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Let’s start with a graph.
This graph shows temperature anomalies on Earth – that is, the difference between the recorded temperature on any given day and the average temperature for the same location on that day over many years. Yellow-red colours indicate the actual temperature was warmer than average, blue-green colours indicate the temperature was cooler than average. The results are averaged across latitudes, so each point on the graph shows the average anomaly for the entire circle of latitude. The data are Goddard Television Infrared Observation Satellite Operational Vertical Sounder surface air temperature readings from NOAA polar weather satellites.
As you might expect, the temperature across Earth varies a bit. Some days are a bit warmer than average and some a bit cooler than average. You might imagine that with all of the different effects that go into the complicated atmospherical systems that control our weather, days would be cooler or warmer than average pretty much at random.
However that’s not what we’re seeing here. There’s a pattern to the anomalies. Firstly, the anomalies in the polar regions are larger (red and dark blue) than the anomalies in the mid-latitudes and tropic (yellow and light blue). Secondly, there are hints of almost regular vertical stripes in the graph – alternating bands of yellow and blue in the middle, and alternating red and dark blue near the poles. If you look at the graph carefully, you may be able to pick out a pattern of higher and lower temperatures, with a period a little bit less than one month.
What could have an effect on the Earth’s climate with a period a little under a month? The answer is, somewhat astonishingly, the moon.
The creators of this graph took the latitude-averaged temperature anomaly data for the 20 years from 1979 to 1998, and plotted it as a function of the phase of the moon:
These graphs show that the temperature anomalies have a clear relationship to the phase of the moon. In the polar regions, the temperature anomaly is strongly positive around the full moon, and negative around the new moon. In the mid-latitudes and tropics the trend is not so strong, but the anomalies tend to be lower around the full moon and positive around the new moon – the opposite of the polar regions.
What on Earth is going on here?
Aggregated measurements show that the polar latitudes of Earth are systematically around 0.55 degrees Celsius warmer at the full moon than at the new moon. This effect is strong enough that it dominates over the weaker reverse effect of the mid-latitudes/tropics anomaly. The average temperature of the Earth across all latitudes is not constant – it varies with the phase of the moon, dominated by the polar anomalies, being 0.02 degrees Celsius warmer at the full moon than the new moon. That doesn’t sound like a lot, but the signal is consistently there over all sub-periods in the 20-year data, and it is highly statistically significant.
The next puzzle is: What could possibly cause the Earth’s average temperature to vary with the phase of the moon?
Well, the full moon is bright, whereas the new moon is dark. Could the moonlight be warming the Earth measurably? Physicist and climate scientist Robert S. Knox has done the calculations. It turns out that the additional visible and thermal radiation the Earth receives from the full moon is only enough to warm the Earth by 0.0007 degrees Celsius, nowhere near enough to account for the observed difference.
There’s another effect of the moon’s regular orbit around the Earth. According to Newton’s law of gravity, strictly speaking the moon does not move in an orbit around the centre of the Earth. Two massive bodies in an orbital relationship actually each orbit around the centre of mass of the system, known as the barycentre. When one body is much more massive than the other, for example an artificial satellite orbiting the Earth, the motion of the larger body is very small. But our moon is over 1% of the mass of the Earth, so the barycentre of the system is over 1% of the distance from the centre of the Earth to the centre of the moon.
It turns out the Earth-moon barycentre is 4670 km from the centre of the Earth. This is still inside the Earth, but almost 3/4 of the way to the surface.
The result of this is that during a full moon, when the moon is farthest from the sun, the Earth is 4670 km closer to the sun than average, whereas during a new moon the Earth is 4670 km further away from the sun than average. The Earth oscillates over 9000 km towards and away from the sun every month. And the increase in incident radiation from the sun during the phases around the full moon comes to about 43 mW per square metre, or an extra 5450 GW over the entire Earth. The Earth normally receives nearly 44 million GW of solar radiation, so the difference is relatively small, but it’s enough to heat the Earth by almost 0.01 degrees Celsius, which is near the observed average monthly temperature variation.
Why are the polar regions so strongly affected by this lunar cycle, while the tropics are weakly affected, and even show an opposing trend? Earth’s weather systems are complex and involve transport of heat across the globe by moving air masses. The burst of heat at the poles during a full moon actually migrates towards lower latitudes over several days – you can see the trend in the slope of the warm parts of the graph. The exact details of the physical mechanisms for these observations are still under discussion by the experts. What is clear though is that there is a definite cycle in the Earth’s average temperature with a period equal to the orbit of the moon, and it is most likely driven by the fact that the Earth is closer to the sun during a full moon.
How might one possibly explain this in a flat Earth model? Well, the “orbital” mechanics are completely different. The phase of the moon should have no effect on the distance of the Earth to the sun. The only moderately sensible idea might be that the full moon emits enough extra radiation to warm up the Earth. But the observations of the moon’s radiant energy and the amount of heating it can supply end up the same as the round Earth case (if you believe the same laws of thermodynamics). The full moon simply doesn’t supply anywhere near enough extra heat to the flat Earth to account for the observations.
One could posit that the sun varies in altitude above the flat Earth, coincidentally with the same period as the moon, thus providing additional heating during the full moon. However one of the main modifications to the geometry of the Earth-sun system made in flat Earth models is to fix the sun at a given distance (usually a few thousand kilometres) above the surface of the Earth, in an attempt to explain various geometrical properties such as the angle of the sun as seen from different latitudes. Letting the sun move up and down would mess up the geometry, and should easily be observable from the surface of the flat Earth.
So, observations of the global average temperature, and its periodic variation with the phase of the moon provides another proof that the Earth is a globe.
Anyamba, E.K., Susskind, J. “Evidence of lunar phase influence on global surface air temperature”. Geophysical Research Letters, 27(18), p.2969-2972, 2000. https://doi.org/10.1029/2000GL011651
Knox, R.S. “Physical aspects of the greenhouse effect and global warming”. American Journal of Physics, 67(12), p.1227-1238, 1999. https://doi.org/10.1119/1.19109 | 0.817965 | 3.819301 |
Those that appreciate a beautiful night sky will be in for a treat. On November 14, the moon will be in the closest proximity to Earth in 70 years. In being so close, it will provide some delightful visuals for stargazers and non-stargazers, alike.
The “Beaver Moon” gets its name from a time of year when early colonists and Indian tribes set their beaver traps. More specifically, they needed to set them before the land froze over. During the colonial period, beavers were treasured for their exceptional and warmth-giving furs.
Unfortunately, there will not be any large rodents crawling on the moon’s surface.
What NASA Is Saying
Of course, NASA has provided plenty of information on the Beaver Moon, saying: “The full moon of November 14 is not only the closest full moon of 2016 but also the closest full moon to date in the 21st century. The full moon won’t come this close to Earth again until November 25, 2034.”
The Moon’s orbit path around the Earth is elliptical, and one side of the orbit’s path (called “perigee”) is closer than the other by about 30,000 miles (50,000 kilometers). On the shorter path, the Earth, Sun and Moon align in what is called “syzygy” in astrological terms.
The end result is a “perigee” moon, or in common parlance, a supermoon. Or, as NASA cheekily refers to as “an extra-super moon.” An “extra-super supermoon” materializes when the moon becomes full on the same days as its perigee, or when the moon’s orbit is at its closes to the Earth’s surface.
A “supermoon” is actually a term derived from modern-day astrology. This terminology received popular attention in recent years as moon sightings became more and more spectacular. Furthermore, the science around the phenomenon was more widely disseminated…putting more souls into the “stargazer” camp.
Also called a perigee full moon, a supermoon can be up to 14% bigger than a full moon. Adding to the spectacle, a supermoon may be 30% brighter than a regular (or apogee) full moon. The clearer that the sky, the more visually stunning this moon will be. An overcast will slightly dim this beaming moon, but it will still be spectacular. That said, please let the sky be clear!
In addition to the scientific rationale for the supermoon, the history surrounding the Beaver supermoon makes the occurrence all the more special. Following the date – November 14, 2016 – the moon will not get closer to the Earth for another 28 years.
Around this date, November 12th, the Taurids Meteor Shower will also take place. This meteor shower occurs once a year, and are a visual feast as well. According to Weather.com, the meteors “as remnants left behind by the passage of the Comet known as 2P/Encke.” About 10 to 15 balls of flame (literally) streak across the sky each hour.
A supermoon will appear one more time in 2016 – on December 14. Make sure to mark your calendars!
How to See History
North America and Europe:
According to experts, the moon will become full on November 14 at 8:52 EST in the U.S. and 1:52 pm UTC, internationally. Those that wish to see the supermoon in the North America and Europe will probably get the best view on the evenings of November 13th and 14th.
On the West Coast of US, those that rise early will probably be able to witness the moon at its fullest around 5:52 am PST; about 28 minutes before the sun rises.
Readers and sky gazers in Asia will be happy to hear that they will likely observe the moon at its absolute fullest. The anticipated time is 9:52 pm Hong Kong Time, 7:22 pm in India.
Get out there!
Even if you’re not a huge fan of stargazing, sky gazing, call if what you will…this is a once-in-a-lifetime chance to see the moon in all of its glory. To witness history.
And if what NASA and other scientists say is true, the privilege of seeing this beautiful moon may just make lovers of the sky out of us all. | 0.844982 | 3.366796 |
Exploiting the Power of Metallicity Studies in the UV: Dissecting the Nearby Spiral Galaxy M83S. Hernandez (sveash[at]stsci.edu)
Metallicities of galaxies at all redshifts are critical for deciphering a plethora of physical and evolutionary processes that take place among and inside galaxies, including star formation, stellar feedback, and interstellar/intergalactic chemical enrichment. In the last decades it has become evident that a large fraction of the stellar mass in the universe was assembled in intense episodes of star formation (SF) at high (z > 1) redshift. Studies of local starbursts and star-forming galaxies can be performed at exquisite signal-to-noise, spatial and spectral resolution, which are not achievable at higher redshift. Such studies provide an invaluable tool for creating a baseline in understanding how gas and stellar properties evolve through cosmic time.
In this Newsletter I present a brief summary of our latest findings in the nearby spiral galaxy M83 (Hernandez et al. 2019). Using young star clusters, we performed a detailed metallicity gradient analysis. Our measurements provide us with hints to the chemical history, as well as physical properties of this face-on, star-forming galaxy. We identify two possible breaks in the metallicity gradient of M83 at galactocentric distances of R ∼ 0.5 and 1.0 R25.The metallicity gradient of this galaxy follows a steep-shallow-steep trend, a scenario predicted by three-dimensional (3D) numerical simulations of disk galaxies. We propose a scenario where the first steep gradient originated by recent star-formation episodes and a relatively young bar (<1 Gyr). The shallow gradient, on the other hand, is created by the effects of dilution of outflowing enriched gas mixing with low-metallicity material present at larger radial distances. And finally, the second break and last steep gradient mark the farthest galactocentric distances where the outward flow has penetrated.
Metallicity of Galaxies
With the purpose of understanding how galaxies are formed and evolve with time, astronomers continuously search for new tools that can provide clues to their past. One of these tools that can lead to strong constraints on the history of cosmic chemical enrichment of galaxies is the measurement of their chemical composition. It is through such studies that we can learn about the evolution of the Universe from a primordial metal-free system to the present-day chemically diversified environment.
The metallicity of a galaxy, [Z], is mainly controlled by two components: 1) chemically processed material in stars, and 2) exchanges between the galaxy and the intergalactic medium (IGM). Given the dependence of metallicity on these two factors, studies focused on metallicity relations and metallicity gradients in galaxies hold a wealth of information on their formation and evolution.
Back in 1979, Lequeux discovered that the masses and metallicities of several star-forming, irregular, and blue compact dwarf galaxies, correlated with each other in the sense that more massive galaxies appeared to have higher metallicities. This same correlation was later confirmed by several other independent studies making this mass-metallicity relation (MZR) widely used for studying star-formation episodes, galactic winds, and chemical enrichment in general. Similarly important, the metallicity gradients in individual galaxies track some of the complex dynamics taking place within them, such as outflows and infall of material. Given the importance of accurate metallicities, it is crucial to obtain reliable metallicity indicators in order to correctly interpret the processes influencing these relations.
In the last decade, new techniques have been developed to study the chemical content of nearby galaxies using blue supergiant stars (BSGs) and red supergiant stars (RSGs), as well as the integrated light of star clusters. These are in addition to the more classical techniques where nebular emission lines at optical and infrared wavelengths are used to infer the metallicity of H Ⅱ regions or absorption-line spectra arising from heavy elements against bright background UV sources are analyzed to make a census of the metals in the interstellar medium (ISM) of galaxies. With current telescopes, star clusters well outside of the Local Group and at distances of several megaparsecs (Mpc), appear not to be resolved into individual stars. This facilitates measurement of their chemical composition through the analysis of their integrated light (IL) spectra. This kind of spectroscopy has shown ample potential; however, until recently most efforts have focused on the optical and infrared regimes. Young stellar populations, for instance, when observed in the near-infrared are strongly dominated by RSGs, which facilitates their analysis through modeling of the whole population as a single RSG star. When studying globular clusters (GCs), on the other hand, one needs to make the assumption that all stars in the cluster are coeval and implement full population synthesis techniques to perform a similarly detailed abundance analysis. By way of contrast, the UV spectral coverage for IL metallicity analyses of clusters is rather unexplored.
Piecing together the History of M83
In our latest publication, Hernandez et al. (2019), we performed a metallicity study of the nearby (4.9 Mpc) face-on star-forming galaxy M83. This was accomplished by merging ground-based optical observations from the X-Shooter spectrograph on the Very Large Telescope (VLT) in Chile with space-based far-ultraviolet observations with the Cosmic Origin Spectrograph (COS) onboard the Hubble Space Telescope (HST). Our sample of young star clusters was comprised of 23 targets covering the inner disk of the galaxy (Figure 1). Our metallicity measurements confirm a relatively steep gradient in the inner disk of the galaxy.
To obtain a more complete picture of the metallicity trends in M83, we combined our measurements with those from Bresolin et al. 2007 and 2009 covering the outer disk of M83 as shown in Figure 2. Based on the trends in this figure, we proposed that M83 exhibits a metallicity gradient with two possible breaks at R ∼ 0.5 R25 and R ∼ 1.0 R25. If the metallicity breaks are genuine, the metallicity gradient of this galaxy follows a steep-shallow-steep trend, a scenario predicted by three-dimensional (3D) numerical simulations of disk galaxies. The first break is located near the corotation radius. This first steep gradient may have originated by recent starformation episodes and a relatively young bar (<1 Gyr) possibly triggered by an interaction or merger. In the numerical simulations the shallow gradient is created by the effects of dilution of chemically enriched material outflowing and mixing with lower metallicity gas present at larger galactic distances. The second break and last steep gradient mark instead the farthest galactocentric distances where the outward enriched gas flow has penetrated the disk.
Our work has demonstrated that the integrated-light method can be used as an alternative metallicity tool to nebular and interstellar gas techniques, applicable not only in the optical and infrared, but also in the UV. By successfully expanding the metallicity analysis of stellar clusters to UV wavelengths we have made it possible to simultaneously study the multi-phase gas and stellar properties. Such analysis can bridge our understanding of galactic outflows, stellar evolution and stellar feedback not only locally, but also at higher redshifts (z ~ 2) where the rest-frame UV light is shifted into the optical/IR wavelengths.
Bresolin, F., 2007, ApJ, 656, 186
Bresolin, F., Ryan-Weber, E., Kennicutt, R. C., & Goddard, Q. 2009, ApJ, 695, 580
Hernandez, Svea, Larsen, Søren, Aloisi, Alessandra, Berg, Danielle A., Blair, William P., Fox, Andrew J., Heckman, Timothy M., James, Bethan L., Long, Knox S., Skillman, Evan D., & Whitmore, Bradley C., 2019 ApJ, 872, 116H | 0.889526 | 4.07945 |
A team of researchers from Iran and the UK have obtained the first 3D map of the local bubble through a survey of diffuse interstellar bands (DIBs), a mysterious absorption feature seen in the stellar spectra, using two telescopes in the northern and southern hemispheres.
The solar systems is located in a very hot and low density environment in which a million degree K temperature prevents matter to remain in ordinary atomic forms. Previous studies have revealed an empty bubble within a radius of about a hundred light years around the solar system, thus dubbed as the Local Bubble. This cavity is thought to have been created by multiple supernovae, which mark the death of stars more massive than the sun, events which could have occurred tens of millions of years ago.
The team led by astronomers from the Institute for Research in Fundamental Sciences (IPM) in Tehran and the Lennard-Jones Laboratories at Keele University in the UK have conducted a four-year long survey to search for other surviving forms of matter, generally complex carbon-based molecules suspected of surviving the harsh conditions.
Given that the previous studies had found no ordinary matter, they had to rely on fingerprints of absorption features on the stellar spectra of distant stars and thus study the spectra of hundreds of stars with a strong enough signal in all directions to detect certain DIB carriers.
