peter Delamere thinks so. He stepped us through a variety of simulations. One of the simulations predicts a partial bow shock. If you increase Qo (the escape rate parameter, predicted to be in the 2-5×1027 N2 molecules) or increase magnetic field strength you can create a full bow shock. Future work includes adding the pickup part of the solar wind model as input. If there is a very slow momentum transfer, perturbed flow could extend out to an AU.
Simulations predict all sorts of shock structures (Mach cones, bow shocks), but these structures depend on the escape rate parameter.
Example of a plasma interaction mode for three escape rates, decreasing from right to left. This is a slide in space of plane vs. distance from. The white lines are sample solar wind proton trajectories. The color scale indicates ion density. The solar wind (and hence, the direction from the sun) is incident from the left. Pluto is at (0,0).
Predictions at Pluto. He anticipates significant asymmetry. The predicted bow show could be as far as 500 Pluto radii.
Heather Elliot (SwRI, San Antonio) in her talk “Analysis Techniques and Tools for the New Horizons Solar Wind around Pluto” described the New Horizons SWAP instrument and the different rate modes (sampling rate and scan types) it will be using during the 2015 encounter.
Measurement of the solar wind taken with the SWAP instrument aboard New Horizons during the last 6 years of cruise. This data set covers AU=10 (Saturn distance) out to AU=23 in 2012. The solar wind is mostly protons (H+). The second most abundant species are alphas (He++). The colors are the intensity of species. The vertical axes are energy per charge units and the horizontal axis is time.
Fitting the SWAP data to a solar wind model requires making adjustments for view angle and during the hibernation period, when they do not have attitude information, they have modeled the Sun-probe-Earth angle to estimate the attitude and this works well to fit their data.
John Cooper (NASA Goddard) spoke about the “Heliospheric Irradiation in Domains of Pluto System and Kuiper Belt.” He is interested in computing the “radiolytic” dosage onto bodies in the outer solar system (that is, the effect of how molecules break down or change molecular band structure due to the influence of radiation, such as by cosmic rays, particles, UV, etc.). For this he needs measurements of the particle flux at large AU. New Horizons joins its cousins Voyager 1 & 2, Pioneer 10 & 11 and Ulysses in exploring the outer solar system.
Location of the NH spacecraft (orange on the left, purple on the right) for two different views of the solar system. Also plotted are deep space missions Voyager and Pioneer, among many. The left view is s top down view of the solar system with the Sun at (0,0), the axes are in AU, where 1 AU (Astronomical Unit) is the distance between the Earth and Sun. The right is a view of time vs. latitude for the crafts. Comparative data sets to New Horizons, which travels along the solar ecliptic, are Pioneer 10 and early Voyager 2 data.
He showed computations of irradiation dosage when applying those particle rates measured by New Horizon’s PEPSSI instrument and instruments aboard Voyager 2 and Pioneer 10.
He maintains a database of all particle instrument flux measurements at the Virtual Energetic Particle Observatory http://vepo.gsfc.nasa.gov.
Thomas Cravens (JHU/APL) with ”The Plasma Environment of Pluto and X-Ray Emission: Predictions for New Horizons,” asked “What happens when you get to within 1000 km of Pluto?“ Pluto is anticipated to be “Comet-Like” in its interaction with the solar wind, however when you get closer to Pluto (around 1000 km), it may more closely resemble “Venus-like” interaction. He is trying to compute where the charge-exchange boundary could be, probably around r~5000km. This is boundary between the kinetic (r>5000km) and fluid (r<5000 km) regimes, essentially probing the ionosphere regime of Pluto.
Switching to slightly lower energies, Casey Lisse (JHU/APL) gave a talk on “Chandra Observations of Pluto’s Escaping Atmosphere in Support of New Horizons.” X ray interactions (charge exchange, scattering and auroral precipitation) require an extensive neutral atmosphere, which is what is expected at Pluto. Interaction of solar wind with comets has consistently shown X-ray emission. He expects to see X-ray emission from Pluto. If detected it would tell us about the size and mass of Pluto’s unbound atmosphere. The best time to look for x-rays at Pluto is about 100 days after a large CME (corona mass ejection) event, which is about the time it takes for CME to get to Pluto at 33 AU.
He and his colleagues applied for, and got, time on NASA’s Chandra X-ray telescope. On Chandra, Pluto & Charon will appear to fill one Chandra pixel using the Chandra HRC instrument. He ended his talk suggesting that looking at background counts with the LORRI and RALPH CCDs might serve as a poorman’s x-ray detector. It is also possible that PEPSSI background counts could be used to infer presence of lower X-rays.
Kandi Jessup (SwRI) gave a talk addressing the “14N15N Detectability at Pluto.” We care about 14N15N because it can be used to determine the 15N to 14N isotropic fractionation. This can help tell us about the evolution of Pluto’s atmosphere. Learning about Pluto’s atmospheric evolution history also provides vital suggestions for the evolution of equivalent TNOs (Trans-Neptunian Objects) and other objects in the Kuiper Belt, and hence, the outermost parts of our Solar System
The measurement will be the UV spectral observations during the solar occultation of Pluto by the Alice instrument during the New Horizons fly-by. N2 is the dominant absorber between 80-100nm. To identify the molecule 14N15N they use an atmosphere model from Krasnopolsky & Cruikshank (1999). That model does not have a troposphere. Next they need absorption cross-sections (a parameter that quantifies the ability of a molecule to absorb a photon of a particular wavelength) for 14N2 and 14N15N. 14N2 is the more dominant species and they are trying to find a very small percentage for 14N15N. Using these simulations they anticipate the Alice instrument will be sensitive enough to detect at least a 14N15N to 14N2 ratio of 0.3%. They will be look at the UV spectrum between 88 and 90 nm where the 15N lines spectrally shifted from 14N line. 14N15N to 14N2 ratio has been measured on Mars (0.58%), Titan (0.55%), and Earth (0.37%). What ratio will Pluto have? New Horizons data will hopefully tell us.
Randy Gladstone (SwRI, San Antonio) spoke about “Ly-alpha at Pluto.” Pluto ultraviolet (UV) airglow line emissions will be very weak, except at HI Lyman-alpha (Ly-a). Ly-a at Pluto could have both a solar (Sun) and an interplanetary (IPM/interplanetary medium) source. Ly-a should be scattered by Hydrogen atoms in Pluto’s atmosphere. He uses the Krasnopolsky & Cruikshank (1999) Pluto atmosphere model that predicts the number of Hydrogen atoms at altitude. There are several observations near Pluto closest approach planned with the New Horizons Alice instrument to measure Lyman-alpha emissions. This data will provide information about the vertical distribution of H and CH4 in Pluto’s atmosphere. Observation of the IPM Lyman-alpha source will be unique and provide important information to model Pluto’s photochemistry, especially for the nightside and winter pole region.
Randy Gladstone (SwRI, San Antonio) ended the session with a talk about “Pluto’s Ultraviolet Airglow.” He presented a model by Michael Stevens (Naval Research Lab), which has been used to explain the Cassini UVIS (Ultraviolet Imaging Spectrograph) observation of UV airglow at Titan over the 80-190 nm wavelength, emissions arising from processes on N2 (Stevens et al 2011). The model is called AURIC, the Atmospheric Ultraviolet Radiance Integrated Code. This model will be used for interpreting Pluto atmosphere data taken at UV wavelength with the New Horizons Alice instrument.
If Pluto was not already an exotic place to visit with all the predictions about its formation, its interior, its surface, it surface-atmosphere interaction, its composition, etc., it certainly will prove to be an amazing place if any or all of these predicted upper atmosphere and mesosphere molecular species, ions, and high energy particles are measured with the New Horizons spacecraft! | 0.834279 | 4.036729 |
The Hubble Space Telescope launched 25 years ago. It’s easy to forget how revolutionary the project was, given that an entire generation of Americans has grown up accustomed to the HST beaming down stunning images of the cosmos on a regular basis. The first space telescope was proposed in 1923 by Hermann Oberth. Even then, it was clear that Earth-based telescopes operated at significant disadvantage. Not only are they impacted by light from cities, the atmosphere itself attenuates and blocks stars that would otherwise be visible. If you want to look at space on Earth, you need much larger telescopes than you’d need in space and some spectra (infrared and ultraviolet) are difficult to observe from Earth at all.
The Hubble Space Telescope wasn’t the first telescope to operate in space, but it set goals and longevity targets that were far beyond any previous projects. The ambitious nature of the project led to cost-overruns and delays, while the loss of the Challenger put a freeze on all US space missions. When the Hubble finally launched in 1990, NASA soon discovered another problem — the company hired to grind the primary mirror had done so incorrectly.
Luckily, Hubble’s unique mission parameters made a solution possible. The telescope sits in a low Earth orbit, which means it can (well, could) be visited by a space shuttle and periodically serviced. Astronauts fitted a corrective lens to the telescope in December, 1993 — and the improvement in optical resolution was stunning.
Since then, Hubble has consistently been one of NASA’s highest-profile and longest-lasting successes. The telescope is popular with the public and it’s been used to answer important questions about the universe and measure astronomic phenomena more precisely than we ever could from ground-based installations. The HST was used to refine our measurement of the Hubble constant (the rate of the Universe’s expansion), confirm the existence of black holes, and observe phenomena like the impact of comet Shoemaker-Levy 9 on Jupiter in unprecedented detail.
The Hubble’s long-term future
Hubble was last serviced in 2009, and without future missions will eventually fail completely. The telescope is currently expected to serve until at least 2020, barring unexpected failure. It could even survive in Earth orbit to 2030 or 2040 depending on solar and atmospheric drag.
The James Webb Telescope, which we’ve also discussed recently, is a partial successor to Hubble, but its instruments are focused in a different area of the electromagnetic spectrum. The chart below shows the wavelengths for the two telescopes, and their respective overlaps.
Unlike Hubble, the James Webb Telescope won’t be serviceable, and it won’t have the same focus on visual wavelengths — but it should be able to peer even farther back in time, pushing back the boundaries of what we can observe about the earliest days of the universe.
NASA celebrated Hubble’s 25th anniversary by releasing a new shot of the Westerlund 2 cluster, seen in our feature image above. Hubble, meanwhile, keeps on trucking — the latest puzzle that has astronomers in a tizzy is the telescope’s observation of a stellar event in the constellation Eridanus. A star appears to have exploded in an event halfway between a nova and a supernova, with far too much energy to classify it as the former, but far too little to count as the latter. One remote possibility is that the event was a kilonova — an exceptionally rare type of collision between two neutron stars.
As birthday presents go, it’s tough to beat that one. For more, check out our single-page list of the 25 best Hubble Space Telescope images. | 0.826931 | 3.811052 |
Eleven year cycle. If that means something to you, you must be an amateur radio operator, or some other student of the Sun. Here’s an older NASA video that’s still interesting.
Despite the wishes of medieval philosophers, the Sun is not a perfect disk. Sunspots are
regions of reduced surface temperature caused by concentrations of magnetic field flux that inhibit convection… may last anywhere from a few days to a few months…. [and affect] space weather, the state of Earth’s ionosphere, and hence the conditions of short-wave radio propagation or satellite communications. wikipedia
We’ve known for a long time that the frequency of sunspots roughly follows an eleven year cycle, with a lot of variation in intensities and somewhat in durations, but it’s been hard to explain why. A recent study (in Solar Physics, which looks like a real journal – you gotta be careful now-a-days) found a “high level of concordance” between the positions of three planets in their orbits and sunspot activity.
The study examined 90 cycles, which means almost 1,000 years of records. That’s a lot of history and the article I read doesn’t say how reliable ancient records are. But for the last two dozen cycles, we have pretty good data. The cycle seems to align with movements of Venus, Earth, and Jupiter in an 11.07 year cycle.
There are some problems. Sunspot cycles have varied from eight to fourteen years in length, so explaining the average by itself isn’t enough. What about the other planets? When you have a bunch to choose from, any correlation may simply be fortuitous. But I’m curious to know if adding more planets to the model will help or hurt the correlations.
By what mechanism could such a relatively small gravitational force impact our star? Perhaps plasma stability analyses can explain it? The math needs to be done.
My spouse, the ham radio operator in the family, is skeptical. There have been other attempts to explain the sunspot cycle that didn’t pan out. Of course, this hypothesis must be examined further.
But every discovery starts with an observation.
Thanks to newsweek.com for their article. | 0.815635 | 3.098776 |
THE outlier in the stellar system closest to our own, the star Proxima Centauri, may not have formed with its two siblings. If so, nor would its planet, Proxima b, which is good news for the chances of life on it.
Proxima Centauri’s orbit is currently bound to Alpha Centauri A and B, but it is unclear if it will remain stable, say Fabo Feng and Hugh Jones at the University of Hertfordshire in the UK. They modelled 100 Proxima clones in orbits around their binary partners.
Over a simulated 10 billion years, Proxima Centauri became unbound from the pair due to an unstable orbit 26 per cent of the time. If it had been born in the system, it is unlikely the orbit would be unstable aeons later (arxiv.org/abs/1709.03560). So, Proxima may have been captured by the stellar pair.
Previous studies have found that Proxima contains much less metal than its binary companions, another hint that it might have come from afar. Feng says a more recent appearance might be good for the habitability of Proxima b. At certain points in its orbit, Proxima Centauri could get so close to the other stars, they could destabilise its planet’s orbit and push it out of the zone with temperatures right for life.
But if Proxima Centauri has only been there a short while, there would have been fewer chances for its planet to be knocked out of this zone.
Proxima b would have had longer in a stable orbit around a single star before feeling the influence of Alpha Centauri A and B. “Life needs time to develop and emerge. This scenario gives it more time,” says Feng.
But a capture would actually make Proxima b’s orbit less stable than if it had formed as part of the larger system, says Scott Kenyon at the Harvard-Smithsonian Center for Astrophysics in Massachusetts. “If the three stars have been orbiting each other for a few billion years, one would think they’d be a nice happy family,” he says.
This article appeared in print under the headline “Proxima may be an interloper from far away” | 0.817264 | 3.619465 |
Since ancient times, stars cause great interest among people. And if several years ago not everyone could afford to buy a telescope, now it is no longer a luxury. But what can be seen in the lens of an amateur telescope, without using professional optics?
Start with a review of the moon. Perhaps this is the first celestial object that can be viewed closer to the simplest and most inexpensive telescope. But, if you want to see some traces of old satellites and alien ships, you will be disappointed. In addition to the craters from the fall of meteorites, you will find nothing else. But it will be quite interesting to study the surface of the moon in detail. The sun is also of great interest, but you can’t look at it without special filters.
We look at the planets
No less popular for observation through a telescope - Mars. It is located at a distance of one and a half times farther from the Sun than the earth. The fourth planet from the sun, so beloved by science fiction writers and documentaries, will be perfectly visible in a more powerful telescope. The minimum apparatus, which is needed for this, can be considered a 150-millimeter reflector or a 100-millimeter refractor. One of the most interesting objects for beginning astronomers is the largest planet Jupiter. In a small telescope (60-90 mm) with a hundred-fold increase, you can clearly see the northern and southern equatorial belts of the planet.
Saturn is not less interesting object to see. Often, many are not interested in the body itself, but in the rings around it. They can be seen even in a low-power telescope.
How to see nebulae and other objects
The contemplation of the Orion Nebula will impress you. If you look at the constellation with the naked eye, then you can see only a slight glow. Through binoculars you will see a small bright cloud, but it is worth picking up more powerful optics and the nebula will immediately appear in all its glory. To do this, you need a telescope with a 300 mm lens, in which you can even see some chromaticity.
The nebula called Pleiades cluster is located in the constellation Taurus and has about a thousand stars. Unfortunately, in a normal telescope you will see only a couple of dozen “points”. In the apparatus with a lens of 125-180 mm, the nebula can be seen as a dim spot with a bright dot in the center. The Andromeda Galaxy is another object chosen by science fiction and space game developers. It is located at a distance of 2, 5 million light years can be considered as such. It can be seen even with powerful binoculars, and in the amateur telescope you will see a clearer picture.
And the most interesting object for beginners is the highest pipe or tower in your city.
If you plan to buy a telescope, but have no idea what to look for, use the services of the TechnoPortal http://technoportal.ua/binokli-teleskopy-mikroskopy/variations-teleskopy.html. This is a convenient price-aggregator, where telescopes of many popular online stores are collected. Here you will find models of telescopes for every taste, find useful information and purchase goods at a favorable price.
And then it remains only to hoist the lens on a tripod, direct it towards the depths of space and, armed with an atlas of the starry sky, begin the review. | 0.848669 | 3.460316 |
New gas giant planet discovered around the star Beta Pictoris
A second exoplanet has been discovered around the star β Pictoris, a fairly young star given that it is only 23 million years old and can also be considered fairly close since it is “only” 63.4 light years away.
Precisely because it is a young star, Beta Pictoris is still surrounded by the disk of dust and various materials which, according to the most accredited theory concerning the formation of planets, represents the “source” of the material which then goes to form the same planets. For this reason, the β Pictoris system has fascinated astronomers in recent years as it is allowing them to observe a planetary system being formed.
The first planet around this star, β Pictoris b, was discovered as early as 2009. Ten years later, analyzing the data obtained with the HARPS tool of the ESO Observatory of La Silla in Chile, the researchers discovered a second planet, β Pictoris c. In both cases, these are two giant gas planets.
β Pictoris c has a mass nine times that of Jupiter and orbits around its star in about 1200 days. It is located relatively close to its star, if we consider the distance between the Sun and Jupiter.
β Pictoris c is in fact separated from the star by a distance that is similar to the one that separates the Sun from the belt of asteroids, which is a little beyond Mars. β Pictoris c is instead 3.3 times more distant from its star than β Pictoris b.
Astronomers hope to find out more information about this young and interesting planetary system by analyzing the data that will be acquired by the GAIA spacecraft and those of another much larger telescope still under construction in Chile.
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Habitable Exoplanets: Red Dwarf Systems Like TRAPPIST-1 will be available on April 19, 2018 at Amazon.com. Here is an introduction to the book:
Finding exoplanets can be said to be more challenging than finding the proverbial needle in a haystack. It has taken centuries of advances to achieve the technology and knowledge required to confirm worlds orbiting stars that are light years away. Only since 1992 have we had proof that our solar system isn’t alone in the Universe. Now we know of hundreds of others and estimate that billions more exist in the Milky Way galaxy alone. The current picture being revealed through the latest state-of-the-art planet hunting telescopes shows us a Universe filled with the potential for life and civilization, even around stars we thought just a mere decade ago were inhospitable to life.
Our ability to confirm planets is heavily influenced by the size of the planet, its parent star, how far out it orbits from that star, and of course the distance of the entire system from Earth. The smaller and further out a planet is positioned, the more uncertain we are that it is in fact a planet and not some anomaly like a cloud of comets. With just a couple of star types that we can disregard in supporting more complex multicellular life forms like ourselves (these stars are Type-O, -B, and -A, due mainly to their short lifetimes of a billion years or less), over 90% of the rest are open to the possibility of supporting life, and over 70% of these in one type of star alone. Spoiler alert – the star type in question is not anything like our Sun!
In Habitable Exoplanets: Red Dwarf Systems Like TRAPPIST-1, you will discover some of the constraints and chances of planets being habitable around the most abundant type of star in the Universe – red dwarfs. These stars (comprising of both late K-type and all M-type) are at least 70% of all stars in the Milky Way galaxy. Their abundance comes from the fact that these stars are comparatively tiny, and thus much easier for the Universe to produce. Small as they may be, they have some interesting attributes that both cast doubt and hope on their ability to host life. While life has been located around our own star type (as we are here to talk about that revelation), it would be shortsighted to ignore the vast majority of stars simply because of some unknowns – many of which are quickly being overturned as you will learn about.
To aid in our understanding of how alien red dwarf systems can be to our solar system, I will be frequently referring to TRAPPIST-1 and the discovery of seven planets in that system. TRAPPIST-1’s configuration is optimal to allow scientists to test many of our assumptions on how planets form, and whether they can retain habitable conditions for the billions of years required for life to evolve. You will discover how a star both helps and hinders the evolution of life, and how any orbiting planets can remain in a state of environmental balance to allow life to grow and evolve. We will also explore one particularly unique quality of red dwarf worlds that may provide an even greater capability for supporting life than we have here on Earth.
A planet’s distance to its star, as well as its size, density, and composition are the primary considerations in determining whether it is setup to support other life-giving attributes like an atmosphere and surface liquid water. These features will also determine if the planet can form a protective magnetic field. For example, Earth is large enough for its interior to create a fluidic dynamo – the physical motion of material – in the outer core, which generates a globally encompassing magnetic field. This field keeps the solar wind at bay, preventing the oxygen-rich atmosphere from bleeding away into space. Even the tamest red dwarf stars are going to toss massive amounts of radiation towards their planets, many times greater than what Earth experiences with our Sun. A magnetic field is the first line of defense against this barrage.
Image courtesy: Mark A Garlick / University of Warwick
An atmosphere plays many roles in a planet being hospitable to life. Without an atmosphere, all exposed liquid water would quickly sublimate into space, and the mass and gravity of a planet will have a strong influence on atmospheric composition. Earth’s atmosphere is composed of 78% Nitrogen, 21% Oxygen, and other trace elements. Oxygen levels in the atmosphere have fluctuated in the past, from as low as nearly 0% to as high as 35%. Oxygen also made – and maintains – the ozone layer, which is critical to shielding life from harmful UV radiation from the Sun. We don’t yet understand what red dwarf planet atmospheres contain in detail, but ozone is thought to be one strong possibility for a couple of reasons we’ll explore later.
Water is the most directly impactful attribute to consider when gauging habitability. On Earth, wherever water is found, life is also found (it’s important to note that this observation is aided by the fact that all the water we look at shares a global biosphere). Life is thought to have first appeared in a mix of chemicals and water under intense heat, possibly deep within the oceans along volcanic ridges. Large bodies of water also help to regulate atmospheric temperatures and ensure a robust hydrologic cycle that seeds water onto otherwise dry land. There should not be too much water though, as that would result in a water world (a planet covered 100% by a single ocean). Water covers 71% of Earth’s surface, providing enough land area for life to evolve into more complex forms, including being able to build a civilization capable of advancing technologically.
There are also exotic attributes of some exoplanets that call into question whether life is possible at all on these worlds. One particularly special attribute is what’s known as a tidally locked position. If the planet is close enough to its parent star, it may be so strongly bound as to not rotate at all with respect to the star. This effect is exactly why our moon always shows the same face toward Earth as it orbits. If it’s found that life is possible on such a planet, that life would experience a world unlike anything we experience on Earth. We will explore in detail this idea in the book, and what it means for the potential of life and civilization.
The remarkable achievement of detecting exoplanets is only the beginning of what will be realized in the decades to come. We live at a time where amateur astronomers can even get in on the action and discover entirely new attributes about these worlds. When a candidate planet is confirmed, we often see the contribution of an amateur astronomer being recognized. One such example is Andrew Grey’s discovery of a system with at least four worlds in a size class called super-Earths (slightly larger than Earth). Mr. Grey accomplished his discovery not with multimillion-dollar equipment, but by sifting through endless streams of data stored in archives from around the world. What computers and scientists may have missed is open for you as the ultimate treasure hunt of a lifetime.
You can start by joining planethunters.org to learn how others analyze the data, just like Mr. Grey has done.
There have been hundreds of scientific papers over the last few years that have talked about exoplanets. Especially in 2016 and 2017, papers have dived into the idea of red dwarf planets having a protective magnetic field, for there to be an atmosphere with life-friendly gases and temperature ranges, and liquid water on their surface. While the knowledge we have gained is still highly evolving, it is quickly beginning to consolidate to provide us a picture of habitability. As soon as we can back up theories with additional evidence from the next generation of telescopes, we hope to have some definitive answers.
To learn more about this intruiging possibility for exoplanets, pick up my upcoming book, Habitable Exoplanets: Red Dwarf Systems Like TRAPPIST-1 on April 19 at: www.amazon.com/author/mathewanderson. I would also suggest you pick up my previous books in the Our Cosmic Story series to get a wider view on how might life and civilizations evolve on other worlds, and the chances for that life to advance enough to one day explore space as we have. | 0.831297 | 3.721581 |
Your daily selection of the latest science news!
According to Universe Today
It is a well known fact among astronomers and cosmologists that the farther into the Universe you look, the further back in time you are seeing. And the closer astronomers are able to see to the Big Bang, which took place 13.8 billion years ago, the more interesting the discoveries tend to become. It is these finds that teach us the most about the earliest periods of the Universe and its subsequent evolution.
For instance, scientists using the Wide-field Infrared Survey Explorer (WISE) and the Magellan Telescopes recently observed the earliest Supermassive Black Hole (SMBH) to date. According to the discovery team’s study, this black hole is roughly 800 million times the mass of our Sun and is located more than 13 billion light years from Earth. This makes it the most distant, and youngest, SMBH observed to date.
The study, titled “An 800-million-solar-mass black hole in a significantly neutral Universe at a redshift of 7.5“, recently appeared in the journal Nature. Led by Eduardo Bañados, a researcher from the Carnegie Institution for Science, the team included members from NASA’s Jet Propulsion Laboratory, the Max Planck Institute for Astronomy, the Kavli Institute for Astronomy and Astrophysics, the Las Cumbres Observatory, and multiple universities.
As with other SMBHs, this particular discovery (designated ULAS J1120+0641) is a quasar, a class of super bright objects that consist of a black hole accreting matter at the center of a massive galaxy. The object was discovered during the course of a survey for distant objects, which combined infrared data from the WISE mission with ground-based surveys. The team then followed up with data from the Carnegie Observatory’s Magellan telescopes in Chile.
As with all distant cosmological objects, ULAS J1120+0641’s distance was determined by measuring its redshift. By measuring how much the wavelength of an object’s light is stretched by the expansion of the Universe before it reaches Earth, astronomers are able to determine how far it had to travel to get here. In this case, the quasar had a redshift of 7.54, which means that it took more than 13 billion years for its light to reach us.
As Xiaohui Fan of the University of Arizona’s Steward Observatory (and a co-author on the study) explained in a Carnegie press release:
“This great distance makes such objects extremely faint when viewed from Earth. Early quasars are also very rare on the sky. Only one quasar was known to exist at a redshift greater than seven before now, despite extensive searching.”
Given its age and mass, the discovery of this quasar was quite the surprise for the study team. As Daniel Stern, an astrophysicist at NASA’s Jet Propulsion Laboratory and a co-author on the study, indicated in a NASA press release, “This black hole grew far larger than we expected in only 690 million years after the Big Bang, which challenges our theories about how black holes form.”
Essentially, this quasar existed at a time when the Universe was just beginning to emerge from what cosmologists call the “Dark Ages”. During this period, which began roughly 380,000 years to 150 million years after the Big Bang, most of the photons in the Universe were interacting with electrons and protons. As a result, the radiation of this period is undetectable by our current instruments – hence the name.
The Universe remained in this state, without any luminous sources, until gravity condensed matter into the first stars and galaxies. This period is known as the “Reinozation Epoch”, which lasted from 150 million to 1 billion years after the Big Bang and was characterized by the first stars, galaxies and quasars forming. It is so-named because the energy released by these ancient galaxies caused the neutral hydrogen of the Universe to get excited and ionize.
Once the Universe became reionzed, photons could travel freely throughout space and the Universe officially became transparent to light. This is what makes the discovery of this quasar so interesting. As the team observed, much of the hydrogen surrounding it is neutral, which means it is not only the most distant quasar ever observed, but also the only example of a quasar that existed before the Universe became reionized.
In other words, ULAS J1120+0641 existed during a major transition period for the Universe, which happens to be one of the current frontiers of astrophysics. As if this wasn’t enough, the team was also confounded by the object’s mass. For a black hole to have become so massive during this early period of the Universe, there would have to be special conditions to allow for such rapid growth.
What these conditions are, however, remains a mystery. Whatever the case may be, this newly-found SMBH appears to be consuming matter at the center of a galaxy at an astounding rate. And while its discovery has raised many questions, it is anticipated that the deployment of future telescopes will reveal more about this quasar and its cosmological period. As Stern said:
“With several next-generation, even-more-sensitive facilities currentlybeing built, we can expect many exciting discoveries in the very earlyuniverse in the coming years.”
These next-generation missions include the European Space Agency’s Euclid mission and NASA’s Wide-field Infrared Survey Telescope (WFIRST). Wheras Euclid will study objects located 10 billion years in the past in order to measure how dark energy influenced cosmic evolution, WFIRST will perform wide-field near-infrared surveys to measure the light coming from a billion galaxies.
Both missions are expected to reveal more objects like ULAS J1120+0641. At present, scientists predict that there are only 20 to 100 quasars as bright and as distant as ULAS J1120+0641 in the sky. As such, they were most pleased with this discovery, which is expected to provide us with fundamental information about the Universe when it was only 5% of its current age.
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New York: An international team of astronomers has discovered 83 "quasars", extremely luminous active galactic nucleus powered by supermassive black holes in the distant universe, from a time when the universe was less than 10 per cent of its present age.
A supermassive black hole becomes visible when gas accretes onto it, causing it to shine as a quasar.
Using the massive Subaru Telescope, located at the Mauna Kea Observatory on Hawaii, the scientists from Japan, Taiwan and and the US, focussed their attention on objects located about 13 billion light years away from Earth.
They found 83 new very distant quasars. Together with 17 quasars, previously known in the survey region, the researchers found there was roughly one supermassive black hole per cubic giga light year.
The finding increases the number of black holes known at that epoch considerably and reveals, for the first time, how common they are in the universe's history.
"The quasars we discovered will be an interesting subject for follow-up observations with current and future facilities," said lead author Yoshiki Matsuoka, from the Ehime University in Japan.
"We will also learn about formation and early evolution of supermassive black holes, by comparing the measured number density and luminosity distribution with predictions from theoretical models," Matsuoka said.
The study also provides new insight into the effect of black holes on the physical state of gas in the early universe in its first billion years.
Supermassive black holes, found at the centres of galaxies, can be millions or even billions times more massive than the sun, and were likely born in the first few hundred million years after the Big Bang that took place 13.8 billion years ago.
"It is remarkable that such massive dense objects were able to form so soon after the Big Bang," said co-author Michael Strauss, Professor at Princeton University.
"Understanding how black holes can form in the early universe, and just how common they are, is a challenge for our cosmological models," Strauss said.
The research appears in a series of five papers published in The Astrophysical Journal and the Publications of the Astronomical Observatory of Japan. | 0.820765 | 3.929664 |
Lunar Atmosphere and Dust Environment Explorer Mission has Many Firsts
WALLOPS FLIGHT FACILITY, Wallops Island, Va. — In an attempt to answer prevailing questions about our moon, NASA is making final preparations to launch a probe at 11:27 p.m. EDT Friday, Sept. 6, from NASA’s Wallops Flight Facility.
The small car-sized Lunar Atmosphere and Dust Environment Explorer (LADEE) is a robotic mission that will orbit the moon to gather detailed information about the structure and composition of the thin lunar atmosphere and determine whether dust is being lofted into the lunar sky. A thorough understanding of these characteristics of our nearest celestial neighbor will help researchers understand other bodies in the solar system, such as large asteroids, Mercury, and the moons of outer planets.
“The moon’s tenuous atmosphere may be more common in the solar system than we thought,” said John Grunsfeld, NASA’s associate administrator for science in Washington. “Further understanding of the moon’s atmosphere may also help us better understand our diverse solar system and its evolution.”
The mission has many firsts, including the first flight of the Minotaur V rocket, testing of a high-data-rate laser communication system, and the first launch beyond Earth orbit from the agency’s Virginia Space Coast launch facility.
LADEE also is the first spacecraft designed, developed, built, integrated and tested at NASA’s Ames Research Center in Moffett Field, Calif. The probe will launch on a U.S. Air Force Minotaur V rocket, an excess ballistic missile converted into a space launch vehicle and operated by Orbital Sciences Corp. of Dulles, Va.
LADEE arrives at Wallops Flight Center, Wallops Island, Virginia in early June after cross country trip from NASA’s Ames Research Center in California.. – NASA /// — CLICK TO ENLARGE
LADEE was built using an Ames-developed Modular Common Spacecraft Bus architecture, a general purpose spacecraft design that allows NASA to develop, assemble and test multiple modules at the same time. The LADEE bus structure is made of a lightweight carbon composite with a mass of 547.2 pounds — 844.4 pounds when fully fueled.
“This mission will put the common bus design to the test,” said Ames Director S. Pete Worden. “This same common bus can be used on future missions to explore other destinations, including voyages to orbit and land on the moon, low-Earth orbit, and near-Earth objects.”
Butler Hine, LADEE project manager at Ames, said the innovative common bus concept brings NASA a step closer to multi-use designs and assembly line production and away from custom design. “The LADEE mission demonstrates how it is possible to build a first class spacecraft at a reduced cost while using a more efficient manufacturing and assembly process,” Hine said.
Approximately one month after launch, LADEE will begin its 40-day commissioning phase, the first 30 days of which the spacecraft will be performing activities high above the moon’s surface. These activities include testing a high-data-rate laser communication system that will enable higher rates of satellite communications similar in capability to high-speed fiber optic networks on Earth.