“DIB’s are one of most mysterious features for astronomers with an unknown origin but they became handy in mapping the local bubble”, Amin Farhang the lead author of the Nature Astronomy article, published today, claims. The survey made use of the Isaac Newton Telescope on La Palma (Spain) and the European Southern Observatory’s New Technology Telescope on La Silla (Chile) using which over 600 high quality spectra were obtained and analysed. Computational methods allowed them to convert the observational data into a 3D density distribution of the DIBs in 578.0 nm and 579.7 nm.
Figure 1: DIB distribution (green contours), overplotted with Dust (blue lines) and neutral NaI gas density (red lines). The colors are the logarithm of gas density and the galactic center is toward the X-axis.
The research establishes that the solar system is surrounded by the carriers of these DIBs. “when the Sun and the Earth move through this material, it is not unthinkable that some of it might find their way onto our planet or elsewhere in the solar system”, Jacco van Loon one of the co-authors suggests posing the question whether it could have brought some vital ingredients for Life on the planet!
This collaborative research was supported by the Iranian National Observatory at IPM, and the Science and Technology Facilities Council (UK) and the Royal Society. The results were published in the latest issue of the Nature Astronomy, July 2019, co-authored by Amin Farhang (IPM), Jacco van Loon (Keele), Habib Khosroshahi (IPM), Atefeh Javadi (IPM) and Mandy Bailey (Open University).
The research benefitted from the Iranian National Observatory training program which was conducted at the Isaac Newton Group of Telescope. | 0.873231 | 4.035471 |
When a star dies in a violent, fiery death, it spews its innards out across the sky, creating an expanding wave of gas and dust known as a supernova nebula. Arguably, the most famous of these supernova remnants is M1, also called the Crab Nebula, a blob-like patch visible in low-powered binoculars.
Ancient Meteorite Reveals Vital Clues about the Solar System’s Birth
Uranus is having Extreme Storms
Chinese astronomers watching the sky on July 4, 1054, noted the appearance of a new or “guest” star just above the southern horn of Taurus. But knowledge of star-fields was not necessary to spot this surprising visitor — according to records, the bright source was visible during the daytime for 23 days, shining six times as brightly as Venus. Those well-versed with the night sky would have been able to see it for 653 days — almost two years — with the naked eye. Other observations of the explosion were recorded by Japanese, Arabic, and Native American stargazer. (Crab Nebula Album).
1968, astronomers in Puerto Rico discovered a pulsing radio source. Determined to be a pulsar, the object is a rapidly-rotating, town-sized star that flashes about 30 times a second. Known as NP0532, or the Crab Pulsar (a remnant of the supernova SN 1054), the neutron star is 100,000 times more energetic than the sun. Though only a few tens of miles across, it shines about as brightly as our nearest sun.
If you ask yourself how a supernova explosion looks like as seen from Earth, here is the answer (Betelgeuse explosion footage as seen from Earth):
Betelgeuse can break at any time !!! This star is gonna blow! 430 light-years away in the constellation of Orion Betelgeuse is dying. It reached the end of it’s life and currently in the terminal throes of shedding vast bubbles of gas into space. Some scientist believe that Betelgeuse will become a second sun.
Have something to say? Let us know in the comments section .
Source: Wikipedia, Space.com, Astronomy.com. | 0.828343 | 3.30686 |
NASA managers say the WFIRST mission, the next in the agency’s line of powerful observatories after the Hubble and James Webb telescopes, could cost around $3.2 billion after budgeting for a novel first-of-its-kind instrument to probe the make-up of planets around nearby stars and a bigger-than-expected launch vehicle.
The observatory will be stationed at the L2 Lagrange point, a gravitational balance point about a million miles (1.5 million kilometers) from Earth, to survey the cosmos for dark energy and detect the the faint starlight reflected off of planets in other solar systems, allowing scientists to measure the composition of their atmospheres and surfaces.
WFIRST could help cosmologists and astronomers get closer to answering two fundamental questions: What is driving the expansion of the universe, and where might scientists find an Earth analog around another star?
The space agency formally kicked off development of WFIRST in February 2016, a year ahead of schedule, after several years of technological research and mission concept studies. Congress approved extra money for the project, allowing NASA to press ahead with the mission on a faster schedule than expected.
The Wide Field Infrared Survey Telescope, or WFIRST, is scheduled to be ready for launch by September 2025, employing one of two primary mirrors donated to NASA by the National Reconnaissance Office, the U.S. government’s spy satellite agency.
The NRO no longer needed the mirrors, which were developed for a cancelled surveillance mission that would have carried a downward-looking telescope to capture detailed images of military and strategic targets around the world.
WFIRST’s repurposed primary mirror, made by Harris Corp., did not come with the detectors and instrument needed to make it a functional telescope. Engineers are also making changes to the mirror for WFIRST’s astronomical mission.
After the NRO gifted NASA the two excess mirrors in 2012, the space agency revamped its plans for the WFIRST mission, doubling the size of the mission’s telescope to accommodate the spy assets.
The mirror measures 7.9 feet (2.4 meters) in diameter, the same size as Hubble’s, giving WFIRST the same sensitivity as NASA’s flagship space observatory. But WFIRST will see a swath of the sky 100 times bigger than Hubble’s field-of-view, allowing it to extend Hubble’s deep vision across the cosmos.
NASA officials originally planned for WFIRST to have a telescope half the size of Hubble, and the observatory was to be placed into a geostationary orbit around 22,000 miles (nearly 36,000 kilometers) above Earth.
That would have allowed WFIRST to fit on a rocket like United Launch Alliance’s Atlas 5.
But the bigger spacecraft, coupled with a decision to station WFIRST at the more distant L2 Lagrange point, will mean the observatory must launch aboard a more powerful — and perhaps more expensive — rocket.
NASA is currently looking at ULA’s Delta 4-Heavy or SpaceX’s Falcon Heavy rocket to send WFIRST into space, according to Dominic Benford, the mission’s program scientist at NASA Headquarters.
The James Webb Space Telescope, a partnership between NASA, the European Space Agency and Canada, is set for launch in October 2018 with an even bigger primary mirror — more than 21 feet (6.5 meters) in diameter — comprised of 18 hexagonal segments. But JWST is like Hubble, crafted to peer deep into the universe, not a wide field surveyor like WFIRST.
“WFIRST is like 100 Hubbles, relative to the field-of-view, and it’s going after science that is really compelling,” said Thomas Zurbuchen, associate administrator of NASA’s science mission directorate.
The high-resolution maps created by WFIRST will require a huge data archive and software to pick out the most promising data.
“This is the first astrophysics mission that I would say brings us into the big data era,” said Jeff Kruk, WFIRST’s acting project scientist at NASA’s Goddard Space Flight Center in Maryland. “This is the first NASA mission that’s going to be undertaking large-scale data mining like this.”
Fitted with two science instruments, WFIRST will observe the universe for more than six years. A wide field imager and spectrometer will survey the cosmos in near-infrared for dark energy research and planet searches, and a coronagraph aboard WFIRST is designed to blot out bright starlight to directly image their planetary systems.
Astronomers using WFIRST’s wide field-of-view will detect thousands of bright supernovae — a giant explosion at the end of a star’s life — to measure how the rate of the universe’s expansion has changed over time, according to NASA.
Dark energy is a mysterious force accelerating the expansion of the universe.
Scientists expect WFIRST to find up to 20,000 exoplanets orbiting other stars, building on the planet-hunting capabilities of NASA’s Kepler telescope.
While Kepler detects planets that pass between the telescope and a host star, WFIRST will use a technique called microlensing, which is the gravitational effect caused when one star passes in front of another.
When such an event occurs, the light rays coming from the background star are bent by the gravity of the foreground star, called the lens star. Planets around the lens star can also distort the brightness of the background star, allowing astronomers to use microlensing to search for alien worlds.
The coronagraph on WFIRST is an experimental addition to the observatory. Engineers want to check the device’s performance before building a coronagraph for a much larger future telescope that could find another planet like Earth.
“In the long run, for finding Earths, you need a much bigger telescope, but this is proof the technology will actually work in space, and it gives you confidence that when you actually go up to a larger telescope, that it will work,” Kruk said April 13 in a presentation to the NASA Advisory Council’s science committee.
Direct imaging is a key step toward measuring the structure and composition of exoplanets, and in determining whether the worlds are habitable.
The James Webb Space Telescope will be capable imaging giant planets several times the size and mass of Jupiter, hot young worlds that are unlikely to harbor life.
WFIRST will see smaller planets the size of Saturn and Neptune that lie closer to their parent stars, and perhaps even rocky “super-Earths” that are somewhat bigger than our own planet.
Project managers are preparing for WFIRST’s systems requirements review in July, followed by the start of the next phase of development — called Phase B — around Oct. 1.
NASA officials want to keep WFIRST’s total cost around $3.2 billion — in current-year economic conditions — and Benford said the space agency could “descope” the mission by removing the coronagraph instrument if it looks like it will bust the budget cap.
“The coronagraph is not required for mission success, so we can back off the coronagraph if necessary,” Benford said in the April 13 meeting of the NASA science advisory committee.
Multiple internal and external cost assessments will be completed in the coming months to inform NASA decision-makers on whether WFIRST should remain intact.
An cost assessment by the Aerospace Corp. in 2015 put WFIRST’s project cost between $2 billion and $2.3 billion. A report issued by the National Academy of Sciences last year said the cost of WFIRST had increased by $550 million since the Aerospace Corp. study, and the review panel recommended NASA slash the observatory’s capabilities, such as removing the coronagraph, if costs continued to grow.
NASA does not want to repeat its experience with JWST.
When astronomers first conceived of the once-in-a-generation mission in the late 1990s, they expected it could launch as soon as 2007 and cost around $1 billion. Its launch is now set for late next year, with a cost nearly nine times the initial estimate, carving money out of NASA’s budget that could have gone to other projects.
“Budget is a big concern,” Benford said. “The concern I’m mostly recognizing now is the overall mission cost of $3.2 billion. We have to make sure that we make the right choices to keep the science capability while keeping under that cost.
“The problem with mission design is you tend to have a function of science vs. cost that is steep,” Benford said. “You lose more science than you lose cost.”
Email the author.
Follow Stephen Clark on Twitter: @StephenClark1. | 0.856101 | 3.082932 |
Just like beautiful planetary alignment in late winter/early spring of 2012 when you could see Venus, Jupiter, Mercury, Mars, and Moon rolling in the skies pretty close together, next year’s sky is going to be even more spectacular with two bright comets — C/2011 L4 (PANSTARRS) and C/2012 S1 ISON — approaching the Sun. Unfortunately, at their brightest next year, both will be quite low in the sky.
Comet PANSTARRS: A Great Comet In 2013?
This comet was discovered by the 1.8-m Pan-STARRS 1 Ritchey-Chretien telescope (Haleakala, Hawaii, USA) on June 6, 2011 with magnitude 19.4 at a distance of nearly 7.9 AU from the Sun. PANSTARRS will pass closest to Earth on 2013 March 5 (1.10 AU). It could be very bright in March, heading north and passing close to the Andromeda Galaxy (M31) in early April in the early morning sky.
Passing perihelion on March 10, 2013, at the distance of only 0.3 AU from the Sun, this comet might reach the brightness from 0 to -1, and some even say up to -4, shining as bright as Venus.
Comet ISON: A Daylight Great Comet In 2013?
This one’s pure awesomeness.
Discovered at magnitude 18.8 on September 21 by the two astronomers, Vitali Nevski from Vitebsk, Belarus, and Artyom Novichonok from Kondopoga, Russia, in about a year from now, Comet C/2012 S1 (ISON) might become the brightest comet anyone alive has ever seen.
According to predictions, the comet will approach to within 0.012 AU of the Sun at the end of November 2013. Then, in January 2014, the comet will approach to within 0.4 AU of Earth. Sometime in late October or early November 2013, ISON should cross the naked-eye visibility threshold. From there, it may reach — or even exceed — the brightness of the Full Moon. | 0.80863 | 3.421085 |
Object: Impact craters on the asteroid Vesta
Size: Up to 500 kilometres wide
Vesta thought its days of being the solar system’s punching bag were over. Despite 3.5 billion years of pummelling, the protoplanet had managed to hold itself together. The bullies of the asteroid playground had mostly settled down, and aside from the occasional shove or taunt, things were starting to look up. If only poor Vesta had known of the two bullies that were still to come.
Fresh images of 4.5 billion year old Vesta show the poor protoplanet was pummelled by a 60-kilometre-wide rock not once, but twice, in the past two billion years. And those strikes dug up enough material to create an entire class of meteorites. If Helen of Troy had “the face that launched a thousand ships”, then Vesta has Rheasilvia and Veneneia, the craters that launched a thousand meteorites.
Astronomers had suspected for decades that Vesta – the solar system’s second-biggest asteroid – was the source of the howardite-eucrite-diogenite, or HED meteorites. This common group of space rocks makes up about 6 per cent of the meteorites seen to fall to Earth: the Meteoritical Bulletin Database lists 1082 that have been found on the ground.
Both the asteroid and HED meteorites give off similar spectral signatures that were different from other classes of meteorites, and both looked like basaltic lava of the sort that is found in Hawaii. Vesta’s orbit around the sun is also just right for sending debris to Earth. Meanwhile, observations with the Hubble Space Telescope in 1997 showed a giant crater in the South Pole. That was the “smoking gun”, says Paul Schenk of the Lunar and Planetary Institute in Houston, Texas. But a few mysteries remained.
Could a single hole in Vesta’s South Pole really have dug up enough material to account for all HED meteorites? How deep is the hole, and how long ago did it form? And how many impacts were there? A group of smaller asteroids called Vestoids are thought to be chips of Vesta knocked off in a giant impact. But some studies of the way they move had suggested that these are divided into two distinct populations – one about a billion years older than the other.
New images from NASA’s Dawn spacecraft are filling in the details. Dawn slipped into orbit on 17 July, 2011 and has mapped nearly 80 per cent of the asteroid’s surface. The images show that Vesta’s northern hemisphere is pockmarked with craters, a record of billions of years of pummelling. “It’s been hammered quite a bit,” Schenk says.
But whatever craters had been preserved in the southern hemisphere were obliterated by one huge impact, which Schenk and colleagues estimate came about a billion years ago. The crater this vast asteroid bully left behind, called Rheasilvia, stretches to 500 kilometres, wider than the distance from London to Dublin and spanning most of Vesta itself. It’s at least 19 kilometres deep, and has a central peak that rises 20 kilometres high, higher than Mauna Kea on Hawaii.
That means the object that hit Vesta must have been 50 to 60 kilometres wide, bigger than the object that made the Chicxulub impact crater thought to be responsible for killing off the dinosaurs. Debris from the crater can be found 100 kilometres away from the rim. The force of the impact formed deep grooves that circle Vesta’s equator.
“It’s the largest possible ring you can make due to an impact,” says Chris Russell of the University of California, Los Angeles. “We’ve never seen anything like that before.”
The team calculated that the impact scooped a million cubic kilometres worth of material out of Vesta’s South Pole, and scattered much of it into space. The HED meteorites plus the Vestoids have a total estimated volume of 100,000 cubic kilometres, so the Rheasilvia impact alone could have been responsible for the lot.
But beneath all the destruction the researchers also found a second impact crater, Veneneia, almost as large as Rheasilvia but half-hidden underneath it. About 400 kilometres wide and 12 kilometres deep, it formed about two billion years ago, Schenk and colleagues determined.
“That was a surprise, that in fact the southern part of Vesta had been subject to two very large impacts,” Russell says. Vesta probably would have been destroyed by the one-two punch, if not for a characteristic that makes it seem more planet than asteroid: an iron core. In its first million years of existence, Vesta was completely molten, Russell says, and the heavier elements like iron sank to its centre to congeal into a solid metallic core.
“It was anchored by that iron core, and survived,” he says. “And fortunately so, because we don’t have many ways of getting back that far in history, to get some evidence of what was going on in those very early days.”
There’s another silver lining to Vesta’s tortured playground years: HED meteorites are so numerous, you could own one. “You can go to a meteorite collection store, and they’ll sell you a piece of Vesta,” says Russell.
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- Basic astronomical data
- The atmosphere
- Interaction with the solar wind
- Character of the surface
- Interior structure and geologic evolution
- Observations from Earth
- Spacecraft exploration
Observations from Earth
Since Galileo’s discovery of Venus’s phases, the planet has been studied in detail, using Earth-based telescopes, radar, and other instruments. Over the centuries telescopic observers, including Gian Domenico Cassini of France and William Herschel of England, have reported a variety of faint markings on its disk. Some of these markings may have corresponded to the cloud features observed in modern times in ultraviolet light, while others may have been illusory.
Important early telescopic observations of Venus were conducted in the 1700s during the planet’s solar transits (see eclipse: Transits of Mercury and Venus). In a solar transit an object passes directly between the Sun and Earth and is silhouetted briefly against the Sun’s disk. Transits of Venus are rare events, occurring in pairs eight years apart with more than a century between pairs. They were extremely important events to 18th-century astronomy, since they provided the most accurate method known at that time for determining the distance between Earth and the Sun. (This distance, known as the astronomical unit, is one of the fundamental units of astronomy.) Observations of the 1761 transit were only partially successful but did result in the first suggestion, by the Russian scientist Mikhail V. Lomonosov, that Venus has an atmosphere. The second transit of the pair, in 1769, was observed with somewhat greater success. Transits must be viewed from many points on Earth to yield accurate distances, and the transits of 1761 and, particularly, 1769 prompted the launching of many scientific expeditions to remote parts of the globe. Among these was the first of the three voyages of exploration by the British naval officer James Cook, who, with scientists from the Royal Society, observed the 1769 transit from Tahiti. The transit observations of the 1700s not only gave an improved value for the astronomical unit but also provided the impetus for many unrelated but important discoveries concerning Earth’s geography. By the time the subsequent pair of transits occurred, in 1874 and 1882, the nascent field of celestial photography had advanced enough to allow scientists to record on glass plates what they saw through their telescopes. No transits took place in the 20th century; the next pair were widely observed and imaged in 2004 and 2012. The next transits of Venus will occur in 2117 and 2125.
In the modern era Venus has also been observed at wavelengths outside the visible spectrum. The cloud features were discovered with certainty in 1927–28 in ultraviolet photographs. The first studies of the infrared spectrum of Venus, in 1932, showed that its atmosphere is composed primarily of carbon dioxide. Subsequent infrared observations revealed further details about the composition of both the atmosphere and the clouds. Observations in the microwave portion of the spectrum, beginning in earnest in the late 1950s and early ’60s, provided the first evidence of the extremely high surface temperatures on the planet and prompted the study of the greenhouse effect as a means of producing these temperatures.
After finding that Venus is completely enshrouded by clouds, astronomers turned to other techniques to study its surface. Foremost among these has been radar (see radio and radar astronomy). If equipped with an appropriate transmitter, a large radio telescope can be used as a radar system to bounce a radio signal off a planet and detect its return. Because radio wavelengths penetrate the thick Venusian atmosphere, the technique is an effective means of probing the planet’s surface.
Earth-based radar observations have been conducted primarily from Arecibo Observatory in the mountains of Puerto Rico, the Goldstone tracking station complex in the desert of southern California, and Haystack Observatory in Massachusetts. The first successful radar observations of Venus took place at Goldstone and Haystack in 1961 and revealed the planet’s slow rotation. Subsequent observations determined the rotation properties more precisely and began to unveil some of the major features on the planet’s surface. The first features to be observed were dubbed Alpha, Beta, and Maxwell, the last after James Clerk Maxwell, the Scottish physicist who first derived some of the basic equations that describe the propagation of electromagnetic radiation. These three features are among the brightest on the planet in radar images, and their names have been preserved to the present as Alpha Regio, Beta Regio, and Maxwell Montes.
By the mid-1980s Earth-based radar technology had advanced such that images from Arecibo were revealing surface features as small as a few kilometres in size. Nevertheless, because Venus always presents nearly the same face toward Earth when the planets are at their closest, much of the surface went virtually unobserved from Earth. | 0.874438 | 3.853005 |
The solar system has another interstellar visitor, but there’s no question of this one being an alien spacecraft. It’s a true comet and the first we’ve ever confirmed comes from interstellar space, and the Hubble Space Telescope captured some amazing imagery of it. Good thing, too — because it’s never coming back.
You probably remember ‘Oumuamua as the interstellar object that launched a thousand headlines — mostly around the idea that it could be an alien ship of some kind. Needless to say that hypothesis didn’t really pan out, but honestly the object was interesting enough without being an emissary from another world.
This new comet, called 2I/Borisov (not as catchy), was first identified in August by an amateur astronomer named Gennady Borisov, who lives in Crimea. Studies by other near-Earth object authorities observed its trajectory and concluded that it did indeed come from interstellar space?
How do they know? Well, for one thing, it’s going 110,000 miles per hour, or 177,000 kph. “It’s traveling so fast it almost doesn’t care that the Sun is there,” said UCLA’s David Jewitt, who leads the Hubble team watching 2I/Borisov. (Note that in the gif above, the streaks don’t indicate its speed — those are from the Earth spinning.)
Basically the angle it’s coming in, plus the speed at which it’s traveling, mean it can’t possibly be in even a super-wide orbit of the sun. It’s just passing through — and in early December will be less than 200 million miles from the Sun. It’s not on track to hit anything, fortunately, which would be a truly cosmic coincidence, so in a couple months it’ll be gone again.
But its short visit is ample opportunity to study its makeup, which appears to be very similar to our own “local” comets. Although it would be cool for 2I/Borisov to be super weird, its similarity is interesting in itself — it suggests that comet formation in other solar systems is not necessarily different.
It is, however, very different from ‘Oumuamua, which appeared to be an inert, oblong rock. Interesting in its own way, but comets are so dynamic: clouds of dust and ice surrounding a much smaller core. Very picturesque, even if the tails don’t always point the way you think they should.
Note that these interstellar visitors are actually thought to be quite common, with perhaps thousands in the solar system at any given moment. But few are big and bright enough to be detected and studied.
Hubble will continue observing 2I/Borisov through January and perhaps beyond. If it’s never going to return, we want to gather as much data as possible while we can. | 0.91637 | 3.882988 |
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Two JPL spacecraft are about to exit our solar system, and like dutiful offspring, they phone home every day.
In 1977, JPL launched Voyager 1 and Voyager 2 to explore the outer planets and beyond. Now, 35 years later, the two spacecraft are still going strong, far beyond the outermost planet, Neptune and even poor demoted Pluto. In fact, the two Voyagers are much farther from Earth than any other spacecraft has ever been — boldly going where no human creation has gone before, to paraphrase Star Trek.
Caltech Professor Ed Stone, who served as Director of JPL from 1991 to 2001, has been Voyager’s Principal Investigator since 1972, five years before launch. Stone, now 76, spoke at a recent Caltech seminar, bringing an enthusiastic audience up to date on his 40-year-long project.
The Voyagers explored the outer planets, their magnetic fields, and 48 of their moons. They discovered the ice-covered surface of Europa and our solar system’s most active volcanoes on Io. They found that Saturn’s rings are 200,000 times thinner than their width, analyzed the dense hydrocarbon atmosphere of Titan, and imaged the rings of Uranus and Neptune. While passing Jupiter, Voyagers survived radiation levels 1000 times the lethal dose for humans.
Voyager 2 arrived at Neptune within 62 miles of its target, equivalent to sinking a golf ball from 4 billion yards, with some mid-course corrections provided by small thrusters that deliver only a 3-ounce force. That’s enough to accelerate a car from 0 to 60 mph in 12 hours flat. But its fuel efficiency is outstanding: launched with nearly 700 tons of rocket fuel, Voyager 2 achieved 30,000 mpg, while traveling 4.4 billion miles to Neptune.
Voyager 1 is now 123 AU from Earth, moving 3.6 AU per year. Earth’s distance from the Sun is 1 AU, so 123 AU equals 11 billion miles. After passing Saturn in 1980, Voyager 1 turned “north” and is rising above the plane of our solar system. Voyager 2 passed Uranus in 1986 and Neptune in 1989, then turned “south”, and is now 100 AU from Earth, moving 3.3 AU per year, as illustrated below.
In December 2004 at 94 AU, Voyager 1 passed the “termination shock”, where the solar wind’s speed drops from 900,000 mph to 250,000 mph. Voyager 2 passed the termination shock in August 2007 at 84 AU. Both are now en route to the “heliopause”, generally considered the edge of our solar system and the start of interstellar space. The heliopause is the limit of the dominion of our Sun’s magnetic field and solar wind, where its magnetic field changes direction and the solar wind stops. Its shape is an oblong due to the Sun’s motion through the surrounding interstellar gas.
Each Voyager records the magnetic fields, solar wind, and cosmic ray levels around it, and reports back to JPL’s Deep Space Network (DSN) at 160 bits/sec. With antennas up to 230 feet across and located around the world, DSN’s sensitivity is truly amazing. Voyager transmits at 23 watts, but when their signals reach Earth they are nearly a billion, billion times weaker. Like some offspring, JPL’s Voyagers call home collect.
Just announced this month, Voyager discovered something completely unexpected: a region dubbed the “magnetic highway” that allows low-energy particles of the solar wind to escape and high-energy particles from interstellar space to enter our solar system. Charts of the changing particle counts are shown below. Stone said: “We believe this is the last leg of our journey to interstellar space.”
Voyagers’ computers, which were state-of-the-art in the early 1970’s, boast 12,000 bytes of memory and tape cassette for data storage. Electronics and instrument heaters are powered by radioactive Plutonium. Despite shutting down non-critical equipment, the Voyagers will exhaust their power and thruster fuel by about 2025. Except for these consumables, they might have been able to call home for another century or two.
After leaving our solar system, the Voyagers will fly by other stars. In 40,000 years, Voyager 1 will be “only” 10 trillion miles from a star in the constellation of Camelopardalis. In 300,000 years, Voyager 2 will pass 25 trillion miles from Sirius, the brightest star in our sky.
The Voyagers are destined—perhaps eternally—to wander the Milky Way. Both carry a greeting for any aliens they might encounter, written on a 12-inch gold-plated copper disk. A committee chaired by Carl Sagan assembled 115 images, a variety of natural sounds, musical selections from different cultures, and oral greetings in 55 languages, all portraying the diversity of life on Earth.
Funded by NASA and managed by Caltech, the Jet Propulsion Laboratory (JPL) is unquestionably the world leader in space exploration. JPL has a long history of outstanding achievements, beginning in 1936 with Caltech’s first rocketry projects. Most recently, JPL dazzled the world with the amazing landing of Curiosity on Mars.
Author- Dr. Robert Piccioni.
© CC, 2012 Creative Commons Licence. This article may be reproduced, stored in a retrieval system, or transmitted, in any form or by means electronic, mechanical, photocopying, or otherwise only with proper citation to the article. No prior written permission is necessary. | 0.85933 | 3.178629 |
A few years ago, I gave a talk about astrobiology at the kick-off meeting for the DARPA Biological Technologies program office. DARPA, or the Defense Advanced Research Projects Administration, is the Department of Defense's think tank for innovative research— a unique organization that brings together scientists across disciplines to direct research on a wide variety of topics related to national security. I arrived as a sort of chaser for their day, spent worrying about problems much closer to home— and over an hour or so, told them about the incredible progress astronomers have made in searching for biology beyond our planet.
Talking about alien life is both exciting and frustrating— there's a lot say about the search for life, yet little known about life itself. For example, if you'd asked even six years ago whether small, rocky planets like the Earth were common or rare, no one could tell you. Now, thanks both to space-based projects like NASA's Kepler Mission, as well as research teams searching with Earth-bound telescopes (such as the one that recently discovered a planet orbiting our neighbor star, Proxima Centauri), we know that the Galaxy is awash in planets. There are so many planets, in fact, that when you gaze into the night sky, each star is likely the sun of another world. By and large, these planets are worlds roughly the size of Earth-- a tantalizing hint that, while we have yet to find life elsewhere, the potential real estate abounds.
Amazingly, the majority of planets exist around the suns you cannot see: tiny red stars, whose feeble shine makes them invisible to the unaided human eye. These little red stars (known as M dwarfs) are extremely populous, comprising 70% of all the stars in our Galaxy— but they were also once the pariahs of planet hunting. Astronomers had any number of reasons to dismiss them as hosts for habitable worlds: their meager energy output meant that planets would have to orbit so close to them, they would become locked by tidal forces— one side in perpetual day, the other in perpetual night. Even if planets did exist around them, surely those planets' atmospheres would freeze and collapse! Or if they escaped that fate, it was thought that energetic flares from their parent stars would shower the unsuspecting planets with high energy ultraviolet and X-ray radiation, sterilizing the surface. Even if some biology survived, in their very red light, most beyond the scope of human vision in the infrared (energies of radiation we experience as heat, which we can see only with night vision goggles), photosynthesis would be limited— or impossible! Not only would life not thrive, it wouldn't even have a fighting chance.
In 2005, however, a small workshop was held at the SETI Institute, with the intent of reevaluating the decades of planetary party-pooping— and I, as a particularly lucky young graduate student, got to attend. Over the week, we examined these assumptions in a fresh light, eventually concluding that none of those supposed showstoppers are really all that show-stopping. While it's true that planets around M dwarfs are likely affected by tides, they may also remain habitable in spite of those effects, and here on Earth, plants can use red light for photosynthesis. Even those pesky flares didn't seem so bad: several years back, my colleague Antigona Segura and I used computer models combined with stellar data to show that even a large flare might not be all that detrimental to habitability: much of the energetic ultraviolet light is filtered by the planet's atmosphere. In any event, evolution can be very enterprising when it comes to protecting organisms in high-radiation environments: some high altitude plants produce their own protective waxes, and more vulnerable critters can just hide underwater, which provides an effective shield from UV radiation. In the years since that SETI workshop, myriad teams have worked hard to make the question of habitability on planets around M dwarfs answerable with nuance and detail, rather than a simple yes or no.
While our understanding of what these alien environments might be like has grown by leaps and bounds in the past decade, many unknowns remain. Stellar activity— the catch-all term for flares, as well as the energetic particles that stream from magnetic stars in ribbons and blobs— still poses a compelling threat to planetary habitability. Even if planets are partly protected from the effects of stellar activity by their atmospheres (or their own magnetic fields), the resulting chemistry in the planet's atmosphere may drive its composition towards poisonous, rather than pleasant— at least for life as we know it. More confounding, stellar activity can also erode planetary atmospheres with time, washing over them and gradually scraping the atmosphere away. If a planet doesn't have an atmosphere, there's no pressure to maintain liquid water on its surface— no matter whether it is the right distance from the warming glow of its star to be considered habitable, or not. Right now, we lack the tools to test whether large numbers of planets have atmospheres or not, although new insights will come from the James Webb Space Telescope in the near future.
If atmospheres of planets around M dwarfs do survive, there is still the question of irradiation from stellar flares. Proxima b, the roughly Earth-sized planet recently announced around our neighboring star, is an interesting case in point.
As data was being gathered for the planet’s discovery, another team of astronomers was studying flares from its small red host star, Proxima Cen (http://www.ifweassume.com/
These unknowns wind into the wooded future, promising paths for both concrete scientific research, and imaginative thought. After all, if 70% of all stars have planets that are largely incapable of hosting life, it makes a big difference for whether life in the universe as a whole is common, or rare. A favorite thought experiment of mine is to consider the implications of challenging planetary environments on our chances for recognizing— or communicating with— intelligent life beyond our own world. I imagine a universe filled with rocky planets around little red stars, and on days I'm feeling optimistic, I imagine the atmospheres of these worlds have survived. Global oceans protect surface life from the vagaries of stellar irradiation, and intelligent (even technologically advanced) life might be more akin to the dolphins of our own planet. What would the relationship of this underwater life be to the sky, and to its place in space?
Fermi's paradox (despite being neither Fermi's, nor a paradox http://blogs.
Astronomy, space travel, and the will to communicate with worlds beyond our own are not only part of a scientific quest, they are the outgrowth of cultural values— values we hold as a species that is both capable of viewing the stars, and of contemplating our place amongst them. What would we learn, if we could ask dolphins about their conception of the universe? Do they want to build crafts that will ferry them (or their robotic avatars) outside the bounds of natural habitability, like humans have done to explore both space and the sea? Or is the ability to actually see the night sky ultimately tied to the desire to know whether these island planets also hold life? What about the planets out there that might be shrouded in haze, obscuring the stars from their inhabitants, even if they aren't underwater? And what if all the planets around M dwarfs are just barren rocks, devoid of atmospheres, where any life might remain sealed under ice caps like the surface of Jupiter's moon, Europa?
The difference between science fiction and science itself is that fiction is content to imagine and dream— but science lives to dive beneath the waves, and figure out the answer. While scientists are often loathe to say that we live in a special time, in some sense we do: we stand at the dawn of knowing that the universe teems with worlds, but not yet knowing if we are alone. At this moment, we must be keenly cognizant of how far we have to go. Otherwise, our assumptions about the completeness of our search, the universality (or not) of the values we hold, and our inability to communicate even with species we share the same swimming space with, will blind us to the possibilities— and limitations— of what we might come to know about life in the universe.
Do Dolphins Dream of Space Travel? Little red stars offer big questions in the search for intelligent life
Dr. Lucianne Walkowicz is an astronomer at The Adler Planetarium in Chicago. | 0.901771 | 3.656188 |
The Voyager 2 spacecraft is now in interstellar space, NASA announced on Monday, making it the second human-made machine to cross a boundary that divides our solar system from the rest of the Milky Way galaxy.
“We’ve been waiting with bated breath for the last couple of months for us to be able to see this,” Nicola Fox, director of NASA’s heliophysics division, said during a news conference at a meeting of the American Geophysical Union in Washington.
Voyager 2 follows its twin, Voyager 1, which made the crossing in 2012. This time the passage into interstellar space is yielding a different set of readings, with new clues to how the sun affects space in the far reaches of the solar system.
The two plutonium-powered spacecraft, launched in 1977 to make a tour of the giant planets, are still operational and continue to explore.