After commissioning, LADEE will begin a 100-day science phase to collect data using three instruments to determine the composition of the thin lunar atmosphere and remotely sense lofted dust, measure variations in the chemical composition of the atmosphere, and collect and analyze samples of any lunar dust particles in the atmosphere. Using this set of instruments, scientists hope to address a long-standing question: Was lunar dust, electrically charged by sunlight, responsible for the pre-sunrise glow above the lunar horizon detected during several Apollo missions?
After launch, Ames will serve as a base for mission operations and real-time control of the probe. NASA’s Goddard Space Flight Center in Greenbelt, Md., will catalogue and distribute data to a science team located across the country.
NASA’s Science Mission Directorate in Washington funds the LADEE mission. Ames manages the overall mission. Goddard manages the science instruments and technology demonstration payload, the science operations center and provides overall mission support. Wallops is responsible for launch vehicle integration, launch services and operations. NASA’s Marshall Space Flight Center in Huntsville, Ala., manages LADEE within the Lunar Quest Program Office.
For more information about the LADEE mission, visit: http://www.nasa.gov/ladee
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The primary mission of the twin STEREO probes is to explore the 3-dimensional makeup of our Sun. Each craft carries a variety of instruments. One of them, the Heliospheric Imager (HI), doesn’t look directly at the Sun, but rather, explores a wide field near the Sun in order to explore the physics of coronal mass ejections (CMEs), in particular, ones aimed at the Earth. But while not focusing on solar ejections, the HI is free to make many other observations, including its first detection of an extrasolar planet.
As the Heliospheric Imager stares at the space between the Earth and Sun, it has made many novel observations. The device first opened its shutters in 2006 the instrument has observed the interaction of CMEs with the atmosphere of Venus, the stripping of a tail of a comet by a CME, atomic iron in a comet’s tail, and “the very faint optical emission associated with so-called Corotating Interaction Regions (CIRs) in interplanetary space, where fast-flowing Solar wind catches up with slower wind regions.”
The spacecraft allows for long periods of time to stare at patches of sky as the satellites precede and follow Earth in its orbit. The spacecraft is able to take pictures roughly every 40 minutes for almost 20 days in a row giving excellent coverage. As a result, the images taken have the potential to be used for detailed survey studies. Such information is useful for conducting variable star studies and a recent summary of findings from the mission reported the detection of 263 eclipsing variable stars, 122 of which were not previously classified as such.
Another type of variable star observed by the STEREO HI, was the cataclysmic sort, in particular, V 471 Tau. This red giant/white dwarf binary in the Hyades star cluster is a strong source of interest for stellar astrophysicists because the system is suspected to be a strong candidate for a type Ia supernova as the red giant dumps mass onto its high mass, white dwarf companion. The star system is extremely erratic in its light output and observations could help astronomers understand how such systems evolve.
Although planetary hunting is at the very edge of the capabilities of the HI’s limitations, eclipses caused by planet sized objects are feasible for many of the brighter stars in the field of view as dim as approximately 8th magnitude. Around one star, HD 213597, the STEREO team reported the detection of an object that seems too small to be a star based on the light curve alone. However, follow up studies will be necessary to pin down the object’s mass more accurately. | 0.912096 | 4.069395 |
Here's a view of the Kit Hill chimney stack taken from almost 6 miles away, taken with a cheap telescope and an old webcam. On the whole it's a fair representation of what can be seen through the eyepiece. Colours are a little washed out because Kit Hill was in shadow but it's just possible to make out people walking around the stack. However, the static image doesn't show the 'heat haze' effect caused by moving currents of air, the eyepiece view isn't as sharp.
Jupiter has been pasted in at the same image scale as the close up. Jupiter's apparent size varies depending on where it and Earth are in their orbits around the Sun. Even at its closest approach (628 million kilometres) Jupiter's angular size is only 50 arc-seconds or 0.014 degrees. Photographing Jupiter is like taking a picture of a 5 pence piece from 320 feet away. (But while high magnification is required to see the planets, some nebulae cover surprisingly large patches of sky.)
The full-size image of Jupiter shows more detail. The major cloud bands are visible and the great red spot, a giant storm at least 300 years old, is at lower right. The dark mark is the shadow of one of Jupiter's moons.
This image was taken using a different telescope, a 5" refractor, and a 4x magnifying Barlow lens. This combination gives about 3.6 times the magnification of the telescope in the top image, when used with the same camera. To image the planets and Moon amateurs use a technique called 'lucky imaging', to overcome distortion caused by atmospheric turbulence. A short video is taken of the target and the clearest frames are selected and combined using free stacking software, such as Registax. For an example of amateur planetary imaging at its best I'd recommend taking a look at Damien Peach's website.
Professional planetary imagers such as NASA either use the Hubble Space Telescope or simply park a spacecraft in orbit around their target, options beyond the budget of most amateurs. The Juno probe is currently at Jupiter and returning spectacular images.
Going back to the telescope in the first image, a Celestron Astromaster 114, is not one I'd recommend. The telescope itself is useful but it's let down by the mount and finder, making it a frustrating business to find objects in the sky. Small Dobsonian telescopes are often recommend for people starting out in astronomy due to their low cost, ease of use and light grasp. They are a type of Newtonian telescope which use a mirror to gather and focus light. Compared to a pair of binoculars they are more stable and produce a brighter image. There are even cardboard self-assembly versions available. | 0.847213 | 3.156487 |
Astronomers have found a goblin in the far reaches of the outer Solar System. No, it’s not a mythical space-faring creature. The Goblin is the nickname given to a new dwarf planet in the outer Solar System. It’s an exciting discovery on its own, and the orbit of The Goblin also supports the possible existence of the long-sought-after – and much larger – Planet X.
Scott Sheppard at Carnegie Institution for Science, Chad Trujillo at Northern Arizona University and David Tholen at the University of Hawaii announced the finding on October 2, 2018, via an electronic circular from the International Astronomical Union’s Minor Planet Center. A paper has been submitted to the The Astronomical Journal. In other words, astronomers just found this object.
They found it during an intensive search for Planet X, a search these astronomers said was:
The orbit of the new dwarf planet places it in a group of small, distant worlds that astronomers call Inner Oort Cloud objects. In other words, it resides in the Oort Cloud – a giant spherical shell of icy objects surrounding our sun, thought of as the realm of comets, far beyond the orbits of Pluto and less distant Kuiper Belt Objects.
The Goblin, also known as 2015 TG387, is about 80 astronomical units (AU) from the sun, with one AU defined as the distance between the sun and Earth. By comparison, Pluto is 34 AU from the Sun, so The Goblin is about two and a half times farther away from the Sun as Pluto, right now.
It’s thought to be quite small, about 300 kilometres (200 miles) in diameter. Its orbit is very elongated, never bringing the object closer to the sun than 65 AU. Besides 2015 TG387, the only other objects with more-distant perihelia – that is, more distant nearest-the-sun points – are 2012 VP113 and Sedna, at 80 and 76 AU respectively.
However, the orbital semi-major axis of The Goblin is larger than that of both 2012 VP113 and Sedna, meaning it travels much farther from the Sun along its orbit than they do. At its most distant point, it is an incredible 2,300 AU from the Sun.
As Scott Sheppard explained:
“These so-called Inner Oort Cloud objects like 2015 TG387, 2012 VP113, and Sedna are isolated from most of the Solar System’s known mass, which makes them immensely interesting. They can be used as probes to understand what is happening at the edge of our Solar System.”
Sheppard and Trujillo also discovered 2012 VP113 in 2014. Finding such objects means that there are probably many more yet to be seen. According to David Tholen:
“We think there could be thousands of small bodies like 2015 TG387 out on the Solar System’s fringes, but their distance makes finding them very difficult. Currently we would only detect 2015 TG387 when it is near its closest approach to the Sun. For some 99 percent of its 40,000-year orbit, it would be too faint to see.”
But it’s not only those objects themselves that are of interest to astronomers. These very distant objects might also be pointing the way to finally locating another major planet in our Solar System. As noted by Sheppard:
“These distant objects are like breadcrumbs leading us to Planet X. The more of them we can find, the better we can understand the outer Solar System and the possible planet that we think is shaping their orbits – a discovery that would redefine our knowledge of the Solar System’s evolution.”
One major clue that The Goblin may be evidence for the larger Planet X is that the location in the sky where 2015 TG387 reaches perihelion is similar to that of 2012 VP113, Sedna, and most other known extremely distant trans-Neptunian objects; this could be explained by something “pushing” them into similar types of orbits. To test this further, Chad Trujillo and Nathan Kaib at the University of Oklahoma ran computer simulations to see how various hypothetical Planet X orbits would affect the orbit of 2015 TG387. Since most previous estimates of Planet X’s size say it is significantly larger than Earth, the simulations included a super-Earth-mass planet at several hundred AU on an elongated orbit, as had been proposed by Caltech’s Konstantin Batygin and Michael Brown in 2016.
So what was the result? Most of the simulations suggested that not only was 2015 TG387’s orbit stable for the entire age of the solar system, but it was actually “shepherded” by Planet X’s gravity – that would keep the much smaller 2015 TG387 away from the much more massive Planet X. Such gravitational shepherding – similar to how Saturn’s smallest moons shepherd its rings – could also explain why these distant objects in the solar system all have similar orbits. According to Trujillo:
“What makes this result really interesting is that Planet X seems to affect 2015 TG387 the same way as all the other extremely distant Solar System objects. These simulations do not prove that there’s another massive planet in our Solar System, but they are further evidence that something big could be out there.”
If Planet X is confirmed to exist, it may indeed turn out to be – as suggested by some scientists – a super-Earth, a rocky planet larger than Earth but smaller than Uranus or Neptune. Many such worlds have already been found in other solar systems, so discovering a previously unknown one here as well would be … well, very exciting!
Bottom line: While the elusive Planet X hasn’t been found yet, the discovery of the dwarf planet nicknamed The Goblin is intriguing, and provides another clue that Planet X should be out there, waiting to be detected by earthly telescopes.
This article was first published on EarthSky. | 0.827021 | 3.698829 |
Impact events are relatively common. The objects known as shooting stars are actually small meteors burning up as they pass through Earth’s atmosphere. If a meteor is large enough, some part of it may reach Earth as a meteorite. These small impacts don’t form big craters, even if they might be large enough to devastate urban areas.
In its long history, Earth has experienced several meteor-impact events large enough to melt terrestrial rock and send it flying for hundreds or even thousands of miles. Following these impact events, the melted rock cooled to form materials known as tektites, which can now be found in several large areas, or “strewn fields,” around the world.
Understanding the impact process for tektite-forming events on Earth can lead to insights into the giant impact event that is believed to have formed the moon billions of years ago. That’s one result of new research from Washington University in St. Louis focusing on volatile elements, “Implications of K, Cu, and Zn isotopes for the formation of tektites.” The research was published Aug. 15 in the journal Geochimica et Cosmochimica Acta.
“We’re comparing tektites with the source of tektites, which is the upper continental crust, to see what changed during the impact,” said co-author Kun Wang, assistant professor of earth and planetary sciences in Arts & Sciences.
By establishing the expected pattern for volatile losses during impact events, Wang and his fellow researchers will be able to work backward from the products of impact events —tektites and lunar rocks alike — to learn about pre-impact conditions.
scraped from https://www.newswise.com/articles/tektites-don-t-come-from-the-moon-but-might-help-scientists-understand-how-it-formed | 0.818832 | 3.218321 |
Observations of Neutron Star Collision Appear to Show the Creation of a Black Hole
A widely studied collision of two neutron stars, detected in August 2017, now appears to have created a black hole, supporting a long-held scientific theory.
In August 2017, for the first time ever, scientists spotted gravitational waves generated by the merger of two superdense stellar corpses known as neutron stars.
This landmark find was a major step forward in understanding the cosmos, astronomers have stressed.
At the time, scientists suggested that this dramatic event, officially cataloged as GW170817, could have created a black hole — and a new analysis backs this supposition up. [Neutron-Star Crash: A Gravitational Waves Discovery in Pictures]
In the new study, researchers analyzed data gathered by NASA's Chandra X-ray Observatory after the gravitational waves — ripples in space-time first predicted by Albert Einstein a century ago — were detected by the Laser Interferometer Gravitational Wave Observatory (LIGO) project.
LIGO data revealed that the object created by the neutron-star merger is about 2.7 times the mass of the sun. It is therefore either the lowest-mass black hole ever identified, or the most massive neutron star, the researchers said.
But the study team is putting its money on the black hole interpretation. If the two neutron stars collided to form a single, heavier neutron star, the resulting object would likely have a strong magnetic field that produces bright X-ray emissions, researchers said. However, the Chandra observations revealed low X-ray levels.
"We may have answered one of the most basic questions about this dazzling event: What did it make?" study co-author Pawan Kumar, of the University of Texas at Austin, said in a statement. "Astronomers have long suspected that neutron star mergers would form a black hole and produce bursts of radiation, but we lacked a strong case for it until now."
If this hypothesis is confirmed, it could shed light on black holes, the darkest objects in the universe. (The lightest-known black holes harbor a minimum of four to five times the mass of the sun.)
Not all black holes form the same way, but this ultra-low-mass black hole would have taken shape after two supernova explosions left two neutron stars in a close-enough orbit for gravitational-wave radiation to help them collide — a strange and complicated journey, study team members said.
It would also be very interesting if astronomers determined that GW170817 generated a single gigantic neutron star. Such a result would challenge theories about the structure and formation of these exotic objects, researchers said.
"GW170817 is the astronomical event that keeps on giving," study co-author J. Craig Wheeler, also of the University of Texas, said in the statement. "We are learning so much about the astrophysics of the densest known objects from this one event."
Fellow study co-author Bruce Grossan, of the University of California at Berkeley, voiced similar sentiments.
"At the beginning of my career, astronomers could only observe neutron stars and black holes in our own galaxy, and now we are observing these exotic stars across the cosmos," Grossan said. "What an exciting time to be alive, to see instruments like LIGO and Chandra showing us so many thrilling things nature has to offer."
The new study was published online May 31 in The Astrophysical Journal Letters.
Original article on Space.com. | 0.870977 | 4.043243 |
‘To see a World in a Grain of Sand…” was a flight of William Blake’s poetic fancy. Closer to the ground is the work of a group of scientists who leverage existing knowledge of the internal combustion engine, which powers motor cars, to make sense of the atmosphere of giant planets in close proximity of distant suns.
O Venot, E Hébrard, M Agúndez, M Dobrijevic, F Selsis, F Hersant, N Iro and R Bounaceur, astronomers and applied combustion experts from the universities of Bordeaux and Lorraine in France, Keele University in the UK, the CNRS lab in Floirac, France and the Observatory of Paris, describe in Astronomy and Astrophysics, the journal of the European Southern Observatory, the value of “importing well-tried methods from any other field whenever they exist,” to solve problems thrown up in research.
A large number of planets in solar systems that exist deep in space have been discovered in the last few decades. While the quest has been to find “Earth-like” planets, or planets with temperature that could support liquid water and hence life, many planets with different characteristics have been discovered too.
One class of such planets is that of Hot Jupiters or planets the size of Jupiter, or over ten times the size of the Earth and orbiting very close to the mother star.
We have good methods to study the fiercely hot atmosphere of the sun and stars, and we have some understanding of their interiors. But it is recently that we have started grappling with atmospheres that are not nearly as hot, in these planets that are nearly 50 times closer to their suns than the Earth.
The temperature of the Sun goes from some 5000°C at the surface to millions of degrees in the core. A feature of gases at such temperatures is that the atoms in their molecules separate and lose their outer electrons, to behave as fast-moving, charged objects.
Models of such objects in behaving as gases have been developed and features of such atmospheres, like the Sun’s, where the outermost layer seems to be hotter than layers that lie below, have been explained.
The atmosphere of Hot Jupiters, in contrast, are comparatively cooler, at 1000°C to 3000°C, and the behaviour is not quite like a gas of charged particles. Nor do the usual laws of motion that work when applied to gases lead to satisfactory results.
When pressures and speeds of movement get exceedingly high, as in Hot Jupiters, the approximations, like treating an atom as an object with zero dimensions, break down and chemical reactions that cannot take place in ordinary conditions become possible.
As Hot Jupiters are very close to their suns, which are at great distances from the Earth, any reflected light from the planets is swamped by the glare of the sun. There are hence no methods of directly seeing what goes on in such atmospheres.
These planets themselves have been detected only thanks to a wobble that such massive satellites impart to the mother star, or by the dip in the intensity of light from the star when the planet passes it during its orbit.
Any information about the atmosphere comes to us by analysing the starlight that passes through the atmosphere of the planet when the planet goes past the star. Variations in the dim reflected light during phases of a large planet in orbit also indicate what gases the atmosphere contains.
The high pressures and temperature, the intense radiation from the mother star and the winds and currents, however, bring about rapid chemical changes in the composition of the atmosphere, the paper in the journal says.
Understanding the course of changes, calls for models that mimic the complex and rapid processes taking place.
Creating such a model, or a sequence of causes and effects that could account for the information that is available, or could suggest features that should be looked for, would need two things, the paper says. One is a list of the different players and their interactions in the process.
And the other is to have data of how the ensemble of reactants would behave in time. The available literature, however, is not good enough to plan, or experimental facilities sufficient to test possible models, the paper says.
Despite the lack of dedicated facilities to study conditions in Hot Jupiters, members of the team had noted that very similar conditions exist within the cylinders of motor car engines. The temperatures in internal combustion engines rise to some 2500°C and pressure rises to 1,500 psi, or over a hundred times the atmospheric pressure.
In recent times, the drive to build more environment-friendly and less polluting petrol engines has led to wide research into the behaviour of gases and the chemical reactions that are encouraged or inhibited at this range of temperatures and pressures.
As the fuels that burn in automobile engines contain hundreds of forms of hydrocarbon molecules, the focus has been on finding models that simulate the main combustion parameters, like when the fuel starts to burn, how the flame spreads, distribution of heat generation.
These are the features that help the design of engines or burners, to estimate the fuel consumption, and to visualise how some of the main pollutants (carbon monoxide, nitrogen oxides, unburned hydrocarbons and particulate matter) are formed. “Most of these models were developed for industrial applications and have been validated in a range of temperatures and pressures,” the paper says.
The paper notes that the fuels that burn in internal combustion engines consist of carbon, hydrogen, oxygen and nitrogen, which are also the main constituents of the molecules and molecular groups found in Hot Jupiter atmospheres. The existing models created for IC engines hence find ready extension to picture the dynamics of Hot Jupiter atmospheres.
Current observations of very hot planets are still tentative and can be interpreted in different ways. But with facilities that are under development, data is expected to become more elaborate and chemical modelling will become an important part of the analysis, the paper says.
Even this bare access is now possible only with the very hot class of exoplanets. With better instruments, the atmosphere of even planets would come within reach.
The nature of molecules present and the dynamics of the atmosphere would be different. Here, again, it is the validated models derived from automobile engine studies that would help model those distant atmospheres, the paper says.
The writer can be contacted at [email protected] | 0.857294 | 3.793069 |
The recent discoveries of terrestrial exoplanets and super-Earths extending over a broad range of orbital and physical parameters suggest that these planets will span a wide range of climatic regimes. Characterization of the atmospheres of warm super-Earths has already begun and will be extended to smaller and more distant planets over the coming decade. The habitability of these worlds may be strongly affected by their three-dimensional atmospheric circulation regimes, since the global climate feedbacks that control the inner and outer edges of the habitable zone - including transitions to Snowball-like states and runaway-greenhouse feedbacks - depend on the equator-to-pole temperature differences, patterns of relative humidity, and other aspects of the dynamics. Here, using an idealized moist atmospheric general circulation model including a hydrological cycle, we study the dynamical principles governing the atmospheric dynamics on such planets. We show how the planetary rotation rate, stellar flux, atmospheric mass, surface gravity, optical thickness, and planetary radius affect the atmospheric circulation and temperature distribution on such planets. Our simulations demonstrate that equator-to-pole temperature differences, meridional heat transport rates, structure and strength of the winds, and the hydrological cycle vary strongly with these parameters, implying that the sensitivity of the planet to global climate feedbacks will depend significantly on the atmospheric circulation. We elucidate the possible climatic regimes and diagnose the mechanisms controlling the formation of atmospheric jet streams, Hadley and Ferrel cells, and latitudinal temperature differences. Finally, we discuss the implications for understanding how the atmospheric circulation influences the global climate.
- planets and satellites: atmospheres
- planets and satellites: fundamental parameters
- planets and satellites: terrestrial planets
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science | 0.832692 | 3.766259 |
Grade: 6 and 7
Teachers: Nelson Portillo, Ramon Azuaje
Target: Rhea and Tethys
Carlota Suarez (team Leader) Colegio Altamira
Fernando Novoa liceo Los Robles
Albenis Salas Liceo Los Robles
Juan Reyes Liceo Los Robles
Fernan Chacon Liceo Los Robles
Salomon Galiz Liceo Los Robles
Jorge Cardenas Liceo Los Robles
Joaquin Cardenas Liceo Los Robles
Rafael Atencio Liceo Los Robles
Juan Diego Contreras Liceo Los Robles
"We chose Rhea and Tethys target 3 because we find that in the case of Rhea,Saturns second largest moon, with an amazon diameter and the fact that one hemisphere always faces Saturn.
It's hot in the side facing the Sun (174 degrees and minus 364 in shaded areas). These phenomenon really draws my attention I find it exclusively unique in this mini solar system", also it has a high reflection area suggesting lots of ice, so these facts drive us nuts! Wow, whats going on in this moon?? Are there any other unusual phenomena going on there? When Voyagers 1 and 2 pictured Rhea they observed that one area had craters 40 km wide on average ,and the other area had craters with less than 40 km diameter! these according to Nasa, JPL indicates that at some time, some type of resurfacing event took place there!* was it recent we ask ?' will it repeat? When? Also we observed at the pictures on JPL's website that Rhea has wispy lines, and Cassini spacecraft later on demonstrated that there are subsidence fractures, with canyons ,some of them several hundred meters high!!
We ask again: whats going on there? The walls are bright, darker material covers them. From where does these materials come from? Are these processes still on the move. We sincerely urge that target 3 should be the primordial objective,We think Rhea, and Tethys on the same frame, could provide some answers to these processes!! Are they interacting gravitationally or chemically??
We say lets give it a "go" to target 3." | 0.825082 | 3.268511 |
NASA scientists believe they have found as many as five stars that bear a stunning resemblance to Eta Carinae, the brightest known superstar in the Milky Way.
Astronomers working with NASA’s Jet Propulsion Laboratory in Pasadena, CA have made a stunning discovery. According to a Tech Times report, researchers studying Eta Carinae, the biggest and brightest solar system in the Milky Way, have discovered up to five potential twin stars by examining their infrared and optical fingerprint in the sky.
Over the course of 2012 to 2014, a NASA team scanned seven different galaxies but were unable to find any stars that resembled Eta Carinae. Last year, the team followed up on their surveys and discovered two possible Eta twins in the M83 galaxy, situated roughly 15 million light-years from the Earth. Subsequent followups revealed three additional potential Eta twins, in the galaxies M101, M51, and NGC6946, ranging from 18 to 26 million light-years from the Earth.
Much like Eta Carinae, the five stars located by NASA researchers could conceal a massive star beneath a huge cloud of gas and dust. The findings were published in the December 2015 edition of The Astrophysical Journal Letters. Further studies will need to be carried out in order to determine whether each of the five stars are truly similar to the supermassive Eta Carinae, but the discovery once again confirms that the forces driving stellar and galactic formation throughout the universe are relatively similar.
Eta Carinae became notorious in the mid-1800s after it withstood a massive stellar explosion. This explosion launched a shroud of debris and gas with roughly 10 times the sun’s mass into space.
The dust from the explosion is still settling around Eta Carinae, which gives it its unique shape. The star is roughly 7,500 light-years from the Carina constellation, but is so bright that it outshines our own sun by a factor of almost 5 million. Eta Carinae is actually a binary system, made of two massive stars. The larger one is roughly 90 times the sun’s mass, and the smaller is only 30 times the sun’s mass. The system’s proximity to Earth’s position in the Milky Way makes it the perfect subject for studying massive stars and the forces that drive their evolution.
A press release from NASA’s Jet Propulsion Laboratory describing the massive stars can be found here. | 0.858005 | 3.372236 |
Title text: Unfortunately, NASA regulations state that Bertrand Russell-related payloads can only be launched within launch vehicles which do not launch themselves.
Russell's Teapot is a philosophical argument that reflects on the difficulty of trying to prove a negative. It involves a hypothetical teapot orbiting a heavenly body, whose existence hasn't been proven, and states that it cannot be disproven (Somebody put it there secretly?). While an instrument could be theoretically engineered to pick out a teapot-sized object of any luminosity, the teapot would be very easy to confuse for other pieces of space debris, and the space to search is extremely large; the task is thus akin to the proverbial search for a needle in a haystack.
Bertrand Russell devised this analogy "to illustrate that the philosophic burden of proof lies upon a person making unfalsifiable claims, rather than shifting the burden of disproof to others." As such, Russell's teapot is very often used in atheistic arguments.
"He wrote that if he were to assert, without offering proof, that a teapot orbits the Sun somewhere in space between the Earth and Mars, he could not expect anyone to believe him solely because his assertion could not be proven wrong." (Wikipedia)
Cueball is trying to settle the teapot argument by actually launching a teapot into space via a crowdfunding campaign. This misses the point of Russell's argument, which is about unfalsifiable claims in rhetoric and not a literal teapot.
"CubeSat-based design" refers to a type of miniaturized satellites that is made up of 10-centimeter cube units (here seemingly consisting of 3 units) and enables cost-effective means for getting a payload into orbit.
The title-text refers to Russell's paradox, also formulated by Bertrand Russell. Russell's paradox was a flaw found in naïve set theory where one could consider "the set of all sets that do not contain themselves" (a "set" is a mathematical term for a "group of things" -- "things" in this case including a set itself). The paradox arises with whether this set, in turn, contains itself: if it does, then it cannot; if it doesn't, then it must. Similarly, like in the barber paradox, the vehicle which launches only vehicles which do not launch themselves is impossible: if the vehicle takes off, it must launch itself as well as the teapot, and thus can never be launched (without violating alleged NASA regulations, at least). That said, he might get around those regulations by using an initial first stage with an offboard power source for the moment of launch, for example a laser striking a parabolic mirror and massively heating air beneath the craft, causing expansion, or a compressed gas cold launch system such as used to clear submarine launched missiles from their tubes before the real rocket motor ignites.
The barber paradox can be stated as follows: "Consider a town in which a man, the barber, shaves precisely those men who do not shave themselves. Does the barber shave himself?" Either answer, yes or no, leads to a contradiction. Sometimes the paradox is incorrectly stated, replacing "precisely those" with "only". Under that scenario, there is no paradox; the barber is merely unkempt.
There is, however, a solution in this case. Instead of launching itself, the teapot-containing vehicle may be fired from a space gun, catapult, or other launcher, and then boost itself the rest of the way. This, while true for the CubeSats themselves, is not true for their carrier.
Randall has talked about CubeSats in later comics as well, specifically in 1992: SafetySat and 2148: Cubesat Launch.
Potential List of Labeled Items
From the top right, clockwise.
| Item #
|| Possible Label
|| Possible Description
|| Classic teapot, the point of the satellite.
|| Holds Teapot in Place
|| Vehicle Equipment Bay
|| With foldable antenna and stabilizers
|| Milk / Lemon Juice
|| add to taste. Either/Or
|| Combustion Chamber
|| Micro-USB connector
|| To charge the Battery
|| Powers the Heater Unit (q.v.)
|| Heater Unit
|| To keep the tea from freezing
|| Display Cabinet
|| Protects the teapot from micrometeorites
- [Cueball is standing in front of a blueprint labeled "CubeSat-Based Design", containing a satellite with a teapot in the top.]
- [Caption below the panel:]
- I'm crowdfunding a project to launch a teapot into orbit around the sun to settle the Russell thing once and for all.
add a comment! ⋅ add a topic (use sparingly)! ⋅ refresh comments!
In this case, nesting the teapot in a catapult/cannon which is launched by another catapult/cannon might perhaps be sufficient to get past NASA regulations. (Catapults/cannons only launching the payload and not themselves...) --Nialpxe, 2017. (Arguments welcome)
- Though there's still the matter of an equal and opposite force pushing the satellite away from its gravitational bonds of the catapult. Even if the 2nd catapult is no longer associated with the Earth or Earth's gravity, the catapult will continue to be a launcher. That's just changing what it is launching *from*. 22.214.171.124 18:31, 24 July 2017 (UTC)ColinHeico
- But make sure it is a mobile cannon, otherwise it would not qualify as a launch vehicle. 126.96.36.199 11:32, 21 July 2017 (UTC)
- I immediately thought "railgun". And the payload can still be a rocket; once it's not touching the ground it's accelerating, not launching. (Also Russell failed to account for female barbers. Honestly, people!) 188.8.131.52 09:42, 22 July 2017 (UTC)
- One such company did exist, Quicklaunch had the idea of launching via a space gun. https://en.m.wikipedia.org/wiki/Quicklaunch 184.108.40.206 (talk) (please sign your comments with ~~~~)
- He didn't need to account for female barbers (or anybody who isn't a man) because the barber in the paradox shaves precisely those men who don't shave themselves. He only shaves men, and all men in the town are only shaved by him or themselves. Everyone else is a completely different story, so they can be shaved by whoever they want (except the barber, who only shaves men). 220.127.116.11 00:14, 23 July 2017 (UTC)
- Only if you assume that females who are barbers don't shave their legs, armpits, or their various lady parts. This only further confuses the paradox. -- Mjm87 (talk) (please sign your comments with ~~~~)
- For much of Bertrand Russell's life, they didn't. http://mentalfloss.com/article/22511/when-did-women-start-shaving-their-pits 18.104.22.168 09:42, 22 July 2017 (UTC)
- Why are we even bringing up the argument of female barbers when the description of the paradox, at least as phrased within this article, specifically states that the barber is a man? —CsBlastoise (talk) 18:30, 4 December 2017 (UTC)
- Never mind, I just checked the page history, and it appears there was no description of the barber paradox in this article at the time the majority of the preceding comments were written. —CsBlastoise (talk) 18:56, 4 December 2017 (UTC)
- You wouldn't even need a cannon/catapult. If you put the satellite on a small rocket, and put that on a much larger rocket, you can have the big one launch itself, the smaller one, and the satellite. The regulation only says the satellite must be in a non-self-launching launch vehicle. It doesn't say it can't *also* be in a self-launching launch vehicle. -- 22.214.171.124 20:06, 24 July 2017 (UTC)
When I first saw this comic I immediately thought of the Utah Teapot, it's a model used in computer graphics because it's simple and has both convex and concave surfaces. Both teapots, I would assume, (I've only just heard of Russel's Teapot so I could be wrong) are well known to different parts of the nerd community? 126.96.36.199 (talk) (please sign your comments with ~~~~)
Hopefully it will support HTCPCP-TEA. 188.8.131.52 17:48, 21 July 2017 (UTC)
i think people just really like teapot examples 184.108.40.206 (talk) (please sign your comments with ~~~~)
- The major problem here is that CubeSats are currently only launched into Low Earth Orbit (LEO) and are expected to re-enter the atmosphere within days to weeks. Russell's teapot is (allegedly) in orbit between Earth and Mars and Cueball's device is not likely to have enough delta-v to leave Earth orbit. SteveBaker (talk) 18:18, 21 July 2017 (UTC)
"A teapot orbits the Sun somewhere in space between the Earth and Mars" This implies that the teapot is physically located between Mars and Earth at all times. Which if true would be a highly irregular orbit requiring constant velocity changes, which is an impossible feat to achieve with current teapot technology. -- Mjm87 (talk) (please sign your comments with ~~~~)
- Nonsense. It would be a highly regular orbit and many asteroids are already there, despite the most of them are between Mars and Jupiter (Asteroid-Belt):--Dgbrt (talk) 21:22, 21 July 2017 (UTC)
- Since we're nitpicking. Having velocity changes does not preclude being in orbit: objects in orbit are always accelerating. Having a constant velocity change does preclude being in orbit, but it also precludes remaining between Earth and Mars, since it would result in eventually leaving the solar system.--220.127.116.11 19:45, 24 July 2017 (UTC)
- Still nonsense. The mean velocity of an (elliptic) orbit is constant, only the direction is changing. And there are many asteroids in stable orbits between Earth and Mars. Leaving the solar system would require many energy at those orbits, all human build probes (Pioneer, Voyager and New Horizons) had to use gravity assist at Jupiter to reach this target.--Dgbrt (talk) 14:12, 26 July 2017 (UTC)
- It sounds to me like you're missing the interpretation Mjm87 is trying to share. Yes, the way Russell meant it was that Russell's Teapot is between Mars and Earth in the same way that Earth is between Mars and the Sun, that this teapot is in a larger orbit than Earth and smaller than Mars. Mjm87's interpretation adds the idea that not only is it in such an orbit, but also in a direct line in between, always. In other words, that someone looking at Mars through a powerful telescope would always be able to see Russell's Teapot "in the way", like a little Mars eclipse. :) Staying in that spot would indeed take strange acceleration. I'm no astrophysicist or anything, but I imagine if I think of our galaxy as a clock face, with Earth always at the 12 o'clock position, that Mars would at some point be at 3 o'clock, at another time be at 9 o'clock, etc. (of course this is a 2D intepretation of a 3D situation, but I hope you get my point. Actually the third dimension would make this orbit even stranger) NiceGuy1 (talk) 05:16, 28 July 2017 (UTC)
I can see both of your points. As mjm87 says, "between the Earth and Mars", taken literally, would mean "on a line between the two planets", which would be a very unusual orbit. And, I agree, it would be impossible without constant velocity changes, so wouldn't be an "orbit" in the usual sense.