“Now we are fortunate enough to have two very brave sentinels that have left our heliosphere and are out truly looking at the other side of the boundary in our interstellar medium,” Dr. Fox said.
The heliosphere is a bubble of gases emanating outward from our sun, and it is buffeted by winds of interstellar particles that blow through the Milky Way. At greater distances, the solar wind diminishes and is overtaken by the interstellar flow.
“We’re inside this bubble the sun creates around itself,” said Edward C. Stone, the project scientist for the mission. “When Voyager was launched, we didn’t know how large the bubble was, we didn’t know how long it would take to get there, and we didn’t know if the spacecraft could last long enough to get there.”
Crossing the boundary, the spacecraft observed a distinct change in its environment.
“There are two winds pushing on each other,” Dr. Stone said, “the solar wind from the inside pushing out and the interstellar wind pushing back in, in balance.”
For Voyager 2, now more than 11 billion miles from Earth, that change occurred on Nov. 5. On that day, instruments aboard the spacecraft detected an increase in the strength of magnetic fields from the interstellar region, and the number of galactic cosmic rays, which originate from far beyond the solar system, jumped. At the same time, the solar wind petered out.
“We're not seeing the solar wind any more,” said John Richardson, the principal investigator for the plasma science experiment. “That means we must be in the interstellar medium.”
The transition to interstellar space did not exactly mirror Voyager 1’s.
Dr. Stone said that Voyager 2 is headed in a different direction, and six years later, the sun is at a different point in its 11-year cycle. “We’re learning a lot about the differences as well as the commonalities,” he said.
Voyager 2’s plasma science experiment provided the first direct look at what happens to the solar wind as the spacecraft enters interstellar space. (Voyager 1 was not able to gather that data, because its plasma instrument failed in 1980.)
Dr. Richardson said the speed of the plasma dropped quickly just in front of the boundary. “We thought it would be a much more gradual decrease,” he said.
The Voyager mission will continue for some time. “Both spacecraft are very healthy if you consider them senior citizens,” said Suzanne Dodd, the project manager.
Ms. Dodd said she hoped the spacecraft could reach their 50th anniversary in 2027, although not all of the instruments will still be operating. As the plutonium power sources aboard the two probes decay, they each lose 4 watts of power each year. Over time, the scientists will have to turn off some of the instruments.
While the Voyagers, speeding away at more than 34,000 miles per hour, are now in interstellar space, they are still considered to be within the solar system, because they have not yet slipped the grip of the sun’s gravity.
In about 300 years, Dr. Stone said, they will enter the Oort cloud, a distant reservoir of comets orbiting the sun. And it will take about 30,000 years for the two spacecraft to come out the far side of the Oort cloud and definitively leave the solar system. | 0.874861 | 3.473 |
Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons (protons and neutrons) and nuclei. According to current theories, the first nuclei were formed a few minutes after the Big Bang, through nuclear reactions in a process called Big Bang nucleosynthesis. After about 20 minutes, the universe had expanded and cooled to a point at which these high-energy collisions among nucleons ended, so only the fastest and simplest reactions occurred, leaving our universe containing about 75% hydrogen, 24% helium by mass. The rest is traces of other elements such as lithium and the hydrogen isotope deuterium. Nucleosynthesis in stars and their explosions later produced the variety of elements and isotopes that we have today, in a process called cosmic chemical evolution. The amounts of total mass in elements heavier than hydrogen and helium (called 'metals' by astrophysicists) remains small (few percent), so that the universe still has approximately the same composition.
Stars fuse light elements to heavier ones in their cores, giving off energy in the process known as stellar nucleosynthesis. Nuclear fusion reactions create many of the lighter elements, up to and including iron and nickel in the most massive stars. Products of stellar nucleosynthesis mostly remain trapped in stellar cores and remnants, except if ejected through stellar winds and explosions. The neutron capture reactions of the r-process and s-process create heavier elements, from iron upwards.
Supernova nucleosynthesis within exploding stars is largely responsible for the elements between oxygen and rubidium: from the ejection of elements produced during stellar nucleosynthesis; through explosive nucleosynthesis during the supernova explosion; and from the r-process (absorption of multiple neutrons) during the explosion.
Neutron star mergers are a recently-discovered candidate source of elements produced in the r-process. When two neutron stars collide, a significant amount of neutron-rich matter may be ejected, including newly formed nuclei.
Cosmic ray spallation is a process wherein cosmic rays impact the nuclei of the interstellar medium and fragment larger atomic nuclei. It is a significant source of the lighter nuclei, particularly 3He, 9Be and 10,11B, that are not created by stellar nucleosynthesis.
Cosmic ray bombardment of solar-system material found on Earth (including meteorites) also contribute to the presence on Earth of cosmogenic nuclides. On Earth, no new nuclei are produced, except in nuclear laboratories that reproduce the above nuclear reactions with particle beams. Natural radioactivity radiogenesis (decay) of long-lived, heavy, primordial radionuclides such as uranium and thorium is the only exception, leading to an increase in the daughter nuclei of such natural decays.
It is thought that the primordial nucleons themselves were formed from the quark–gluon plasma during the Big Bang as it cooled below two trillion degrees. A few minutes afterwards, starting with only protons and neutrons, nuclei up to lithium and beryllium (both with mass number 7) were formed, but hardly any other elements. Some boron may have been formed at this time, but the process stopped before significant carbon could be formed, as this element requires a far higher product of helium density and time than were present in the short nucleosynthesis period of the Big Bang. That fusion process essentially shut down at about 20 minutes, due to drops in temperature and density as the universe continued to expand. This first process, Big Bang nucleosynthesis, was the first type of nucleogenesis to occur in the universe, creating the so-called primordial elements.
A star formed in the early universe produces heavier elements by combining its lighter nuclei – hydrogen, helium, lithium, beryllium, and boron – which were found in the initial composition of the interstellar medium and hence the star. Interstellar gas therefore contains declining abundances of these light elements, which are present only by virtue of their nucleosynthesis during the Big Bang, and also cosmic ray spallation. These lighter elements in the present universe are therefore thought to have been produced through billions of years of cosmic ray (mostly high-energy proton) mediated breakup of heavier elements in interstellar gas and dust. The fragments of these cosmic-ray collisions include helium-3 and the stable isotopes of the light elements lithium, beryllium, and boron. Carbon was not made in the Big Bang, but was produced later in larger stars via the triple-alpha process.
The subsequent nucleosynthesis of heavier elements (Z ≥ 6, carbon and heavier elements) requires the extreme temperatures and pressures found within stars and supernovae. These processes began as hydrogen and helium from the Big Bang collapsed into the first stars after about 500 million years. Star formation has been occurring continuously in galaxies since that time. The entire variety of the elements and isotopes found in today's universe were created by Big Bang nucleosynthesis, stellar nucleosynthesis, supernova nucleosynthesis, and by nucleosynthesis in exotic events such as neutron star collisions. On Earth, mixing and evaporation has altered this composition to what is called the natural terrestrial composition. The heavier elements produced after the Big Bang range in atomic numbers from Z = 6 (carbon) to Z = 94 (plutonium). Synthesis of these elements occurred through nuclear reactions involving the strong and weak interactions among nuclei, and called nuclear fusion (including both rapid and slow multiple neutron capture), and include also nuclear fission and radioactive decays such as beta decay. The stability of atomic nuclei of different sizes and composition (i.e. numbers of neutrons and protons) plays an important role in the possible reactions among nuclei. Cosmic nucleosynthesis, therefore, is studied among researchers of astrophysics and nuclear physics ("nuclear astrophysics").
History of nucleosynthesis theory
The first ideas on nucleosynthesis were simply that the chemical elements were created at the beginning of the universe, but no rational physical scenario for this could be identified. Gradually it became clear that hydrogen and helium are much more abundant than any of the other elements. All the rest constitute less than 2% of the mass of the Solar System, and of other star systems as well. At the same time it was clear that oxygen and carbon were the next two most common elements, and also that there was a general trend toward high abundance of the light elements, especially those with isotopes composed of whole numbers of helium-4 nuclei (alpha nuclides).
Arthur Stanley Eddington first suggested in 1920, that stars obtain their energy by fusing hydrogen into helium and raised the possibility that the heavier elements may also form in stars. This idea was not generally accepted, as the nuclear mechanism was not understood. In the years immediately before World War II, Hans Bethe first elucidated those nuclear mechanisms by which hydrogen is fused into helium.
Fred Hoyle's original work on nucleosynthesis of heavier elements in stars, occurred just after World War II. His work explained the production of all heavier elements, starting from hydrogen. Hoyle proposed that hydrogen is continuously created in the universe from vacuum and energy, without need for universal beginning.
Hoyle's work explained how the abundances of the elements increased with time as the galaxy aged. Subsequently, Hoyle's picture was expanded during the 1960s by contributions from William A. Fowler, Alastair G. W. Cameron, and Donald D. Clayton, followed by many others. The seminal 1957 review paper by E. M. Burbidge, G. R. Burbidge, Fowler and Hoyle is a well-known summary of the state of the field in 1957. That paper defined new processes for the transformation of one heavy nucleus into others within stars, processes that could be documented by astronomers.
The Big Bang itself had been proposed in 1931, long before this period, by Georges Lemaître, a Belgian physicist, who suggested that the evident expansion of the Universe in time required that the Universe, if contracted backwards in time, would continue to do so until it could contract no further. This would bring all the mass of the Universe to a single point, a "primeval atom", to a state before which time and space did not exist. Hoyle is credited with coining the term "Big Bang" during a 1949 BBC radio broadcast, saying that Lemaître's theory was "based on the hypothesis that all the matter in the universe was created in one big bang at a particular time in the remote past." It is popularly reported that Hoyle intended this to be pejorative, but Hoyle explicitly denied this and said it was just a striking image meant to highlight the difference between the two models. Lemaître's model was needed to explain the existence of deuterium and nuclides between helium and carbon, as well as the fundamentally high amount of helium present, not only in stars but also in interstellar space. As it happened, both Lemaître and Hoyle's models of nucleosynthesis would be needed to explain the elemental abundances in the universe.
The goal of the theory of nucleosynthesis is to explain the vastly differing abundances of the chemical elements and their several isotopes from the perspective of natural processes. The primary stimulus to the development of this theory was the shape of a plot of the abundances versus the atomic number of the elements. Those abundances, when plotted on a graph as a function of atomic number, have a jagged sawtooth structure that varies by factors up to ten million. A very influential stimulus to nucleosynthesis research was an abundance table created by Hans Suess and Harold Urey that was based on the unfractionated abundances of the non-volatile elements found within unevolved meteorites. Such a graph of the abundances is displayed on a logarithmic scale below, where the dramatically jagged structure is visually suppressed by the many powers of ten spanned in the vertical scale of this graph.
There are a number of astrophysical processes which are believed to be responsible for nucleosynthesis. The majority of these occur within stars, and the chain of those nuclear fusion processes are known as hydrogen burning (via the proton-proton chain or the CNO cycle), helium burning, carbon burning, neon burning, oxygen burning and silicon burning. These processes are able to create elements up to and including iron and nickel. This is the region of nucleosynthesis within which the isotopes with the highest binding energy per nucleon are created. Heavier elements can be assembled within stars by a neutron capture process known as the s-process or in explosive environments, such as supernovae and neutron star mergers, by a number of other processes. Some of those others include the r-process, which involves rapid neutron captures, the rp-process, and the p-process (sometimes known as the gamma process), which results in the photodisintegration of existing nuclei.
Big Bang nucleosynthesis
Big Bang nucleosynthesis occurred within the first three minutes of the beginning of the universe and is responsible for much of the abundance of 1H (protium), 2H (D, deuterium), 3He (helium-3), and 4He (helium-4). Although 4He continues to be produced by stellar fusion and alpha decays and trace amounts of 1H continue to be produced by spallation and certain types of radioactive decay, most of the mass of the isotopes in the universe are thought to have been produced in the Big Bang. The nuclei of these elements, along with some 7Li and 7Be are considered to have been formed between 100 and 300 seconds after the Big Bang when the primordial quark–gluon plasma froze out to form protons and neutrons. Because of the very short period in which nucleosynthesis occurred before it was stopped by expansion and cooling (about 20 minutes), no elements heavier than beryllium (or possibly boron) could be formed. Elements formed during this time were in the plasma state, and did not cool to the state of neutral atoms until much later.
Stellar nucleosynthesis is the nuclear process by which new nuclei are produced. It occurs in stars during stellar evolution. It is responsible for the galactic abundances of elements from carbon to iron. Stars are thermonuclear furnaces in which H and He are fused into heavier nuclei by increasingly high temperatures as the composition of the core evolves. Of particular importance is carbon because its formation from He is a bottleneck in the entire process. Carbon is produced by the triple-alpha process in all stars. Carbon is also the main element that causes the release of free neutrons within stars, giving rise to the s-process, in which the slow absorption of neutrons converts iron into elements heavier than iron and nickel.
The products of stellar nucleosynthesis are generally dispersed into the interstellar gas through mass loss episodes and the stellar winds of low mass stars. The mass loss events can be witnessed today in the planetary nebulae phase of low-mass star evolution, and the explosive ending of stars, called supernovae, of those with more than eight times the mass of the Sun.
The first direct proof that nucleosynthesis occurs in stars was the astronomical observation that interstellar gas has become enriched with heavy elements as time passed. As a result, stars that were born from it late in the galaxy, formed with much higher initial heavy element abundances than those that had formed earlier. The detection of technetium in the atmosphere of a red giant star in 1952, by spectroscopy, provided the first evidence of nuclear activity within stars. Because technetium is radioactive, with a half-life much less than the age of the star, its abundance must reflect its recent creation within that star. Equally convincing evidence of the stellar origin of heavy elements is the large overabundances of specific stable elements found in stellar atmospheres of asymptotic giant branch stars. Observation of barium abundances some 20-50 times greater than found in unevolved stars is evidence of the operation of the s-process within such stars. Many modern proofs of stellar nucleosynthesis are provided by the isotopic compositions of stardust, solid grains that have condensed from the gases of individual stars and which have been extracted from meteorites. Stardust is one component of cosmic dust and is frequently called presolar grains. The measured isotopic compositions in stardust grains demonstrate many aspects of nucleosynthesis within the stars from which the grains condensed during the star's late-life mass-loss episodes.
Supernova nucleosynthesis occurs in the energetic environment in supernovae, in which the elements between silicon and nickel are synthesized in quasiequilibrium established during fast fusion that attaches by reciprocating balanced nuclear reactions to 28Si. Quasiequilibrium can be thought of as almost equilibrium except for a high abundance of the 28Si nuclei in the feverishly burning mix. This concept was the most important discovery in nucleosynthesis theory of the intermediate-mass elements since Hoyle's 1954 paper because it provided an overarching understanding of the abundant and chemically important elements between silicon (A = 28) and nickel (A = 60). It replaced the incorrect although much cited alpha process of the B2FH paper, which inadvertently obscured Hoyle's 1954 theory. Further nucleosynthesis processes can occur, in particular the r-process (rapid process) described by the B2FH paper and first calculated by Seeger, Fowler and Clayton, in which the most neutron-rich isotopes of elements heavier than nickel are produced by rapid absorption of free neutrons. The creation of free neutrons by electron capture during the rapid compression of the supernova core along with the assembly of some neutron-rich seed nuclei makes the r-process a primary process, and one that can occur even in a star of pure H and He. This is in contrast to the B2FH designation of the process as a secondary process. This promising scenario, though generally supported by supernova experts, has yet to achieve a satisfactory calculation of r-process abundances. The primary r-process has been confirmed by astronomers who had observed old stars born when galactic metallicity was still small, that nonetheless contain their complement of r-process nuclei; thereby demonstrating that the metallicity is a product of an internal process. The r-process is responsible for our natural cohort of radioactive elements, such as uranium and thorium, as well as the most neutron-rich isotopes of each heavy element.
Explosive nucleosynthesis occurs too rapidly for radioactive decay to decrease the number of neutrons, so that many abundant isotopes with equal and even numbers of protons and neutrons are synthesized by the silicon quasi-equilibrium process. During this process, the burning of oxygen and silicon fuses nuclei that themselves have equal numbers of protons and neutrons to produce nuclides which consist of whole numbers of helium nuclei, up to 15 (representing 60Ni). Such multiple-alpha-particle nuclides are totally stable up to 40Ca (made of 10 helium nuclei), but heavier nuclei with equal and even numbers of protons and neutrons are tightly bound but unstable. The quasi-equilibrium produces radioactive isobars 44Ti, 48Cr, 52Fe, and 56Ni, which (except 44Ti) are created in abundance but decay after the explosion and leave the most stable isotope of the corresponding element at the same atomic weight. The most abundant and extant isotopes of elements produced in this way are 48Ti, 52Cr, and 56Fe. These decays are accompanied by the emission of gamma-rays (radiation from the nucleus), whose spectroscopic lines can be used to identify the isotope created by the decay. The detection of these emission lines were an important early product of gamma-ray astronomy.