On the other hand, I took Russell's words the way Dgbrt seems to have, as meaning "between the orbits of Earth and Mars", as this is the way most astronomers would interpret it. A don't know that there are "many" asteroids that remain between Earth and Mars, but there are quite a few crossing the space, and at least a few with average distances in that range. - N Kalanaga 18.104.22.168 (talk) (please sign your comments with ~~~~)
- There is also quantifier scope ambiguity there. I believe that there is a large constellation of teapot statites, and at any given moment at least one of them is directly between Earth and Mars. --22.214.171.124 06:29, 22 July 2017 (UTC)
Since Russell was going for absurdity, I favour the more absurd interpretation namely Mjm87's. Capncanuck (talk) 08:21, 22 July 2017 (UTC)
- Taking "on a line between the two planets" literally would simply reduce to "inside the orbit of Mars". The Earth moves faster than Mars and right now the Sun is exactly between them on that line. NASA, ESA, and ISRO can not communicate with their orbiters and rovers until the beginning of August (see Solar conjunction). So the meaning "between the orbits of Earth and Mars" is still much more plausible.--Dgbrt (talk) 16:11, 22 July 2017 (UTC)
- What if it's in the Earth-Mars L1 point? Then it's always on a line between the two planets. Promethean (talk) 06:02, 26 July 2017 (UTC)
- Lagrangian points exist for Earth-Sun, Mars-Sun, or Moon-Earth (small object orbits a larger one). There is nothing similar for Earth-Mars. Earth moves faster around the sun and the closest approach happens every 26 months at a distance not less than 55 Mio. km. 13 months later the maximum distance is approx. 400 Mio. km and the sun is in the middle as it happens right now!--Dgbrt (talk) 13:46, 26 July 2017 (UTC)
Don't worry we have been working on it. Launching the project in a few months.
Zackdougherty (talk) 03:10, 22 July 2017 (UTC)
- Actually, it couldn't be on a direct line between Earth and Mars because then it would be tremendously easier to find (or disprove)! If the teapot can be anywhere between the orbits, then that is a vastly larger space to look for a teapot and therefore more difficult to disprove. Similarly, it is unlikely there are a whole constellation because then it would be more likely to find at least one. 126.96.36.199 03:19, 25 July 2017 (UTC)
Could some people (smarter than myself) make an attempt at labeling the items on the cube sat that Randall left at squiggles? Maybe starting from the top, clockwise? I'll start a table, but I'm sure someone will need to fix it. DanB (talk) 03:24, 25 July 2017 (UTC)
- Personally, I suspect such a diagram wouldn't have the top labelled as "Teapot", but as "Payload". :) To me it looks even longer, so perhaps "Top Secret Specialty Payload" or something? NiceGuy1 (talk) 05:05, 1 August 2017 (UTC)
The title text refers to Russell's paradox, and it is funny that Russell came to it thinking about teaspoons : "The class of teaspoons, for example, is not another teaspoon, but the class of things that are not teaspoons, is one of the things that are not teaspoons." See https://math.stackexchange.com/questions/1046863/how-can-a-set-contain-itself for the exact source.
188.8.131.52 08:29, 28 July 2017 (UTC)
Amusingly Russell's original words, atleast as far as I've seen them quoted, literally described the teapot as being a planet. They stated something like "what if I said that orbiting the sun between Earth and Mars was a small planet the shape and size of a teapot...". The "thought experiment" dies a pretty quick death when you consider the current IAU definition of a planet, that it must be large enough to pull itself into a sphere from self-gravity(no marks for the teapot) and it needs to be gravitatonally dominant in it's orbital regions (no chance for something so low in mass), although that latter point tends to provoke the Pluto debate. Either way , by the strict definition, there isn't a teapot shaped "planet".Also if you don't call the teapot a planet, but do stick to Russell's words about an elliptical orbit you can probably calculate that something so small waving about between the orbits of Earth and Mars will end up being ejected due to a gravitational tug or resonance somewhere, probably from Jupiter (given Jupiter's mass it perturbs just about anything even when things are inside the orbit of Mars), once again profound philosophy gets an unfortunate surprise from orbital dynamics.184.108.40.206 23:39, 2 August 2017 (UTC)
- Nope. Russell said: "...a teapot orbits the Sun somewhere in space between the Earth and Mars." He didn't say the teapot is a planet. And in 1952 the IAU definition from 2006 didn't exist and Pluto was still a planet. --Dgbrt (talk) 18:55, 3 August 2017 (UTC)
How come that noone mentioned **418**? 220.127.116.11 18:43, 7 August 2017 (UTC) | 0.844963 | 3.13054 |
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CAPTURING COSMIC RAYS WITH A DIGITAL CAMERA
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CAPTURING COSMIC RAYS WITH A DIGITAL CAMERA
Rudy E. Kokich
Cosmic Rays are extremely energetic subatomic particles which fly through the universe at speeds approaching the speed of light. They were discovered in the early 1900's by Wolf, Pacini, Hess, and Millikan, who carried out extensive research on ionizing radiation using shielded electrometers, which measure electric charge on a metal plate or a ball. They showed that ionizing radiation was present deep under ground and under water, that its levels were much higher at higher altitudes, and that the levels varied at different latitudes on the Earth's surface. The results suggested that this radiation originated in outer space, and was composed of charged particles which are influenced by the Earth's magnetic field. The extreme energy of this radiation was demonstrated by the fact that it penetrated without significant attenuation to electrometers enclosed in thick metal containers.
With the development in subsequent decades of high altitude air travel and space travel, research on cosmic rays, and their effects on the human body and delicate electronic circuits became ever more important. By comparing ground-based and space-based research, it was confirmed that cosmic rays are not electromagnetic radiation, but subatomic particles which can be divided into two types: primary and secondary.
Primary cosmic rays are charged subatomic particles arriving from outer space at nearly light speed velocities. 88% are protons, or nuclei of Hydrogen. 10% are nuclei of Helium composed of two protons and two neutrons, also known as alpha particles. 1% are nuclei of heavier, more complex elements in the periodic table, present in approximately the same relative abundance as in the solar system. And 1% are isolated electrons. It is not known why electrons are markedly less efficiently accelerated than atomic nuclei.
In particle physics, energy is measured in electronvolts (eV). One eV, equal to approximately 1.6 x 10-19 joules (J), is the energy change on a single electron as it moves across the electrical potential difference of 1 Volt. On the average, a primary cosmic ray particle carries the energy of 4.8 x 10-11 J, which corresponds to 3 x 108 eV, or to the velocity of 2/3 the speed of light. However, few particles move at nearly the speed of light, and carry the energy of 3 x 1020 eV, which is - incredibly - sufficient to light a 100W light bulb for 1 second. This is also equivalent to the kinetic energy of a baseball flying at 100 miles per hour. By comparison, the highest energy particles produced by the upgraded Large Hadron Collider are in the range of 13 x 1012 eV, some 23 million times weaker. Such Very High Energy Cosmic Rays are fortunately very rare, with the estimated incidence of only a single event per square kilometer of Earth's surface per century.
Main sources of the primary cosmic ray particles are presumed to be shock waves from supernova events and magnetic fields around neutron stars, pulsars, and accretion discs around black holes in active galactic centers. Since the particles are charged, and deviated by strong galactic, interplanetary, and planetary magnetic fields, the direction of the original source can not be directly determined. The Sun also serves as an intermittent source of relatively low energy cosmic ray nuclei and electrons, which are accelerated by the shock waves in the solar corona and by solar flares. During periods of high solar activity, local density of charged particles may increase between 100 and 1 million times, and last up to several days.
When primary cosmic rays enter the Earth's atmosphere, they collide with atoms and molecules in the air resulting in Secondary Cosmic Rays: showers of high energy subatomic fragments which in turn decay into other particles and gamma rays. At the Earth's surface, the most common secondary particles are Muons, negatively charged Leptons, similar to electrons, but with 207 times greater rest mass. Only 3% of the cosmic rays on the surface are primary cosmic rays.
Muons are thought to be generated with the mean energy of 6 GeV (6 x 109 eV) at the altitude of 15,000 meters. They interact very little physically with ordinary matter but, since they carry a negative charge, they do lose energy by ionizing atoms near which they pass. The longer the path through a material, the greater the energy loss. At sea level, where they constitute about half the natural background radiation, the mean energy of muons is around 4 GeV. This allows them to penetrate deep under water, and over 700 meters under ground. To fully shield from most secondary cosmic rays would require a wall of iron 2 meters, or 6 feet thick.
Like other elementary particles, the muon can exist as ordinary matter: called negative muon, or antimatter: called antimuon or positive muon. Positive muons decay 100% of the time into positrons, antineutrinos, and neutrinos. However, negative muons of ordinary matter may follow one of two paths. Some decay into electrons, neutrinos, and antineutrinos, while others may rejoin matter by capture into very tight orbits around atomic nuclei where they combine with a proton to produce a neutron and a neutrino.
Muons are unstable elementary particles with a half-life of 2.2 µs (microseconds). This means that every 2.2 millionths of a second half of all the muons spontaneously decay into more stable particles. During that time light covers only 660 meters. Virtually no muons would survive long enough to traverse the 15,000 meter trip through the Earth's atmosphere were it not for the relativistic effects of time dilation. Due to their velocity, which is near the speed of light, time on a muon passes about 40 times more slowly than in our frame of reference, and its half-life is proportionately longer. This allows it a sufficient life span to travel through the atmosphere.
Muons can be detected with cloud chambers, Geiger counters, and scintillator detectors, but can also be recorded with common digital camera CCD and CMOS chips which are sensitive to charged particles. Muon flux at the surface of the Earth averages approximately 1 particle per square centimeter per minute. The surface area of the APS-C camera sensor (22.3 x 14.9 mm) is 3.3 cm2, which means that we can expect on average 3 muon strikes on the sensor during a 1 minute exposure.
The following methods were used to obtain images listed below:
- Camera: Canon T3i, lens removed and replaced with a light-tight body cap.
- Camera set to BULB for long exposures, with remote control shutter switch attached.
- Sensitivity set to ISO 1600. Higher sensitivities result in too much thermal noise. Less sensitivity results in less distinctive muon trails.
- Image quality in camera's Menu set to maximum resolution 18M (5184x3456), JPG format.
- In camera's Menu, go to Custom Functions, C.FnII:Image, turn on Long exp. noise reduction. This feature automaticaly takes an appropriate dark exposure to eliminate defective pixels in the original photo. In spite of this, some isolated defective or hot pixels may still appear on long exposure photos at high sensitivity settings. However, it is statistically extremely unlikely for several defective pixels to appear in a cluster or a row, adjacent to one another.
- On the Canon T3i camera, turning off Live View before taking a long exposure eliminates amplifier glow.
Examples of Amplifier Glow, and Defective or Hot Pixels and Thermal Noise on magnified images
- Since most cosmic rays arrive at high angles to the horizon, the camera is placed on its back so that the CMOS sensor is horizontal, and maximally exposed to the cosmic ray flux.
- The length of exposure should be 1 to 3 minutes. Longer exposures result in more thermal noise. Shorter exposures are less likely to capture cosmic rays. Keep in mind that the camera will then automatically take a "dark" exposure of equal duration.
- Images, which appear entirely black at low magnification, are magnified about 5x (approximately 20% crop) with image processing software, slowly scanned, and examined for "dots", "clusters", and "streaks". These are further magnified to reveal muon trails similar to those shown below.
-Image processing software used here for magnification and cropping was XnView, but a number of other excellent freeware programs are suitable.
-Pixel "clusters" are caused by muons striking the sensor at high angles, while "streaks" are created by muons striking at lower angles. There is no statistical confidence that single, isolated, illuminated pixels, or "dots", are caused by muon collisions rather than residual defective or "hot" CMOS pixels. Isolated "dots" should be excluded from the muon count.
Several interesting cosmic ray studies are available to amateurs and students.
The camera may be placed upright, with the sensor in the vertical position, which should, in theory, result in more "streaks", and fewer muon trails overall.
The camera may be covered with a thick metal pot, which should not result in the decrease in the muon flux since muons readily pass through matter.
Daytime and night-time muon flux may be compared during periods of known high and low solar activity.
It is reasonable to assume that the total number of illuminated pixels in a "cluster" or a "streak" is proportional to the energy level of the incident muon. With data from a large number of muon trails it is possible to draw a histogram with the number of illuminated pixels on the X-axis, and the number of muon trails on the Y-axis. Such a histogram would reflect the distribution of relative muon energy under the given experimental conditions.
There are several venues where tourists may visit deep under ground. One is the nickel mine in Sudbury, Ontario. Another is Ruby Falls in Chattanooga, Tennessee. If an opportunity presents to take measurements, muon flux and mean energy should be significantly lower deep under ground than on the surface.
Conversely, taking measurements during high altitude airplane flights should show more numerous and more energetic muon trails and, possibly, an occasional primary cosmic ray trail.
- noisejammer, Snickersnee, LB16europe and 4 others like this | 0.830022 | 3.281307 |
May is the best time to try and spot one of the most enduring unsolved mysteries in our Solar System. Ashen Light is a faint glow allegedly seen on the unlit portion of Venus, during its crescent phase, similar to the earthshine often observed on the Moon, though not as bright. It is more commonly observed while Venus occupies the evening sky, as now, than when it is in the morning sky. But no one really knows for sure what causes it.
So what’s the history of our knowledge about this enigmatic glow?
The phenomenon was first noted in 1643, by Italian astronomer Giovanni Battista Riccioli. Though many notable astronomers have reported sightings in the 369 years since, including Sir William Herschel and more recently, Sir Patrick Moore, many others have failed to see the effect, leading to claims that it is due to nothing more than observer error, an illusion, atmospheric effect or equipment malfunction. Things are not helped by the fact that nobody has managed to capture an image of Ashen Light, yet.
As the month progresses, Venus nears the Sun, ready for its transit on June 5th to 6th and the planet’s crescent phase will increase in diameter during the month, from 37 arcseconds to 56 arcseconds. The best option for amateur astronomers hoping to catch a fleeting glimpse is to use an occulting bar to block the bright crescent, making any glow present on the unlit portion of Venus, more visible.
There is much controversy and many theories as to the cause of Ashen Light. The Keck 1 telescope on Hawaii reported seeing a subtle green glow and suggested it could be produced as ultraviolet light from the Sun splits molecules of carbon dioxide, known to be common in Venus’ atmosphere, into carbon monoxide and oxygen, but the green light emitted as oxygen recombines to form O2 is thought too faint to explain the effect. Another more likely theory is that multiple lightning strikes are illuminating Venus’ skies. Though the Cassini spacecraft flew by Venus twice on it’s voyage to Saturn and failed to detect the high frequency radio noise we associate with thunderstorms on Earth, in 2007 Venus Express did detect low frequency ‘whistler waves’ that can also result from lightning. It could also be the Venusian equivalent of aurorae.
By far the most bizarre theory, and my personal favourite, was proposed in the early 19th century by the Bavarian astronomer Franz von Gruithuisen, who suggested that Ashen Light was the result of fires lit to clear land for farming on Venus, or to celebrate the coronation of a new Venusian Emperor!
For further reading, a paper on Ashen Light by C. T. Russell and J. L. Phillips | 0.849485 | 3.971735 |
UH Part of World’s Largest Digital Sky SurveyJanuary 28, 2019, 10:05 AM HST (Updated January 28, 2019, 10:05 AM)
The Space Telescope Science Institute (STScI) in Baltimore, Maryland, in conjunction with the University of Hawaiʻi Institute for Astronomy (IfA), is releasing the second edition of data from Pan-STARR—the Panoramic Survey Telescope & Rapid Response System—the world’s largest digital sky survey. This second release contains over 1.6 petabytes1 of data, making it the largest volume of astronomical information ever released. The amount of imaging data is equivalent to two billion selfies, or 30,000 times the total text content of Wikipedia. The catalog data is 15 times the volume of the Library of Congress.
The Pan-STARRS observatory consists of a 1.8-meter telescope equipped with a 1.4 billion pixel digital camera, located at the summit of Haleakalā, on Maui. Conceived and developed by the IfA, it embarked on a digital survey of the sky in visible and near-infrared light in May 2010. Pan-STARRS was the first survey to observe the entire sky visible from Hawaiʻi multiple times in many colors of light. One of the survey’s goals was to identify moving, transient, and variable objects, including asteroids that could potentially threaten the Earth. The survey took approximately four years to complete, scanning the sky 12 times in five filters. This second data release provides, for the first time, access to all of the individual exposures at each epoch of time. This will allow astronomers and public users of the archive to search the full survey for high-energy explosive events in the cosmos, discover moving objects in our own solar system, and explore the time domain of the universe.
Dr. Heather Flewelling, a researcher at the Institute for Astronomy in Hawaiʻi, and a key designer of the PS1 database, states that “Pan-STARRS DR2 represents a vast quantity of astronomical data, with many great discoveries already unveiled. These discoveries just barely scratch the surface of what is possible, however, and the astronomy community will now be able to dig deep, mine the data, and find the astronomical treasures within that we have not even begun to imagine.”
“We put the universe in a box and everyone can take a peek,” said database engineer Conrad Holmberg.
The four years of data comprise 3 billion separate sources, including stars, galaxies, and various other objects. This research program was undertaken by the PS1 Science Consortium—a collaboration among 10 research institutions in four countries, with support from NASA and the National Science Foundation (NSF). Consortium observations for the sky survey were completed in April 2014. The initial Pan-STARRS public data release occurred in December 2016, but included only the combined data and not the individual exposures at each epoch of time.
“The Pan-STARRS1 Surveys allows anyone access to millions of images and catalogs containing precision measurements of billions of stars, galaxies, and moving objects,” said Dr Ken Chambers, director of the Pan-STARRS Observatories. “While searching for Near Earth Objects, Pan-STARRS has made many discoveries, from ʻOumuamua passing through our solar system, to lonely planets between the stars; it has mapped the dust in three dimensions in our galaxy and found new streams of stars; and it has found new kinds of exploding stars and distant quasars in the early universe. We hope people will discover all kinds of things we missed in this incredibly large and rich dataset.”
The Space Telescope Science Institute hosts the storage hardware, the computers that handle the database queries, and the user-friendly interfaces to access the data. The survey data resides in the Mikulski Archive for Space Telescopes (MAST), which serves as NASA’s repository for all of its optical and ultraviolet-light observations, some of which date to the early 1970s. It includes all of the observational data from such space astrophysics missions as Hubble, Kepler, GALEX, and a wide variety of other telescopes, as well as several all-sky surveys. Pan-STARRS marks the nineteenth mission to be archived in MAST.
The data can be accessed online. | 0.870946 | 3.285148 |
A stunning and unrecorded image of the solar system, the fruit of a collaboration between a famed scientific thinker and author, a geographer, a wallpaper manufacturer, and an educational publisher.
This spectacular chart represents the Copernican model of the solar system, with the eight known planets, the asteroid belt and a pair of comets orbiting the Sun, the latter complete with sunspots (The image is wildly out of scale, but it does get the point across.) This central diagram is surrounded by the signs of the zodiac and a monthly calendar, with the whole framed by a spectacular architectural border. Embedded within this are diagrams explaining the seasons, lunar and solar eclipses, and the phases of the Moon; along with a chart of basic statistics about the planets, including their distances from the Sun, diameters, volumes, &c.
The chart’s visual impact is in part a function its size (more than three feet by four feet), but is primarily a result of its having been printed by the pochoir technique. Almost never seen on cartographic material, this involves the use of a sequence of stencils to guide successive applications of color—usually layers of gouache, as here. “The pochoir process, characterized by its crisp lines and brilliant colors, produces images that have a freshly printed or wet appearance.” (Smithsonian Libraries) Here, the impact of the technique is heightened by the treatment of the architectural border exclusively in shades of gray (en grisaille). The printers were the Hoock Brothers in Paris, better known as manufacturers of wallpaper, a field where the brilliance of pochoir was much in demand.
The chart’s “notions de cosmographie” are attributed to Camille Flammarion (1842-1925), the noted astronomer, scientific speculator and author; and one Naud-Evrard, a member of the Geographical Society about whom little is known (He did collaborate with Emile Leavsseur to produce two spectacular wall maps of the Americas, also printed au pochoir, which may be viewed here.) The publisher was Charles Delagrave (1842-1934), an educational publisher with a specialization in maps and atlases.
The chart is not explicitly dated, but a footnote specifies that in the years 1801-1880 no fewer than 219 asteroids were discovered orbiting between Mars and Jupiter. It was certainly published by 1882, in which year it was advertised in the Catholic Literary Circular (vol. II no. 5, p. 104), 8 shillings unmounted, 16 shillings mounted.
In all, a stunning and extraordinarily rare image. | 0.832378 | 3.519101 |
Barnard’s Star is a familiar name in both the history of astronomy and popular culture, but did you realise that it’s the closest stellar body to the Sun that you can see from the British Isles and similar latitudes? We tell you some fascinating facts about this famous runaway star and show you how to locate it.
The diminutive yet distinctive constellation of Lyra is home to dazzling star Vega, the Ring Nebula (M57) and the celebrated double-double star epsilon (ε) Lyrae. But did you know that Lyra harbours yet another ‘pair of pairs’ that are somewhat easier to resolve in smaller telescopes? Ade Ashford shows you how to locate the beautiful Struve Σ2470 and Σ2474.
Comet 45P/Honda–Mrkos–Pajdušáková passes just 0.08318 astronomical units (7.73 million miles, or ~32 lunar distances) from Earth on the morning of 11 February. Early risers can catch the magnitude +7 comet speeding through the constellations of Hercules, Corona Borealis (CrB) and Boötes at up to 9 degrees/day.
At the beginning of August, keen observers in the heart of the UK can celebrate the return of truly dark skies around 1am BST. But the naked-eye stars are out by 11pm, and if you cast your gaze two-thirds of the way from southeast horizon to overhead at this time you can see the so-called Summer Triangle in all its glory. Here’s our guide to some of the celestial highlights therein.
On the afternoon of 21 March, Comet 252P/LINEAR brushed by Earth just 14 lunar distances away. The comet’s separation from Earth now exceeds 20 million miles, but it’s still a suitable target for binoculars and small telescopes — if you know exactly where to look. Here’s our UK observing guide for 252P/LINEAR in the constellation Ophiuchus between midnight and moonrise over the coming week. | 0.899515 | 3.154764 |
The Europa Mission
February 11 & 12
After many years of study, NASA has approved a new start for a spaceflight mission to investigate the mysteries of Jupiter's moon Europa. Galileo spacecraft data suggest that an ocean most likely exists beneath Europa’s icy surface and that the "ingredients" necessary for life (liquid water, chemistry, and energy) could be present within this ocean today, implying that Europa may be a habitable world. Future exploration of Europa has been deemed an extremely high priority for planetary science, given the potential for revolutionizing our understanding of habitats for life. Over the past several years, JPL has led the effort to mature a mission concept that makes multiple flybys of Europa to investigate its habitability, and recently NASA selected a suite of highly capable remote sensing and in situ instruments for the Europa mission. The mission design enables globally distributed regional coverage of the moon’s surface, with 40+ close flybys at altitudes from 25 to 100 km. The Europa multiple flyby mission provides a cost-efficient means to explore Europa and investigate its habitability through understanding the satellite’s ice shell and ocean, composition, and geology. The mission would also investigate current activity, such as plumes, and would provide the high-resolution surface characterization necessary to enable future Europa landers.
Barry Goldstein, Europa Mission Project Manager
Dr. Bob Pappalardo, Europa Mission Project Scientist | 0.84606 | 3.075735 |
Over the next three mornings, set your alarm clock for about 75 minutes before local sunrise. If your skies are clear, you'll be able to see a "planetary triple play" low in the east-northeast sky.
Three bright planets in the August night sky will be stretched out in a diagonal line in the weekend pre-dawn sky. Going from upper right to lower left will be Jupiter, Mars and Mercury. And as a bonus, visiting each planet during these three mornings will be a waning sliver of a crescent moon.
To see the planets, plan to rise early at about 4:45 a.m. local daylight time. You can see a gallery of August stargazing events here to plan your skywatching activities this month. But for this weekend, here is a viewer’s timetable for early risers:
Aug. 3: Jupiter rises around 3:15 a.m. local daylight time. It is the most brilliant "star" before dawn. If you are outside during morning twilight, look toward the east-northeast to spot this last starry light that fades out before the coming of day. Jupiter lingers a few degrees to the right of the 3rd-magnitude star Mebsuta of the constellation Gemini, the Twins. Also this morning, situated about 7 degrees to Jupiter's right and slightly higher will be a slender waning crescent moon, 11 percent illuminated by the sun. Astronomers measure the brightness of objects in the night sky in magnitude, a scale in which brighter objects have lower numbers, with negative numbers denoting extremely bright objects.
Aug. 4: Mars is a yellow-orange dot of light, shining at a very modest magnitude of +1.6 (it would be categorized as second magnitude; just 1/25th as bright as Jupiter) and rises about two hours and 20 minutes before sunrise. In the following weeks, Mars will climb a little higher and as a consequence becomes easier to see, so too do the "Twin Stars" of Gemini, Pollux and Castor, situated to the left of Mars. And on this morning, about 5 degrees below and to the right of Mars will be a somewhat thinner (6-percent illuminated) waning crescent moon. As a reference, your closed fist held outstretched at arm's length covers about 10 degrees of the night sky.
Aug. 5: Look for Mercury very low in the east-northeast about an hour before sunrise. This small, fleet world gets lower each dawn in early August, but it also rapidly brightens, from magnitude -0.6 this morning to -1.3 (a trifle fainter than the brightest star, Sirius) by Aug. 13. On this morning, an exceedingly thin crescent moon – just 2 percent illuminated and about 36 hours from new – will lie about a half dozen degrees below and to the right of Mercury.
Keep in mind as you watch this changing celestial scene that each object is situated at a different distance from Earth. The nearest object of course, is the moon, near its apogee – the farthest point in its orbit from Earth – about 252,000 miles (405,000 kilometers).
Next is Mercury at 91 million miles (146 million km), followed by a still-distant Mars at 222 million miles (358 million km) and finally there’' Jupiter, more than a half billion miles out at 554 million miles (892 million km) away.
Editor's Note: If you have an amazing picture of Jupiter, Mars, Mercury or any other night sky view that you'd like to share for a possible story or image gallery, send photos, comments and your name and location to managing editor Tariq Malik at [email protected].
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmer's Almanac and other publications, and he is also an on-camera meteorologist for News 12 Westchester, N.Y. Follow us @Spacedotcom, Facebook and Google+. Original article on SPACE.com. | 0.902927 | 3.356874 |
During the clear night sky and as long as the city lights usually are not close or shiny enough to interfere with your bare eye imaginative and prescient, it is all the time a good idea to grab a blanket and some candles and head to your own home’s roof or the nearest hill. Via more than a century of operation, as human understanding of the universe has superior, so has the ASP — connecting scientists, educators, newbie astronomers and the public to share astronomical analysis, conduct skilled development in science education, and provide assets that have interaction students and adults alike in the journey of scientific discovery.
Tables Astronomy constants, physical constants, planets (orbital properties, physical characteristics, atmospheres), one hundred nearest stars, and one hundred brightest stars as seen from the Earth. Sometimes referred to as Barnard’s Runaway Star, it is top-of-the-line known stars in the historical past of astronomy and in in style culture.
Novice astronomers have contributed to many important astronomical discoveries, and astronomy is likely one of the few sciences the place amateurs can nonetheless play an energetic function, particularly in the discovery and statement of transient phenomena. Simply six mild-years from Earth, the second-closest star system to our Solar hosts a planet not less than thrice the mass of our own.
Astronomers of early civilizations performed methodical observations of the night time sky, and astronomical artifacts have been discovered from much earlier intervals. Our solar system is positioned within the outer reaches of the Milky Way Galaxy, which is a spiral galaxy.
Our solar system consists of the sun, planets, dwarf planets (or plutoids), moons, an asteroid belt, comets, meteors, and different objects. But the number of constellations and stars we’re in a position to see every year is actually a really small quantity out of the plethora of stars in the sky.
The supreme importance of the starry night time is nicely attested to by an unimaginable information of the sky movements. Astronomy is the examine of the physics and components of the observable Universe comparable to the celebs , planets , galaxies , clusters and the Universe itself by remark and idea.
Dark matter and dark power are the current main subjects in astronomy, 65 as their discovery and controversy originated in the course of the examine of the galaxies. From the Middle Kingdom, constellations had been often depicted on coffins as star clocks, displaying the length of time stars had been visible or invisible. | 0.862252 | 3.181815 |
North Korea’s missile launches of July 2017 demonstrate that it has developed ballistic missiles (Figure 1) with intercontinental range (ICBMs). This, plus its parallel development of nuclear weapons, has added a grave new threat to world order. This is a grim topic, but because it has such immediate importance — and encompasses fundamental physical principles — it deserves to be discussed in our introductory physics classes.
The missile launch of July 4 flew for 37 minutes (Ref. 1), and the one launched on July 28 was aloft for 47 minutes (Ref. 2). Based on this information, analysts in the United States and Japan estimate the maximum range of the former to be 6,700 km, and the latter to be 10,400 km, placing Los Angeles, Denver, Chicago, New York, Boston and other North American population centers within targeting range of Pyongyang. The purpose of this post is to show, using mathematics and concepts appropriate to the introductory calculus-based mechanics course, how to estimate missile range from the (observable) flight time. Following a treatment of Kepler’s Laws, it should be possible to present this material in a single class period.
Note: See also Post 15: The Range of North Korean Ballistic Missiles: Update (Jan 14, 2018) for a better approach to this issue. In particular, the numerical technique for estimating the burnout speed from the total flight time is no longer necessary.
B. Determining the Burnout Speed of a Ballistic Missile
To simplify the discussion, assume the missile altitude at burnout (when rocket fuel is exhausted) is negligible compared to the Earth’s radius, neglect atmospheric drag, and also neglect the Earth’s rotation. North Korea uses highly “lofted” trajectories to test its ICBMs; that is, they are launched at much steeper angles (approaching 90º) than they would be to achieve maximum range. In this section, we will assume that the missile is launched vertically, and calculate its flight time and maximum altitude as functions of its burnout speed . For small and , this is an easy task, as the gravitational acceleration is roughly constant, and the familiar equations of kinematics are applicable: and . (Note: is twice the time from launch to maximum altitude.) But a lofted ICBM will reach an altitude comparable to the Earth’s radius , so the gravitational acceleration varies significantly during the missile’s flight. This complicates the analysis considerably.
Let be the gravitational constant, be the mass of the Earth, and be the instantaneous distance of the missile from the center of the planet. Launched vertically, the speed of the missile at maximum altitude () is zero, so by energy conservation,
where and is the escape velocity from the planet’s surface.
Our first task is to find the flight time in terms of the burnout speed . One way to proceed is to integrate the equation of motion numerically. The most straightforward numerical technique is the second-order Taylor approximation (Ref. 3), in which the stepwise equations for position and speed are reminiscent of the kinematic equations for projectile motion:
where the acceleration and is the time step. A simple Excel spreadsheet is adequate for the integration. Figure 2 shows the computed altitude for a projectile that has reached its maximum altitude at , for the three values = 0.5, 0.6 and 0.7. The intersection of each curve with the x-axis () marks half the total flight time of the missile.
Some instructors may prefer an analytic expression for . A power series solution for , due to Foong (Ref. 4), is outlined in the Appendix and is displayed in Fig. 2 along with the numerical solution. Figure 3 shows the total flight time as a function of , calculated numerically as well as by the power series approximation. Knowing , one may find directly from Fig. 3.
C. Finding the Maximum Range of the Missile
When the burnout speed is low (), the maximum altitude and range of the missile are small, and its trajectory is adequately described as a parabola over a flat Earth. At the higher speeds needed for intercontinental targeting, the parabolic approximation is no longer adequate, and the trajectory must be treated properly as a segment of an ellipse having one focal point at the center of the planet. (This follows from Kepler’s Laws.) Changing the launch angle changes the eccentricity of the ellipse — which affects the range of the missile — but not the length of its semi-major axis . The goal of this section is to find the optimum launch angle (the one that yields the maximum range), and to calculate that range as a function of the burnout speed . This can be done easily by appealing to the reflection property of an ellipse (Ref. 5).