The most convincing proof of explosive nucleosynthesis in supernovae occurred in 1987 when those gamma-ray lines were detected emerging from supernova 1987A. Gamma-ray lines identifying 56Co and 57Co nuclei, whose half-lives limit their age to about a year, proved that their radioactive cobalt parents created them. This nuclear astronomy observation was predicted in 1969 as a way to confirm explosive nucleosynthesis of the elements, and that prediction played an important role in the planning for NASA's Compton Gamma-Ray Observatory.
Other proofs of explosive nucleosynthesis are found within the stardust grains that condensed within the interiors of supernovae as they expanded and cooled. Stardust grains are one component of cosmic dust. In particular, radioactive 44Ti was measured to be very abundant within supernova stardust grains at the time they condensed during the supernova expansion. This confirmed a 1975 prediction of the identification of supernova stardust (SUNOCONs), which became part of the pantheon of presolar grains. Other unusual isotopic ratios within these grains reveal many specific aspects of explosive nucleosynthesis.
Neutron star collision
Neutron star collisions are now believed to be the main source of r-process elements. Being neutron-rich by definition, collisions of this type had been suspected of being a source of such elements, but definitive evidence was difficult to obtain. In 2017 strong evidence emerged, when LIGO, VIRGO, the Fermi Gamma-ray Space Telescope and INTEGRAL, along with a collaboration of many observatories around the world, detected both gravitational wave and electromagnetic signatures of a likely neutron star collision, GW170817, and subsequently detected signals of numerous heavy elements such as gold as the ejected material began to cool.
Black hole accretion disk nucleosynthesis
Cosmic ray spallation
Cosmic ray spallation process reduces the atomic weight of interstellar matter by the impact with cosmic rays, to produce some of the lightest elements present in the universe (though not a significant amount of deuterium). Most notably spallation is believed to be responsible for the generation of almost all of 3He and the elements lithium, beryllium, and boron, although some 7
are thought to have been produced in the Big Bang. The spallation process results from the impact of cosmic rays (mostly fast protons) against the interstellar medium. These impacts fragment carbon, nitrogen, and oxygen nuclei present. The process results in the light elements beryllium, boron, and lithium in the cosmos at much greater abundances than they are found within solar atmospheres. The quantities of the light elements 1H and 4He produced by spallation are negligible relative to their primordial abundance.
Beryllium and boron are not significantly produced by stellar fusion processes, since 8Be is not particle-bound.
Theories of nucleosynthesis are tested by calculating isotope abundances and comparing those results with observed abundances. Isotope abundances are typically calculated from the transition rates between isotopes in a network. Often these calculations can be simplified as a few key reactions control the rate of other reactions.
Minor mechanisms and processes
Tiny amounts of certain nuclides are produced on Earth by artificial means. Those are our primary source, for example, of technetium. However, some nuclides are also produced by a number of natural means that have continued after primordial elements were in place. These often act to create new elements in ways that can be used to date rocks or to trace the source of geological processes. Although these processes do not produce the nuclides in abundance, they are assumed to be the entire source of the existing natural supply of those nuclides.
These mechanisms include:
- Radioactive decay may lead to radiogenic daughter nuclides. The nuclear decay of many long-lived primordial isotopes, especially uranium-235, uranium-238, and thorium-232 produce many intermediate daughter nuclides before they too finally decay to isotopes of lead. The Earth's natural supply of elements like radon and polonium is via this mechanism. The atmosphere's supply of argon-40 is due mostly to the radioactive decay of potassium-40 in the time since the formation of the Earth. Little of the atmospheric argon is primordial. Helium-4 is produced by alpha-decay, and the helium trapped in Earth's crust is also mostly non-primordial. In other types of radioactive decay, such as cluster decay, larger species of nuclei are ejected (for example, neon-20), and these eventually become newly formed stable atoms.
- Radioactive decay may lead to spontaneous fission. This is not cluster decay, as the fission products may be split among nearly any type of atom. Thorium-232, uranium-235, and uranium-238 are primordial isotopes that undergo spontaneous fission. Natural technetium and promethium are produced in this manner.
- Nuclear reactions. Naturally-occurring nuclear reactions powered by radioactive decay give rise to so-called nucleogenic nuclides. This process happens when an energetic particle from radioactive decay, often an alpha particle, reacts with a nucleus of another atom to change the nucleus into another nuclide. This process may also cause the production of further subatomic particles, such as neutrons. Neutrons can also be produced in spontaneous fission and by neutron emission. These neutrons can then go on to produce other nuclides via neutron-induced fission, or by neutron capture. For example, some stable isotopes such as neon-21 and neon-22 are produced by several routes of nucleogenic synthesis, and thus only part of their abundance is primordial.
- Nuclear reactions due to cosmic rays. By convention, these reaction-products are not termed "nucleogenic" nuclides, but rather cosmogenic nuclides. Cosmic rays continue to produce new elements on Earth by the same cosmogenic processes discussed above that produce primordial beryllium and boron. One important example is carbon-14, produced from nitrogen-14 in the atmosphere by cosmic rays. Iodine-129 is another example.
- Stellar evolution
- Supernova nucleosynthesis
- Cosmic dust
- Extinct isotopes of superheavy elements
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Newly found galaxy collisions in the nearby universe. Image credit: NOAO. Click to enlarge
More than half of the largest galaxies in the nearby universe have collided and merged with another galaxy in the past two billion years, according to a new study using hundreds of images from two of the deepest sky surveys ever conducted.
The idea of large galaxies being assembled primarily by mergers rather than evolving by themselves in isolation has grown to dominate cosmological thinking. However, a troubling inconsistency within this general theory has been that the most massive galaxies appear to be the oldest, leaving minimal time since the Big Bang for the mergers to have occurred.
?Our study found these common massive galaxies do form by mergers. It is just that the mergers happen quickly, and the features that reveal the mergers are very faint and therefore difficult to detect,? says Pieter van Dokkum of Yale University, lead author of the paper in the December 2005 issue of the Astronomical Journal.
The paper uses two recent deep surveys done with the National Science Foundation?s 4-meter telescopes at Kitt Peak National Observatory and Cerro Tololo Inter-American Observatory, known as the NOAO Deep Wide-Field Survey and the Multiwavelength Survey by Yale/Chile. Together, these surveys covered an area of the sky 50 times larger than the size of the full Moon.
?We needed data that are very deep over a very wide area to provide statistically meaningful evidence,? van Dokkum explains. ?As happens so often in science, fresh observations helped inform new conclusions.?
Van Dokkum used images from the two surveys to look for telltale tidal features around 126 nearby red galaxies, a color selection biased to select the most massive galaxies in the local universe. These faint tidal features turn out to be quite common, with 53 percent of the galaxies showing tails, broad fans of stars trailing behind them or other obvious asymmetries.
?This implies that there is a galaxy that has endured a major collision and subsequent merger event for every single other ?normal? undisturbed field galaxy,? van Dokkum notes. ?Remarkably, the collisions that precede the mergers are still ongoing in many cases. This allows us to study galaxies before, during, and after the collisions.?
Though there are not many direct star-to-star encounters in this merger process, such galaxy collisions can have profound effects on star formation rates and the shape of the resulting galaxy.
These mergers do not resemble the spectacular mergers of blue spiral galaxies that are featured in several popular Hubble Space Telescope images. But these red galaxy mergers appear to be much more common. Their ubiquity represents a direct confirmation of predictions by the most common models for the formation of large-scale structure in the Universe, with the added benefit of helping solve the apparent-age problem.
?In the past, people equated stellar age with the age of the galaxy,? van Dokkum explains. ?We have found that, though their stars are generally old, the galaxies that result from these mergers are relatively young.?
It is not yet understood why the merging process does not lead to enhanced star formation in the colliding galaxies. It may be that massive black holes in the centers of the galaxies provide the energy to heat or expel the gas that needs to be able to cool in order to form new stars. Ongoing detailed study of the newly found mergers will provide better insight into the roles that black holes play in the formation and evolution of galaxies.
A series of images of different galaxies in this study that, taken together, represent a time sequence of a typical red galaxy merger, is available here. More information, including an animation of the mergers, is available from Yale University.
Based in Tucson, AZ, the National Optical Astronomy Observatory (NOAO) consists of Kitt Peak National Observatory near Tucson, AZ, Cerro Tololo Inter-American Observatory near La Serena, Chile, and the NOAO Gemini Science Center. NOAO is operated by the Association of Universities for Research in Astronomy (AURA) Inc., under a cooperative agreement with the National Science Foundation.
Original Source: NOAO News Release | 0.842292 | 4.054777 |
The Biggest Full Moon of the Year Rises on Tuesday — Here's How and When to See It (Video)
2020’s brightest and best supermoon will light up the sky on Tuesday evening.
So far, 2020 has been a year of supermoons. First there was February’s “Super Snow Moon,” which was quickly followed by March’s “Super Worm Moon.” However, these were mere celestial warm-up acts. Now comes the third – and not even the last –supermoon of the year, the “Super Pink Moon.” Lighting up the sky on the evening of Tuesday, April 7, the Super Pink Moon is destined to be the biggest, brightest, and best supermoon of the year.
Here’s how, when, and where to see the Super Pink Moon.
Related: More space travel and astronomy news
What is the Super Pink Moon?
The Super Pink Moon is April’s full moon, which just happens to coincide perfectly with a specific point in the moon’s orbit that brings our satellite the closest it comes to us in the entire year. That point is called perigee, and when it occurs, the moon can be around 14% bigger in apparent size than usual. To appreciate its larger apparent size, it’s best to look east at moonrise (which is around sunset for a full moon) or west at moonset (close to sunrise). When a supermoon is close to the horizon, you can easily appreciate its extra size and brightness.
Why is it called the Super Pink Moon?
It’s called “super” because on Tuesday, April 7, the moon will be the closest it gets to Earth in all of 2020. A “supermoon” is not an astronomical term, but it’s generally defined as when the moon is less than 223,694 miles from Earth.
Meanwhile, April’s full moon is traditionally known as a “Pink Moon” in North America because it coincides with the springtime blooms of the “moss pink” wildflower, though it’s also been called the Sprouting Grass Moon, Fish Moon, Hare Moon, and Egg Moon.
What does the Super Pink Moon have to do with Easter?
Few people realize that Easter is actually a lunar festival. April’s full moon is known as the Paschal Moon (“paschal” meaning “relating to Easter”) by the Christian church, which uses it to determine the date of Easter. Traditionally, Easter is held on the first Sunday after the first full moon on or after the spring equinox. Since the spring equinox occurred on March 20, and the Super Pink Moon falls on April 7, Easter Sunday will be held on April 12.
When are the best times to see the Super Pink Moon?
The best time to view a full moon — whether it's a supermoon or not— is always as it appears on the eastern horizon. If you have an east-facing backyard or view from a window (the higher the better), get in position on Tuesday, April 7 at 7:07 p.m. EDT if you’re in New York and at 7:11 p.m. PDT if you're in Los Angeles. Sunset is a few minutes later in both locations, so it should look spectacular. For any other locations, check the exact time of your local moonrise.
Will the Super Pink Moon look pink?
Not specifically — that’s not why it's called a “Pink Moon”— but if you catch it at moonrise, it can take on a rosy, pinkish-orange hue for a few minutes. In any case, a full supermoon-rise is always a magical sight in a clear sky.
When is the next full moon?
The next full moon will occur on May 7, 2020. Though it won’t be quite as large as the Super Pink Moon, the timing of the moon’s full phase and its perigee are close enough for May’s full moon to be called the “Super Flower Moon”— the fourth and final supermoon of 2020. | 0.853065 | 3.183815 |
While in orbit for 25 years, the Hubble Space Telescope took about a thousand photographs, but the famous galaxy-filled image of the Ultra-Deep Field (an image of a small region of space made up of data from the Hubble Space Telescope from September 24, 2003 year January 16, 2004) stands out from the rest.
The image was taken during a two-month observation of a small part of the sky in the constellation Pec. Astronomers specifically chose this relatively starless region.
But it turned out that this section of the sky is filled with 10,000 galaxies, challenging the theory of the formation of galaxies in the first days of the universe. The image was later supplemented with even more detailed photographs taken by the new Hubble infrared and visible light cameras, which made it possible to see the galaxies that were formed 1 billion years after the Big Bang.
“The Ultra-Deep Field image really changes our understanding of the history of the Universe,” said astronomer Jennifer Lotz from the Space Telescope Research Institute in Baltimore at a recent meeting of the American Astronomical Society.
However, in addition to these galaxies, the background of the image remains dark, but this is not because there is nothing there, just the light emitted from more distant objects remains inaccessible to the Hubble equipment.
James Webb Space Telescope through the eyes of an artist
This work will be continued by Hubble’s successor with the James Webb Space Telescope or JWST (the James Webb Space Telescope), which is scheduled to launch in October 2018. JWST is different from other infrared telescopes, such as the NASA Spitzer space telescope and the Herschel European Space Observatory, the size of its main mirror, the area of which allows it to collect more photons of light.
The 7, 9-foot mirror of the Hubble telescope was real art when it was designed and built in the late 1970s. The Spitzer telescope mirror is 2.75 feet across. However, the mirror of the telescope of James Webb is amazing: 21 feet! To start it, the hexagonal mirror segments will be folded like origami.
The ability to see the first light-emitting objects that appeared immediately after the Big Bang is one of hundreds of studies designed for JWST.
Infrared light, which the human eye cannot see, but which we perceive as heat, opens the door for direct observation of young stars and the development of exoplanets.
"JWST will help make a huge contribution," astronomer Rupali Chandar of the University of Toledo said at a symposium this week in Baltimore. Based on Hubble data, Chandar suggests that the difference between old globular star clusters and young open clusters is due only to the time of their evolution, and not to the nature of their origin.
“Hubble showed us that this dichotomy really does not exist,” said Chandar, adding that JWST can see not only relatively close galactic clusters, but also those that originated when the Universe was in its infancy.
Astronomers will also use the James Webb telescope to study chemicals in the atmosphere of planets located outside the solar system.
As well as the Hubble and Kepler telescopes, JWST is able to see the planets passing in front of their parent stars. During such transits, starlight passes through the atmosphere of an exoplanet. If this happens, the light that eventually reaches the Earth will contain the chemical fingerprints of any atmospheric gases. | 0.836824 | 3.94154 |
April 11, 2019
Earth and the Sun share an electric circuit.
“Everybody talks about the weather, but nobody does anything about it.”
— Charles Dudley Warner
The Magnetospheric Multiscale satellites were launched March 12, 2015 on a mission to study Earth’s electromagnetic fields. The MMS constellation, as well as the Geospace Electrodynamic Connections mission and the Magnetospheric Constellation mission, are part of a widespread, international consortium known as the Global Electric Circuit Project.
MMS, along with TIMED, Cluster, ARTEMIS, and other satellites, is analyzing the Sun’s influence on Earth’s thermosphere, about 100 kilometers in altitude. The solar wind of charged particles first interacts with atmospheric particles in the thermosphere. However, that region is not well understood, especially since TIMED detected a tenfold decline in the thermosphere’s temperature since 2002.
Temperatures in the thermosphere are the result of solar radiation. Atmospheric oxygen becomes ionized when it absorbs ultraviolet light, so it is electrically charged. That energy increases molecular motion, otherwise known as “heat”. Although a mercury thermometer would register temperatures below zero in the thermosphere, it can be over 1500 Celsius during solar maximum.
As written previously, there is an electric potential between the ground and the ionosphere, creating what is called the “fair weather field”, which generates two picoamps per each square meter of ground. Using the formula, Q = 4π R2 εo E = R2 Eo / k, when εo = permittivity of free space (8.85 x 10-12 F/m), it can be shown that Earth is negatively charged with almost 500,000 Coulomb.
Earth is part of a circuit in the Solar System, so the 22 year solar cycle influences Earth’s environment. Although solar energy varies over time, corresponding with sunspot cycles, it amounts to less than one-tenth of one percent. Electricity from space is injected into the thermosphere along massive Birkeland currents. Electric charge flow declines in amperage when the solar wind is at a minimum, which, in turn, decreases the strength of Earth’s magnetosphere. As it declines in strength, it is less able to deflect cosmic rays. Since cosmic rays are charge carriers, collisions between charged and neutral particles drag air molecules along with them, influencing low level cloud cover. More clouds reflect more radiation from the Sun back to space—clouds are white because they are acting like mirrors to all forms of visible light. More reflection means less solar energy, more cloud cover, and so on.
The Sun is returning to a more passive state, otherwise called, “solar minimum”. Changes in the correspondence between electric field strength, cosmic rays, Earth’s magnetosphere, cloud cover, and climate are continuing to be investigated. The Sun’s influence on Earth’s overall climate, as well as short term weather events, can no longer be ignored. | 0.82073 | 3.881358 |
Aurora from Saturn moon 'circuit'
Saturn enjoys a flickering "Northern Lights" phenomenon thanks to a flow of electrons to and from its moon Enceladus, researchers say.
A report in Nature suggests these aurora would be faint, and in the ultraviolet part of the light spectrum.
The find by the Cassini spacecraft is similar to the electrical "circuit" between Jupiter and three of its moons.