In Figure 4, line is tangent to the ellipse at point P. The reflection, or focal property states that and make equal angles with the tangent line. So at point P, angle φ = φ′ , and at point P′, angle γ = γ′. If the ellipse were a reflective surface, any light ray emanating from one focus would, after reflection, pass through the other focus. For example, a parabola is an ellipse with one focus at infinity. As is well known, light rays originating at infinity (parallel rays) converge at the focal point of a parabolic mirror.
Next we review the energetics of orbital motion governed by an inverse square central force. If the eccentricity ε of the elliptical orbit is zero, the trajectory is circular with radius r. The orbital speed is found by equating the centripetal acceleration to the gravitational force per unit mass, , so
where E is the total mechanical energy of the missile and m is its mass. When , a similar relation holds (Ref. 6): the energy per unit mass is fixed — not by the orbital radius r but by the length of the semi-major axis a:
An ICBM’s energy and semi-major axis are set by its burnout speed , which we have assumed is reached when the missile is close to the Earth’s surface ():
Using and , we obtain
Figure 5a shows the missile trajectory as an ellipse with focus at the Earth’s center (the center of force). The launch point P and the target point Q both lie on the planet’s surface, and the actual missile trajectory is the segment of the ellipse lying outside of the planet (). The range of the missile is , where θ is the angle between (or ) and the major axis of the ellipse. The location of the second focus depends on , which is governed by the missile launch angle. For all points P (and, by symmetry, Q), , regardless of the location of along the major axis. Since , then . By inspection, the angle θ is maximized when is perpendicular to the major axis. Therefore,
Besides calculating the maximum range, it is interesting to find the launch angle associated with it. In Figure 5b, let once again be tangent to the ellipse at the launch point P. Using the reflection property discussed above, angle β = β′, so . (Note: β is the launch angle measured with respect to the local vertical direction at P.) Since is a right triangle, angle . Therefore,
In the literature, the launch angle is more commonly measured relative to the local horizontal, i.e., , or
Note that as , and , or 45°, just as we would expect from basic kinematics. If (the condition for low Earth orbit), and , i.e., the missile should be launched parallel to the Earth’s surface.
According to US Pacific Command, the Hwasong-14 missile launched by North Korea on July 4 was aloft for 37 minutes. From Figure 2, this indicates that , or km/s. Eqn. 1 then tells us that the missile reached a maximum altitude km during its test flight. From Eqn. 4, , or (radians), so the maximum range is km. The launch angle associated with this range is rad, or 31°. These results are in good agreement with those of Dr. David Wright, Senior Scientist at the Union of Concerned Scientists, who estimated (Ref. 7) the maximum altitude to be “more than 2800 km” and the maximum range to be “roughly 6700 km.”
D. Questions for Students
1. The July 4 missile flew for 37 minutes and splashed down about 950 km from its launch site. Show that the launch angle must have been close to 90°. (Ans: km/s, while km/s. , or °)
2. The July 28 missile flew for 47 minutes. Find the maximum altitude during the test flight, the maximum range , and the optimum launch angle . (Ans: km, km, and °)
3. Your calculation of above assumed that burnout occurred at zero altitude. Realistically, burnout occurs at an altitude of several hundred kilometers. The “official” estimate of the range of the July 28 missile was 10,400 km. Using the launch angle calculated above, estimate the burnout altitude of the missile. (Ans: about 250 km)
- Choe Sang-Hun, “U.S. Confirms North Korea Fires an Intercontinental Ballistic Missile,” New York Times, July 4, 2017
- Choe Sang-Hun and Eileen Sullivan, “North Korea Launches Ballistic Missile, the Pentagon Says,” New York Times, July 28, 2017
- Robert W. Stanley, “Numerical methods in mechanics,” Am. J. Phys. 52(6), 499-507 (1984)
- S. K. Foong, “From Moon-falls to motions under inverse square laws,” Eur. J. Phys. 29, 987-1003 (2008)
- For a simple proof of the reflection property, see Physics from Planet Earth, J. C. Amato and E. J. Galvez, Taylor & Francis/CRC Press (2015) p. 471
- ibid, section 8.2, “Kepler’s Laws”
- David Wright, Union of Concerned Scientists blog, July 3, 2017: http://allthingsnuclear.org/dwright/north-korea-appears-to-launch-missile-with-6700-km-range
The series approximation shown in Figures 2 and 3 is derived by Foong in Ref. 4. If the missile is at its peak altitude at time , then ; i.e., is an even function of time, and may be expressed as a power series:
The coefficients are chosen to satisfy the equation of motion
Following Foong, we introduce dimensionless variables and , where . We then rewrite the power series as , which must satisfy the equation of motion expressed in dimensionless units:
Expanding the parentheses and multiplying,
For the equality to hold over the entire flight time of the missile, the coefficient of each power of τ must equal zero, so and . See Ref. 4 for the values of higher order coefficients. Returning to the physical variables r and t, our power series solution is
where is given as a function of in Eqn. 3. The truncated series containing just the terms shown above is plotted in Fig. 2 for = 0.5, 0.6 and 0.7. The agreement with the numerical solution is quite good for . | 0.824641 | 3.148937 |
Researchers have confirmed two predictions of Albert Einstein’s general theory of relativity, concluding one of NASA’s longest-running projects. The Gravity Probe B experiment used four ultra-precise gyroscopes housed in an Earth-orbiting satellite to measure two aspects of Einstein’s theory about gravity. The first is the geodetic effect, or the warping of space and time around a gravitational body. The second is frame-dragging, which is the amount a spinning object pulls space and time with it as it rotates.
Gravity Probe-B determined both effects with unprecedented precision by pointing at a single star, IM Pegasi, while in a polar orbit around Earth. If gravity did not affect space and time, GP-B’s gyroscopes would point in the same direction forever while in orbit. But in confirmation of Einstein’s theories, the gyroscopes experienced measurable, minute changes in the direction of their spin, while Earth’s gravity pulled at them.
The project as been in the works for 52 years.
The findings are online in the journal Physical Review Letters.
“Imagine the Earth as if it were immersed in honey,”.said Francis Everitt, Gravity Probe-B principal investigator at Stanford University. “As the planet rotates, the honey around it would swirl, and it’s the same with space and time,” “GP-B confirmed two of the most profound predictions of Einstein’s universe, having far-reaching implications across astrophysics research. Likewise, the decades of technological innovation behind the mission will have a lasting legacy on Earth and in space.”
NASA began development of this project starting in the fall of 1963 with initial funding to develop a relativity gyroscope experiment. Subsequent decades of development led to groundbreaking technologies to control environmental disturbances on spacecraft, such as aerodynamic drag, magnetic fields and thermal variations. The mission’s star tracker and gyroscopes were the most precise ever designed and produced.
GP-B completed its data collection operations and was decommissioned in December 2010.
“The mission results will have a long-term impact on the work of theoretical physicists,” said Bill Danchi, senior astrophysicist and program scientist at NASA Headquarters in Washington. “Every future challenge to Einstein’s theories of general relativity will have to seek more precise measurements than the remarkable work GP-B accomplished.”
Innovations enabled by GP-B have been used in GPS technologies that allow airplanes to land unaided. Additional GP-B technologies were applied to NASA’s Cosmic Background Explorer mission, which accurately determined the universe’s background radiation. That measurement is the underpinning of the big-bang theory, and led to the Nobel Prize for NASA physicist John Mather.
The drag-free satellite concept pioneered by GP-B made a number of Earth-observing satellites possible, including NASA’s Gravity Recovery and Climate Experiment and the European Space Agency’s Gravity field and steady-state Ocean Circulation Explorer. These satellites provide the most precise measurements of the shape of the Earth, critical for precise navigation on land and sea, and understanding the relationship between ocean circulation and climate patterns.
GP-B also advanced the frontiers of knowledge and provided a practical training ground for 100 doctoral students and 15 master’s degree candidates at universities across the United States. More than 350 undergraduates and more than four dozen high school students also worked on the project with leading scientists and aerospace engineers from industry and government. One undergraduate student who worked on GP-B became the first female astronaut in space, Sally Ride. Another was Eric Cornell who won the Nobel Prize in Physics in 2001.
“GP-B adds to the knowledge base on relativity in important ways and its positive impact will be felt in the careers of students whose educations were enriched by the project,” said Ed Weiler, associate administrator for the Science Mission Directorate at NASA Headquarters. | 0.890378 | 3.727143 |
VARIES project proposes antimatter starship mission
As Douglas Adams said, “Space is Big. Really Big." And that’s the major obstacle for traveling between the stars. But a new proposal published in the Journal of the British Interplanetary Society promises to shrink that distance just a bit. Physics and technology consultant Richard Obousy claims that an antimatter starship that creates its own fuel from the vacuum of space itself would be capable of making a return journey to the nearest star and back within one lifetime.
Sometimes it’s a bit difficult to grasp just how vast space is. The American space probe Voyager 1 was launched in 1977, yet is only now reaching the edge of our Solar System despite hurtling along at 38,000 mph (61,000 kph). At its present velocity, it would take 70,000 years to reach the nearest star – and it’s not even pointed in the right direction. Even NASA’s Solar Probe, a mission to study the Sun’s corona that will use an interplanetary slingshot maneuver to reach record speeds, would take 6,450 years. Needless to say, the odds of getting funding for a mission that will take longer to reach its destination than the whole of recorded history aren't that great.
What’s worse, a mission to another star won’t be worth much if it doesn’t produce any tangible results. Even if you could build a probe capable of reaching another system, a flyby mission isn’t going to be worth much if the probe blurs through it inside of a few hours at speeds too fast to see anything. Not to mention that all the data and samples aren’t going to be worth a bean if Mission Control doesn’t receive the results. That means any interstellar craft has to be fast enough to get to the next star, slow down and orbit the star long enough to do the science and then return to Earth with the results.
The upshot is that such a mission would require incredible amounts of energy that even some sort of fusion drive would have trouble delivering. Based on current science, the only energy source that has a shot of throwing a starship across the void and back in a reasonable time, say 50 years, is antimatter. That’s the idea behind Obousy’s VARIES proposal: Vacuum to Antimatter-Rocket Interstellar Explorer System.
The principle behind VARIES is as simple as it is theoretically cutting edge. It’s based on something from quantum mechanics called a “Schwinger pair production." According to quantum theory, particles in a vacuum don’t exactly exist. They’re only “sort of” there as an expression of probability. We don’t notice this on our scale because the probabilities balance themselves out. However, on a quantum scale, it’s a different story. One upshot of this is that it’s believed that if you tip the scales of probability by subjecting a vacuum to a powerful electric field, it will cause particles of matter (or antimatter) to spontaneously appear.
If this phenomenon pans out, VARIES would exploit it by way of an unmanned starship with huge solar panels that would collect the sun’s rays. These would, in turn, power banks of x-ray free electron lasers to charge the vacuum and create antimatter, which would then be collected and stored aboard as fuel for the journey.
This sounds very simple, but the engineering would be herculean, to say the least. In addition to building the solar power system and the lasers, the starship would also need magnetic bottles to store the antimatter. Otherwise, one instant of contact between ship and antimatter would vaporize both in a flash of gamma rays. Then magnetic nozzles would be required to handle the fuel as well as radiation shielding and all the other precautions needed to protect a craft flying through interstellar space at speeds where striking a dust mote is like hitting an atom bomb.
If all of these obstacles can be overcome the VARIES mission would proceed in stages. After fueling up in solar orbit, the ship would accelerate to a fraction of the speed of light. It would then coast, studying the interstellar medium as it traveled. After a few years, the ship would turn tail and decelerate until it reached its destination. It would then go into orbit around the star and conduct its exploration program while refueling in the new sun’s rays. Then it would leave the for home, accelerating, coasting and decelerating as before.
At present, VARIES is still merely a proposal with a long research shopping list attached, but if things work out, the path to the stars might be a little closer to reality.
Obousy's paper can be downloaded here as a PDF. | 0.86779 | 3.473888 |
Liquid Martian brines may be more common than once thought, but they are unlikely to play host to anything that looks like life as we know it, a paper in Nature Astronomy has found.
Stable liquid water is considered as one of the necessary ingredients for life to emerge, but under current Mars conditions, it is both too cold and its atmosphere too thin for it to last without freezing or subliming into vapour. But liquids containing high concentrations of salts can last much longer – longer than many thought, according to Edgard Rivera-Valentín, research scientist with the Universities Space Research Association at the Lunar and Planetary Institute, and his team.
After writing software using an experimentally validated thermodynamic model and a Martian climate model, with recalibrated environmental data from the Thermal and Electrical Conductivity Probe on the Phoenix lander (available on the NASA Planetary Data System Geosciences Node), the team looked into where these brines could form on Mars and for how long, and found they would be potentially "common," but extremely cold.
They postulated that up to 40 per cent of the Martian surface, at all latitudes down to the equator, could host stable brines. These brines could last for up to six consecutive hours on the surface, for up to 2 per cent of the entire Martian year.
I've seen things you people wouldn't believe. Light-powered nanocardboard robots dancing in the Martian sky searching for alien lifeREAD MORE
The authors also found that brines in the subsurface could last up to 10 per cent of the Martian year at a depth of 8cm. However, should their existence be confirmed, they would be "inhospitable for Earth's microorganisms" – and could "not sustain terrestrial life".
Martian brines attracted a wave of interest in 2018 when GeoScience published [PDF] research around the potential for aerobic life to draw "sufficient" O2 from any brines.
Evidence pointing to brines on Mars's surface has previously been surfaced. In 2015, Nature reported a study that used the Compact Reconnaissance Imaging Spectrometer for Mars instrument onboard the Mars Reconnaissance Orbiter examining from four different locations and found evidence for hydrated salts at all four locations.
Using an experimental approach on Earth, Rivera-Valentín and his colleagues used data modelling to show the presence of Mars brines may be much more common than thought.
Managing expectations of Mars explorers, they explained that only the lowest eutectic solutions can form, leading to brines with temperatures of less than 225 K (about -48˚C). "Our results indicate that (meta)stable brines on the Martian surface and its shallow subsurface (a few centimetres deep) are not habitable because their water activities and temperatures fall outside the known tolerances for terrestrial life," the paper explains.
The up-side here is that the brines cannot be classified as "Special Regions" according to Planetary Protection policies. This means that the places where these "stable brines" are found to exist could be targets for future Martian exploration, since they would limit the damage meatbag humans could potentially do to the Red Planet.
The authors note that the "risk of biological contamination from Earth is negligible". So, presuming we ever manage to send a crewed vehicle to the Red Planet, the lucky old Office of Planetary Protection and its international counterparts wouldn't need to build a sterile spacecraft for the purpose. ®
Sponsored: Webcast: Simplify data protection on AWS | 0.880542 | 3.775402 |
The distance to the Andromeda Galaxy is 2.54 million light-years, or 778 kiloparsecs.
The Andromeda Galaxy can be seen with the unaided eye, so skywatchers have been observing it for thousands of years. Charles Messier cataloged it as M31 in his 1764 list. Back then, astronomers thought that Andromeda was a nebula, and based on its size, Messier guessed that it was only about 2,000 times further than the star Sirius.
Astronomers discovered variable star called novae in Andromeda in 1917, and quickly realized that they were 10 times less bright than similar objects in the Milky Way. Astronomers Heber Curtis proposed that Andromeda was a separate “island universe”, located about 500,000 light-years away. Edwin Hubble ended the controversy once and for all in 1925 when he identified Cepheid variable stars in Andromeda, and calculated that the galaxy was actually 1.5 million light-years away.
Modern astronomers are continuing to calculate the distance to Andromeda. In 2003, astronomers calculated that Andromeda is 2.57 million light-years away. And in 2004, astronomers redid Hubble’s Cepheid variable calculations, and determined that Andromeda was 2.51 million light-years. Another group used a different technique in 2005 to calculate that Andromeda was 2.52 million light-years away. And yet another technique in 2005 put it at 2.56 million light-years away. And so, the agreed distance of 2.54 million light-years is an average of the distances measured so far.
There are several galaxies closer to Earth than Andromeda. The Large Magellanic Cloud is only 160,000 light years away, and the Canis Major Dwarf Galaxy is a mere 25,000 light-years from Earth. But Andromeda is the largest grand spiral galaxy to us.
We have written many articles about galaxies for Universe Today. Here’s another article about the closest galaxies to the Milky Way.
We have also recorded an episode of Astronomy Cast about galaxies – Episode 97: Galaxies. | 0.829083 | 3.250591 |
A fossilised remnant of the early Milky Way harbouring stars of hugely different ages has been revealed by an international team of astronomers. This stellar system resembles a globular cluster, but is like no other cluster known. It contains stars remarkably similar to the most ancient stars in the Milky Way and bridges the gap in understanding between our galaxy’s past and its present.
Terzan 5, 19,000 light-years from Earth, has been classified as a globular cluster for the forty-odd years since its detection. Now, an Italian-led team of astronomers have discovered that Terzan 5 is like no other globular cluster known.
The team scoured data from the Advanced Camera for Surveys and the Wide Field Camera 3 on board Hubble, as well as from a suite of other ground-based telescopes . They found compelling evidence that there are two distinct kinds of stars in Terzan 5 which not only differ in the elements they contain, but have an age-gap of roughly 7 billion years .
The ages of the two populations indicate that the star formation process in Terzan 5 was not continuous, but was dominated by two distinct bursts of star formation. “This requires the Terzan 5 ancestor to have large amounts of gas for a second generation of stars and to be quite massive. At least 100 million times the mass of the Sun,” explains Davide Massari, co-author of the study, from INAF, Italy, and the University of Gröningen, Netherlands.
Its unusual properties make Terzan 5 the ideal candidate for a living fossil from the early days of the Milky Way. Current theories on galaxy formation assume that vast clumps of gas and stars interacted to form the primordial bulge of the Milky Way, merging and dissolving in the process.
“We think that some remnants of these gaseous clumps could remain relatively undisrupted and keep existing embedded within the galaxy,” explains Francesco Ferraro from the University of Bologna, Italy, and lead author of the study. “Such galactic fossils allow astronomers to reconstruct an important piece of the history of our Milky Way.”
While the properties of Terzan 5 are uncommon for a globular cluster, they are very similar to the stellar population which can be found in the galactic bulge, the tightly packed central region of the Milky Way. These similarities could make Terzan 5 a fossilised relic of galaxy formation, representing one of the earliest building blocks of the Milky Way.
This assumption is strengthened by the original mass of Terzan 5 necessary to create two stellar populations: a mass similar to the huge clumps which are assumed to have formed the bulge during galaxy assembly around 12 billion years ago. Somehow Terzan 5 has managed to survive being disrupted for billions of years, and has been preserved as a remnant of the distant past of the Milky Way.
“Some characteristics of Terzan 5 resemble those detected in the giant clumps we see in star-forming galaxies at high-redshift, suggesting that similar assembling processes occurred in the local and in the distant Universe at the epoch of galaxy formation,” continues Ferraro.
Hence, this discovery paves the way for a better and more complete understanding of galaxy assembly. “Terzan 5 could represent an intriguing link between the local and the distant Universe, a surviving witness of the Galactic bulge assembly process,” explains Ferraro while commenting on the importance of the discovery. The research presents a possible route for astronomers to unravel the mysteries of galaxy formation, and offers an unrivaled view into the complicated history of the Milky Way.
The researchers also used data from the Multi-conjugate Adaptive Optics Demonstrator at ESO’s Very Large Telescope and the Near Infrared Camera 2 at the W. M. Keck Observatory (http://www.keckobservatory.org/).
The two detected stellar populations have ages of 12 billion years and 4.5 billion years respectively.
F.r. Ferraro, D. Massari, E. Dalessandro, B. Lanzoni, L. Origlia, R. M. Rich, A. Mucciarelli. The age of the young bulge-like population in the stellar system Terzan 5: linking the Galactic bulge to the high-z Universe. Astrophysical Journal, 2016 | 0.849157 | 3.98532 |
I am totally amazed by the processes that happen in stars, the life cycle of stars and the cataclysmic possibilities of when stars run out of fuel. Despite my amazement at what happens in stellar evolution, I am even more amazed by the weird objects that remain after supernovae. Who can not be mesmerised by the weird physics and seemingly unnatural characteristics of neutron stars and black holes? There is no end to my fascination of these objects and finding out more about them. Fortunately there’s been a lot going on recently in our understanding of these weird objects, caused in part by the phenomenal effects of what happens when they combine.
Last year, the Laser Interferometer Gravitational Wave Observatory (LIGO) announced on the 16th October they had observed both the light and the gravitational waves from the merger of two neutron stars. This collision gave the world a wealth of information to build an understanding of neutron stars and what happens when they collide.
Science is all about coming up with an idea and checking if it’s true based on observation and experiment.
Computer models have been used to describe what we might see if two neutron stars combine, and the collision last year gave us the opportunity to witness the real event and compare the models. Using the data from LIGO and Virgo researches have been able to calculate a new theoretical maximum size of a neutron star at a radius of 13.6km. This is a bit bigger than what was previously thought (research by Annala, Gorda, Kurkela and Vuorinen, in Physical Review Letters, 120, 25 April 2018). This small difference in size makes a big difference in understanding what happens when neutron stars collide and what they are made of. Basically neutron stars are not as squishy as once we thought as they are not quite dense enough to squish neutrons into their component quarks.
There’s a number of options when the weird objects collide, such as neutron star vs neutron star, black hole vs black hole or neutron star vs black hole. Because neutron stars are so very dense, it takes a lot to extract bits off them and this is exactly what happens when a neutron star collides with a black hole or another neutron star.
Most people were probably quite excited when it was announced last year that gold and other heavy elements were probably formed in collisions of neutron stars rather than in supernovae, well I was excited to think that the gold coin I have was originally from a neutron star!!!! So scientists know that the heavy elements form from a process called the rapid neutron capture process also known as the r-process. This is where a nucleus of an atom attracts a heap of neutrons rather rapidly. Unfortunately you just can’t go adding neutrons because things get unstable rather quickly and the nucleus decays. Quite often some of those added neutrons decay into a proton, an electron and an anti neutrino – WOW! So for the r-process to work another neutron has to be captured before another neutron decays so the nucleus keeps building into stuff like gold! For this to happen, you need quite a few neutrons. Lucky, because neutron stars have a lot of neutrons, 1.4 times the mass of the Sun worth of neutrons! So when these come together and tear themselves apart they make a lot of gold – an alchemist’s dream come true. We know that there’s enough of these weird object collisions to make the heavy elements we observe in the universe and now we have observed one of these collision to prove it.
So what happens when neutron stars collide? Fortunately the event of 2017 gave us a very good understanding and the research conducted on the results collected by LIGO and VIRGO published by Kazen, Metzger, Barnes, Quataert and Ramirez-Ruiz in Nature give a great description on what happens. Basically as the two neutron stars get closer and closer together the tidal forces start ripping bits off the surface of the stars, these pieces are still incredibly dense and they create a bit of a tail around the spinning pair. Also the mechanism starts to compress more material towards the poles of the two stars and then as they impact each other – or more like a really fast merge, remember they’re spinning super fast – the super dense and hard surface rupture is releasing an enormous amount of energy, flinging material out at about 30% of the speed of light. The pattern that the authors above figured out from the LIGO data is that the heavy elements created around the neutrons flung out from the stars fuses together through the r-process. They are confident about it by studying the data and measuring the light curve that lasted a few days afterwards, which was consistent with radioactive decay from heavy elements created through the r-process heating the ejected material. The other thing to keep in mind is that when the two neutron stars merge the result is a black hole of a couple solar masses, so there’s a rapid end to stuff getting flung out of the collision.
But even weirder than that is what happens when black holes collide. It’s worth noting that when these combine we get bigger black holes, kind of adding the two together and subtracting a bit of mass for the energy. An interesting study was done on a 19 Solar Mass black hole merger, which was the lowest mass of a black hole merger seen by LIGO so far. From this merger they determined that about 0.85 of a Solar Mass was lost in energy – which shows just how powerful these events are.
There obviously a lot more for us to learn about these collisions and the work of LIGO is instrumental for this research. | 0.853677 | 3.625151 |
Last September, NASA launched a pair of twin spacecrafts, named Ebb and Flow, to get a closer look at the moon's gravity. The mission was called Gravity Recovery and Interior Laboratory, better known as GRAIL.
The spacecraft chase each other around the moon, varying from four to more than 125 miles apart. The change in distance between the two probes varies as they move over areas of greater and lesser gravity. As the first spacecraft goes over a mountain, for example, it will speed up. Since topographic features of different densities and composition — like mountains versus valleys — exert different gravitational pulls, researchers match changes in gravity with structures like mountains, impact craters, and volcanic landforms. The result is a more complete picture of the moon's interior.
During the mission phase, which stretched from March to May 2012, the two washing-machine-sized spacecraft created a high-resolution map of the moon's gravity field that revealed many never-before-seen details about the moon's internal structure, including evidence of volcanic structures beneath the moon.
The findings were presented Wednesday, Dec. 5, at the American Geophysical Union meeting in San Francisco and published online by the journal Science.
"We used gradients of the gravity field in order to highlight smaller and narrower structures than could be seen in previous datasets," GRAIL scientist Jeff Andrews-Hanna of the Colorado School of Mines said in a statement.
"This data revealed a population of long, linear gravity anomalies, with lengths of hundreds of kilometers, crisscrossing the surface. These linear gravity anomalies indicate the presence of dikes, or long, thin, vertical bodies of solidified magma in the subsurface. The dikes are among the oldest features on the moon, and understanding them will tell us about its early history," he added.
So, it would seem that there are hidden volcanoes on the moon!
The movie below shows the variations in the lunar gravity field as measured by the twin spacecraft. Red corresponds to mass excesses (like mountains) and blue corresponds to mass deficiencies (like craters). | 0.828074 | 3.778772 |
Three leading-edge research groups in the field of galaxy formation have published their findings that most large galaxies have formed and developed without the involvement of galaxy mergers. This historic support for the top-down theory of galaxy formation provides an important missing piece to the universe’s cosmological puzzle and essentially proves that the Cold Dark Matter theory has no valid basis.
Avishai Dekel,et al, published a scientific paper recently, Michael J. Disney,et al, published a paper late last year and Jerome Drexler authored relevant books in 2006 and 2008.The most obvious immediate effect could be a paradigm shift away from the Cold Dark Matter theory of weakly interacting massive particles (WIMPs).
The UC Santa Cruz (UCSC) central doctrine for Cold Dark Matter has been that small galaxies form first and larger galaxies are formed through mergers of smaller galaxies.
This is called hierarchal galaxy formation, a central principle of the UCSC Cold Dark Matter WIMP theory. Such a hierarchal galaxy merging procedure would probably lead to a complex galaxy formation process based upon a number of independent variables representing various parameters of the merging galaxies.
A Nature article, authored by Professor Michael J. Disney of UK’s Cardiff University and five associates, is entitled, “Galaxies appear simpler than expected.”
It turns out that through a statistical analysis of the radio and optical data from 200 galaxies, five of the six “independent” variables actually are dependent on some single unknown independent variable. The last sentence of the abstract makes a key statement, “Such a degree of organization [of galaxies] appears to be at odds with hierarchical galaxy formation, a central tenet of the cold dark matter model in cosmology.”
More from Professor Disney’s abstract: “Here we report that a sample of galaxies that were first detected through their neutral hydrogen radio-frequency emission, and are thus free from optical selection effects shows five independent correlations among six independent observables, despite having a wide range of properties. This implies that the structure of these galaxies must be controlled by a single parameter, although we cannot identify this parameter from our data set. Such a degree of organization appears to be at odds with hierarchical galaxy formation, a central tenet of the cold dark matter model in cosmology.”
Professor Avishai Dekel of the Hebrew University of Jerusalem, with nine associates, comes to the same general conclusion as Disney via a different set of data and different arguments in a Nature article several months later. It is entitled, “Cold streams in early massive hot haloes as the main mode of galaxy formation.” A news release from The Hebrew University begins as follows:
“New understanding of the origin of galaxies advanced by Hebrew U astrophysicists
A new theory as to how galaxies formed in the Universe billions of years ago has been formulated by Hebrew University of Jerusalem cosmologists. The theory takes issue with the prevailing view on how the galaxies came to exist.
The new theory, motivated by advanced astronomical observations and based on state-of-the-art computer simulations, maintains that the galaxies primarily formed as a result of intensive cosmic streams of cold gas (mostly hydrogen) and not, as the current theory contends, due primarily to galactic mergers. The researchers show that these mergers had only limited influence on the cosmological makeup of the universe as we know it.
The galaxies are the building blocks of the Universe… . Every galaxy is embedded in a spherical halo made of dark matter that cannot be seen but is detected through its massive gravitational attraction. The exact nature of this matter is still unknown.”
There are currently two schools of thought on galaxy formation. There is the old bottom-up theory, supported by the vast majority of the world’s universities, which states that small galaxies form first and larger galaxies are formed through mergers of the small galaxies.
The principal subject of this newswire article is the top-down theory of galaxy formation, that Drexler, Disney, and Dekel support, which generally states that galaxies form and grow via some source of hydrogen not involving galaxy mergers.
Drexler describes and explains his top-down theory of galaxy formation in two of his three books. His May 22, 2006 book entitled, “Comprehending and Decoding the Cosmos: Discovering Solutions to Over a Dozen Cosmic Mysteries by Utilizing Dark Matter Relationism, Cosmology, and Astrophysics,” covers this subject in Chapters 19, 21, 31, 36, 40 and 41. His March 1, 2008 book entitled, “Discovering Postmodern Cosmology: Discoveries in Dark Matter, Cosmic Web, Big Bang, Inflation, Cosmic Rays, Dark Energy, Accelerating Cosmos,” discusses the top-down theory of galaxy formation in Chapters 9 and 19. See also the instructional Web site at http://www.jeromedrexler.org.
Drexler’s well-proven relativistic-proton dark matter theory permits a more complete top-down theory of galaxy formation than that provided by others. Drexler’s May 2006 book’s definition of his top-down theory is “that long, large dark matter filaments form galaxy clusters where the dark matter filaments intersect/collide and then galaxies form from the remnants of these collisions.” Drexler’s March 2008 book’s definition of the top-down theory is the same except for the addition of the then new words “of the cosmic web” between the words “filaments” and “form.”
Thus in Drexler’s 2006 galaxy-formation theory the evolving star-forming galaxies are fed with streams of warm-hot protons directly from the relativistic-proton dark matter itself rather than from a posited separate source of protons or hydrogen. Note that this star-forming galaxy system has Occam razor simplicity. | 0.812125 | 4.04075 |
It appears that a whole population of miniature black holes might be lurking in the cosmos, waiting to reveal their secrets.
The discovery came after an international team of astronomers developed a new way to search for black holes.
These cosmic entities – which have a gravitational pull so strong that not even light can escape – can form when massive stars collapse at the end of their life. The stellar black holes discovered so far have a mass at least 5 times that of the Sun.
If the dying star is below a certain mass, however, it will collapse into a small, dense neutron star. Neutron stars are generally no bigger than about twice the mass of the Sun – any bigger, and they’d collapse into a black hole. This leaves a gap between the biggest neutron stars and the smallest black holes, which has remained unfilled – until now.
Read more about black holes:
The new technique makes use of the fact that black holes can often be found in a binary system – 2 stars locked together in mutual orbit. When one of the stars dies and becomes a black hole, it can stay in the system, its presence revealed by changes in the living star’s light spectrum as it orbits its invisible companion.
The researchers used data from APOGEE (Apache Point Observatory Galactic Evolution Experiment), which collected light spectra from around 100,000 stars across the Milky Way.
The team honed in on 200 stars that looked like they might be orbiting a black hole. Further data-crunching then revealed a giant red star orbiting a low-mass black hole, estimated to be about 3.3 times the mass of the Sun.
“What we’ve done here is come up with a new way to search for black holes,” said Prof Todd Thompson at The Ohio State University, lead author of the study, “but we’ve also potentially identified one of the first of a new class of low-mass black holes that astronomers hadn’t previously known about.
“If we could reveal a new population of black holes, it would tell us more about which stars explode, which don’t, which form black holes, which form neutron stars. It opens up a new area of study.” | 0.913 | 3.797125 |
What are exoplanets and how do we find them?
Dr. David Charbonneau is a professor of astronomy at Harvard University and an astronomer at the Harvard Smithsonian Center for Astrophysics. His research focuses on the development of novel techniques for the detection and characterization of planets orbiting nearby Sun-like stars. He led the first studies of the compositions of exoplanets and of their atmospheres, and he is a member of the NASA Kepler Mission to find Earth-like planets.
Dr. David Charbonneau: The first thing to know when you’re thinking about how we study planets around other stars is that we never get to see the planets directly. The way that most planets have been found is we wait for the planet to pass in front of the star. When it passes in front of the star, it blocks some of the light from the star; we can see the star get a little bit fainter and a little bit brighter as it passes out from our point of view.
Then, based on that we can infer, for example, the size of the planet. If it’s a bigger planet, it will block more light. In terms of understanding the properties of the planets, what we really would like to measure are their sizes, their masses, and, if we put those two ideas together, therefore, their density and maybe what they’re made of. Are they made of dense things like rock, like the Earth, or are they made of puffy things like gas, like Jupiter?