Electrons flow to and from Enceladus' poles in a vast loop, and aurora result where they hit Saturn's magnetic field.
The aurora creation process is similar to that which happens at high latitudes on Earth; here, the paths of fast-moving charged particles from the solar wind are curved by the Earth's magnetic field and emit the displays we know as the Northern and Southern lights.
In contrast, the fields created by Jupiter and Saturn envelop the planets' moons, and what is known as electrodynamic coupling brings particles directly from the moons, completing what is actually an electrical circuit.
The mechanism behind Jupiter's aurora is presumed to be sulphur from its moon Io's volcanic activity, split by sunlight into electrons and ions.
On Saturn's moon Enceladus, however, the suspected source of electrons is "cryovolcanism" - volcanic activity that shoots up liquids or, in Enceladus' case, salty ice.
The Cassini spacecraft has been studying Saturn and its moons since it arrived in 2004, having made 12 close passes of Enceladus.
On the close encounter that occurred on 11 August 2008, scientists detected a great stream of ions (molecules with electrons removed) coming from the moon.
Lead author of the study Abigail Rymer of Johns Hopkins University confirmed that the ions were associated with the vast electron loops.
"I immediately pulled up the electron data and, sure enough, there was a very strong electron beam propagating away from Saturn toward Enceladus," Dr Rymer said.
"It was actually a fairly rare opportunity to capture that, since when Cassini flies close to a moon we are generally looking at the moon -- not away from it."
The team was able to collect images of the point where the loops re-enter Saturn's magnetic field, interacting with it to form aurora.
"I think it's a very exciting, very interesting discovery," said Andrew Coates, a co-author of the paper from University College London.
"Five or six years ago we didn't know that Enceladus was putting any material into the Solar System - now we get exciting effects like these magnetic and electric current links into the ionosphere of Saturn, producing this (aurora) spot," he told BBC News.
The team says that the aurora are about a tenth the intensity of those seen on Jupiter, and that they vary widely in intensity - by as much as a factor of three.
That, they assume, is down to variations in the output of the geysers that are feeding the process - a process that Professor Coates says seems likely to be happening elsewhere.
"It's probably a universal process; it could be something that's happening in other places like [Neptune's moon] Triton, or extrasolar planets where there are 'hot Jupiters'." | 0.828454 | 3.881023 |
Five Billion Years of Solitude: The Search for Life Among the Stars starts off strong with the history of the human quest to understand the universe, going back to the ancient Greeks:
Atoms and void, Democritus argued, were all that existed, and were thus the source of all things—including living beings and their thoughts and sensory perceptions. In a universe infinite in space and time, he said, the endless dance of atoms would inevitably lead to countless other worlds and other lives, all in an eternal process of growth and decay. Not all worlds would be like ours—some would be too inhospitable for life, and others would be even more bountiful than Earth. We should be universally cheerful, Democritus believed, at our fortune to exist in a welcoming world with so many pleasures. His constant mirth at humanity’s tragicomic existence led his contemporaries to call him “the laughing philosopher.” Looking up at the dark Aegean sky, Democritus speculated that the stars, like everything else, were not made of a special celestial substance, but of atoms. They were simply suns, much farther away than our own, some so distant that in aggregate they formed the Milky Way’s pale glow.
In 1963 General Dynamics buried a time capsule with predictions about life in 2063 A.D.:
Mercury astronaut John Glenn, the first American to orbit the planet, predicted that within a century we would have linked atomic power plants to “anti-gravity devices,” fundamentally rewriting the laws of physics and revolutionizing life and transportation on Earth and in the heavens alike. Another Mercury astronaut, Scott Carpenter, expressed his hope that the anti-gravity “scheme” would help humans colonize the Moon, the Martian moon Phobos, and Mars. The prominent astronomer Fred Whipple suggested that Earth’s population would have stabilized at 100 billion, and that planetary-scale engineering of Mars would have altered the Red Planet’s climate to allow its 700,000 inhabitants to be self-sufficient. The director of NASA’s Office of Manned Space Flight, Dyer Brainerd Holmes, suggested that in 2063 crewed vehicles would be reaching “velocities approaching the speed of light,” and that society would be debating whether to send humans to nearby stars. A majority of the twenty-nine respondents predicted a peaceful world, harmoniously unified under a democratic world government and freed from resource scarcity.
The strangest entry of all was the long, decidedly pessimistic response of Harold Urey, the Nobel-laureate chemist. … He lamented how technological progress had cut off his children from many of the bucolic joys of his own upbringing, such as riding “in a sleigh behind a matched team of blacks, on a clear night with stars above and white snow around . . . nestled warm and cozy beneath a buffalo robe.” Looking ahead, Urey glimpsed a not-too-distant future in which things could fall apart, when the centers of the modern world could not hold, a time when growth would stagnate. He postulated no proximate causes other than already-existing cracks in civilization’s façade. Schemes for world government were unfavorable, he believed, because governments tended to grow bloated and cumbersome from “fantastic national debt” that outstripped both inflation and revenue. The ruinous deficits would be produced by “the curious psychology of politicians” paired with “the development of war machines by applied scientific methods,” and would be exacerbated by the need to provide healthcare and social security for a large, aging populace. Turning society over entirely to the whims of large, private corporations was no alternative, Urey observed, because companies would inevitably conspire to pursue short-term profits against the public interest and common good. through some uneasy and uncertain balance between government regulation and private enterprise could the status quo of growth be maintained. Even then, it could not be maintained indefinitely. [emphasis added]
The author, Lee Billings, writes about how California’s state government has been starved of revenue:
Housing prices and infrastructural necessities rose as capital continued pouring in, and property taxes rose with them, until in the 1970s wealthy, established Californians rebelled. They voted to keep property taxes artificially low, and shifted the state toward a dysfunctional political culture where time and time again voter-led “ballot initiatives” earmarked spending while also eliminating sources of revenue. Since the turn of the millennium, the state had been in near-constant budgetary crisis. When the real-estate bubble burst in 2007, it helped kick off the Great Recession of 2008, which reduced California’s coffers to catastrophic lows. Funding was slashed for public assistance to the poor and disabled, for state colleges and courts, for municipal emergency services, and more.
Billings doesn’t stop to ask the question that we’d expect scientists to ask: “Compared to what?” Since California is the 4th highest tax state in the U.S., as a percentage of residents’ income collected, why can’t they afford to run their schools, fire departments, etc. like the rest of the states do?
An important question for calculating the probability of finding an extraterrestrial civilization is how long such a civilization might last. Billings devotes a lot of the book to speculating that our penchant for digging coal, oil, and natural gas out of the ground and setting it on fire will result in, not simply global warming, but extinction of the human species. The experts he interviews, however, contradict this perspective: James Kasting says “We’re squandering Earth’s resources. We’re doing terrible things to biodiversity. I have no doubt we’re living in the midst of another major mass extinction of our own making. I take what little comfort I can from knowing we probably can’t drive life itself to extinction or push the planet into a runaway greenhouse. The carbonate-silicate cycle will erase the fossil-fuel pulse in a timescale of a million years, and then the long decline of atmospheric CO2 will continue.”
Billings describes NASA as the world’s most wasteful non-military enterprise:
The chimeric [Space Shuttle] vehicles that finally emerged were elegant, versatile, and irreparably flawed. Instead of achieving 50 flights per year as originally projected, the entire shuttle fleet collectively flew 135 times during the program’s thirty-year lifetime. The shuttles lofted payloads to orbit at a cost estimated anywhere between $18,000 and $60,000 per kilogram—more expensive than the expendable launchers they were built to replace. The shuttle program’s failures came in part from the fact that many of its “reusable” components required extensive refurbishment by a small standing army of technicians after each flight. They also came from the shuttle’s inescapable operational risks, which led to the tragic losses of two orbiters and crews. Space shuttle Challenger exploded shortly after launch in 1986 due to a sealant failure in one of its boosters, and the Columbia disintegrated during reentry in 2003 after a piece of foam insulation punctured a wing. Politically driven compromises made early in the shuttle design process proved to be major factors in both disasters.
The Shuttle does prove useful for repairing the Hubble Space Telescope, but Billings notes that “Critics of NASA’s human spaceflight program noted that for the estimated cost of each shuttle servicing mission, an entirely new Hubble could have been built and launched via expendable rockets, all without risking human lives,…”
Why can’t NASA find planets with fancy new orbiting instruments? “As was typical of so many government projects begun during Bush’s administration, the only thing Constellation seemed to excel at was transferring billions of dollars of public, federal money into the coffers of well-connected private contractors who too often delivered precious little in return. … After years of middling results and more than $10 billion in expenditures, Constellation was canceled in 2010 by President Barack Obama… The [planet finding] mission [of some other experiment] was repeatedly downgraded and its launch continually delayed, piling on empty expenses until, after consuming more than half a billion dollars, in 2010 SIM was quietly cancelled and its nearly complete flight hardware junked or repurposed.”
After describing NASA’s seemingly inexhaustible ability to squander money, Billings expresses dismay that the public doesn’t want to fund more exoplanetary research. Billings seems to think that it is impossible to get rich people to fund astronomy but does not justify this belief. Given that rich people funded nearly all of the work of astronomers for thousands of years, shouldn’t at least one of the world’s 1645 billionaires want to fund a planet-finding satellite? A planet, once found and named, is forever. Poverty or disease relieved today may return tomorrow.
Readers: Why don’t we see more private space-based science? My first job was writing software to analyze data from the Pioneer Venus orbiter. The mission cost about $225 million in late 1970s dollars. Presumably some costs have gone up since then but other costs should be lower, e.g., the $1 million PDP-11/70 that I used to analyze the data could be replaced with a smartphone app. Private funds are contributing significantly to the $1 billion telescope taking shape in the Chilean desert (article). Why wouldn’t private donors want to escape the Earth’s atmosphere? [coincidentally, the New York Times has a March 14 article on private funding of science]
There are some thought-provoking questions in this book but I can’t recommend it overall. If you’re desperate for something about how a planet can undergo dramatic change, check out Snowball Earth. | 0.898912 | 3.163841 |
In the primordial Solar System the most plausible sources of the water accreted by the Earth were in the outer asteroid belt, in the giant planet regions and in the Kuiper belt. We investigate the implications on the origin of Earth's water of dynamical models of primordial evolution of solar system bodies and check them with respect to chemical constraints. We find that it is plausible that the Earth accreted water all along its formation, from the early phases when the solar nebula was still present to the late stages of gas-free sweepup of scattered planetesimals. Asteroids and the comets from the Jupiter-Saturn region were the first water deliverers, when the Earth was less than half its present mass. The bulk of the water presently on Earth was carried by a few planetary embryos, originally formed in the outer asteroid belt and accreted by the Earth at the final stage of its formation. Finally, a late veneer, accounting for at most 10% of the present water mass, occurred due to comets from the Uranus-Neptune region and from the Kuiper belt. The net result of accretion from these several reservoirs is that the water on Earth had essentially the D/H ratio typical of the water condensed in the outer asteroid belt. This is in agreement with the observation that the D/H ratio in the oceans is very close to the mean value of the D/H ratio of the water inclusions in carbonaceous chondrites. | 0.870357 | 3.401245 |
A museum in Maine is offering $25,000 for a piece of meteorite that struck St. Louis, FOX2Now reported. The object was observed mid-flight and thought to have come from the asteroid belt between Mars and Jupiter. The museum’s reward shows our fascination with space and its astronomical objects.
According to the FOX2Now article, the Maine Mineral and Gem Museum announced that the cash reward of $25,000 would be given to the first person who brought in a piece of the meteorite, weighing at least one kilogram, which is just over two pounds. The article goes on to say that the museum was so quick to express interest in the meteorite because its grand opening is December 12, one month to the day after the meteorite reached Earth from outer space. While residents of St. Louis and surrounding areas search the great outdoors for pieces of the space rock, the interest in the celestial object serves as another reminder of humanity’s unending love for astronomical objects from outer space.
There are so many types of objects in outer space—whether natural or man-made—that the appropriate terminology for them can seem daunting. After all, humanity looked to the night sky long before we had invented complex verbal language or had discovered what the objects were. Comets may be the best example of this sort of astronomical confusion-turned-definition.
“Comets appear as diffuse luminous patches in the sky, often with long tails,” said Dr. Alex Filippenko, Professor of Astronomy and the Richard and Rhoda Goldman Distinguished Professor in the Physical Sciences at the University of California, Berkeley. “A comet is basically a dirty snowball or an icy dirt ball—a ball of rock, dust, and ice that comes in from the deep freeze of the outer Solar System. The ice consists of frozen water, ammonia, methane, carbon dioxide, and other molecules that evaporate away as the comet approaches the Sun, because the comet gets heated.”
The long tail that characterizes most comets is composed of this dirt and ice that breaks away from the comet and is then left behind. Dr. Filippenko was quick to point out that the idea of the comet’s tail “burning” is a misconception. Its fiery appearance owes to sunlight reflecting off the scattering pieces; it’s not the only misconception we’ve made with comets.
“The tail of the comet kind of looks like long hair and this led to the name comet, which comes from the Greek for ‘long-haired star,’ Aster cometes,” Dr. Filippenko said.
Meteors and Meteorites
Meteors are often called “falling stars” or “shooting stars,” but they have little or nothing to do with stars.
“Meteors are actually small pebbles or chunks of ice from the asteroid belt or comet debris,” Dr. Filippenko said. “When they are wandering through the Solar System, they are called meteoroids. When meteoroids enter Earth’s atmosphere at a height of around 60 or 70 miles, roughly the top part of the mesosphere, they compress the air and heat it a lot, causing it to glow brightly.”
In order to understand meteor showers, it can be easier to think of things the other way around, with the Earth rising to meet them.
“What’s happening during a meteor shower is that Earth is passing through the orbit of an old disintegrated comet or a younger comet that is shedding lots of rocks and ice clumps,” Dr. Filippenko said. “A given shower always happens at about the same time of year, because Earth crosses the orbit of a disintegrating comet at about the same time each year.”
With a better understanding of what we see drifting through the night sky, we can more fully appreciate all the cosmos has to offer—even if it doesn’t net us $25,000.
Dr. Alex Filippenko contributed to this article. Dr. Filippenko is Professor of Astronomy and the Richard and Rhoda Goldman Distinguished Professor in the Physical Sciences at the University of California, Berkeley. He earned his B.A. in Physics from the University of California, Santa Barbara, and his Ph.D. in Astronomy from the California Institute of Technology. | 0.880399 | 3.185629 |
The Chandra X-Ray Observatory has taken a brand new, deep look inside the Tycho Supernova Remnant and found a pattern of X-ray “stripes.” The three-dimensional-like nature of this incredible image notwithstanding, nothing like these stripe-like features has ever been seen before inside the leftovers of an exploding star, but astronomers believe they could explain how some cosmic rays are created. Additionally, the stripes provide support for a theory about how magnetic fields can be dramatically amplified in supernova blast waves.
Cosmic rays are made up of electrons, positrons and atomic nuclei and they constantly bombard the Earth. In their near light-speed journey across the galaxy, the particles are deflected by magnetic fields, which scramble their paths and mask their origins. Supernova remnants have long been thought to be the source of cosmic rays, up to the “knee” of the cosmic ray spectrum at 10^15 eV, but so far, no specific sources have been located.
In 2010, the Fermi gamma ray telescope found evidence – also from supernova remnants – where radiation is emitted that is a billion times more energetic than visible light.
But the stripes seen by Chandra, shown above in high-energy X-rays (blue), are thought to be regions where the turbulence is greater and the magnetic fields more tangled than surrounding areas. Electrons become trapped in these regions and emit X-rays as they spiral around the magnetic field lines. Regions with enhanced turbulence and magnetic fields were expected in supernova remnants, but the motion of the most energetic particles — mostly protons — was predicted to leave a messy network of holes and dense walls corresponding to weak and strong regions of magnetic fields, respectively.
Therefore, the detection of stripes was a surprise.
The size of the holes was expected to correspond to the radius of the spiraling motion of the highest energy protons in the supernova remnant. These energies equal the highest energies of cosmic rays thought to be produced in our Galaxy. The spacing between the stripes corresponds to this size, providing evidence for the existence of these extremely energetic protons.
“We interpret the stripes as evidence for acceleration of particles to near the knee of the CR spectrum in regions of enhanced magnetic turbulence, while the observed highly ordered pattern of these features provides a new challenge to models of diffusive shock acceleration,” writes Kristoffer A. Eriksen and his team in their paper, “Evidence For Particle Acceleration to the Knee of the Cosmic Ray Spectrum in Tycho’s Supernova Remnant.” | 0.869764 | 4.162308 |
When objects get hot, they give off light. You can notice this with glowing coals, incandescent light bulbs and the like. It turns out the light a hot object gives off follows a specific pattern known as a blackbody spectrum. If you look at the intensity of a blackbody spectrum as a function of its color (or wavelength), you notice shape of the function depends on the temperature of the object giving off light.
Since the whole universe was in hot dense state at the beginning, it released a great deal of light. As the universe expanded its temperature cooled, but we still see a blackbody spectrum radiating from every direction. This is known as the cosmic microwave background (CMB).