The way that astronomers learn about the mass of a planet is through the dance of the planet and star. Think about it as if you’re watching two dance partners on the dance floor, but one dance partner was 10 or 20 or 100,000 times heavier than the other one, but that heavier dance partner would still do-si-do back and forth. We can study the light from the star, see that it’s dosi-doing back and forth, and we call that the wobble method or the Doppler method. That allows us to know that there’s a planet there, even if we don’t see the planet. It allows us to measure the mass of the planet because a heavier planet would cause the star to wobble more.
Furthermore, we like to figure out the temperature of the planet and, fortunately, that’s very easy. The temperature really is set by the distance from the star, and we can infer the distance of the star by measuring how long it takes the planet to go around in its orbit. We’ve been able to measure the size and the mass and the temperature for thousands of worlds, and now we have a very good understanding of which of those planets are a little more like Earth, both in terms of being rocky and being temperate, and which are really not like the Earth, maybe because they have a lot of gas or maybe because they’re much, much, much hotter or much colder.
Once we get past the stunning reality that we can discover new planets and identify their properties in our solar system and beyond we have to ask important questions like how in fact can we discover and identify properties of new planets? The physical properties of a new planet may seem unattainable as we are unable to even see these planets directly but in fact we are able to gain valuable and rather extensive information about these planets.
- Course Categories: Biblical Studies, Church History, Ethics, General Theology, Pastoral Theology
- Science Topics: Physics and Cosmos
astronomy, science and religion, How we discover exoplanets, stars, wobble method, doppler method, Dr. David Charbonneau | 0.865536 | 3.919822 |
A new model that’s shaped somewhere between a croissant and a beach ball could resolve a long debate about the protective bubble around our solar system, researchers report.
You are living in a bubble. Not a metaphorical bubble—a real, literal bubble. But don’t worry, it’s not just you. The whole planet, and every other planet in the solar system, for that matter, is in the bubble too. And, we may just owe our very existence to it.
Space physicists call this bubble the heliosphere. It is a vast region, extending more than twice as far as Pluto, that casts a magnetic “force field” around all the planets, deflecting charged particles that would otherwise muscle into the solar system and even tear through your DNA, should you be unlucky enough to get in their way.
The heliosphere owes its existence to the interplay of charged particles flowing out of the sun (the so-called “solar wind“) and particles from outside the solar system. Though we think of the space between the stars as being perfectly empty, it is actually occupied by a thin broth of dust and gas from other stars—living stars, dead stars, and stars not yet born.
Averaged across the whole galaxy, every sugar-cube-sized volume of space holds just a single atom, and the area around our solar system is even less dense.
The solar wind is constantly pushing out against this interstellar stuff. But the farther you get from the sun, the weaker that push becomes. After tens of billions of miles, the interstellar stuff starts to push back. The heliosphere ends where the two pushes balance out. But where is this boundary, exactly, and what does it look like?
Merav Opher, a professor of astronomy at Boston University, has been examining those questions for almost 20 years. And lately, her answers have been causing a stir.
The heliosphere’s shape: Croissant or beach ball?
Because our whole solar system is in motion through interstellar space, the heliosphere, despite its name, is not actually a sphere. Space physicists have long compared its shape to a comet, with a round “nose” on one side and a long tail extending in the opposite direction. Search the web for images of the heliosphere, and this is the picture you’re sure to find.
But in 2015, using a new computer model and data from the Voyager 1 spacecraft, Opher and her coauthor James Drake of the University of Maryland came to a different conclusion: they proposed that the heliosphere is actually shaped like a crescent—not unlike a freshly baked croissant, in fact. In this “croissant” model, two jets extend downstream from the nose rather than a single fade-away tail.
“That started the conversation about the global structure of the heliosphere,” says Opher.
Hers wasn’t the first paper to suggest that the heliosphere was something other than comet-shaped, she points out, but it gave focus to a newly energized debate.
“It was very contentious,” she says. “I was getting bashed at every conference! But I stuck to my guns.”
Then, two years after the “croissant” debate began, readings from the Cassini spacecraft, which orbited Saturn from 2004 until 2017, suggested yet another vision of the heliosphere.
By timing particles echoing off the boundary of the heliosphere and correlating them with ions measured by the twin Voyager spacecraft, Cassini scientists concluded that the heliosphere is actually very nearly round and symmetrical: neither a comet nor a croissant, but more like a beach ball. Their result was just as controversial as the croissant.
“You don’t accept that kind of change easily,” says Tom Krimigis, who led experiments on both Cassini and Voyager. “The whole scientific community that works in this area had assumed for over 55 years that the heliosphere had a comet tail.”
Now, Opher, Drake, and colleagues Avi Loeb of Harvard University and Gabor Toth of the University of Michigan have devised a new three-dimensional model of the heliosphere that could reconcile the “croissant” with the beach ball.
Two groups of particles
Unlike most previous models, which assumed that charged particles within the solar system all hover around the same average temperature, the new model breaks the particles down into two groups.
First are charged particles coming directly from the solar wind. Second are what space physicists call “pickup” ions. These are particles that drifted into the solar system in an electrically neutral form—because they aren’t deflected by magnetic fields, neutral particles can “just walk right in,” says Opher—but then had their electrons knocked off.
The New Horizons spacecraft, which is now exploring space beyond Pluto, has revealed that these particles become hundreds or thousands of times hotter than ordinary solar wind ions as they are carried along by the solar wind and sped up by its electric field. But it was only by modeling the temperature, density, and speed of the two groups of particles separately that the researchers discovered their outsized influence on the shape of the heliosphere.
That shape, according to the new model, actually splits the difference between a croissant and a sphere. Call it a deflated beach ball, or a bulbous croissant: either way, it seems to be something that both Opher’s team and the Cassini researchers can agree on.
The new model looks very different from that classic comet model. But the two may actually be more similar than they appear, says Opher, depending on exactly how you define the edge of the heliosphere. Think of transforming a grayscale photo to black and white: The final image depends a lot on exactly which shade of gray you pick as the dividing line between black and white.
Why does it matter?
Why worry about the shape of the heliosphere, anyway?
Researchers studying exoplanets—planets around other stars—are keenly interested in comparing our heliosphere with those around other stars. Could the solar wind and the heliosphere be key ingredients in the recipe for life?
“If we want to understand our environment we’d better understand all the way through this heliosphere,” says Loeb, Opher’s collaborator from Harvard.
And then there’s the matter of those DNA-shredding interstellar particles. Researchers are still working on what, exactly, they mean for life on Earth and on other planets. Some think that they actually could have helped drive the genetic mutations that led to life like us, says Loeb.
“At the right amount, they introduce changes, mutations that allow an organism to evolve and become more complex,” he says. But the dose makes the poison, as the saying goes. “There is always a delicate balance when dealing with life as we know it. Too much of a good thing is a bad thing,” says Loeb.
When it comes to data, though, there’s rarely too much of a good thing. And while the models seem to be converging, they are still limited by a dearth of data from the solar system’s outer reaches. That is why researchers like Opher are hoping to stir NASA to launch a next-generation interstellar probe that will cut a path through the heliosphere and directly detect pickup ions near the heliosphere’s periphery.
So far, only the Voyager 1 and Voyager 2 spacecrafts have passed that boundary, and they launched more than 40 years ago, carrying instruments of an older era that were designed to do a different job. Mission advocates based at Johns Hopkins University Applied Physics Laboratory say that a new probe could launch some time in the 2030s and start exploring the edge of the heliosphere 10 or 15 years after that.
“With the Interstellar Probe we hope to solve at least some of the innumerous mysteries that Voyagers started uncovering,” says Opher. And that, she thinks, is worth the wait.
Their work appears in Nature Astronomy.
The researchers thank the staff at NASA Ames Research Center for the use of the Pleiades supercomputer. Support for this work also came from NASA and the Breakthrough Prize Foundation.
Source: Boston University | 0.895382 | 3.899648 |
Japan has lost contact with its newest space telescope. The spacecraft, which was carrying an instrument from NASA, was intended to study the high-energy universe in X-rays and gamma rays, and observe such objects as supermassive black holes and galaxy clusters.
Radar observations indicated that Hitomi, which launched on February 17 into low-Earth orbit, is in at least five pieces—and a plot of its orbit revealed a dramatic change on Saturday, when the spacecraft lost contact with Earth.
(Update: Watch new video that shows the spacecraft tumbling in orbit.)
That means, says astrophysicist Jonathan McDowell, that some kind of “energetic event” has occurred—something more than a simple failure of communications.
“Loss of comm + orbit change + radar detecting 5 pieces of debris is much worse than just loss of comm,” tweeted McDowell, of the Harvard-Smithsonian Center for Astrophysics.
—Jonathan McDowell (@planet4589) March 27, 2016
It’s not clear exactly what has happened on board Hitomi. Scientists are currently investigating the situation, and the Japanese space agency, JAXA, reports that it has gotten a trickle of a signal from the spacecraft. That means it’s possible the five pieces detected by radar are things like insulation, rather than large chunks of debris resulting from a catastrophic explosion; it’s also possible the spacecraft is tumbling, McDowell says, and that signals from Hitomi are periodically sweeping across the Earth.
Still, despite all the bad news, the spacecraft might not be lost.
“I truly have not given up hope,” McDowell says, noting that equally bad space situations in the past have been successfully resolved. “We lost contact with SOHO for months and fully recovered it. ALEXIS had a solar panel break loose and was tumbling, but they learnt how to fly it and began science mission a couple months late. So it’s a long shot—and I refuse to put a number on the probability—but there is precedent for things being this bad and it turning out OK.”
JAXA is no stranger to second chances. Late last year, the Japanese space agency managed to place its Akatsuki spacecraft in orbit around Venus, after failing on the first try. When Akatsuki originally tried to orbit Earth’s twisted sister, a valve broke and sent the spacecraft on a long, 5-year journey through the solar system. But, eventually, Akatsuki caught up with its target and slipped into Venus’ gravitational clutches.
The moral of the story? Space is hard. Things go wrong. But if we never try, we’ll never succeed. | 0.869517 | 3.442284 |
This may be the largest remaining piece of the space telescope Hitomi.
New observations suggest that Hitomi, Japan’s flagship X-ray telescope, is tumbling through space in ten or more pieces—and is likely unrecoverable.
“The available data now seem to indicate a real break-up rather than just “some” debris shedding,” writes satellite tracker Marco Langbroek. “If true, then Hitomi is beyond saving.”
The Japanese Aerospace Exploration Agency (JAXA) lost consistent contact with Hitomi (also known as ASTRO-H) on March 26. Early reports showed the spacecraft’s orbit had rapidly changed—and that it had then shed at least five pieces of debris, size unknown. Video footage captured from the ground revealed an object tumbling through space, an ominous observation consistent with the intermittent radio signals JAXA was still receiving from the spacecraft. Altogether, the evidence suggested that some sudden event had disabled Hitomi, which would have peered into the hearts of galaxies and studied the maelstrom of matter swirling around black holes.
Whether that event was some kind of onboard explosion (more probable), or a collision with space debris (less probable) is still unclear.
Now, new radar observations from the U.S. Joint Space Operations Center indicate that Hitomi has broken up into at least ten pieces, and that two of these pieces are very large indeed. Even more worryingly, the spacecraft has gone quiet, with Japan no longer receiving the intermittent trickles of signals thought to come from a tumbling Hitomi.
“Sadly, I now believe that the radio signals were the dying sighs of a fatally wounded ASTRO-H,” tweeted Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics. “As far as I know, JAXA hasn’t officially given up though!”
Those ten pieces were likely all present on March 26, when the first reports of debris from Hitomi came in, but they weren’t separated enough in space to be reliably observed.
Now, orbital data show that some of those pieces are on quickly decaying trajectories and will burn up in Earth’s atmosphere within a week or so, writes astrophysicist Peter Coles of Sussex University. Those fragments are small, the kinds of things a spacecraft could plausibly shed and still function.
Today’s updated Hitomi debris plot. All the objects now have more than one data point; 3 are decaying rapidly pic.twitter.com/oeUyboyXRH
— Jonathan McDowell (@planet4589) April 3, 2016
The two largest fragments, however, suggest that whatever happened to Hitomi is probably a terminal event. Video footage shows that these fragments, now called piece A and piece L, are roughly the same size and are tumbling through space, with one flying about 7 minutes in front of the other.
Japanese Spacecraft Tumbling in Orbit (L Piece)
The first of those pieces, now called piece L, was captured on video last week and mistakenly thought to be the main body of Hitomi. But it’s not. New observations suggest the tumbling fragment is a large, dense piece of Hitomi—perhaps its extendable optical bench, where the spacecraft’s hard X-ray detectors are. An April 2 video from satellite tracker Paul Maley, taken on the ground in Arizona, suggest fragment L is still tumbling through space, flashing about once every 10 seconds.
Fragment A, which is now thought to be the bulk of Hitomi, is trailing piece L by several minutes. Maley’s video shows that A is flashing about once every second.
“It is spinning quite fast with bright flashes,” Maley describes, noting that fragment A is also visible with the unaided eye. “The only question is, what are the real identities of the objects in orbit? Given the brightness of the two that I have seen, one is most likely the primary payload, the other is something sizable but what it is I do not know.”
Pieces A and L are trailed by a third large-ish fragment called K, which is about 26 minutes behind the pair.
The whole situation is unfolding into a heartbreaking disaster for Japan and for astronomers, who’d hoped this attempt to put an X-ray observatory in orbit would be successful (to really see the universe in X-rays, you need a satellite above the Earth’s atmosphere). Since 2000, Japan has tried twice to operate a space-based X-ray telescope; the first crashed during launch, and the second suffered from a leaky helium tank. So, hopes were high for Hitomi, which launched on February 17, and means pupil of the eye.
It could take years for the spacecraft’s two largest fragments to re-enter Earth’s atmosphere, and it’s possible that bits of them could survive the plunge to our planet.
“They aren’t decaying fast, may be a few years before they reenter,” McDowell says. “But when they do we’ll be paying close attention.” | 0.847143 | 3.758046 |
The contribution of explosions known as novae to the lithium content of the Milky Way is uncertain. Radioactive beryllium, which transforms into lithium, has been detected for the first time in one such explosion. See Letter p.381
The origin of lithium observed in today's Universe is a long-standing problem. It is known that a fraction of this light chemical element was created during the Big Bang, along with hydrogen and helium, and that another fraction has formed since then through nuclear reactions induced by energetic cosmic rays. But comparison of chemical-evolution models and observed stellar lithium abundances in the Milky Way indicates that part of the lithium should also have been synthesized in old low-mass stars, such as red giants, and in stellar explosions known as novae. However, although lithium has been observed in giants, its detection in novae has remained elusive. On page 381 of this issue, Tajitsu et al.1 provide the first observational evidence of lithium synthesis in novae. The authors detected radioactive beryllium-7 (7Be), the parent nucleus of lithium-7 (7Li), during a nova explosion called V339 Del (Nova Delphini 2013).
It has long been known that almost all of the chemical elements are produced in stars by the nuclear fusion of light elements into heavier ones, starting with hydrogen fusion2. The synthesized elements can then be expelled to the interstellar medium — from which new stars will form — either by stellar winds or during supernova explosions and their dimmer relatives, novae. However, the main origin of the light elements lithium, beryllium and boron is not linked to nuclear reactions in stars. Instead, it is related to nucleosynthesis processes that are less efficient than stellar ones. This is why these elements are much less abundant in the Milky Way and the Solar System than heavier elements.
Lithium has a complex origin. It is produced in three ways: by nucleosynthesis during the Big Bang; by nuclear reactions in the interstellar medium that are induced by energetic cosmic rays and are also responsible for the origin of beryllium and boron; and by nuclear reactions in stellar sources, such as red giants3. The stellar sources are required to reproduce the rise of lithium abundance in the Milky Way after the formation of the Solar System about 4.5 billion years ago.
Inside stars, 7Be, the subject of Tajitsu and colleagues' study, is formed by the fusion of helium-3 and helium-4. This radioactive element then captures an electron and transforms into its daughter nucleus, 7Li, within a short timescale (7Be has a half-life of 53.22 days), releasing a 478-kiloelectronvolt-energy photon (Fig. 1). But efficient production of 7Li requires this nuclear reaction to occur in hot, external stellar layers, and requires freshly produced 7Be to be transported into cooler subsurface layers before it transforms into 7Li. In this way, 7Li is immune to destruction once it is created. This process, known as the Cameron–Fowler 7Be transport mechanism, is responsible for 7Li production in stars4,5.
Novae are thermonuclear explosions, and take place on top of white dwarfs that pull hydrogen-rich material from a companion star. As more hydrogen accumulates on the white dwarf, it builds up a shell that reaches pressures and temperatures sufficient to trigger explosive runaway fusion of the hydrogen. This leads to the fast expansion and subsequent ejection of the white dwarf's outer layers, and is accompanied by a sudden large increase in the star's brightness. During this process, 7Li is thought to be produced through the Cameron–Fowler 7Be transport mechanism.
The first studies of lithium production in novae were made in the 1970s6,7, but it was not until 1996 that the details of the process were pinned down8. It was realized that the initial chemical composition of the white dwarf that undergoes a nova was a crucial determinant of the amount of 7Li synthesized in the explosion; depending on the mass of its progenitor star, the white dwarf is made of either carbon and oxygen (CO novae) or oxygen and neon (ONe novae).
In CO novae, the carbon content makes the hydrogen fusion proceed faster than in ONe novae, owing to the operation of the CNO cycle of fusion reactions. Such faster evolution prevents the destruction of 3He and 7Be (Fig. 1), and so results in a larger production of 7Be and 7Li. The amount of 7Li produced by a CO nova corresponds to about 10−10 of the Sun's mass, but this value largely depends on the total ejected mass.
In their study, Tajitsu et al. report the detection of highly blue-shifted absorption lines of the singly ionized radioactive isotope of 7Be, 7Be II, in the near-ultraviolet spectra of the CO classical nova V339 Del, between 38 and 52 days after the explosion. The spectra were obtained using the Subaru Telescope of the National Astronomical Observatory of Japan, which delivers high spectral resolution (about 0.0052 nanometres) and so allowed the authors to tease apart the lines of 7Be II from those of 9Be II, both of which occur at wavelengths around 312–313 nm.
The finding lends support to the hypothesis that the Cameron–Fowler 7Be transport mechanism is at work in novae, as predicted theoretically 40 years ago6. The observations indicate that nova V339 Del produced at least as much 7Be and 7Li as predicted by theory.
The implications of these results are manifold. First, they mean that novae may play a larger part in lithium production than previously thought. Second, they may increase the probability of detecting the 478-keV γ-ray photons emitted in the 7Be-to-7Li reaction9, which have remained elusive despite observational efforts made by γ-ray missions10,11. Third, and perhaps most importantly, they suggest that measurements of 7Be lines in the near-ultraviolet range and within the lifetime of the element may well provide a way of estimating the contribution of novae to the lithium abundance in the Milky Way and in the Universe in its entirety.Footnote 1
Tajitsu, A., Sadakane, K., Naito, H., Arai, A. & Aoki, W. Nature 518, 381–384 (2015).
Burbidge, E. M., Burbidge, G. R., Fowler, W. A. & Hoyle, F. Rev. Mod. Phys. 29, 547–650 (1957).
Romano, D., Matteucci, F., Molaro, P. & Bonifacio, P. Astron. Astrophys. 352, 117–128 (1999).
Cameron, A. G. W. Astrophys. J. 121, 144–160 (1955).
Cameron, A. G. W. & Fowler, W. A. Astrophys. J. 164, 111–114 (1971).
Arnould, M. & Nørgaard, H. Astron. Astrophys. 42, 55–70 (1975).
Starrfield, S., Truran, J. W., Sparks, W. M. & Arnould, M. Astrophys. J. 222, 600–603 (1978).
Hernanz, M., José, J., Coc, A. & Isern, J. Astrophys. J. 465, L27–L30 (1996).
Clayton, D. D. Astrophys. J. 244, L97–L98 (1981).
Harris, M. J., Leising, M. D. & Share, G. H. Astrophys. J. 375, 216–220 (1991).
Harris, M. J. et al. Astrophys. J. 563, 950–957 (2001).
About this article
Deciphering the Local Interstellar Spectra of Secondary Nuclei with the Galprop/Helmod Framework and a Hint for Primary Lithium in Cosmic Rays
The Astrophysical Journal (2020)
Frontiers in Microbiology (2019) | 0.889342 | 4.204401 |
How did knowledge spread in Galileo’s world?
Johann Schreck joined the Jesuit order in 1611, the same year that he used Galileo's telescope to observe the satellites of Jupiter. Upon becoming a Jesuit, Schreck joined the Jesuit mission in China, taking with him a scientific library of approximately 7,000 volumes as well as a Galilean telescope. Schreck's story is the beginning of a century-long exchange of scientific ideas between Europe and Asia.
Is there a mathematical basis of the universe?
Johann Kepler's "Mystery of the Universe" is one of the brilliant illustrations in the history of astronomy. Kepler used the five regular Pythagorean solids to refute the major objections to Copernicanism. In this work he demonstrated that vast empty regions lying between the planetary spheres, which were required by Copernicus, were not wasted space. Rather, these gaps perfectly matched, within the limits of observational error, the geometry of the 5 regular Pythagorean solids.
Why were experimental variables (like tilt) so important?
Galileo described his experiment with an inclined plane in Two New Sciences. In this work, Galileo furthered a research tradition in physics known as "impetus." This tradition, begun in the 6th century CE with John Philoponos, sought to explain motion. A body falling straight down accelerates too fast to be measured, so Galileo constructed his inclined plane in order to study it in slow motion. Galileo's inclined plane provided experimental confirmation of the law of free fall.
How does the Sextant symbolize the person who worked on the famed Hevelius star catalog and star atlas throughout its production, from observation to publication?
Elisabeth Hevelius, wife of Johann Hevelius, was an astronomer in her own right. They worked together in the observatory of their Gdansk home to measure angular widths and distances with a great sextant, which required two observers at a time. The Sextant was among the new constellations they proposed in Uranographia (1690), the most detailed and influential celestial atlas of the 17th century. The Uranographia contains 54 beautiful double page engraved plates of 73 constellations, and 2 oversized folding plates of planispheres.
Can you identify simple musical intervals?
The ancient Pythagoreans envisioned the heavens as a musical scale, comprised of celestial spheres rotating according to harmonious music. For Robert Fludd, a seventeenth-century physician, the universe was a monochord, its physical structure unintelligible without an understanding of music. In this activity, explore the relationship between mathematics, astronomy, and music.
Why write science in a creative style?
Catherine Whitwell wrote an introduction to the night sky as a conversational dialogue between a mother and daughter. It contains 23 engraved plates drawn by Whitwell herself, including four hand colored folding plates. One of the plates depicts the constellations of Corvus the Crow, Crater the Cup and Hydra the Water Snake. Another plate conveys a dramatic impression of the Full Moon at night, shown against a striking black background.
Where will the quest of discovery lead you?
Science is a quest of discovery, the challenge of boldly exploring where no one has gone before. That is the appeal and rhetorically durable theme which has made this woodcut so appealing.
Many have reprinted this illustration through the years, sometimes without knowing its original source. It first appeared in this popular work on meteorology. Flammarion was an astronomer and popular science writer who worked at the Juvissy Observatory in Paris. He was mistaken in his belief that scientists, writers and theologians in the Middle Ages and Renaissance regarded the Earth as flat.
What is the difference between a calculating machine and a computer?
In notes appended to Ada Lovelace's translation of one of the first introductions to Charles Babbage's "Analytical Engine," she included an in-depth analysis of the significance and potential of Babbage's machine design. These dense notes, much longer than the text she translated, explained how Babbage's machine had the potential of becoming a programmable computer, instead of merely a calculator.
Why did people come to Hildegard’s convent?
Hildegard of Bingen, Abbess of convents at Rupertsberg and Elbingen in the 12th century, explained their herbal remedies and medical procedures in her book Physica. In addition to this work on medicine, Hildegard wrote other works on cosmology and theology, corresponded in nearly 400 letters with abbots, popes and emperors, and created at least 70 musical compositions. This OER explores the significance of Hildegard of Bingen. | 0.875203 | 3.538684 |
So far, NASA has landed four rovers on Mars. These are solar-powered robots with six wheels and robotic arms that can take soil samples and operate cameras. Sojourner landed in 1997, Spirit and Opportunity in 2003, while the more advanced Curiosity was landed last summer.
"Manoeuvrability is a challenge. The Spirit rover was lost after it became stuck in the sand on Mars. The vehicles just cannot get to many of the places from which samples have to be taken", say Pål Liljebäck and Aksel Transeth at SINTEF ICT.
The researchers are busy working on a feasibility study assigned to them by the ESA. The ESA and the researchers believe that by combining a rover that can navigate over large distances with a snake robot that can crawl along the ground and can get into inaccessible places, so many more possibilities could be opened up.
At the moment, soil samples from Mars are analysed on board the rover itself, and the results are communicated back to Earth. However, The ESA also wants to examine options that could allow samples to be returned to Earth. Snake robots could assist with collecting such samples, since they enable access to tight spots that the rovers cannot reach.
|SINTEF researchers Pål Liljebäck and Aksel Transeth, and Knut Robert Fossum of NTNU's CIRiS, are playing with Wheeko the snake robot. Photo. SINTEF/Thor Nielsen.
An arm becomes a snake robot
"We are looking at several alternatives to enable a rover and a robot to work together. Since the rover has a powerful energy source, it can provide the snake robot with power through a cable extending between the rover and the robot. If the robot had to use its own batteries, it would run out of power and we would lose it", explains Aksel Transeth.
"One option is to make the robot into one of the vehicle's arms, with the ability to disconnect and reconnect itself, so that it can be lowered to the ground, where it can crawl about independently".
The researchers envisage using the rover to navigate over large distances, after which the snake robot can detach itself and crawl into tight, inaccessible areas. A cable will connect the robot to the vehicle. The cable will supply power and tractive power, i.e. it can be winched back to the rover. Communication between the pair will be facilitated via signals transmitted down the cable.
"The connection between the robot and the rover also means that the snake robot will be able to assist the vehicle if the latter gets stuck", says Liljebäck. "In such a situation, the robot could lower itself to the ground and coil itself around a rock enabling the rover pull itself loose by means of the cable winch, which the rover would normally use to pull the snake robot towards the rover".
Snake robot hoisted up
Another scenario illustrating how the vehicle and the snake robot can work together is for the robot to be located underneath or on top of the rover. That would require a hoisting mechanism to pick up the robot, lift it up and connect it to the rover.
The researchers report that they are now carrying out a concept study. Being on Mars is a different matter to being on Earth, and they must check whether the technology for a snake robot can also work on that planet. A more specific proposal will be submitted in December, but part of the study is to identify challenges and any potential snags.
Report to the ESA
"At the Department of Applied Cybernetics, we have been working closely with the Norwegian University of Science and Technology's (NTNU's) Department of Engineering Cybernetics on snake robots for many years, and our teams have had some ideas about this for a long time", say Transeth and Liljebäck.
"It is only now that we are starting to see some actual applications, and it is wonderful to be given this opportunity to provide the ESA with information about future technologies in this field. What we hope is that our ideas will trigger the ESA into initiating a targeted development process around this kind of system".
By Åse Dragland
Videoes of the robots: http://robotnor.no/research/serpentine-robots-for-planetary-exploration-serpex/
On Bloomberg TV, London: http://www.bloomberg.com/video/robot-snakes-on-a-plane-to-mars-it-could-happen-3ogHmKIpQ6u_j03e6LNOHQ.html
- The ESA is the client for a feasibility study being carried out by SINTEF (June - December 2013). Funding: NOK 500,000. CIRiS, a department of NTNU's social research institute Samfunnsforskning AS, is also taking part, and will be looking into the project's logistic and operational aspects.
- So far, NASA has landed four rovers on Mars: Sojourner in 1997, Spirit and Opportunity in 2004, and Curiosity in 2012. The latter is highly advanced and comes with a built-in laboratory.
- The ESA has new missions planned for 2016 and 2028. | 0.830061 | 3.058684 |
J and K band AO imaging of HD 87646 taken at Palomar observatory. Credit: Ma et al., 2016. (Phys.org)—An international team of astronomers reports the discovery of a giant planet and a brown dwarf in a close binary system designated HD 87646. The findings, described in a paper published Aug. 11 on arXiv.org, reveal that HD 87646 is the first close binary system with more than one substellar circum-primary companion known to date. Citation: Giant planet and brown dwarf discovered in a close binary system HD 87646 (2016, August 16) retrieved 18 August 2019 from https://phys.org/news/2016-08-giant-planet-brown-dwarf-binary.html Explore further © 2016 Phys.org More information: Very Low-Mass Stellar and Substellar Companions to Solar-like Stars From MARVELS VI: A Giant Planet and a Brown Dwarf Candidate in a Close Binary System HD 87646 , arXiv:1608.03597 [astro-ph.EP] arxiv.org/abs/1608.03597AbstractWe report the detections of a giant planet (MARVELS-7b) and a brown dwarf candidate (MARVELS-7c) around the primary star in the close binary system, HD 87646. It is the first close binary system with more than one substellar circum-primary companion discovered to the best of our knowledge. The detection of this giant planet was accomplished using the first multi-object Doppler instrument (KeckET) at the Sloan Digital Sky Survey (SDSS) telescope. Subsequent radial velocity observations using ET at Kitt Peak National Observatory, HRS at HET, the “Classic” spectrograph at the Automatic Spectroscopic Telescope at Fairborn Observatory, and MARVELS from SDSS-III confirmed this giant planet discovery and revealed the existence of a long-period brown dwarf in this binary. HD 87646 is a close binary with a separation of ∼22 AU between the two stars, estimated using the Hipparcos catalogue and our newly acquired AO image from PALAO on the 200-inch Hale Telescope at Palomar. The primary star in the binary, HD 87646A, has Teff = 5770±80K, log(g)=4.1±0.1 and [Fe/H] = −0.17±0.08. The derived minimum masses of the two substellar companions of HD 87646A are 12.4±0.7MJup and 57.0±3.7MJup. The periods are 13.481±0.001 days and 674±4 days and the measured eccentricities are 0.05±0.02 and 0.50±0.02 respectively. Our dynamical simulations show the system is stable if the binary orbit has a large semi-major axis and a low eccentricity, which can be verified with future astrometry observations. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. HD 87646, located around 240 light years away, is a bright G-type star with a fainter K-type stellar companion. The primary star in the system, HD 87646A, is about 12 percent more massive than the sun and has a radius of about 1.55 solar radii. The system has a separation of only 22 AU between the two stars.A team of researchers, led by Bo Ma of the University of Florida, has been observing HD 87646 since 2006 using a set of telescopes. The scientists employed the W.M. Keck Exoplanet Tracker (KeckET), at the Sloan Digital Sky Survey (SDSS) 2.5m telescope, mounted on the Apache Point Observatory in New Mexico to reveal the presence of a new giant planet that received designation HD 87646b. KeckET is a new generation multiple object Doppler instrument, capable of simultaneously observing more than 50 stars.The planetary status of HD 87646b was confirmed thanks to the radial velocity observations conducted by utilizing the Kitt Peak National Observatory (KPNO) in Arizona, the High-Resolution Spectrograph at the Hobby-Eberly Telescope (HET) in Texas, the “Classic” spectrograph at the Automatic Spectroscopic Telescope, mounted on the Fairborn Observatory in Arizona and the Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS) at SDSS. Moreover, these observations allowed the researchers to detect new even larger companion in the system – a brown dwarf designated HD 87646c.”Our SDSS MARVELS pilot survey and additional observations at the HET, KPNO 2.1m telescope, and Fairborn Observatory confirm the detection of two massive substellar companions in a close binary system HD 87646,” the team wrote in the paper.According to the study, HD 87646b has a minimum mass of about 12.4 Jupiter masses and an orbital period of approximately 13.5 days. HD 87646c is much more massive, having 57 Jupiter masses and much longer orbital period, circling the star every 673 days.The team also conducted dynamical simulations of the system, which allowed them to draw conclusions that HD 87646 is stable if it has a large binary semi-major axis and a relatively low binary eccentricity.However, the question of how this system was formed still baffles the authors of the paper. Given the fact that HD 87646 is the first known system to have two massive substellar objects orbiting a star in a close binary and the masses of the two objects are close to the minimum masses for burning deuterium and hydrogen, these peculiarities raise questions about the system’s formation and evolution.”The large masses of these two substellar objects suggest that they could be formed as stars with their binary hosts: a large molecular cloud collapsed and fragmented into four pieces; the larger two successfully became stars and formed the HD 87646 binary, and the other smaller ones failed to form stars and became the substellar objects in this system. This scenario might be relevant for the binary stars but seems problematic for the two substellar objects on orbits within one AU because it is unclear whether fragmentation on such a small scale can occur,” the paper reads.Other hypothesis offered by the scientists is that the two newly discovered giant objects were formed like giant planet in a protoplanetary disk around HD 87646A. However, they added that such massive disks are rare in close binaries, and further investigation is needed to confirm this explanation. Astronomers discover new substellar companion to the Pleiades member star
Kolkata: iaAn earthquake measuring 4.8 on the Richter scale struck West Bengal’s Bankura district on Sunday, authorities said. According to Regional Meteorological Centre Kolkata, the earthquake occurred at 10.39 a.m. at a depth of 10 kilometres in Bankura region. Tremors were felt in Purulia, Jhargram and other adjoining areas.