If you compare the CMB to a blackbody curve. The data matches the curve exactly. I mean really exact. The error bars on the data are too small to see on a reasonably sized graph. Of course this means we can use this curve to determine the temperature of the universe, which is about 2.725 Kelvin.
The cosmic microwave background isn’t perfectly even. There are small fluctuations in the observed temperature. In the early universe some regions were slightly more dense and hot, while others were less dense cooler. These kind of random variations are expected on a certain scale.
What isn’t expected are variations on a larger scale. And yet we see some larger scale variations in the CMB. In the figure below, the upper image plots the observed cosmic microwave background, while the lower image plots the “anomalies”. That is, the variations in the CMB that are above and beyond the variations expected by our cosmological models. You can see for example that one part of the universe appears decidedly warmer than another part.
These anomalous variations exist outside the model at a statistical level known as 3-sigma. In other words, there is only about a 1% chance that they are just due to random variations allowed by our cosmological model. That might seem like long odds, but in science don’t consider an effect “real” unless it is at a 5-sigma level, or more than 1 in a million odds.
The reason these anomalies raise a few eyebrows is that if they are a real effect they hint at either some exotic physics, or evidence of a multiverse (cue the popular presses!). But in a recent paper in Astronomy and Astrophysics shows these anomalies may not be as significant as we thought, due to the Sachs-Wolfe effect.1
Since the cosmic microwave background is a remnant of the early universe, the light we observe has travelled through the observable universe for billions of years to reach us. This means it has travelled through regions of galactic clusters, and through voids between galaxies. The gravitational variation of these clusters and voids can cause the CMB light to cool or warm slightly.
The Sachs-Wolfe effect has been known for decades, but in this paper the effect was specifically applied to these anomalies. What the authors found was that while the effect lessens the significance of the anomalies, it doesn’t completely eliminate them.
So it seems increasingly likely that our cosmological model works, and there isn’t any exotic physics going on. But there are still a few anomalous anomalies.
Rassat, A., and J-L. Starck. “On preferred axes in WMAP cosmic microwave background data after subtraction of the integrated Sachs-Wolfe effect.” Astronomy & Astrophysics 557 (2013): L1. ↩︎ | 0.816395 | 4.112038 |
White dwarfs are one of the most fascinating topics in the history of astronomy: celestial bodies were discovered for the first time, possessing properties that are very far from those with which we deal in terrestrial conditions. And, in all likelihood, the resolution of the riddle of white dwarfs laid the foundation for studies of the mysterious nature of matter hidden somewhere in different corners of the Universe.
There are many white dwarfs in the universe. At one time, they were considered rare, but a careful study of the photographic plates obtained at Mount Palomar Observatory (USA) showed that their number exceeds 1500. It was possible to estimate the spatial density of white dwarfs: it turns out that in a sphere with a radius of 30 light-years there Continue reading
In one of his speeches, A. Einstein said (in 1929): “To be honest, we want to not only find out how it works, but also if possible to achieve the goal of a utopian and daring-looking – to understand why nature is such. “This is the Promethean element of scientific creativity.”
Galaxies have been the subject of cosmogonic research since the 1920s, when their true nature was reliably established, and it turned out that these are not nebulae, i.e. not clouds of gas and dust, which are not far from us, but huge star worlds lying from us at very great distances from us. Discoveries and research in the field of cosmology have clarified in recent decades much of what concerns the background of galaxies and stars, the physical state of discharged matter from which they formed in very distant times. The whole of modern Continue reading
In the 1840s, with the help of Newtonian mechanics, Urbain Le Verrier predicted the position of the then undetected planet Neptune based on an analysis of perturbations of the orbit of Uranus. Subsequent observations of Neptune at the end of the 19th century led astronomers to suggest that, in addition to Neptune, another planet also has an impact on the orbit of Uranus. In 1906, Percival Lowell, a wealthy resident of Boston who founded the Lowell Observatory in 1894, initiated an extensive project to find the ninth planet in the solar system, which he named Planet X. By 1909, Lowell and William Henry Pickering had suggested several possible celestial coordinates for this planet. Lowell and his observatory continued to search for the planet until his death in 1916, but to no avail. In fact, on March 19, 1915, two low-level images of Pluto were obtained at his observatory without Lowell’s knowledge, but he was not recognized on them.
Mount Wilson Observatory could also claim the discovery of Pluto in 1919. That year, Milton Humason, on behalf of William Pickering, searched for the ninth planet, and Pluto’s image fell on a photographic Continue reading | 0.850604 | 3.866203 |
Proxima Centauri, the star closest to the Sun, has an Earth-sized planet orbiting it at the right distance for liquid water to exist. The discovery, reported today in Nature, fulfils a longstanding dream of science-fiction writers — a potentially habitable world that is close enough for humans to send their first interstellar spacecraft.
“The search for life starts now,” says Guillem Anglada-Escudé, an astronomer at Queen Mary University of London and leader of the team that made the discovery.
Proxima’s planet is at least 1.3 times the mass of Earth. The planet orbits its red-dwarf star — much smaller and dimmer than the Sun — every 11.2 days. “If you tried to pick the type of planet you’d most want around the type of star you’d most want, it would be this,” says David Kipping, an astronomer at Columbia University in New York City. “It’s thrilling.”
Earlier studies had hinted at the existence of a planet around Proxima. Starting in 2000, a spectrograph at the European Southern Observatory (ESO) in Chile looked for shifts in starlight caused by the gravitational tug of an orbiting planet. The resulting measurements suggested that something was happening to the star every 11.2 days. But astronomers could not rule out whether the signal was caused by an orbiting planet or another type of activity, such as stellar flares.
Although the planet orbits at a distance that would permit liquid water, other factors might render it unlivable. It might be tidally locked — meaning that the same hemisphere always faces the star, which scorches one side of the planet while the other remains cool. The active star might occasionally zap the planet with destructive X-ray flares. And it's unclear whether the planet has a protective, life-friendly atmosphere.
One day, the Proxima planet might be seen as the birth of a new stage in planetary research. “It gives us the target and focus to build the next generation of telescopes and one day maybe even get to visit,” says Kipping. “It's exactly what we need to take exoplanetary science to the next level.”
Read more: nature.com | 0.935357 | 3.57625 |
When Earthly astronomers train their telescopes on exoplanets beyond our solar system, they’re lucky to see even a single dot of light. How can they figure out whether it might have suitable conditions for life? To find out how they might know more, a team of scientists turned the problem on its head: They took images of a habitable planet—Earth—and transformed them into something alien astronomers light-years away would see.
The team started with about 10,000 images of our planet taken by NASA’s Deep Space Climate Observatory (DSCOVR) satellite, which sits at a gravitational balance point between Earth and the sun, allowing it to see only the daytime side of the planet. The images were taken at 10 specific wavelengths every 1 to 2 hours during 2016 and 2017.
To simulate an alien point of view, the researchers reduced the images into a single brightness reading for each wavelength—10 “dots” that, when plotted over time, produce 10 light curves that represent what a distant observer might see if they steadily watched exoplanet Earth over 2 years.
When researchers analyzed the curves and compared them with the original images, they figured out which parameters of the curves corresponded to land and cloud cover in the images. Once they knew those relationships, they picked out the parameter most closely related to land area, adjusted it for the 24-hour rotation of the Earth, and constructed the above contour map, soon to be published in The Astrophysical Journal Letters.
The black lines, which mark the median values for the land parameter, serves as an approximate coastline. Rough outlines of Africa (center), Asia (upper right), and the Americas (left) are clearly visible. While this is obviously no substitute for an actual image of an alien world, it may allow future astronomers to assess whether an exoplanet has oceans, clouds, and icecaps—key requirements for a habitable world. | 0.867275 | 3.58094 |
NASA's Dawn spacecraft is currently orbiting the giant asteroid Vesta, the first of two space rocks its mission will visit. This will be our best look yet at an asteroid, and what the probe digs up could help scientists answer several questions about this and the hundreds of thousands of asteroids that populate the solar system.
Most asteroids, including Vesta, reside in the doughnut-like ring of the main asteroid belt that peppers the space between Mars and Jupiter. Other asteroids whirl in tight circles closer to the sun than the Earth, while a large number of them share planets' orbits. Not all asteroids are so happy to stay put, though: Some asteroids' orbits take them on planet-crossing swings through the inner solar system.
Given this variety of asteroids, some notably strange ones have popped up over our two centuries-plus of observations since the first asteroid, Ceres, was spotted in 1801.
In honor of Dawn's historic mission, which arrives at Vesta in the early morning hours of Saturday (July 17 EDT), here are seven of the solar system's strangest asteroids. (Note that space rocks out beyond the orbit of Jupiter, although somewhat asteroidal in nature, are classified as different bodies, and so we'll leave those alone for now.)
Ceres: A Water-Logged Sphere?
The biggest asteroid by far is Ceres — which explains why it was discovered first — and it makes up about a third of the asteroid belt's mass. The object is so hefty that it's the only asteroid that has the gravitational strength to pull itself into a sphere.
On account of this roundness, Ceres is also considered a "dwarf planet," a designation it shares with four other objects in the solar system, including Pluto.
After scoping out Vesta, the Dawn spacecraft will journey on to Ceres, arriving in 2015. Once there, the spacecraft will gather data to help scientists learn more about Ceres' composition. The object is probably the "wettest" asteroid, with large stores of water in its interior as ice, though also possibly as a liquid layer beneath the surface.
Baptistina: Mother of the Dinosaur Killer
It's a name that, had they survived into modern day, dinosaurs (intelligent ones with language, at least) would curse: Baptistina.
Baptistina is the name of one of the youngest families of asteroids in the asteroid belt. (Families of asteroids are swarms of objects that share orbital characteristics, and are often named after their most prominent member.)
According to computer models, Baptistina and its swarm were spawned some 160 million years ago by a smashup between a 37-mile-wide body (60 kilometer) body and another object about 106 miles (170 kilometers) in diameter. That cataclysm created hundreds of large objects, some of which then drifted into a collision course with Earth.
One or several of these rocky shards of shrapnel then plowed into our planet 65 million years ago and helped doom the dinosaurs. The impact gouged out the Chicxulub crater, now buried by the Yucatan peninsula and the Gulf of Mexico.
The 100-million-year Baptistina barrage did not spare the moon, either. A meteorite scooped out the giant Tycho crater about 109 million years ago.
Hektor, the Biggest Trojan
Like Kleopatra, Hektor is very elongated, with length and width dimensions of approximately 230 by 124 miles (370 by 200 kilometers). Hektor has a moon as well. Unlike Kleopatra, however, Hektor is not found in the main asteroid belt; instead, the dark, reddish body dominates as the biggest of Trojan asteroids stuck in Jupiter's orbit.
These rocks lurk in what are known as the L4 and L5 Lagrangian points — two of the five zones in an orbit where the gravity of two bodies (in this case, Jupiter and the Sun) balances out. L4 and L5 lie ahead and behind, respectively of Jupiter.
In reference to the combatants in the ancient poet Homer's epic Iliad, the L4 asteroids are known as the Greek camp and the L5 group is the Trojan camp. Although named for the Trojan hero, Hektor is actually in the Greek camp.
Kleopatra: A Metal Dog Bone with Moons!
Many asteroids, believe it or not, have a moon, and some even sport two satellites. Kleopatra has two moons, which were named Alexhelios and Cleoselene earlier this year. To boot, the metallic asteroid has an unusual dog-bone shape.
The asteroid is roughly 135 by 58 by 50 miles (217 by 94 by 81 kilometers) in length, height and width. Its moons Alexhelios and Cleoselene are, respectively, about 3 miles (5 kilometers) and 1.9 miles (3 kilometers) in diameter.
Themis: Icy Giver of Life?
Themis, a large main belt asteroid, stands out as the first and only asteroid known thus far to have ice on its surface.
In 2009, observations in infrared light confirmed the presence of this ice, as well as carbon-containing, or organic, molecules.
These characteristics make the icy asteroid Themis and similar bodies called main belt comets good candidates for having delivered water and carbon — some of the ingredients of life — to the surface of a young, hot, dried-out Earth some four billion years ago.
Toutatis: A Tumbling Dumbbell
Named after a Celtic god, the asteroid Toutatis is one of the oddest space rocks. Instead of rotating in an orderly fashion about an axis, the double-lobed object chaotically tumbles. This unpredictable movement partially derives from Toutatis being composed of two bodies barely in contact with each other and from the influences of both Earth and Jupiter's gravity.
Toutatis' path through the solar system has it sweep close to Earth, but because the asteroid's orbit is chaotic, its exact path — and how close it might come to us — centuries from now cannot be well predicted.
Like some other asteroids, Toutatis is said to be a like a "rubble pile" — fragments of rock that have gravitationally come back together after a collision, but left many gaps between them.
Apophis: The Alleged Doomsday Rock
Toutatis has made some close shaves to Earth, and passed within 1,000,000 miles (1.61 million kilometers) of Earth, or about four Moon distances, back in 2004. Yet some rocks have made notably closer passes, and the one that has most alarmed astronomers and the public alike is Apophis.
Discovered in 2004 and named after the Greek word for the evil Egyptian god of darkness, Apophis will return to the neighborhood in 2029. At the time, scientists calculated that its impacting Earth on that future pass were as high as 1 in 40, but subsequent measurements have now relegated that possibility to almost nil.
Panic peaked in December 2004, and Apophis achieved a ranking of 4 on the Torino scale, the 10-point scale that rates the risk of an object colliding with Earth (10 being an unquestioned apocalypse). Although Apophis is now deemed zero for its 2029 pass, it will zoom a mere 18,600 miles (30,000 kilometers) above Earth's surface.
A number of these other so-called Near Earth Objects, or NEOs, have yet to be cataloged. Yet some that have pose no threat, and benignly share Earth's orbit. At least four examples exist of asteroids that follow Earth in horseshoe-shaped orbits; a new one, designated 2010 SO16, was found earlier this year. | 0.835455 | 3.902752 |
6 Naked-Eye Astronomical Concepts
The term "observational astronomy" is self explanatory. It talks about the things we can learn about space and universe by mere observation of night sky. It includes all we can see with our own eyes or through a telescope. I would limit the discussions only to naked-eye observations in this article.
We could confirm several scientific principles by mere observation of the night sky. Some of these may be basic, but understanding the elementary concepts is the first step before taking a deeper dive into the advanced ones.
Astronomical Concepts to Appreciate With Naked-Eye Observations
- Differentiating planets from stars
- Sun's position in the sky influences Earth's seasons
- Moon is lit by the Sun.
- Moon is closer to Earth than Sun is.
- Moon causes the ocean's tides.
- Venus and Mercury are in inferior orbits
1. Differentiating Planets From Stars
When we travel in a train, the nearer objects would appear to move out of sight faster than the farther objects. Almost all the stars are so far away they would appear stationary in relation to each other. But planets change their position against the background stars every night since they are closer to us and they all go around the sun albeit in different orbits.
To begin with, one should learn to identify the major constellations like Orion, Big dipper or Pegasus. This is the critical first step in becoming familiar with the night sky. Then one should check if the relative positions of nearby stars change in relation to constellations after a few days.
The ones that change their positions against the background stars should be the planets. We know that the orbits of all the solar system planets form the shape of a disc around the Sun. The disc shape of the orbits has relevance in planet hunting because the planets follow the same path taken by Sun from east to west. We also call this path the ecliptic.
Mercury, Venus, Mars, Jupiter and Saturn are the five planets visible to the naked eye and so we call them the naked-eye planets. One needs a powerful telescope to spot the other two planets, Neptune and Uranus.
Maximum Brightness of Visible Planets
2. Sun's Position in the Sky Influences Earth's Seasons
Sun does not rise or set in the same direction. There is a gradual shift in Sun's position through the year. In reality, it is not the Sun that is shifting its position but it is the axis of Earth's rotation that keeps tilting. The equatorial region faces the Sun on most occasions.
The northern hemisphere gets heated more when the axis of rotation tilts northward. Because of the tilt in the axis, northern and southern hemispheres get heated in varying measures. The differential heating results in a corresponding differential pressure leading to wind formation. It causes the winds to flow through the oceans and carry moisture to the land.
The ensuing monsoon rains are the lifeline for many life forms including our own human race. Thus, we see how the cosmos can influence things on Earth. Northern Hemisphere has summer months from June to August when the Sun appears to be overhead. The Sun seems to shift southward in the winter months from December to February. One can confirm the same by looking at the shadow cast by Sun that changes its direction between summer and winter months.
3. Moon is Lit by the Sun
We all know that the Moon is lit by the Sun. We can confirm the same by our own observation with the naked eye. Let us watch moon on a night, when it is a crescent. Both the lit and the unlit side of the crescent moon would be visible.
The lit side will always face the sun. This is a part confirmation that Moon is lit by the Sun. We can also observe the full moon that would rise when the Sun would be setting. This means that the Sun and Moon are on two sides of our planet. Thus, we get to see the lit face of Moon only on a full moon day when the Sun and Moon are on either side of Earth.