August 4, 2017 A researcher who played a role in halting the spread of the WannaCry ransomware has been indicted by U.S. authorities for allegedly creating the Kronos malware with another individual.As Motherboard reports, U.K.-based researcher Marcus Hutchins, known online as MalwareTech, was arrested in Las Vegas this week, where he was attending the Black Hat and Defcon security conferences.The indictment, filed on July 11 in Wisconsin District Court, says that “Defendant Marcus Hutchins created the Kronos malware,” alongside another person, whose name has been redacted from the filing. Between July 2014 and July 2015, the two “intentionally cause[d] damage without authorization to 10 or more protected computers,” it says.A spokeswoman for the FBI’s Nevada office referred PCMag to the Department of Justice, which did not immediately respond to a request for comment.Hutchins made headlines in May when he stopped the spread of the WannaCry by accident. He noticed the ransomware “queried an unregistered domain, which I promptly registered.” But WannaCry looks to connect to that unregistered domain. If it can’t connect, “it ransoms the system,” MalwareTech explained. If it connects to the domain, though, “the malware exits” and the system is not compromised. After the registration, WannaCry connected to the domain and was stopped in its tracks.According to the indictment, Hutchins’s alleged co-conspirator posted a video that demonstrated how the Kronos malware worked on July 13, 2014. The person then offered to sell the Kronos banking trojan for $3,000 “on an internet forum.”Hutchins reportedly helped this person update the Kronos malware in February 2015, after which it was advertised for sale on the (now-defunct) AlphaBay dark web forum. In June 2015, it sold for about $20,000 in digital currency, the indictment says.As some have pointed out online, Hutchins requested a Kronos sample on the day the video in question went up.Anyone got a kronos sample?— MalwareTech (@MalwareTechBlog) July 13, 2014Fellow researcher Andrew Mabbitt, who traveled to Las Vegas with Hutchins and several other colleagues, says he refuses to believe the charges. “He spent his career stopping malware, not writing it,” Mabbitt says of Hutchins.Mabbitt says he will be “crowdfunding legal fees soon.” The Electronic Frontier Foundation, which often steps in to assist with cases like this, tweeted that it is “deeply concerned about security researcher Marcus Hutchins’ arrest. We are looking into the matter, and reaching out to Hutchins.” Register Now » This story originally appeared on PCMag Free Webinar | Sept. 9: The Entrepreneur’s Playbook for Going Global Growing a business sometimes requires thinking outside the box. 3 min read
The National Security Agency (NSA) will be publicly releasing their reverse engineering framework called GHIDRA, for the first time at the RSA Conference (Rivest, Shamir, and Adleman security conference) to be held in March 2019. According to the official announcement on the RSA blog, the framework will be introduced by NSA’s Senior Advisor Robert Joyce. According to NSA, GHIDRA has ‘an interactive GUI capability that enables reverse engineers to leverage an integrated set of features that run on a variety of platforms including Windows, Mac O, and LINUX and supports a variety of processor instruction sets’. This is what we know about GHIDRA so far: In March 2017, WikiLeaks leaked CIA Vault 7 documents which highlighted the various tools utilized by the CIA. The leaked documents included numerous references to a reverse engineering tool called ‘GHIDRA’ that was developed by the NSA at the start of the 2000s. For the past few years GHIDRA has been shared with other US government agencies with cyber teams that look at the inner workings of malware strains or suspicious software. GHIDRA is a ‘disassembler’ that breaks down software into its assembly code so that humans can analyze malware and other suspected malicious software. GHIDRA is built in Java, that runs on Linux, Mac and Windows operating systems and has a graphical user interface. With GHIDRA, developers can analyze the binaries of all major operating systems, including mobile platforms like Android and iOS. NSA is expected to add GHIDRA on NSA’s code repository hosted by Github where the spy agency has released several other open source programs. Some people who are familiar with this tool and have shared opinions on HackerNews, Reddit, and Twitter. They have compared GHIDRA with IDA, another well-known reverse engineering tool. Source: HackerNews Head over to RSA’s official blog to check out the announcement. Alternatively, check out Siliconangle for more insights on this news. Read Next NSA’s EternalBlue leak leads to 459% rise in illicit crypto mining, Cyber Threat Alliance report NSA researchers present security improvements for Zephyr and Fucshia at Linux Security Summit 2018
Fancy some Unicorn poop? New map tracks London’s best food finds Travelweek Group Tags: Food, London Wednesday, August 8, 2018 LONDON — Ever wanted to try Unicorn poop? You can get some in London with help from a new map featuring the city’s most delicious – and bizarre – food fads.Wren Kitchens, a privately-owned family business that manufactures and sells kitchen products, has released its own interpretation of London’s Tube map that shows commuters and tourists where to go in Zone 1 for culinary treasures.Credit: Wren’s KitchenIf you’ve got a hankering for a macaron ice cream sandwich (who doesn’t?!), go to Charing Cross. There’s something called a Matcha Freakshake on Liverpool street, and a super trendy charcoal brioche burger at Paddington.Always a fan favourite, rainbow bagels can be hunted down in the east end of Zone 1 at Aldgate East, while avocado enthusiasts will surely flip over avocado bubble waffles at Piccadilly Circus.And what about the elusive unicorn poop? Follow the map to Old Street for a bowl full of this much-talked-about fruity, colourful cereal.More news: TRAVELSAVERS welcomes Julie Virgilio to the teamPhoto Credit: https://www.wrenkitchens.com/blog/food-tube-ultimate-guide-deliciously-instafamous-summer-city/ << Previous PostNext Post >> Posted by Share | 0.825944 | 3.393615 |
On Monday, Mercury will pass between the Earth and the sun, a event that only takes place about 13 times every 100 years.
Scientists are planning to watch the transit of Mercury using Earth-based and in-space telescopes. The observations they gather could help researchers learn more about Mercury’s atmosphere.
The last transit of Mercury was in 2006, and the next one will be in 2019.
“Astronomers get excited when any two things come close to each other in the heavens,” Louis Mayo, program manager at NASA’s Goddard Space Flight Center, said in a statement. “This is a big deal for us.”
“Three of NASA's solar telescopes will watch the transit for just that reason.”
The transit — which lasts for about 7.5 hours — will be visible for millions of people around the world beginning at 7:12 a.m. and lasting until 2:42 p.m. ET, according to NASA.
The East Coast of the United States will be able to see the entire transit, while the West Coast will be able to see most of the event after the sun rises.
Do not try to look directly at the sun during the transit.
While Mercury will pass in front of the star from Earth’s vantage point, the small world doesn’t block that much light, meaning that it will still be very dangerous to look directly at the sun without proper protection using a telescope, binoculars or with the naked eye.
If you are interested in seeing the transit yourself, you’ll need some kind of magnification like a telescope or binoculars with a solar filter in place to see it.
You can also watch the transit live with NASA in near real-time thanks to the Solar Dynamics Observatory beaming back high-definition images of the sun from its post in space. NASA scientists will also participate in a Facebook Live event discussing observations of the transit from 10:30 to 11:30 a.m. ET on May 9.
Two other spacecraft will also watch the transit, according to NASA. The Solar and Heliospheric Observatory (SOHO) and Japan’s Hinode will also observe the sun during the transit.
“It used to be hard to observe transits,” Joseph Gurman, SOHO project scientist, said in the statement.
“If you were in a place that had bad weather, for example, you missed your chance and had to wait for the next one. These instruments help us make our observations, despite any earthly obstacles.”
Researchers use transits for science outside of the solar system as well. Some telescopes keep an eye on stars far from Earth to see when their light dips a slight amount, sometimes signaling that a planet has passed in front of its host star.
Have something to add to this story? Share it in the comments. | 0.820184 | 3.373962 |
Authors: M. Caleb, C. Flynn, M. Bailes, et al.
First Author’s Institution: Australian National University, ACT, Australia
Status: Published in MNRAS, open access
Fast Radio Bursts more commonly known as FRBs, have been a hot topic in recent years. These loud bursts of radio emissions appear in radio observation data at seemingly random times from random positions on the sky (see Fig. 1). Ever since the first FRB was found in archival data from the Parkes Observatory in Australia by Duncan Lorimer and his undergraduate student David Narkovic, we’ve seen an explosion in searches and resources devoted to finding more FRBs. The initial discovery of FRBs was highly scrutinized because unfortunately even astronomers can make mistakes. As of today, radio astronomers are trying to collect as much data on FRBs as possible to constrain all of the hypothesized origins of these extragalactic bursts of radio emissions.
Transient signals in our Radio Sky
FRBs are typically bright (high signal to noise), short lived (bursts on the order of milliseconds), and have a characteristic dispersion in frequency (meaning that they exist across multiple radio frequencies; an example of this can be seen in the Lorimer Burst). This dispersion in frequency is one way that can tell us that FRBs are not terrestrial , because it shows that the radio signal passed through a cold plasma, aka the Intergalactic Medium (IGM). This dispersion of an FRB signal can be quantified by the dispersion measure, DM. This relationship can be seen below, where is the dispersion constant, the beginning and the end observing frequencies, and the pulse width.
This quantity can also help us understand the properties of the IGM that the signal passed through, as DM can tell us about the electron density along its path. Now that we know the typical features of an FRB we can understand the type of instrument it takes to detect one. We need a radio telescope that has both high frequency and time resolution, and preferably one that has a lot of collecting area (this will translate to a higher sensitivity). This brings us to the radio interferometer used by the author’s of todays astrobite, the upgraded Molonglo Observatory Synthesis Telescope, or UTMOST. These upgrades allow for the improved detection of FRBs and coupled with the core MOST part of the telescope it has an ~ 8 field of view and 18,000 of collecting area. This means that UTMOST is pretty ideally situated to detect and survey for FRBs, and as we’ll now find out has already begun its job.
Catching FRBs in Radio Interferometers
Looking for FRBs isn’t easy, as can be seen from Figure 1, which demonstrates that there are no particular regions of the sky where they can be found. So being able to observe as much of the sky at any given moment can be extremely important. Our astrobite today highlights the first ever FRB detection in an interferometer (…actually the first 3!) over the course of 180 days of observing. The 3 UTMOST FRB detections can be seen in Figure 2, which are named FRB 160317, FRB 160410, and FRB 160608 (FRB naming convention is simple, it’s just FRB YYMMDD). In these initially detected FRBs they find the very characteristic burst width of 21 ms, 4 ms, 9 ms and dispersion measures of 1165 , 278 , 682 respectively. All three of these FRBs have DMs that are significantly higher than the dispersion you could expect from our own Milky Way (approx. 10-100 ), and thus the authors suggest that they must be from beyond our own galaxy. Additionally by extrapolating these 3 detections at the frequency of 843 MHz, they calculate that there should be 78 FRBs per day visible across the whole sky. This translates to approximately 0.02 FRBs per day when using UTMOST (due to it’s field of view). The all-sky FRB rate found with these 3 observations also goes counter to some of the most recent statistical understanding, as they appear to be almost a factor of 2 more than expected in the low frequency range. They suggest as a possible solution in light of these new detections that FRBs may exhibit a steeper spectral index than previously thought.
In addition to UTMOST in the Southern Hemisphere, the Canadian Hydrogen Intensity Mapping Experiment (CHIME) is currently being built in the Northern Hemisphere. While CHIMEs’ main purpose is the mapping of the 21cm cosmological signal it might be fit for FRB searches giving us an eye on the sky in the north. The current constraints on FRBs are still very much in their infancy, but with these newly minted radio interferometers (HIRAX too!) with much larger fields of view I think we can declare FRB hunting season open. Increasing the number of detections and bolstering our statistics of these extragalactic events will mean that we can eventually put the question of what causes an FRB to rest. | 0.800204 | 4.042662 |
At some point this decade, a new space observatory will be launched into orbit; one unlike any that we have seen before with extraordinary equipment and capabilities. WFIRST, the Wide-Field InfraRed Survey Telescope, could potentially revolutionize what astronomers know about our universe and how it behaves by focusing on three major categories: dark energy, exoplanet detection, and infrared astrophysics.
WFIRST has two major features that make it stand out above other observatories within its niche: it has an enormously wide field of view (roughly 100 times the area of Hubble’s while maintaining the same level of resolution), as well as being equipped with a coronagraph. Coronagraphs block out the glare from a star’s corona to allow its observatory to directly observe things such as the planets that may orbit the star, and protoplanetary disks if the star happens to be younger. Coronagraphs have been utilized in the past with observatories like Hubble, but WFIRST’s coronagraph will be far more advanced and sophisticated.
To study dark energy, WFIRST will use its primary mirror, which has a diameter comparable to Hubble’s, as well as its wide-field instrument. With its immense imaging power, WFIRST can study the distribution of mass and matter throughout the universe and how the distributions may have changed as a result of the universe’s accelerating expansion. There are a handful of other ways in which WFIRST will attempt to study dark energy, but in short, understanding dark energy will unlock the secrets of how our universe came to be and the circumstances of its demise. | 0.870054 | 3.721598 |
METEOR, METEORITE. The term meteor, in ac-cordance with its etymology (//.eTecupos), meant originally something high in the air. It has been applied to a large variety of phenomena, most of them of brief duration, which have place in the atmosphere. Disturbances in the air are aerial meteors, viz., winds, tornadoes, whirlwinds, typhoons, hurricanes, &c. The vapour of water in the atmosphere creates by its forms and precipitations the aqueous meteors, viz., clouds, fogs, mists, snow, rain, hail, &c. The effect of light upon the atmosphere and its con-tents causes certain luminous meteors, viz., rainbows, halos, parhelia, twilight, mirage, &c. Discussion of all these, and of like phenomena, belongs to METEOROLOGY (q.v.).
Another class of luminous meteors, known as shooting or falling stars, fireballs, bolides, &c, have their place in the upper parts of the atmosphere. But by reason of their origin from without they, and the aerolites or meteor-ites which sometimes come from them, belong properly to astronomy. The term meteor is often used in a restricted sense as meaning one of these latter phenomena. The present article will treat of them alone.
The most remarkable of the meteors (and the most instructive) are those which are followed by the falling of stones to the earth. These have since the beginning of the present century attracted so much attention, and the phenomena have been so frequently examined and described by scientific men, that they are very well understood. The circumstances accompanying the fall of stones are tolerably uniform. A ball of fire crosses the sky so bright as to be visible, if it appears in the daytime, sometimes even at hundreds of miles from the meteor; and if it appears in the night it is bright enough to light up the whole landscape. It traverses the sky, generally finishing its course in a few seconds. It suddenly goes out, either with or without an apparent bursting in pieces, and after a short period a loud detonation is heard in all the region near the place where the meteor has disappeared. Sometimes only a single stone, sometimes several are found. For some falls they are numbered by thousands. About three thousand were obtained from the fall of L'Aigle in 1803, scattered over a region about 7 miles long and of less breadth. A like number was obtained from the fall of Knyahinya on June 9, 1866. At Pultusk a still larger number were collected, scattered over a larger space, by a fall in January 1868. From the Emmet county (Iowa) fall, May 10, 1879, a similarly large number have been secured.
These meteors leave behind them in the air a cloud or train that may disappear in a few seconds, or may remain an hour. They come at all times of day, at all seasons of the year, and in all regions of the earth. They come irrespective of the phases of the weather, except as clouds conceal them from view.
Let us describe one or two of these meteors more in detail. On the evening of the 2d of December 1876, persons in or near the State of Kansas saw, about eight o'clock in the evening, a bright fireball rising from near where the moon then was in the western sky. It increased in- brilliancy as it proceeded, becoming so bright as to compel the attention of every one who was out of doors. To persons in the northern part of the State the meteor crossed the southern sky going to the east, to those in the southern part it crossed the northern heavens. To all it went down near to the horizon a little to the north of east, the whole flight as they saw it occupying not over a minute.
The same meteor was seen to pass in nearly the same way across the heavens from west-south-west to east-north-east by inhabitants of the States of Nebraska, Iowa, Missouri, Wisconsin, Illinois, Michigan, Kentucky, Indiana, Ohio, Pennsylvania, and West Virginia. But besides this there were heard near the meteor's path, four or five minutes after its passage, loud explosions like distant cannonading, or thunder, or like the rattling of empty waggons over stony roads. So loud were these that per.ple and animals were frightened. East of the Mississippi river these explosions were heard everywhere within about 60 miles of the meteor's path; and in Bloomington, Indiana, sounds were heard supposed to come from the meteor even at a distance of nearly 150 miles from it. Over central Illinois it was seen to break into fragments like a rocket, and over Indiana and Ohio it formed a flock or cluster of meteors computed to be 40 miles long and 5 miles broad. The sky in New York State was wholly overcast. Persons in Ohio and Pennsylvania, who from their situation could look over the cloud last, saw the meteor passing on eastward over New York. From many places in the State itself came accounts of rattling of houses, thundering noises, and other like phenomena, which at the time were attributed to an earthquake.
At one place in northern Indiana a farmer heard a heavy thud as of an object striking the ground near his house. The next morning he found on the snow a stone of very peculiar appearance weighing three-quarters of a pound, which from its character there is every reason to believe came from the meteor. By putting together the various accounts of observers, the meteor is shown to have become first visible when it was near the north-west corner of the Indian Territory, at an elevation of between 60 and 100 miles above the earth. From here it went nearly parallel to the earth's surface, and nearly in a right line, to a point over central New York. During the latter part of its course its height was 30 or 40 miles. It thus traversed the upper regions of the air through 25° of longitude and 5° of latitude in a period of time not easily determined, but probably about two minutes. A part of the body may have passed on out of the atmosphere, but probably the remnants came somewhere to the ground in New York, or farther east.
A somewdiat similar meteor was seen in the evening of July 20, 1860, by persons in New York, Pennsylvania, New England, &c, which first appeared over Michigan, at a height of about 90 miles. The light was so brilliant as to call thousands from their houses. It passed east-south-east, and over New York State, at a height of about 50 miles, broke into three parts which chased each other across the sky. At New York city it was seen in the north, while at New Haven it was in the south. At both places the apparent altitude was well observed, and its true height proved to be about 42 miles above the earth's surface between the two cities. It finally disappeared far out over the Atlantic Ocean. It is doubtful whether any one heard any sound of explosion that came from this meteor, and no part of it is known to have reached the ground. The velocity was at least 10 or 12 miles per second, or fifty times the velocity of sound. These two meteors were evidently of the same nature as those which have furnished so many stones for our museums, except that the one was so friable that it has given us but one known fragment, while the other was only seen to break in two, not even a sound of explosion being known to have come from the meteor.
Next to the stone-producing meteor is the fireball, or bolide, which gives generally a less brilliant light than the former, but in essential appearances is like it. The meteor of July 20, 1860, above described, though unusually brilliant, was one of this class, and represents thousands of bolides which have been seen to break in pieces. The bolides leave trains of light behind them just as the stone meteors do ; they travel with similar velocities both apparent and actual, and in all respects exhibit only such differences of phenomena as would be fully explained by differences in size, cohesion, and chemical constitution of stones causing them.
Next to the bolide is a smaller meteor which appears as if one of the stars were to leave its place in the heavens, shoot across the sky, and disappearall within the fraction of a second. Some meteors of this class are as bright as Venus or Jupiter. Some are so small mat though you look directly at the meteor, vou doubt whether you see one or not. In the telescope still smaller ones are seen that are invisible to the naked eye. Meteors comparable in bright-ness to the planets and the fixed stars are usually called shooting stars.
These various kinds of meteors differ from all other luminous phenomena so as to stand in a group entirely alone. Though they have been sometimes regarded as separable among themselves into three or four different species, and for purposes of description may still be so divided, yet they all seem to have a like astronomical character, and the differences are only those of bigness, chemical constitution, velocity, &c. There appears to be no clear line of distinction between the stone-producing and the detonating meteors, nor between those heard to explode and those seen to break in pieces, nor between these and the simple fireballs, nor between the fireball and the faintest shooting star.
Altitudes of Meteors.The first important fact about the meteors is the region in which they become visible to us. In hundreds of instances observations have been made upon the luminous path of a meteor at two or more stations many miles apart. When such stations and the path are properly situated relatively to each other, observa-tions carefully made will show a parallax by which the height of the meteor above the earth, the length and di-rection of the path, and other like quantities may be com-puted. The general result from several hundred instances is that the region of meteor paths may be in general regarded as between 40 and 80 miles above the earth's surface. Some first appear above 80 miles, and some descend below 40 miles. But an altitude greater than 100 miles, or one below 25, except in the case of a stone-furnishing meteor, must be regarded as very doubtful. Thus the meteor paths are far above the usual meteoro-logical phenomena, which (except auroras and twilight) have not one-tenth of the height of the meteors. But with reference to all other astronomical phenomena they are very close to us. The comets, for example, are well-nigh a millionfold, and even the moon is a thousandfold, more distant from us.
Velocities of Meteors.When the length of a luminous path is known, and the time of describing it has been observed, it is easy to compute the velocity in miles. Unfortunately the large meteors, describing long paths, come at rare intervals, and unexpectedly, and it is a happy accident when one is observed by a person accustomed to estimate correctly short intervals of time. On the other hand, the total time of visibility of the shooting stars, which come so frequently that they may be watched for, is usually less than a second. It is not easy to estimate correctly such an interval, where the beginning and ending are not marked by something like a sharp click. Hence all estimates and computations of velocities of meteors are to be received with due regard to their uncertainty. We may only say in general that the velocities computed from good observations are rarely if ever under 8 or 10 miles a second, or over 40 or 50 miles, and that some have far greater velocities than others. The average velocity seems to be nearly 30 miles.
What makes the Luminous Meteor.The cause of a meteor is now universally admitted to be something that enters the earth's atmosphere from without, with a velocity relative to the earth that is comparable with the earth's velocity in its orbit, which is 19 miles per second. By the resistance it meets in penetrating the air the light and other phenomena of the luminous train are produced. Under favourable circumstances, portions of these bodies reach the earth's surface as meteorites.
Meteoroids.A body which is travelling in space, and which on coming into the air would under favourable circumstances become a meteor, may be called a meteor-oid.
The meteoroids are all solid bodies. It would hardly be possible for a small quantity of gas out in space to retain such a density as would enable it on coming into the air to go 10 or 100 miles through even the rare upper atmosphere, and give us the clear line which a shooting star describes. Even if a liquid or gaseous mass can travel as such in space, it would be instantly scattered on striking the air, and would appear very unlike a shooting star or bolide.
Numbers of Meteors.Of the larger meteors there are ir the mean six or eight per annum which in the last fifty years have furnished stones for our collections. A much larger number have doubtless sent down stones which have never been found. Thus Daubree estimates for the whole earth an annual number of six or seven hundred stone-falls.
But of the small meteors or shooting stars the number is very much larger. Any person who should in a clear moonless night watch carefully a portion of the heavens would, in the mean, see at least as many as eight or ten shooting stars per hour. A clear-sighted and practised observer will detect somewhat more than this number. Dr Schmidt of Athens, from observations made during seventeen years, obtained fourteen as the mean hourly num-ber on a clear moonless night for one observer during the hour from midnight to 1 A.M. A large group of observers, as has been shown by trial, would see at least six times as many as a single person. By a proper consideration of the distribution of meteor paths over the sky, and in actual altitude in miles, so as to allow for mists near the horizon, it appears that the number over the whole globe is a little more than ten thousand times as many as can be seen in one place. This implies that there come into the air not less than twenty millions of bodies daily, each of which, under very favourable conditions of absence of sunlight, moon-light, clouds, and mists, would furnish a shooting star visible to the naked eye. Shooting stars invisible to the naked eye are often seen in the telescope. The numbers of meteors, if these are included, would be increased at least twentyfold.
How densely Space is filled with Meteoroids.By assuming that the absolute velocity of the meteors in space is equal to that of comets moving in parabolic orbits (we have good reason to believe that this is nearly their true velocity), we may prove from the above numbers that the average number of meteoroids in the space that the earth traverses is, in each volume equal to that of the earth, about thirty thousand. In other words, there is in the average to every portion of space equal to a cube whose edge is about 210 miles one meteoroid large enough to make a shooting star bright enough to be visible to the naked eye. Such meteoroids would, upon an equable distribution, be each in round numbers 250 miles from its near neighbours. All these num-bers rest upon Dr Schmidt's horary number fourteen, and for a less practised observer and a less clear sky they would be correspondingly changed. How much they would need to be altered to represent other parts of space than those near the earth's orbit is a subject of inference rather than of observation.
Motion in Space.The meteoroids, whatever be their size, must by the law of gravitation have motions about the sun in the same way as the planets and comets, that is, in conic sections of which the sun is always at one focus. The apparent motions of the meteors across the sky imply that these motions of the meteoroids relative to the sun cannot as a rule be in or near the plane of the ecliptic. For if they were there, since the motion of the earth is also in the ecliptic, the motion of the meteoroids relative to the earth would be in the same plane. This would involve that all the meteor paths as seen on the sky would if pro-duced backward cross the ecliptic above the horizon. In fact there is no tendency of this kind. Hence the meteor-oids do not move in orbits that are near the ecliptic as the planets do, but like the comets they may and usually do have orbits of considerable inclinations.
Numbers through the Night.There are more meteors seen in the morning hours than in the evening. If the meteors had no motion of their own in space, the earth would by its motion receive the meteors only on the hemi-sphere that was in front. There would be no meteors seen in the other hemisphere. On the other hand, if the meteors had such large velocities of their own as that the earth's velocity might be neglected in comparison, and if the directions of the meteors' motions were towards all points indiscriminately, then as many would be seen in one part of the night as another. In fact there are about three times as many seen in the morning hours as in the evening. The law of change from evening to morning gives a means of proving that the mean velocity of meteors is so great that they must in general be moving in long orbits about the sun. In this respect also the meteoroids resemble comets, and are unlike planets, in their motions. Of the stone-furnishing meteors more are seen in the day than in the night, and more in the earlier hours of the night than in the later. This is probably due to the fact that more persons are in a position to see the stone-falls at the periods of greater abundance.
Star Showers.While the average number of shooting stars for a single observer at midnight may be regarded as tolerably constant, there have been special epochs when many more have been seen. In certain instances the sky has been filled with the luminous trains, just as it is filled by descending snowflakes in a snowstorm, making a veritable shower of fire. One of the best-observed, though by no means the most brilliant, of these showers occurred on the evening of the 27th of November 1872. Some of the observers of that shower, counting singly, saw at the rate of eight or ten thousand shooting stars in the course of two hours. The distances of the meteoroids in the middle of the swarm which the earth then passed through, each from its nearer neighbours, would be 30 or 40 miles.
The following quotations show the impression made by star showers in times past :
"In the year 286 [of the Hegira] there happened in Egypt an earthquake on Wednesday the 7th of Dhu-l-Ka'dah, lasting from the middle of the night until morning ; and so-called flaming stars struck one against another violently while being borne eastward and westward, northward and southward, and no one could bear to look toward the heavens on account of this phenomenon."
" In the year 599 [of the Hegira], on the night of Saturday, on the last day of Muharram, stars shot hither and thither in the heavens, eastward and westward, and flew against one another like a scattering swarm of locusts, to the right and left; people were thrown into consternation, and cried to God the Most High with confused clamour."
"These meteors [November 12, 1799] might be compared to the blazing sheaves shot out from a firework."
"The phenomenon was grand and awful; the whole heavens appeared as if illuminated with sky rockets."
November 13, 1833. "Thick with streams of rolling fire; scarcely a space in the firmament that was not filled at every instant."
'' Almost infinite number of meteors ; they fell like flakes of snow."
November Meteors or Leonids.These quotations all refer (except possibly the first) to a shower which has appeared in October and November of many different years since its first known occurrence on the 13th of October 902 A.D. Dates of these showers are given in the following table :
Oct. 13, 902. Oct. 17, 1101. Oct. 28, 1602. Nov. 13, 1833.
Oct. 15, 931. Oct. 19, 1202. Nov. 9, 1698. Nov. 14, 1866.
Oct. 14, 934. Oct. 23, 1366. Nov. 12, 1799. Nov. 14, 1867.
Oct. 15, 1002. Oct. 25, 1533. Nov. 13, 1832. Nov. 14, 1868.
On several years after 1833, and before and after 1866-68, there were unusual numbers of those meteors seen on the mornings of November 13, 14, and 15, though per-haps they would have been unnoticed had there not been special watching for them. It will be seen that all these showers are at intervals of a third of a century, that they are at a fixed day of the year, and that the day has moved steadily and uniformly along the calendar at the rate of about a month in a thousand years. The change of twelve days in the 17th century is due to the change from old to new style.
The only explanation of this periodical display that is now seriously urged, and the one which is universally accepted by astronomers, is that there is a long thin stream of meteoroids, each of which is travelling about the sun in a conic section. These conic sections are all nearly parallel, and have nearly the same major axis, extending out about as far as to the orbit of Uranus, and each requir-ing the common period of thirty-three .and a quarter years. The length of the stream is such that the most advanced members are six or eight years ahead of the hindermost, and they all cross the earth's orbit with a velocity of about 26 miles a second. Since the earth plunges through the group nearly in the opposite direction, the velocity with which they enter the air is 44 miles a second. One of the facts which have greatly aided us in arriving at this explanation is that these meteors in all the years and through all hours of the night cross the sky as we look at them in lines which diverge from a point near the centre of the sickle in the constellation Leo; hence the paths in the air are parallel. This implies that their velocities relative to the sun are all parallel and equal to each other. The radiation from Leo has given to them the name Leonids.
Orbit of the Leonids.This orbit, common to all the Leonid meteors, is inclined to the ecliptic at an angle of 17° (or rather 163°, since the motion is retrograde), has a major axis of 10'34, a periodic time of 33'27 years, and a peri-helion distance a little less than unity.
The above orbit, and that alone, explains the several appearances of the November meteors, the annual and the thirty-three year periods, the radiation from Leo, and the change of day of the month in the course of the centuries. This it does so completely that the result has never been questioned by astronomers. Shortly after the publication by Professor Adams in 1867 of the last link in the chain of the proof of this orbit, there was also published the definitive orbit of the comet 1866 I. That the comet was running almost exactly in the orbit of the meteors was at once recognizer!. In fact the comet is itself, in a sense, a meteoroid, and the principal member, so far as we know, of the group. Leonids had been seen in 1863, two years and two months in advance of the comet, while those of 1866 were ten months behind it. Those of later years (a few Leonids were seen even in 1870) were extended along the line of the comet's path behind it. The leaders of this long file of meteoroids had passed up beyond the orbit of Jupiter long before those which brought up the rear had crossed that planet's orbit going down toward the sun. The thickness of the stream is less than the ten-thousandth part of its length. In the densest part that we have recently passed throughnamely, that traversed in 1833 the density of the stream may be expressed by saying that each meteoroid must in the mean have been 10 or 20 miles from its nearest neighbours.
What makes this Comet and these Meteors describe the same Orbit about the Sun?Its path might have been inclined to the ecliptic at any angle instead of 163°. Or, with this inclination, its plane might have cut the earth's orbit at any other place than where the earth is on the 14th of November. Or, happening to have these two elements in common, it might have passed the earth's orbit nearer the sun or farther away from it than the earth is. Or, having these three things in common, it might, by a slight difference in velocity, have had a periodic time much more or much less than thirty-three years. Or, with all these in common, it might have crossed the earth's orbit at a far different angle than the meteors. These several independ-ent elements for the comet and the meteors are substan-tially identical, and this identity proves almost beyond doubt that between the two either there is now an actual or else there has been in the past a causal connexion. That there is now any physical connexion is thoroughly disproved by the immense magnitude of the stream, and by the isolation and distances from each other of the individual components. ' It seems difficult to find any cause that should bring into such a strangely shaped group bodies that had originally orbits distributed at random. Hence we are apparently forced to conclude that these meteoroids have something common in their past history. In fact they seem to have been once parts of a single body, and these common elements are essentially those of the parent mass. By some process not yet entirely explained they have become separated from the comet, thrown out of the control of its attractive power, and so left to travel each one in its own orbit. If the cause of separation was not too violent, each new orbit would necessarily be but slightly different from that of the comet. Very small variations in velocity, and hence in periodic time, would in the course of ages scatter the several individuals along the orbit even to the length of many hundreds of millions of miles.
The Meteor Group is not the Comet's Tail.These meteoroids must be carefully distinguished from the comet's tails. The former follow or precede the comet exactly in the comet's path; the particles that compose the latter are driven off by the sun's repulsion directly away from the comet's path. The meteoroids and the comet have orbits with nearly common elements; the orbits of the particles of the tail have elements that are unlike each other, and unlike those of the comet. The meteoroids are undoubtedly solid masses; the tails are pulverulent or gaseous.
Twin Comets of 1366.The comet 1866 I. is probably not the only one that has been connected with the November meteors. In 1366, a few days after the earth went through the meteor stream, a comet appeared in the northern heavens, and, passing directly in the line of the stream so close to the earth as to describe an arc of 90° in a single day, disappeared in the constellation Aquarius. Immedi-ately upon its disappearance a second comet was seen in the north, which followed nearly in the same path. The Chinese accounts are not sufficiently exact to furnish independent orbits for them, but both comets were undoubtedly members of the Leonid stream. The comet 1866 I. may be identical with one of them.
The Andromeds and Biela's Comet.Mention has been made of the star shower of November 27, 1872. The periodical comet known as Biela's, which makes three revolutions in twenty years, passes very near the earth's orbit at a longitude corresponding to November 27, but by reason of its direct motion the node has had considerable motion in longitude as the result of perturbations. Meteors having the same orbits as Biela's comet would have a radiant in the constellation Andromeda, that is, would cross the sky in lines diverging from a point in that constellation. They might, however, be at dates after or even before November 27.
Unusual numbers of meteors were seen December 7, 1798, by Brandes. A like abundance was seen December 7, 1838 ; and, as they had been expected, and radiation was now looked for, they were found to diverge from a point in Andromeda. Hence they have been called Andromeds. Since 1852 Biela's comet itself has been entirely lost. The star shower of November 27, 1872, previously referred to, had a radiant in Andromeda, and in every way appeared as though its meteors had once been parts of Biela's comet. A sprinkle three days earlier, on the night of November 24, had the same radiant, and came from a less dense outlying parallel stream. A small comet was seen in the southern sky by Bogson in the direction opposite to the radiant shortly after the shower. Biela's comet had been found in 1845-46 to be in two parts, which at its next return to perihelion in 1852 had separated to eight times their former distance. But the meteor streams of 1872 could hardly have been separated from the comet so recently, and the Pogson comet if of the same origin must also have left the parent mass at an earlier date than 1845. No ordinary perturba-tions would in a short period have so changed the orbits. The parts of the small stream traversed by the earth, December 183S and December 1798, were far from the comet, and these fragments must have been thrown oil' much earlier.
The Perseids and the Comet 1862 III.There is a third epoch when meteors appear in unusual numbers, viz., the 9th to 11th of August. This "sprinkle," as it may be called, has been seen con-stantly at the time named for nearly fifty years, and there are on record accounts of similar appearances in the earlier years before its annual character had been discovered. Some observers have thought that there were evidences of a variation having a long period, but the proof seems as yet unsatisfactory, and the display may be regarded as tolerably constant from year to year. On every 10th of August we may confidently expect a display of meteors that shall be at least four or five times as numerous as those of ordinary nights. The radiant is in the constellation Perseus, and hence the name Perseids.
The comet 1862 III., which has a period of more than a hundred years, passes close to the earth's orbit, nearly cutting it at the place of this shower, and has a velocity and direction corresponding to this radiant. Hence a connexion of the Perseid meteors with this comet is presumed, like that which the Leonids and Andromeds have with the comet 1866 I. and Biela. The meteors are distri-buted along this orbit more regularly than along either of the other two, and at the same time the breadth of this group is a hundred times greater than that of the Leonids. We must for the present regard it rather as a meteor ring, the meteoroids being scattered along the entire conic section which the comet describes. This ring has an inclination of 113° with the ecliptic.
Meteors of April 20-21Lyraids.About the 20th of April there have been several quite brilliant star showers, the earliest on record having been in the year 687 B.C. On that day meteors have been observed which radiated from Lyra, and to these the name Lyraids has been given. The comet 1861 I. passes near the earth's orbit in that longitude, and any meteors having such a connexion with it as is proved for the Leonids with comet 1866 I. would also radiate from Lyra.
Again, at several other periods of the year, meteors have been seen in unusual numbers which seem to be connected with certain comets.
Meteor Radiants.We have thus definite proof that the earth at certain epochs plunges through meteor streams, and that these streams travel along the same track as cer-tain comets. The question is at once askedDo not the sporadic meteors, those which are seen on any and all nights of the year, belong to similar streams 1 An immense amount of labour has been spent in observing the paths of meteors, and classifying them, so as to detect and prove the existence of radiant points. As many as a thousand such radiants have been suggested by the different investigators. Some of these are duplicates, some will prove to be acci-dental coincidences; but a goodly number may reasonably be expected to endure the test of future observations. Such will show the existence of meteor streams, and per-haps will be connected with comets that are now known, or that may hereafter be discovered.
The radiants have been spoken of as if they were points in the heavens. This is so nearly true as to justify all the conclusions that have been deduced above. But in fact a radiant, even in the star showers in which it is most sharply defined, must be regarded as a small area. The apparent meteor paths when produced backward do not exactly meet in a point. If they be treated as proceeding from a small area, it does not appear that this is a long narrow one. Hence it may be shown that the paths of the meteors in the air are not exactly parallel either to a line or to a plane. This can hardly be due to a want of parallelism of the paths before the meteoroids meet the earth, but is rather due to their glancing as they strike the air. These facts add not a little to the difficulties to be overcome by the energetic observers and investigators who are trying to deduce order out of an apparent chaos.
Meteorites.The fragments wdiich fall immediately after the disappearance of large meteors have been carefully collected and preserved in mineralogical museums, and have been studied with special interest. The largest collections in Europe are in Vienna, Paris, London, and Berlin, some of these representing over three hundred localities. In the United States there are large collections at New Haven, Amherst, and Louisville.
In several respects these fragments differ at first sight from terrestrial rocks.
They are when found almost always covered in part or entirely with a very thin black crust, generally less than of an inch in thickness. This crust may have a bright lustrous surface, or it may be of a lustreless black. It has evidently been melted, yet so rapidly as not to change in the least the parts of the stone immediately adjacent. Streaks showing the flow of the melted matter are often seen on the surface. Upon some surfaces are what appear to be deposits of the melted matter that has flowed off from the others. Some surfaces are only browned, showing an apparently recent fracture, and some cracks are found in stones which are not yet completely broken in two.
The surfaces very often have small cup-like cavities, sometimes several inches in diameter, sometimes like deep imprints in a plastic mass made by the ends of the fingers, and sometimes still smaller. These " cupules " have not only various sizes in different stones, but even in the same stone differ considerably from one surface to another. They appear in meteorites that are almost exclusively iron, as well as in those mainly destitute of that metal, and they may be regarded as a characteristic of meteorites.
The meteorites have usually metallic iron as one of their component parts. Native iron is very rare indeed among terrestrial minerals, and its presence in the meteorites is therefore characteristic. Sometimes the iron forms the principal part of the body, giving it the appearance of a mass of that metal. Sometimes it forms only a connected framework which is filled in with mineral matter. Some-times particles of iron are scattered through a stony mass; and a few meteorites are said to be destitute of metallic iron altogether. The metallic iron is always accompanied with nickel.
The stony meteors when broken or cut through have usually a greyish interior, and often exhibit a peculiar globular structure. From the small rounded grains that give it this appearance, the name chondrite (from ^ovSpos, a ball) has been applied to this kind of meteorite. Some-times the irregular fragments are compacted into a kind of breccia.
The pieces as we find them are always ajmarent frag-ments of some larger mass, and there is no structural appearance which would indicate that the mass might not be a fragment of a still larger one. In some of the falls fragments picked up at a distance of miles from each other fit together in their simply browned surfaces, showing that they were true fragments recently separated. In some cases surfaces of the stones are partially polished. In some a cross section of the stone exhibits thin black lines as though the melted matter of the surface had been forced into the crevices of the partially broken stone.
The stones when seen to fall, if at once picked up, are usually too warm to be taken in the hand. But cases are on record in which the stones were excessively cold. They sometimes, on striking the ground, j>enetrate into it from 1 to 3 feet. In extreme cases large ones have struck much deeper into soft earth. Sometimes they are broken to pieces by the impact with the hard earth.
The stones are usually not very large. Although the light of the meteor is such as sometimes to be seen over a region 1000 miles in diameter, and the detonation gives phenomena suggestive of an earthquake over many counties, yet a stone exceeding 100 S) is quite exceptional in our col-lections. The total weight secured at any fall has rarely if ever amounted to a thousand pounds. The average weight of nine hundred and fifty perfect specimens of the Pultusk fall in the Paris museum is 67 grammes, or less than 2^ oz. One of the Hessle meteorites in the Stockholm museum weighs less than 1 grain. Many of the Emmet county mete-orites (May 10, 1879) are not much larger, though the largest specimen of that fall weighs nearly 500 BJ.
Meteors traversing the Atmosphere.We can now get a very good idea of the history of that part of a meteorite's life between its entrance into the air and its arrival at the earth. It is entirely invisible until it has reached that height at which the density of the air is enough to create con-siderable resistance. Up to that time it moves almost exclusively in obedience to the sun's attraction. The earth's attraction may be neglected, especially during the passage through the air. Since the velocity is a hundred times that of sound, the elasticity of the air is impotent to remove it from in front of the meteorite, or to prevent a high degree of condensation. Perhaps the air is liquefied immediately in front of the stone. Heat is developed in it enormously, and the stone being pressed closely against the hot air is melted, with an intense light. The condensed air charged with the melted matter is pushed aside, and left behind nearly in the wake of the meteor to form the train. The brightness of the train rapidly diminishes behind the meteor, so that the light of the meteor and the train, modi-fied by irradiation, make the whole appear to a distant eye of the shape of a pear or candle-flame. The stone being a poor conductor of heat, and itself rigid, is not heated in the interior either by condensation or conduction, and may reach the ground with its surface only heated, while the interior is as cold as it had been out in space.
If the stone is a small one it will soon be used up by this intense fire. Until its front surface is rounded by the flame, the irregular resistances may cause such a stone to glance. But if the stone is larger it will lose velocity less rapidly. As it comes down into the region where the air is more dense, it will in spite of loss of velocity meet greater resistance. The air pressed hard against it burns it un-equally, forming cupules over its surface. The pressure of the air cracks the stone,perhaps scaling off small frag-ments, perhaps breaking it into pieces of more uniform size. In the latter case the condensed air in front of the meteor being suddenly relieved will expand, giving the terrific explosion which accompanies such breaking up. In either case a fragment may have still velocity enough to burn on for an instant in its new path and then come invisibly to the earth, covered with a coating, the greater part obtained after the principal explosion. In the latter part of the course the original velocity has almost all dis-appeared, so that the sound travels faster than the meteor. The air's resistance exceeds the earth's attraction, and the stones strike the ground only with the force of a spent cannon ball. It is no doubt in violent disruption that some of the fractures are made in such a way as to give the rubbed and polished surfaces.
Trains of Meteors.The smaller meteors generally have no perceptible train. Only in exceptional cases do the trains of ordinary shooting stars remain visible longer than a fraction of a second. An unusual number of the Leonids have a bluish train. But the brighter shooting stars and the larger meteors sometimes have trains that endure for minutes, and in extreme cases for an hour. Such trains are at first long narrow lines of light, though much shorter than the track of the meteor. They begin at once to broaden in the middle and to fade away at one or both ends. Presently they become curved, sometimes with two or three convolutions. The white cloud floats slowly away among the stars, coiling up more and more, and finally fades out of sight. The cause of all this seems to be as follows. The heated air charged with the debris of the meteor is by the meteor's impact driven off horizontally, causing the narrow train to spread into a cloud. The currents of air differing in direction at different altitudes twist the cloud into its varied fantastic forms. Attempts to obtain the spectrum of the trains have been made, and sodium and magnesium lines have been thought to be detected in them. The observation, however, is one that is not easy to make or confirm. The trains have often colours other than white, and in the case of the brighter meteors different colours are seen in the different parts of the train.
Magnitude.Some computations have been made of the size of the shooting star meteoroids from the mechanical equivalent of the light developed by their disintegration. If all the energy of the meteor is changed into light, then these computations would be conclusive. But a part is spent in disintegrating and burning the stone, a part in heating the air, and a part in giving direct motion to portions of air. A computation based on the light developed gives only a lower limit to the size.
It seems probable that the larger meteors might be safely regarded as weighing on entering the air only a few hundreds or at most a few thousands of pounds. The smallest visible shooting stars may be equal in size to coarse grains of sand, and still be large enough to furnish all the light exhibited by them. The largest shooting stars furnish matter enough to fill with thin trains cubic miles of space, but this need not require a very large mass.
Meteoric Irons.There have been found at various times on the surface of the earth masses of metallic iron combined with nickel. These have been so like the irons which have been known to fall, both in their structure and in composition, that they have been without hesitation classed among the meteoric irons. A mass of this character weighing 1635 lb, found in Texas, is in the Yale College Museum. The Charcas (Mexico) iron in the Paris museum is about the same size. A ring-shaped mass, somewhat smaller, from Tuczon, is in the United States National Museum in Washington. A still larger mass is in the British Museum, and many other large masses are in public collections or private possession.
Widmannstatten Figures.If in any of the meteoric irons, whether seen to fall or found on the earth, a section is cut and polished and then etched with acids, a series of peculiar lines are developed which are known as Widmannstatten figures. The lines of iron nnattacked by the acid consist of an irregular grouping of parallel rulings often lying along the faces of a regular octahedron. The exhibition of these figures and the combination of iron with nickel have been usually considered conclusive evidence of the meteoric origin of any iron mass.
Nickel Iron of Ovifak.In 1870 Baron Nordenskiold, in his voyage to Greenland, found on the shore of the island of Disco fifteen iron masses, the largest of which weighed 20 tons, all in an area of half an acre. In the basaltic rocks not far distant other iron masses were found embedded in the basalt. The presence of nickel with the iron, and the development of lines like the Widmannstatten figures, were at once accepted as proof of their meteoric origin, in spite of the combination with basalt. A more complete examina-tion has, however, established the terrestrial origin of these irons, and given reasons to hope for new discoveries of relations existing between the earth and the meteors. The additional discovery of small particles of metallic iron in certain other igneous rocks proves that the union of the Ovifak irons with basalt is not excep-tional.
Chemical Constitution of the Meteorites.No new element has been found in the meteorites. Three elements most widely distri-buted and most important among the meteoritesiron, silicon, and oxygenare also most abundant in our earth. Daubree gives the following lists of elements, arranged somewhat in the degree of their importance, in meteorites (Maskelyne adds lithium and antimony):
Iron. Titanium. Arsenic.
Magnesium. Tin. Phosphorus.
Silicon. Copper. Nitrogen.
Oxygen. Aluminium. Sulphur.
Nickel. Potassium. Chlorine.
Cobalt. Sodium. Carbon.
Chromium. Calcium. Hydrogen.
Minerals in Meteorites.Among the minerals in the meteorites there are several which occur in the rocks on the earth. Among these are cited by Daubree peridote, pyroxene, enstatite, triclinic felspar, chromite, magnetic pyrites, iron oxide, graphite, and probably water. Several minerals, however, are found which, so far as now known, are peculiar to the meteorites :metallic nickel-iron, phosphide of iron and nickel (schreibersite), sesquisulphide of chromium and iron (daubreelite), sulphide of calcium (oldhamite), and chloride of iron (lawrencite).
Meteorites of different falls are in general unlike ; but there are many instances in which the stones of two falls are so similarly constituted that it is not easy to distinguish them.
In four falls (Alais, Cold Bokkeweld, Kaba, and Orgeuil) the stones contain little or no iron. In these carbon appears not as graphite but in union with hydrogen and oxygen, and also with soluble and even deliquescent saline matters. The combinations arc such as to suggest the existence of humus and organic remains. But after careful search nothing of this kind has been detected in them. In general the meteorites show no resemblance in their mechanical or mineralogical structure to the granitic and surface rocks on the earth. One condition was certainly necessary in their formation, viz., the absence of free oxygen and of enough water to oxidize the iron and other elements. Perhaps it is to this fact that are due the resemblances between these minerals and those of the deep-seated rocks of the earth in the formation of which free oxygen and water were also not present.
Gases in Meteorites.The meteoric stones and irons when reduced to fine particles and placed in the vacuum of a Sprengel air-pump give off small quantities of gases which may be reasonably pre-sumed to have been occluded by the irons at some time in their earlier history. Professor Graham found hydrogen in meteoric irons. Professor Wright has shown that a moderate heat drives off from the stony meteorites carbonic acid and carbonic oxide with a small amount of hydrogen. As the heat increases the proportion of hydrogen (and even some nitrogen) increases till at a full red heat the hydrogen given off is by far the largest portion. From the irons similar gases are given off, but the carbon compounds are not so large a component as hydrogen. The spectra seen in the tails of comets are not strikingly like those of any of these gases. But it is impossible to reproduce in the laboratory the conditions under which the matter of comet's tails is giving off its light. We cannot therefore say that these gases may not be the important parts of the cometic coma and tails.
Meteoroid as Part of a Comet.Assuming that the meteorite and meteoroid once formed an integral part of a comet, not a little information is given us of the nature of this mysterious body. There is room also for speculation.
First, the comet may be a single hard body which comes from the cold of space into the heat of the sun, and there has frag-ments broken off, just as a stone is shattered in a hot fire. The nucleus of some of the comets must be very small because invisible in the telescope, and an impulse that would raise a stone on the earth only a few inches would send it permanently away from such a comet. The exposure of new surfaces to the heat of the sun might give occasion for the development of gas to form the comet's tail.
Or, secondly, the comet may be a tolerably compact aggregation of small bodies not in contact, each one being of the size of a meteoroid, and kept near to the rest, not by cohesion, but by their combined attraction. The total mass being small, some members of the group near the comet's perihelion passage can be by the sun's perturbing action thrown out into orbits quite independent of the comet itself, and yet such as relative to the sun shall resemble that of the main group. Perturbations resembling tidal waves might be preparing other members to be cast off at the next perihelion passage of the comet.
In either case, if we suppose," as seems probable, that the comet came from outside the solar system, and that a disturbance by a large planet changed the original hyperbolic orbit into an ellipse, the comet must have passed that planet as a very compact group, if not in a single mass, else the disturbance that changed the orbit would have scattered the group beyond the power of a future recog-nition of the common origin of the fragments.
Meteoroids as Fuel of the Sun.The idea has been held by distinguished physicists that the meteoroids in falling into the sun furnish by their concussion a supply for the heat which the sun is constantly sending off into space,that they are in fact the fuel of the sun. Such a view, however, receives but little support from facts which we know about meteors. The meteoroids of the August and two November periods are evidently permanent members of the solar system moving in closed orbits. The same is by inference highly probable for most of the other meteoroids, and may be true of all of them. Permanent members of the solar system, however, if they ever fall into the sun, do so only after a long period of perturbation. If any meteoroids come from stellar spaces and have any uniform or random distribution of velocities or direc-tions, only a very small portion of these would hit the sun's surface. The far greater portion would go on in hyperbolic orbits. But the earth receives the impact of its portion of these foreign meteoroids, both in their inward and outward course, and in addition encounters a full share of the permanent members of the solar system, of which the sun receives very few or none. It is not hard to show that a supply of meteoroids to the sun sufficient to make good its daily loss of heat would require that the twenty million meteoroids which the earth daily encounters, even if all were from stellar space, should have an average weight of hundreds of tons. The facts do not warrant the admission of any such magni-tude even for the large meteors, much less for the ordinary and small shooting stars. Whatever be the source of the sun's heat, all the meteoroids of which we know anything are totally inade-quate to supply the waste.
The literature of meteors and meteoroids is very much scattered. It is mainly contained in the scientific journals and in transac-tions of learned societies. The series of valuable Reports of the Luminous Meteor Committee of the British Association contains not only the record of an immense amount of original observations, but also year by year a digest of most of the important memoirs.
Meteoric science is a structure built stone by stone by many builders. In this article no attempt has been made to assign to each builder the credit for his contribution. (H. A. N.) | 0.859621 | 3.562769 |
What does our Solar System really look like? If we were to somehow fly ourselves above the plane where the Sun and the planets are, what would we see in the center of the Solar System? The answer took a while for astronomers to figure out, leading to a debate between what is known as the geocentric (Earth-centered) model and the heliocentric (Sun-centered model).
The ancients understood that there were certain bright points that would appear to move among the background stars. While who exactly discovered the “naked-eye” planets (the planets you can see without a telescope) is lost in antiquity, we do know that cultures all over the world spotted them.
The ancient Greeks, for example, considered the planets to include Mercury, Venus, Mars, Jupiter and Saturn — as well as the Moon and the Sun. The Earth was in the center of it all (geocentric), with these planets revolving around it. So important did this become in culture that the days of the week were named after the gods, represented by these seven moving points of light.
All the same, not every Greek believed that the Earth was in the middle. Aristarchus of Samos, according to NASA, was the first known person to say that the Sun was in the center of the universe. He proposed this in the third century BCE. The idea never really caught on, and lay dormant (as far as we can tell) for several centuries.
Because European scholars relied on Greek sources for their education, for centuries most people followed the teachings of Aristotle and Ptolemy, according to the Galileo Project at Rice University. But there were some things that didn’t make sense. For example, Mars occasionally appeared to move backward with respect to the stars before moving forward again. Ptolemy and others explained this using a system called epicycles, which had the planets moving in little circles within their greater orbits.
But by the fifteen and sixteenth centuries, astronomers in Europe were facing other problems, the project added. Eclipse tables were becoming inaccurate, sailors needed to keep track of their position when sailing out of sight of land (which led to a new method to measure longitude, based partly on accurate timepieces), and the calendar dating from the time of Julius Caesar (44 BCE) no longer was accurate in describing the equinox — a problem for officials concerned with the timing of religious holidays, primarily Easter. (The timing problem was later solved by resetting the calendar and instituting more scientifically rigorous leap years.)
While two 15th-century astronomers (Georg Peurbach and Johannes Regiomontanus) had already consulted the Greek texts for scientific errors, the project continued, it was Nicolaus Copernicus who took that understanding and applied it to astronomy. His observations would revolutionize our thinking of the world.
Published in 1543, Copernicus’ De Revolutionibus Orbium Coelestium (On the Revolutions of the Heavenly Bodies) outlined the heliocentric universe similar to what we know today. Among his ideas, according to Encyclopedia Britannica, was that the planets’ orbits should be plotted with respect to the “fixed point” Sun, that the Earth itself is a planet that turns on an axis, and that when the axis changes directions with respect to the stars, this causes the North Pole star to change over time (which is now known as the precession of the equinoxes.)
Putting the Sun at the center of our Solar System, other astronomers began to realize, simplified the orbits for the planets. And it helped explain what was so weird about Mars. The reason it backs up in the sky is the Earth has a smaller orbit than Mars. When Earth passes by Mars in its orbit, the planet appears to go backwards. Then when Earth finishes the pass, Mars appears to move forwards again.
Other supports for heliocentrism began to emerge as well. Johannes Kepler’s rules of motions of the planets (based on work from him and Tycho Brahe) are based on the heliocentric model. And in Isaac Newton’s Principia, the scientist described how the motions happen: a force called gravity, which appears to be “inversely proportional to the square of the distance between objects”, according to the University of Wisconsin-Madison.
Newton’s gravity theory was later supplanted by that of Albert Einstein, who in the early 20th century proposed that gravity is instead a warping of space-time by massive objects. That said, heliocentric calculations guide spacecraft in their orbits today and the model is the best way to describe how the Sun, planets and other objects move. | 0.903966 | 3.896222 |
China’s Tianwen-1 Mars mission is almost ready. Now officially named—meaning ‘questions to heaven’—, China’s first dedicated Mars orbiter and rover are lined up for launch in July (pictures), along with NASA’s Mars 2020 Perseverance rover and the UAE’s Hope Mars Mission. Primarily due to parachute challenges, ExoMars has been delayed until 2022. Tianwen-1’s orbiter has a high resolution, 0.5m per pixel camera comparable to HiRise, as well as radar, magnetometers, and spectrometers (likely calibrated to detect methane). The mission will be controlled using Asia’s largest steerable radio telescope—built specifically to enable this and other deep space missions. The rover weighs in at 240 kg (for comparison, their Yutu lunar rover is 140 kg, while NASA’s upcoming Perseverance is 1,025 kg), and will carry ground-penetrating radar (paper) to look for subsurface water, multispectral cameras, a Laser-Induced Breakdown Spectroscopy instrument, and other science payloads. It is targeting an early 2021 rocket-propelled landing in Utopia Planitia, the same region where Viking 2 landed, and that NASA suggested could hold buried water ice equivalent in volume to Lake Superior. So far, only NASA has successfully operated a rover on Mars. The Tianwen name is intended to be the moniker for all future Chinese interplanetary missions. Related: Along with the Chinese space station and lunar sample return mission, China is also exploring an asteroid sample return mission, a Voyager-like Interstellar Heliosphere Probe, a Mars sample return mission, and other potential planetary missions.
And let’s talk about that Mars 2020 helicopter. Inside a debris shield attached to the belly of the Perseverance rover is a twin-rotor, solar-powered helicopter, now named Ingenuity (by a high school student from Alabama, one of 28,000 submissions). Once a suitable location is found in Jezero Crater—approximately 60-90 Martian days after landing—the helicopter will drop off the rover and take flight for a few minutes at a time (JPL animation of how it’ll fly), becoming the first aircraft on another celestial body. Carrying no science instruments, the 2 kg rotorcraft is an engineering test for future, larger, Martian aerial explorers. It uses counter-rotating coaxial rotors about 1.1 m in diameter to handle Mars’ atmospheric density that is only 1-2% that of Earth’s, heaters to survive the -140° C night, a downward-pointing camera for navigation, a Snapdragon processor running Linux, a radiation-tolerant FPGA, two flight controller MCUs (for redundancy), and redundant 900 MHz Zigbee links that can send 250 kbit/s over distances of up to 1 km. Due to Mars’ inconsistent magnetic field, instead of a compass, the drone will use a solar tracker camera, the downward-facing camera for visual navigation (pdf), and inertial navigation. See the Mars Helicopter Technology Demonstrator (pdf) for more technical details.
Space-to-Earth power beaming experiments. An Atlas V launch carrying the U.S. military’s reusable X-37B space plane is planned for May 16—this is the X-37B’s sixth mission (the first with a service module attached) and will carry Air Force & NASA experiments and a U.S. Naval Research Laboratory (NRL) beamed microwave power experiment (aka far-field wireless power transmission). Beamed power has been a recurring theme for the NRL recently, with a laser power transmission demonstration last fall—the 2 kW laser delivered power to a receiver using wavelength tuned photovoltaic cells to convert the photonic energy into 400W of DC power. Astronaut Jessica Meir recently shared a related demonstration sponsored by the NRL that showed a simple LED/diode circuit receiving energy from the station’s WiFi access point. The DoE has an explainer page on space-to-ground PV power transmission, complete with cute satellite animations. Meanwhile, Casey Handmer has a strongly held, yet reasonable skeptic’s view of microwave-based transmission given current technology.
| News in brief. SpaceX's Starship SN4 test-fired a single Raptor engine twice and passed high-pressure testing (7.5 bar) in the lead up to a likely 150 m hop—three engines will eventually be used on higher altitude tests, and six on the orbital version; for the first time, a Fast Radio Burst has been detected from (probably) within the Milky Way—if it repeats, we may be able to figure out what causes these energetic radio flashes; China’s next-gen crew capsule returned to Earth after functioning as planned (unfortunately, its secondary cargo capsule with an inflatable heat shield did not) and its core stage became the largest unguided reentry since 1991; Yevgeny Mikrin, the head of Russian human spaceflight passed away at 65 from COVID-19; the Trump administration is working on an international agreement for lunar mining called the Artemis Accords; Airbus and Xenesis signed a contract for a payload slot on the recently attached Bartolomeo ISS platform, for hosting a demonstration 10+ Gbps optical communications terminal; and, Virgin Orbit’s first orbital launch could happen later this month over the ocean southwest of Los Angeles (they also just signed a Space Act Agreement with NASA to explore the development of supersonic vehicles).|
- Tom Cruise is apparently working with NASA (and maybe SpaceX) to shoot a movie on the ISS. In other entertainment news, a trailer for Steve Carell’s Space Force on Netflix has dropped. (Compare it with a real recruitment ad for the U.S. Space Force.)
- A new closest black hole to Earth has been found (paper pdf)—the second-closest is thought to be about 3,300 lightyears away. The new object is a stellar-mass black hole located 1,000 light-years away and orbited by two companion stars that are visible to the naked eye—a first of its kind. It’s unusual in its blackness, lacking a violent accretion disk, and its inferred existence hints at the hundreds of millions of similarly-sized black holes that are likely waiting to be found in our galaxy.
- The nearly 100 environmental rules rolled back by the Trump administration. These are really important.
- Everywhere that it’s raining right now.
- An air-breathing plasma thruster concept with thrust per kW similar to a jet engine (paper). However, the test unit was tested at only 1 kW, so it would need to scale by four orders of magnitude to compete with a jet engine. As Chris Lee wrote for Ars, “Extrapolating linear trends over four orders of magnitude is a good way to be disappointed in life.”
- Astronaut urine could be a beneficial superplasticizer for use in concrete on the Moon (paper). Urea, the second-largest component in urine, increases the malleability of lunar concrete before it fully cures. This might be the one time that you shouldn’t use the bathroom before the trip.
This week we’re experimentally adding a jobs section to the newsletter. Please let us know what you think, good or bad. And if you know of an open position, especially at your company, send us a note! | 0.921684 | 3.033407 |
At the heart of every galaxy lies a supermassive black hole, where gravity is so strong that nothing — not even light — can escape its boundary.
In the movie “Interstellar,” a fictional black hole called Gargantua takes center stage. The film came out exactly five years ago, in November 2014. In it, Matthew McConaughey and Anne Hathaway play astronauts who travel through a wormhole — a tunnel that allows for nearly instantaneous travel between far-distant points — to explore three planets that orbit Gargantua, 10 billion light-years from Earth.
In the end, McConaughey's character navigates his ship into the supermassive black hole, inside which he discovers a fifth dimension, inter-dimensional omniscient beings, and the ability to communicate with his estranged daughter across time and space.
Director Christopher Nolan and his visual effects team strove for superior scientific accuracy in “Interstellar” — they even hired theoretical physicist and Nobel laureate Kip Thorne as a consultant.
“Neither wormholes nor black holes have been depicted in any Hollywood movie in the way that they actually would appear,” Thorne said in an interview prior to the movie's release. “This is the first time the depiction began with Einstein's general relativity equations.”
Indeed, the movie's depiction of Gargantua was lauded as the most accurate film portrayal of a black hole ever.
But in the last five years, a handful of major discoveries about black holes have given physicists new insights about what these massive objects look like and how they behave. Based on that information, Gargantua wasn't completely accurate, though it still comes close in many respects. Here's what “Interstellar” got right and wrong.
The first image of a black hole ever captured
Supermassive black holes form when stars collapse in on themselves at the end of their life cycles. On average, they're millions of times more massive than the sun.
Scientists struggled for decades to capture one on camera, because black holes are so massive and spin so quickly that they distort space-time, ensuring that nothing can break free from their gravitational pull. Because even light can't escape, these forces create a unique shadow in the form of a perfect circle at the black hole's center.
The outer border of that center is known as the black hole's event horizon, or “point of no return.”
But in April, a group of scientists from the international Event Horizon Telescope (EHT) Collaboration released the first-ever photograph of a supermassive black hole to the public. Though the image was fuzzy, it showed that, as predicted, black holes look like dark spheres surrounded by a glowing ring of light.
“As a cloud of gas gets closer to the black hole, they speed up and heat up,” Josephine Peters, an astrophysicist at the University of Oxford, previously told Business Insider. “It glows brighter the faster and hotter it gets. Eventually, the gas cloud gets close enough that the pull of the black hole stretches it into a thin arc.”
The unprecedented photo shows the supermassive black hole at the center of the Messier 87 galaxy, which is about 54 million light-years away from Earth. The black hole's mass is equivalent to 6.5 billion suns.
To capture the image, astronomers relied on years of data from eight telescopes synced up across the globe. So the image is a reconstructed view, not a photograph.
“It feels like looking at the gates of hell, at the end of space and time,” Heino Falcke, an Event Horizon Telescope collaborator, said when the photo was published.
The EHT team's next target is likely Sagittarius A*, the black hole in the center of our own galaxy.
We simulated what it might look like to hang out near a black hole
Since the April EHT image was so blurry, NASA scientists created a visualization of what a black hole might look like close-up and in action.
The animation shows how gravity surrounding the black hole would twist light from the orbiting cloud of gas, dust, dead stars, and other space detritus (called the accretion disk). That would appear as a rainbow of fire bending around a dark abyss.
The black hole would change in appearance depending on how you looked at it. A side view, like the one below, would show the accretion disk slithering around the event horizon.
The disk would appear brighter on one side than the other because M87's black hole is likely spinning, which also spins the cloud of dust and gas orbiting it. So the material moving towards our eyes would seem brighter than the material moving away — a bit like the beacon of a lighthouse.
If you were to look at the black hole from above or below, however, the accretion disk would form a near-perfect circle and the light would appear more evenly distributed. The difference is clear in the animation below.
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According to Thorne, the reason the black hole in “Interstellar” doesn't match the M87 black hole image is that Nolan elected to omit that brightening and dimming phenomenon.
Thorne told Gizmodo that “the human eye would likely not be able to discern the brightness differences on the two sides of the hole when the overall brightness is so extreme.” That's why the film's black hole appears to have same brightness all the way around.
Scientists confirmed that there's a supermassive black hole at the center of our galaxy
Supermassive black holes are common in the universe — they've been found at the center of almost every galaxy scientists have examined. The black hole at the center of the Milky Way, Sagittarius A*, is 25,000 light-years away and 4 million times as heavy as our sun.
Sagittarius A*'s accretion disk is about 100 million miles wide, or a little wider than the distance between Earth and the sun.
In October 2018, astronomers revealed that they'd observed Sagittarius A* sucking in blobs of hot gas at 30% of the speed of light — 201 million mph. That triggered three powerful bursts of radiation that were detected by telescopes on Earth.
At the time, the study authors said the flares “provide long-awaited confirmation that the object in the center of our galaxy is, as has long been assumed, a supermassive black hole.”
Josephine Peters, an astrophysicist at the University of Oxford who wasn't involved in the study, previously told Business Insider that the observations followed material “as close as you can get to a black hole without being consumed by it.”
But Peters added that Sagittarius A* “is still incredibly mysterious.”
The more scientists learn about black holes like Sagittarius A*, the better directors like Nolan can depict them in Hollywood blockbusters. | 0.889398 | 3.913013 |
- A 2.5-mile-wide asteroid called 6478 Gault was discovered in 1988.
- The space rock recently grew two long, bright tails like a comet, which astronomers struggled to explain.
- The Hubble telescope studied the tails in detail, while ground-based observatories helped confirm the asteroid was rapidly spinning.
- Researchers figured that sunlight gradually spun up Gault’s rotational speed to unstable levels – something called a “YORP effect.”
- Gault is spinning so quickly that a small pebble hitting the asteroid might have caused it to slough off dirt and dust, forming its tails.
In space, no one can hear an asteroid scream. But astronomers just used the Hubble telescope to see one destroying itself.
A 2.5-mile-wide asteroid called 6478 Gault was first discovered in 1988, and it seemed like many of the other 800,000 known space rocks.
But in January, astronomers saw something strange in survey telescope images: Gault had become “active” and sprouted a big, bright tail – much like a comet‘s – that stretched more than 500,000 miles long. A dimmer second tail was found several weeks later.
Some space rocks that initially look like asteroids are later found to be comets when they pass close to the sun. The boost in solar energy can warm up ice and other frozen compounds hidden under layers of dust, turning those materials into gases and leading the rock to spew out comet debris to form a long, glowing tail.
Gault didn’t seem to fit the bill, though, since it lurks about 214 million miles away from the sun in a fairly circular orbit between Mars and Jupiter. In other words, it never swung close to the sun. So scientists wondered if another space rock had collided with Gault, splashing its dusty guts all over space.
Now, thanks to multiple observations by NASA and the European Space Agency’s Hubble Space Telescope, the mystery appears to be solved: Gault is spinning itself to pieces.
“This self-destruction event is rare,” Olivier Hainaut, an astronomer with the European Southern Observatory, said in a press release. “Active and unstable asteroids such as Gault are only now being detected by means of new survey telescopes that scan the entire sky, which means asteroids such as Gault that are misbehaving cannot escape detection any more.”
Hainaut and his colleagues around the world have submitted a study about the discovery to Astrophysical Journal Letters, which accepted it for publication in the future.
The team determined an odd behaviour called the “YORP effect” is to blame for the ongoing demise of Gault, which could vanish
You YORP me right round
The YORP effect is named after four scientists that helped lead to its discovery: Ivan Yarkovsky, John O’Keefe, Vladimir Radzievskii, and Stephen Paddack.
What powers it is sunlight. When we step outside, light from the sun feels warm on our skin, but not like a force powerful enough to physically move us. Yet in the vacuum of space, things behave differently: There’s no friction, and objects can orbit a star and persist for millions if not billions of years.
Even on human-made objects, like a thin reflective sheet, sunlight can generate enough force to propel a vehicle through space. (Scientists are currently exploring how to mimic that effect by shooting powerful laser beams at tiny spacecraft to zoom them toward other star systems at a fraction of light-speed.)
The YORP effect describes a phenomenon in which sunlight hits an asteroid unevenly, or part of the rock’s surface preferentially absorbs that energy. In that case, the disparity can gradually accelerate a comet’s spin. Over time, that can lead the space rock to start spinning so fast that it rips itself apart.
That, the researchers figured, could explain why Gault grew tails so far from the sun (see above animation).
The effect is something like a parent swinging a kid around by her arms; once the parent rotates fast enough, the kid will eventually lift off the ground. In the case of Gault, Hubble’s images – plus follow-up observations by telescopes on Earth – suggested that the asteroid was spinning about once every two hours. The researchers calculated that this was fast enough to counteract Gault’s gravity at the surface, allowing dirt and dust to lift off or tumble.
But what caused Gault’s sudden outburst and tail formation in late 2018, after untold years of inactivity?
“Even a tiny disturbance, like a small impact from a pebble, might have triggered the recent outbursts,” Jan Kleyna, an astronomer at the University of Hawaii and the study’s lead author, said in a press release. “It could have been on the brink of instability for 10 million years.”
Hainaut said the long-term future of Gault is unknown. It might eventually break apart into two big chunks, or the rubble might glue itself back together under its own gravity, forming a newly shaped asteroid.
“In all cases, this will release a lot of dust, which will be spectacular,” Hainaut told Business Insider in an email. “The radiation pressure from the sun will disperse the dust, leaving either the new Gault or the binary/multiple system behind.”
Given the number of asteroids in the solar system, Kleyna, Hainaut, and their colleagues now expect ever-improving all-sky survey telescopes to see sudden outbursts like Gault’s about once a year.
This story has been updated.
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After much speculation and bated breath, two-time UC Berkeley alumnus Barry C. Barish (BA ‘57, PhD ‘62) has been awarded this year’s Nobel Prize for Physics.
Barish shares the prize with fellow Caltech physicist Kip Thorne and MIT physicist Rainer Weiss. The trio earned the recognition for their groundbreaking detection of gravitational waves—ripples in the fabric of space that spread through the universe.
All three are members of the LIGO Scientific Collaboration—a team of more than 1,000 scientists, researchers, and technicians working with laser interferometers to measure gravitational waves.
Albert Einstein had predicted the existence of such waves as part of his general theory of relativity more than 100 years ago, but he and his contemporaries believed they would be impossible to detect.
So what are these waves, why are they important, and how did the team find them?
We asked UC Berkeley astronomy professor and unofficial ambassador of astrophysics Alex Filippenko to provide some answers. Filippenko was named the US National Professor of the Year in 2006, and is a perennial favorite among students for his energetic lectures and a passion for the subject that borders on obsession.
Filippenko explained that, according to Einstein’s theory, large bodies in the universe create “dimples” in the shape of space. Picture a bowling ball rolled across a trampoline.
“In Einstein’s general theory of relativity, what mass does, or what energy does, is warp, that is, bend the shape of space,” said Filippenko. “And it actually affects the passage of time as well. So matter creates this sort of a dimple around it, in the shape of space. Like a little curvature—and so the moon goes around earth, following its natural a path, in an intrinsically curved space.
“Imagine a piece of rubber stretched across a drumhead, and then stick a brick or bowling ball in it. If you then flick a ping pong ball onto the drum, that ping pong ball will roll around on the surface in a curved path, not in a straight line the way it would had there not been that brick or bowling ball. That’s what gravity is, in Einstein’s view,” said Filippenko. “It’s not really a force, it’s that objects produce a warping in the shape of space.”
Sometimes, these giant celestial bodies come into close contact with each other, and begin to spiral into each other’s orbits. The holes they cause in space overlap, their dimples bump around and finally merge, blasting an even stronger wave of ripples through space.
“It’s a little bit like if you were to take two fists and stick them into a pool of water, and then rotate them about each other—a wave would propagate outward from your two fists in the pool,” said FIlippenko.
When the waves rush outward—at the speed of light, scientists predict—they distort the shape of objects in their path. Things get stretched, and squashed, stretched and squeezed, this way and that—but only by a fraction. The scientific challenge of the last century was to design, execute, and perfect a way to capture those distortions.
Enter LIGO, the Laser Interferometer Gravitational-Wave Observatory. Built in the 1990s, but conceived decades prior, LIGO is basically a pair of giant wave detectors, spaced thousands of kilometers apart. Each detector looks like a large L, with two armlike tunnels that house finely calibrated lasers of equal length: 2.5 miles. If a gravitational wave passes by, the arms are designed to contract or lengthen ever so slightly, throwing the light of the lasers off by a tiny, but crucial, degree.
Barish, who received his bachelor’s in physics from UC Berkeley in 1957 and his PhD in experimental particle physics in 1962, was instrumental in not only improving LIGO’s technical issues, but also in smoothing out logistical bumps that inevitably arise in a project of its size. In particular, he led the effort to obtain funding from congress at a time when many regarded it as a “pie in the sky type of project,” Filippenko said.
“He was the voice of calm and reason that got a lot of people through some extremely difficult and touchy situations, from what I understand,” Filippenko said, “getting people to work together, to cooperate and be friendly, and not be at each other’s throats because Person A thinks it should be done one way and Person B thinks it should be done another way. He was Mr. Compromise and was able to get the collaboration working smoothly, and that’s no small feat.”
Over the years, the LIGO team worked to improve the instrument’s senstivity and in September 2015, it detected its first gravitational wave.
The cosmic culprit: Two black holes—each about 30 times the mass of our sun—that collided 1.3 billion years ago. The change detected in LIGO’s arms? 1/1000 the length of a proton.
“We were overjoyed,” said Filippenko, speaking of the astronomy community at large. “It was almost disbelief that this tiny, tiny variation in the length of these arms could actually be detected. This was a feat that was thought to be impossible, or at least extraordinarily difficult, a few decades ago. So this is extremely exciting, and it’s very well deserved.”
For Filippenko and others, the real significance of LIGO is what its capabilities mean for future research. The ability to study gravitational waves opens a new window into the universe, and a way to study cosmological phenomena and celestial bodies that would have been otherwise invisible.
“This is like Galileo first looking at celestial objects through an optical telescope back in December of 1609,” said Filippenko. “That’s the kind of thing we’re talking about, 400 years later.”
Posted on October 5, 2017 - 4:22pm | 0.863563 | 3.919498 |
Authors: Anshu Gupta, Kim-Vy Tran, Jonathan Cohn, Leo Y. Alcorn, Tiantian Yuan, Vicente Rodriguez-Gomez, Anishya Harshan, Ben Forrest, Lisa J. Kewley, Karl Glazebrook, Caroline M. Straatman, Glenn G. Kacprzak, Themiya Nanayakkara, Ivo Labbe, Casey Papovich, and Michael Cowley
First Author’s Institution: School of Physics, University of New South Wales, Sydney, NSW 2052, Australia
Status: Accepted to ApJ
How, exactly, galaxies form is still a very much open question in astrophysics. It’s not like we can watch a galaxy evolve, most are about 12 billion years old, and even the youngest we’ve discovered is about 500,000 million years old.
There are two ways to work around this problem. The first is a simple matter of looking back into time. Light takes a finite amount of time to travel to us, and so the further away we look, the older that light is. So the further a galaxy is, the younger we see it. Instead of watching a single galaxy evolve over time, we can compare further (“younger”) galaxies to closer (“older”) galaxies, and interpolate what may have happened to cause any changes.
The second way to work around our observational conundrum is to watch galaxies evolve in simulation space. The authors of today’s paper used IllustrisTNG100, part of a suite of large cosmological simulations of galaxy evolution. Figure 1 shows a subset of luminous matter in the TNG100 simulation.
Observed Mass, Movement and Star Formation History
The kinematic properties (how things are moving) of star-forming galaxies is strongly linked to how they gained their mass. Today’s authors compared the velocity dispersion of “younger” galaxies at redshift z=3.0–3.8 to “older” galaxies from previous studies of redshift z~2 and found that their most massive galaxies had smaller velocity dispersions than massive “older” galaxies.
By looking at the spectra of these galaxies, today’s authors could also extract their star formation history. Basically, this looks at how old current stars are to extract the star formation rate over time. The top panels of figure 3 show the authors’ results (keep in mind, time reads as newer on the left and older on the right). The bottom two panels show results from previous studies of galaxies at z~2. While the less massive galaxies in the authors’ survey (top left panel) show the same pattern of increasing star formation rate, the most massive galaxies on the right have a relatively flat star formation history. This is in contrast to massive galaxies at z~2, which show an increasing star formation rate over time.
Both the odd star formation histories and velocity dispersions point to something happening between z=3 and z=2 that changed massive galaxies. To determine what that might be, the authors turn to simulations.
Into the Simulation
The IllustrisTNG100 simulation starts with a distribution of mass at a redshift of z=127 and runs until present day, z=0. As it runs, the random fluctuations in density at z=127 turn into galaxies, which grow, form stars and merge. The authors wanted to look at how these galaxies acquired their stars over time.
There are basically two ways that a galaxy can gain stars: either by forming them from gas belonging to the galaxy (in situ) or by accreting the stars from other, mostly smaller, galaxies (ex situ). Figure 4 shows the fraction of stellar mass that was accreted ex situ, rather than formed in the galaxy. It shows that for the most massive galaxies (in red), the fraction of ex situ stellar mass increases between z=3 (pink dotted line) and z=2 (black dotted line). Meanwhile, the ex situ stellar mass fraction remained largely constant for less massive galaxies (blue).
Uniting Simulations and Observations
The authors speculate that this increase in ex situ stellar mass fraction seen in simulations may be responsible for the increase in velocity dispersion seen in observed massive galaxies between z=3 and z=2. Turbulence and gravitational instabilities driven by accretion of stars and gas would increase the randomness of velocities (i.e. the velocity dispersion).
This could also explain the difference in star formation history between massive galaxies at z=2 and z=3 (figure 3). Gas is necessary for the formation of stars and if the galaxies at z=2 have been able to gain gas from accretion, they would be able to increase their star formation rate, as seen in the bottom right panel of figure 3. In contrast, a smaller ex situ stellar mass fraction for z=3 galaxies indicates that there has been less accretion and less opportunity to gain new gas and thus form new stars, leading to the flat star formation trend seen in the top right panel of figure 3.
Essentially, the younger galaxies at z=3 have had less time to merge with other galaxies, leading to smaller velocity dispersions and less star formation.
The authors note that their conclusions are limited by many factors, including a small sample size. However, these are promising results and show how much can be gained by comparing observations and simulations. | 0.809324 | 4.024209 |
A new understanding of Mars is beginning to emerge, thanks to the first year of NASA’s InSight lander mission. Findings described in a set of six papers published today reveal a planet alive with quakes, dust devils and strange magnetic pulses.
Five of the papers were published in Nature Geoscience. An additional paper in Nature Communications details the InSight spacecraft’s landing site, a shallow crater nicknamed “Homestead hollow” in a region called Elysium Planitia.
InSight is the first mission dedicated to looking deep beneath the Martian surface. Among its science tools are a seismometer for detecting quakes, sensors for gauging wind and air pressure, a magnetometer, and a heat flow probe designed to take the planet’s temperature.
While the team continues to work on getting the probe into the Martian surface as intended, the ultra-sensitive seismometer, called the Seismic Experiment for Interior Structure (SEIS), has enabled scientists to “hear” multiple trembling events from hundreds to thousands of miles away.
Seismic waves are affected by the materials they move through, giving scientists a way to study the composition of the planet’s inner structure. Mars can help the team better understand how all rocky planets, including Earth, first formed.
Mars trembles more often — but also more mildly — than expected. SEIS has found more than 450 seismic signals to date, the vast majority of which are probably quakes (as opposed to data noise created by environmental factors, like wind). The largest quake was about magnitude 4.0 in size — not quite large enough to travel down below the crust into the planet’s lower mantle and core. Those are “the juiciest parts of the apple” when it comes to studying the planet’s inner structure, said Bruce Banerdt, InSight principal investigator at JPL.
Scientists are ready for more: It took months after InSight’s landing in November 2018 before they recorded the first seismic event. By the end of 2019, SEIS was detecting about two seismic signals a day, suggesting that InSight just happened to touch down at a particularly quiet time. Scientists still have their fingers crossed for “the Big One.”
Mars doesn’t have tectonic plates like Earth, but it does have volcanically active regions that can cause rumbles. A pair of quakes was strongly linked to one such region, Cerberus Fossae, where scientists see boulders that may have been shaken down cliffsides. Ancient floods there carved channels nearly 800 miles (1,300 kilometers) long. Lava flows then seeped into those channels within the past 10 million years — the blink of an eye in geologic time.
Some of these young lava flows show signs of having been fractured by quakes less than 2 million years ago. “It’s just about the youngest tectonic feature on the planet,” said planetary geologist Matt Golombek of JPL. “The fact that we’re seeing evidence of shaking in this region isn’t a surprise, but it’s very cool.”
At the Surface
Billions of years ago, Mars had a magnetic field. It is no longer present, but it left ghosts behind, magnetizing ancient rocks that are now between 200 feet (61 meters) to several miles below ground. InSight is equipped with a magnetometer — the first on the surface of Mars to detect magnetic signals.
The magnetometer has found that the signals at Homestead hollow are 10 times stronger than what was predicted based on data from orbiting spacecraft that study the area. The measurements of these orbiters are averaged over a couple of hundred miles, whereas InSight’s measurements are more local.
Because most surface rocks at InSight’s location are too young to have been magnetized by the planet’s former field, “this magnetism must be coming from ancient rocks underground,” said Catherine Johnson, a planetary scientist at the University of British Columbia and the Planetary Science Institute. “We’re combining these data with what we know from seismology and geology to understand the magnetized layers below InSight. How strong or deep would they have to be for us to detect this field?”
In addition, scientists are intrigued by how these signals change over time. The measurements vary by day and night; they also tend to pulse around midnight. Theories are still being formed as to what causes such changes, but one possibility is that they’re related to the solar wind interacting with the Martian atmosphere.
In the Wind
InSight measures wind speed, direction and air pressure nearly continuously, offering more data than previous landed missions. The spacecraft’s weather sensors have detected thousands of passing whirlwinds, which are called dust devils when they pick up grit and become visible. “This site has more whirlwinds than any other place we’ve landed on Mars while carrying weather sensors,” said Aymeric Spiga, an atmospheric scientist at Sorbonne University in Paris.
Despite all that activity and frequent imaging, InSight’s cameras have yet to see dust devils. But SEIS can feel these whirlwinds pulling on the surface like a giant vacuum cleaner. “Whirlwinds are perfect for subsurface seismic exploration,” said Philippe Lognonné of Institut de Physique du Globe de Paris (IPGP), principal investigator of SEIS.
Still to Come: The Core
InSight has two radios: one for regularly sending and receiving data, and a more powerful radio designed to measure the “wobble” of Mars as it spins. This X-band radio, also known as the Rotation and Interior Structure Experiment (RISE), can eventually reveal whether the planet’s core is solid or liquid. A solid core would cause Mars to wobble less than a liquid one would.
This first year of data is just a start. Watching over a full Martian year (two Earth years) will give scientists a much better idea of the size and speed of the planet’s wobble.
A division of Caltech in Pasadena, JPL manages InSight for NASA’s Science Mission Directorate. InSight is part of NASA’s Discovery Program, managed by the agency’s Marshall Space Flight Center in Huntsville, Alabama. Lockheed Martin Space in Denver built the InSight spacecraft, including its cruise stage and lander, and supports spacecraft operations for the mission.
A number of European partners, including France’s Centre National d’Études Spatiales (CNES), the German Aerospace Center (DLR) and the United Kingdom Space Agency (UKSA), are supporting the InSight mission. CNES provided the Seismic Experiment for Interior Structure (SEIS) instrument to NASA, with the principal investigator at IPGP (Institut de Physique du Globe de Paris). Significant contributions for SEIS came from IPGP; the Max Planck Institute for Solar System Research (MPS) in Germany; the Swiss Federal Institute of Technology (ETH Zurich) in Switzerland; Imperial College London and Oxford University in the United Kingdom; and JPL. DLR provided the Heat Flow and Physical Properties Package (HP3) instrument, with significant contributions from the Space Research Center (CBK) of the Polish Academy of Sciences and Astronika in Poland. Spain’s Centro de Astrobiología (CAB) supplied the temperature and wind sensors. | 0.868497 | 3.806177 |
Presentation on theme: "Can amateur observers discriminate the core of dense globular clusters like M3 and M15? Rodney Howe AAVSO SID Analyst Strikis Iakovos - Marios Hellenic."— Presentation transcript:
Can amateur observers discriminate the core of dense globular clusters like M3 and M15? Rodney Howe AAVSO SID Analyst Strikis Iakovos - Marios Hellenic Amateur Astronomy Association Elizabeth Observatory of Athens Ido Bareket מצפה הכוכבים ברקת במכבים http://www.bareket-astro.com Bareket observatory, Israel http://www.bareket-astro.com Stouraitis Dimitrios Hellenic Amateur Astronomy Association Galilaio Astronomical Observatory
Video of Globular Cluster M3 Large file download ~16MB Note the variable stars scattered around the cluster! http://ncastro.org/Contrib/Howe_R/M3.wmv
Or, perhaps use a Period Luminosity ratio for RR Lyrae stars: A correlation between the periods and mean luminosities of Cepheid variables. The period-luminosity relation was discovered by Henrietta Leavitt in 1912. The longer a Cepheid's pulsation period, the more luminous the star. Since measuring a Cepheid's period is easy, the period-luminosity relation allows astronomers to determine the Cepheid's intrinsic brightness and hence its distance. If the Cepheid is in another galaxy, the Cepheid's distance gives the distance to the entire galaxy. luminositiesCepheid variablesLeavitt period-luminosity relation http://www.daviddarling.info/encyclopedia/P/period-luminosity_relation.html
Classical method for determining cluster distances. Luminosity Distances Indirect distance estimate: Measure the object's Apparent Brightness, B Assume the object's Luminosity, L Solve for the object's Luminosity Distance, dL, by applying the Inverse Square Law of BrightnessInverse Square Law of Brightness Apparent Brightness is inversely proportional to the square of the distance to the source We call this the Luminosity Distance (dL) to distinguish it from distances estimated by other means (e.g. geometric distances from parallaxes). The only observable is the object's Apparent Brightness, B. The missing piece is the luminosity, (L), which must be inferred in some way. http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit4/cosdist.html
Method: Build up a calibrated H-R Diagram for nearby stars with good parallax distances. Get Spectral Type & Luminosity Class of the distant star from its spectrum. Locate the star in the calibrated H-R Diagram Read off the Luminosity Compute the Luminosity Distance (dL) from is measured Apparent Brightness.
Measure field RR Lyrae distances by parallax (these two images are 7 years apart!)
RR Lyrae Stars, Horace A. Smith, 1995, Cambridge Astrophysics Series
Amateur Astronomers have no consistent way of defining the core of a globular cluster, thus differentiating the core from the periphery. This segregation is important for characterizing the gravitational dynamics of the cluster, particularly in the core. The periods of RR Lyrae variable stars introduce segregation errors due to their inherent variation. Current core sizing is a function of the luminosity versus distance from the core center. However, once in the core, the variations in the RR Lyrae stars introduce significant error in the luminosity determination. Hence, by characterizing the RR Lyrae quantities and oscillation periods, we can reduce the core dimension error.
(Ido Bareket) “One approach for better identification of the 'core' area vs. the other outer region areas can be done by finding any potential correlation between the angular size of the target - and its standard deviation of the stars, VS. their distance from the core. There may be another more elegant solutions, but I don't aware of such. I believe that it will be easier to do this manually though. At least with these small lists of targets.” How do we discriminate the core?
Outer region cluster RR Lyrae phases from stellar pulsation sources Iakovos writes: “As for the M3 Globular Cluster images I did a random selection of about 100 stars in the outer parts of the cluster images and did the photometry profile in just one window... Then I started to erase those which did not have an RR-Lyrae type of variation and this is how I finally stopped to those 20 stars “... http://www.aavso.org/vsots_rrlyr
Cutting up the cluster to identify period/luminosity ratios
But, which Pixel Value should we choose? Perhaps the Full Width Half Maximum (FWHM)?
FWHM is just the yellow part of the flux density.
Or, by cutting up the images by visual inspection; 32 images for 3 nights of M3 (Ido Bareket), 46 images one night of M15 (Iakovos Strikis)
And then compare magnitude (digital number) differences between outer image regions (more dark sky) and inner regions (no dark sky)
Cut right to the core! To follow the period changes over time.
However, core Period/Luminosity concerns, with amateur telescopes and cameras; Iakovos writes: “As for the decrease of the flux density of the M15 core... I also think it is not real, and I believe that it is caused from the camera stabilization.... All cameras need about 1+1/2 hours to be thermal stabilized... If I start to image before that time the linearity of the camera (and sensitivity) are going to be changed until the camera gets thermal stabilized “...
How about treating the cluster as just one star?
Tom Krajci’s observatory for AAVSO http://picasaweb.google.com/tom.krajci/Autoscope22# http://picasaweb.google.com/tom.krajci/Autoscope22#
October, 2010; 277 images over 4 nights of M15 K28 (Krajci-28) is a 28-cm Celestron C-11 located at the Astrokolkhoztelescope facility near Cloudcroft, New Mexico (UT-7). This telescope was donated to the AAVSO by Tom Krajci. (K28 is a Celestron CPC-1100 fork mounted 11-inch Schmidt-Cass, using an ST-8 at 1x1 binning. Image scale is approx. 1.056 arcsec/pixel, and frame FOV = 27 x 18 arc minutes.) http://www.aavso.org/aavsonet
Also, Johnson-Cousins filters U,B,V,R,I were used in previous work for visual inspection. Now Sloan filters u,g,r,i,z are being used in the one star approach.
How might we do photometry and treat the cluster as one star, and with a mix-match of filters? Photometric Standard Fields (Stetson Catalog) Here is a current list of my photometric standard fields. U,B,V,R,I give the number of standards in each filter, where a standard has at least 5 observations made under photometric conditions and sigma(mag) < 0.02 mag in a given filter. The coordinates given are the (2000.0) coordinates of the field center. This may be followed by field size in arcminutes (RA, Dec). Each field is represented by three files: 1. *.pos -- The (2000.0) positions of the stars in (a) RA, Dec in decimal degrees; (b) RA, Dec in hexagesimal HH MM SS.S sDD MM SS; (c) offsets in arcsec from a given reference position; (d) position, in pixels, in the image described below. 2. *.pho -- The photometric data [mag, sigma(mag), N(obs)] for U, B, V, R, I, plus a measure of variability: sigma(1 obs). 3. *.fits -- A composite image of the field. All images consist of short integers, and have increasing East and y increasing North. The scale is an integer number of pixels per arcsecond, usually two pixels per arcsecond (0.500 arcsec/px) but sometimes, depending on the seeing, three or even four pixels per arcsecond. The scale factor (number of pixels per arcsecond) is the third number in the header keyword OFFSCA. If the field size is given, that means the field is ready now; the others are in various stages of progress. Feel free to encourage progess on any fields of particular interest to you. Field RA Dec RA size Dec size UBVRI positions photometry image NGC707821 30 08.3+12 11 4424.332.275497813080258NGC7078.posNGC7078.phoNGC7078.fits.gzG26_721 3 1 00 -09 47 11111NGC7078.posNGC7078.phoNGC7078.fits.gz http://www3.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/community/STETSON/standards/
We’ll have to use a photometry software package that can overlay all 243 Stetson stars onto the 277 October (4 nights) M15 images: VPHOT is an AAVSO online photometry data reduction tool which can do this.
VPHOT is used to create instrumental magnitude comparisons for each of the K28 – M15 Sloan filtered images.
Perhaps there is a color (g- r) index that can help discriminate what is going on in the core of these globular clusters? Midx = ((g-r) / (g+r))
These are Stetson star color plots over time (Right Accession) and sorted by the Johnson-Cousins Blue filter. V and R filters show some ‘scruff’ in RA.
RR Lyrae Stars, Horace A. Smith, 1995, Cambridge Astrophysics Series
RR Lyr c and RR Lyr ab population distributions in M3 and M15 http://iopscience.iop.org/1538-4357/530/1/L41/pdf/995789.web.pdf
But where are these two different populations? And can Period/Luminosity flux density distributions help determine the core from outer regions? Stanek video of 12 images in one night (4 of each, Red, Green and Blue filters), 1998 on the 1.2 m. telescope at F.L. Whipple Observatory in Arizona. https://www.cfa.harvard.edu/~jhartman/M3_movies.htmlF.L. Whipple Observatoryhttps://www.cfa.harvard.edu/~jhartman/M3_movies.html
We can make period/luminosity plots of VPHOT data. This is one night of data for 243 Stetson stars and 44 K28 images. But how do we find the two populations and their period/luminosities?
Here are 4 nights of M15 K28 images, which do show a positive slope for the aggregate light curves for different filter magnitudes (g – r) in this case, but then the residuals show something else. R code from Grant Foster’s book ‘Analyzing Light Curves A practical Guide’, 2010, Lulu Press
Can amateur astronomers understand all this? Photo from home page of Natalia Dziourkevitch: http://www.aip.de/~nsdhttp://www.aip.de/~nsd
How about just enjoying the show. And keep the camera focused!
“ Not sure I'm saying this right, but it would be something like this: there is a P/L ratio differences between core and outer region, which would be a Bayesian prior, which would inform the decision to describe the core region. For example: when the core's P/L ratio is negative at some slope, large enough to be significant when compared to the positive P/L ratio slope for the outer region's RR Lyr stars, then this difference in slope of the P/L ratio would help inform the algorithm used to describe the core, and we could be confident we've identified the core, in-part because of the difference in the slope of the P/L ratios? That way whether or not we use some B - V color relationship to define the P/L ratio, or a flux density period/luminosity ratio over time (multiple images), we could still determine a significant change of the P/L slopes between core and outer region? Such that, where there is a 'significant' change in these slopes, which identifies the core. This all depends on the idea that the P/L ratio of the core RR Lyr stars is less than the P/L ratio of the outer region's RR Lyr stars.” Jamie Riggs Core Period/Luminosity | 0.841644 | 3.458308 |
It’s being called one of the biggest astronomical discoveries of the century: a potentially habitable Earth-like planet is orbiting the closest neighbor to our sun, a red dwarf star known as Proxima Centauri. Scientists with the European Southern Observatory (ESO) confirmed the planet’s existence yesterday in a new study published in the journal Nature, on the heels of rumors reported earlier this month in the German weekly magazine Der Spiegel.
Proxima Centauri, a small red dwarf star, has only about 12 percent the mass of the sun and about 1/600th the luminosity. It is so dim that it cannot be seen from Earth with the naked eye. Proxima Centauri is located in the star system Alpha Centauri, which also includes the larger but more distant binary star pair known as Alpha Centauri AB.
Some of the researchers involved in the new study began searching for hints of an exoplanet orbiting Proxima Centauri back in 2000. During the first half of this year, telescopes around the world were trained on the star, looking for the slight movement in the colors of the starlight, called a “Doppler wobble,” that would be caused by a gravitational planet in orbit. These observations, combined with the earlier research, data and published studies, enabled the astronomers to confirm the existence of a planet at least 1.3 times the mass of Earth that orbits Proxima Centauri every 11.2 days.
The newly discovered planet, dubbed Proxima b, is only about 5 million miles away from Proxima Centauri. By contrast, some 93 million miles separate Earth from the sun. Because Proxima Centauri is so much cooler and fainter than the sun, however, the temperature on Proxima b is low enough that water could potentially exist on its surface without evaporating, a vital condition for life.
Scientists still can only speculate about whether liquid water does in fact flow on Proxima b, or whether the planet has an atmosphere. They also want to explore whether, like Earth, the planet has a magnetic field around it protecting it from some of the radiation it receives from its star. Some of the biggest questions they have are around how the planet formed: How close to the star was it at the time of formation? Did it initially have water, or did it form dry? Could its atmosphere have been destroyed by powerful radiation during formation?
Answers to these questions could determine if Proxima b has conditions similar to those of Earth, or if its conditions more closely resemble those of other planets, such as Venus (extremely hot) or Mars (cold and dry). As the astronomer Guillem Anglada-Escudé of Queen Mary University of London, who led the team that made the new discovery, said in a news conference: “There are viable models and stories that lead to a viable Earth-like planet today.”
Despite its proximity to Earth, astronomers cannot view Proxima b with a telescope because it is lost in the glare of Proxima Centauri, but they hope the next generation of technology will change this in a decade or so. The researchers said the planet is a potential target for robotic exploration, a possibility that is already being explored by the Breakthrough Starshot Initiative, the privately funded effort led by Russian entrepreneur Yuri Milner, famed theoretical physicist Stephen Hawking and Facebook founder Mark Zuckerberg, among others. The project aims to create and send ultra-fast light-driven nanocraft (iPhone-sized spacecraft) to Alpha Centauri within two or three decades.
At the same time, programs such as Mission Centaur are also focusing on Alpha Centauri, seeking other potentially Earth-like exoplanets that may be orbiting the three stars in the system. The authors of the new study did encounter extra signals in some of their observations of Proxima Centauri, suggesting hints of other possible planets yet to be discovered. | 0.884157 | 3.843617 |
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