We can get the final proof by observing the Sun and Moon on the new moon day. Some of us would not have seen a new Moon in our lives as the new Moon is visible as a dark grey circle in day time closer to Sun. It is unsafe looking at the Sun as the Sunrays have a blinding effect. We can block the Sun from our view by placing our hand in front before locating the New Moon. Once we locate the New Moon closer to the Sun, we could conclude that we are looking at the unlit side of moon. The lit side should be on the other side facing the Sun.
4. Moon is Closer to Earth Than Sun is
We can find the proof for this during a solar eclipse. It is not advisable to stare straight at the Sun on any day. So please take enough precautions such as using a solar filter to look at the eclipse.
One can also consider options like a pinhole projector or a mirror projector. We can make both at home as a DIY project. Solar filter is a safe way to view the solar eclipse. It is not safe to look at Sun anytime and not just during eclipse alone, as some might think. Looking straight at Sun could cause serious damage to the vision.
One can see the disk of the Moon coming in front of the Sun and block the light from reaching Earth during the solar eclipse. So if Moon can block sunlight from reaching us, it should be at a shorter distance compared to Sun.
5. Moon Causes the Ocean's Tides
High tide always occurs when Moon is right overhead or underneath. Low tide happens when Moon is near the eastern or western horizon. This explains how the gravitational pull of the Moon causes the ocean's tides.
The high and low tides become more pronounced during New Moon or Full Moon days. This is because Sun's gravitational pull also has an influence on tides, though Moon has a more decisive effect on tides. During a full moon or new moon, Sun, Earth, and Moon are all aligned in a straight line. The gravitational force of Sun and Moon adds up to make the tides more pronounced.
One can observe the tidal movements by visiting a nearby beach and making periodic observations at a gap of 3 hours. One would then understand the link between Moon's position and the height of the tides.
6. Venus and Mercury Are in Inferior Orbits
Venus and Mercury are two planets found closer to where Sun is. Venus is visible as an evening star or morning star just for a few hours after sunset or before sunrise. We would always find Mercury closer to the sun. It is visible for around half an hour after sunset or before sunrise.
We cannot see both the planets in the night sky after 10 PM or before 3 AM. So from our line of vision, these planets always lie somewhere closer to Sun. Such a scenario is possible only for inferior planets with orbits closer to Sun than ours.
Please let me know if you have observed proofs for any other astronomical concepts. | 0.863413 | 3.584789 |
Galaxies and planetary systems
In the previous topic entitled “The Birth of the Universe”, the Quranic account was presented. After describing the beginning state as a singularity, a verse was quoted which describes the early universe as hot, hazy and gaseous. Gravity would shape the gaseous material into “multiple cosmic systems”. What are these systems? According to the Quran they are planetary and galactic structures.
Planetary system (solar system)
A planetary system is made of a whole community of worlds. A typical solar system (typical means similar to ours) would consist of the following bodies:
This body is centrally placed and is by far the largest member around which all the other bodies rotate. Our sun (an average star) makes up more than 99 percent of the total mass of the solar system. This confers upon it the bulk of the gravitational influence and for this reason it is responsible for maintaining the orbits of its other members.
These are significantly large celestial bodies which follow elliptical pathways around its parent star. Planets do not generate their own light, but are visible due to reflected star light.
These revolve around their parent planets. Our moon is unique in the sense that it is about one fifth of the Earth’s size whereas all the other satellite members are much smaller compared to their parent planets.
Asteroids are chunks of rock and iron in orbit around the sun. In our solar system they are described as cosmic rubble since they are made of unused material that has remained after the formation of our solar system four and a half billion years ago. The Earth has been the site of many asteroid impacts in the distant past. Fortunately large asteroid impacts have become a rare occurrence.
Just like asteroids comets are left over debris from the time the solar system formed. Because they are so far from the sun, their bodies take the shape of frozen lumps of ice, gas and organic material. Large-period comets (the most common type), derive their name from their very large orbits which may take millions of years to complete. The less common short-period comets, like Haley’s Comet, which visits our cosmic neighbourhood every 86 years, possess a head and a tail.
Meteors and meteorites
These are mainly chipped-off fragments from asteroids which bombard the Earth on a daily basis. They rarely pose any threat since most are reduced to ashes by heat generated by friction on entering the atmosphere. The resulting fireworks in the sky are termed a meteor. However, when they are much larger, they may escape total incineration and crash into the earth as meteorites.
The Quran and the solar systems
Let’s look as to how the Quran describes the layout of the solar system. Once again I must emphasize that the amazing scientific truths expressed in the Quran should be traceable to the original documents of earlier revelations. Remember the message given to Muhammad in the form of the Quran is essentially the same as that of the earlier original Books. As stated in the article, The Birth of the Universe, verses not quoted will have a footnote that can be checked at the end of the article.
Since the sun is a star, the Quranic description of the sun applies to stars as well. The Quran describes stars as bodies that generate their own light (10-5)1. They move in orbits of their own (36-38)2. There are different sizes of stars and the large ones in particular exert powerful gravitational forces (15-16)3. Stars have a life cycle- the various phases they pass through are referred to in the following verses: Red-giant phase (75-94, 55-375 and 81-66), white dwarf (81-1)7, supernovae (86-1, 2, 38 and 53-499) and black holes (15-163). These verses are discussed under the article, “The life cycle of stars”.
In 37-6 a key Arabic word (kawakib) means the Earth; it is also a title applied to the planet Venus and hence may be applicable to planets in general. Since planets share certain features, a description of the Earth may also have a bearing on the other planets. Verse 79-3010 describes the Earth as oval-shaped while 7-54 states: “(God) makes the night cover the day each pursuing each other in rapid succession”. If darkness follows light in a repetitive cycle on a spherical body (and assuming illumination by the sun as we understand it) as suggested by these two verses, it follows logically that such a body must be rotating and therefore all the other planets. In 24-3511 the same Arabic word kawakib (translated as planets) appears which is compared to glittering pearls. Comparing planets to glittering pearls is appropriate since planets, like pearls, are more or less spherically- shaped and like pearls, shine as a result of reflected light borrowed from the sun. Planets also move in elliptical orbits according to 21-3312.
Comets in the Quran are referred to as “…..Heavenly bodies that recede, continue to run their courses, go into hiding before returning” (81-15). Thus comets pursue an orbital path and go “into hiding” before returning to their departure point. The phrase” go into hiding” is a hint at their very large orbits. They spend long periods of time away before returning after their “hibernation”. In another verses (114-1) the Arabic word khunnas which describes a comet in 81-15 above, is applied to a person who steps forward to whisper into the ear of another and steps back again. What is characteristic about this motion is that the head or face of the whisperer remains in the direction of the person being whispered to while his back continues to point in the opposite direction. Similarly, when a comet approaches the sun, some of the ice evaporates and the comet grows a tail which is attached to its head. Speeding towards the sun its head faces the sun while its tail (back) projects in the opposite direction. As it is flung around the sun and recedes from it, its face continues to point towards the sun and its tail (back) away from it, just like the whispering motion described.
Reference to asteroids is made in the following verse: “We could cause the Earth to swallow them (disbelievers), or cause fragments of a celestial body to fall down upon them” (34-9). This is a familiar theme in the Quran; it uses a natural phenomenon to convey a religious principle, the threat of divine retribution. Meteorites (including comets and asteroids) are hinted at in 22-65: “It is (His gravitational laws) that hold the celestial bodies (in their orbits) so that they may not fall upon the Earth other than with His leave”. The verse alludes to the possibility of space objects striking the Earth, a fact disclosed hundreds of years after the Quran appeared. My insertion (bracketed words) may be explained as follows. It is permissible in fact sensible to interpret where appropriate God as God’s laws. The Arabic word Rabb describes one of the key titles of God, the Law Giver. In the Quran God is at the centre of existence and He interacts with the natural world through His laws. The term Sunnah-Allah in the Quran signifies His Ways or His divine laws. This line of reasoning is supported by verse 31-2013 which states that the entire creation is subject to His laws. The other bracketed phrase (in their orbits) is derived from 21-3312 which points to the motion of celestial bodies in their individual orbits. My insertion of gravity is deduced from 77-2514 and 55-5 quoted in the next section. The latter two verses will; be discussed in the article dealing with gravity.
Such is the composition of the solar system: the planets, moons, asteroids, comets and meteorites revolving around a centrally placed sun: “Indeed, We have created multiple orbits above you” (23-17), and as stated before, they move in accordance with precise mathematical laws: “The sun and the moon (and all other celestial bodies) follow pathways (exactly) computed” (55-5).
Alien solar systems
Our solar system is not unique. So far, more than two thousand solar systems have been discovered. Their multiplicity is addressed in two verses: ”Do you not see how God has created multiple solar systems (consisting of) several layers one above the other, (and created them) in stages and has placed in every one of them a moon that reflects light and a sun that generates light” (71-15). The many Earth-like worlds is addressed in 65-13: ”God is He who created multiple cosmic systems and of the Earth a similar number”. These two verses will be discussed in the article extra-terrestrial existence.
Contemplate the following verse: ‘’Consider the planets, stars and groups of stars that set, rise and set (again). They move along with steady motion, drifting silently and smoothly, unperturbed through space, yet outstrip each other swiftly in speed” (79-1,2,3). The first part of the verse refers to the apparent rising and setting of astronomical bodies, an illusionary motion created by the rotation of the Earth. What follows is a reference to real motion of planets, stars and groups of stars. Groups of stars may be interpreted as galaxies as shown below. Note that the description of the motion of celestial bodies as silent and smooth is based on Einstein’s equivalence principle. For instance, we on Earth do not sense its motion although it is hurtling through space at a 100 000km per hour. This concept will be dealt with under a future article, celestial motion. Groups of stars are a major component of a galaxy. Although the constituent stars of a galaxy “cluster”, they are separated by enormous distances as pointed out in 55-7, meaning that such systems must stretch across vast regions of space like galaxies do: “He raised the celestial bodies to great heights and set up the balance”. The sun like other stars moves in an orbit of its own (36-38) quoted above. Since 79-1,2,3 above refers to aggregate of stars and since every star moves in its own orbit, we may infer that such collection of stars rotate around a centre which in essence is a galaxy. Note also from the same verse that stars have different and enormous velocities. The stars that are close to the centre of the galaxy where gravity is concentrated generally move faster than their distant counterparts. The importance of gravity in maintaining the structure of the cosmos (which must include galaxies) are mentioned in 77-2514, 55-7 (quoted above) and 13-215 which will be addressed under the subject of gravity. In 19-65 reference is made to the presence of material (like gas and dust) between stars and galaxies: “It is God that created the heavens and the Earth and all that is between them”. Heaven, a translation from the Arabic word sama includes all the celestial bodies. The above verses describe the key feature of a galaxy. Summarizing, the layout of the universe is a network of stars, galaxies and planetary systems, and includes gas, dust, dark matter etc. as indicated by the phrase “all that is between them” in 19-6516.
- “He it is who made the sun a source of light and the moon (a body) that reflects light and ordained that it (the moon) moves across space and measured out stages for her that you might know the number of years and the measure (of time)” (10-5).
- “The sun moves in an orbit of its own” (36-38).
- “We have set up (unseen) structures in space (derived from) large stars which become manifest through their great (gravitational) forces, and are gateways” (15-16).
- “When the sun and the moon becomes united in a single mass” (75-9).
- “When the sky becomes red inclining towards yellow and other colours” (55-37).
- “When the oceans are made to boil over” (81-6).
- “When the sun becomes folded up” (81-1).
- “Consider heavenly space and the night visitant therein which suddenly appears after a cataclysm. And what would make thee realize how great the night visitant is? It is a star of piercing brightness” (86-1, 2, 3).
- “It is He alone that sustains the star which appears when heat and energy is generated (in its core) which gives it its bright appearance” (53-49).
- “(Long after the origin of the universe), He began shaping the Earth, gradually increasing it in size until it reached its oval configuration” (79-30).
- “The glass is as if it were luminary bodies (kawakib) glittering like pearls” (24-35).
- “Each (celestial body) floats silently and effortlessly in its elliptical orbit with its own kind of motions” (21-33).
- “He has subjected whatever is in the heavens and whatever is in the Earth (to His laws)” (31-20).
- “Have We not made the Earth draw to itself the living and the non-living?” (77-25).
- “Your Lord is He who raises the celestial bodies with an invisible pillar and is firmly established on the thrown of authority. He has subjected the sun and the moon (and all other celestial bodies) to (His gravitational laws), each pursuing a course for a term appointed (in accordance with those laws). He governs everything that exists” (13-2).
- “Your Sustainer is He who created the heavens and the Earth and all that is between them” (19-65). | 0.929826 | 3.084134 |
Recently, an interstellar object named ‘Oumuamua entered our solar system. It was the first such observed object in recorded history. Scientists were thus already watching ‘Oumuamua when, as it came closer, it did something surprising: it sped up. Notably, it did this without outgassing, which happens with comets and explains their changing speeds.
What, in the absence of outgassing, accounts for ‘Oumuamua’s unexpected acceleration? Avi Loeb, the chairman of Harvard’s astronomy department, floated a potential explanation: alien technology. As one might guess, this led to controversy. Filling Space spoke with Dr. Loeb to learn about his thoughts on ‘Oumuamua and the search for extraterrestrial intelligence (SETI).
Have you been surprised by reactions to your comments on ‘Oumuamua?
Yes, I did not anticipate this much reaction. We wrote a regular scientific paper aimed at explaining an anomaly in the data, namely the extra force exhibited by ‘Oumuamua’s trajectory in addition to the Sun’s gravity, in the absence of visible cometary outgassing. We suggested ‘Oumuamua may be pushed by sunlight, like the light-sails we are currently developing in the Breakthrough Starshot initiative that I am involved in.
For comparison, last year I published another paper that explained an anomaly of an unusually cold gas in the early universe, as reported by the EDGES experiment. In that paper, we conjectured that dark matter has some small electric charge to explain away the anomaly. The dark matter paper was accepted for publication within a few weeks and received little attention from the media.
The reaction to the light-sail paper was different. I did not plan to have a press release about it, but the editor of The Astrophysical Journal Letters wrote to me in an e-mail: “You should consider a press release on this one”. Before I had time to act, though, two bloggers reported on our posting on arXiv (where I regularly post papers before they get accepted for publication, in order to get comments from the community before the paper is finalized). Within days, the item went viral on social media.
Since then I have received dozens of requests on a daily basis from TV, radio, and newspaper outlets. Over the past few days, I had five film producers request to make documentaries about my work and life, and so on. So, yes… this was totally unexpected. But I do my best to use this public attention for a good purpose: to explain that most of the time frontier science involves uncertainty due to lack of data, that innovation and risk-taking is essential for making discoveries, that prejudice should be banned from the scientific discourse, and that mistakes should be tolerated in order for innovation to prevail.
During your career, have you witnessed any changes in the scientific community’s opinions on the possibility of extraterrestrial life?
History teaches us an important lesson. The search for extrasolar planets encountered similar resistance in its early days. Observing proposals to search for low-hanging fruits such as hot jupiters were rejected by conservative time allocation committees who argued that such easy-to-detect planets should not exist based on what we know about the Solar System. All progress broke loose as soon as some observers dared to challenge this prejudice, demonstrating that hot jupiters are abundant. The Kepler satellite revealed that about a quarter of all the stars have a habitable Earth-size planet, where liquid water may exist and the chemistry of life may flourish on its surface. This shifted public opinion in the direction that the search for primitive life should be part of the mainstream in astronomy.
But the search for intelligent life remains outside the mainstream. I am trying to change that in two ways. First, by speaking out in the way that I did on ‘Oumuamua. And second, by writing a textbook with my postdoc, Manasvi Lingam, on the search for both biological and technological signatures of extraterrestrial life. The book should be completed by summer 2019.
How did you become interested in the search for extraterrestrial life, and what would you recommend to individuals trying to enter that field?
I was intrigued by the question: “Are we alone?”. If the answer is “no”, I will continue to be intrigued by the follow-up question: “Are we as smart as they are?”. My advice to any young scientist is: “Follow your childhood curiosity rather than your ego, and you will have a fulfilling life”. | 0.87866 | 3.056009 |
We reached the Moon in a tin can, built a humble space station, and have a plan to reach Mars in a bigger tin can. But we need to reach the stars. And we will.
Yes, I know what you are thinking: "It's impossible."
And right now, you are right. Our current propulsion engines are, simply put, pathetic. We are still in the Stone Age of space travel. As cool as they are, rocket engines—which eject gas at high speeds through a nozzle on the back of a spacecraft—are extremely inefficient, requiring huge volumes of fuel runs out faster than you can say "Beam me up, Scotty."
Solid boosters, hybrid, monopropellant, bipropellant rockets... all these would be impossible to use in interstellar travel, with maximum speeds going up to a maximum of 9 kilometers per second. Rockets won't work even using the effect of planetary gravity to gain impulse. Voyager—the fastest man-made spacecraft out there racing at 17 kilometers per second—would need 74,000 years in deep space to reach Proxima Centauri, the red dwarf star located at 4.22 light-years in the Alpha Centauri system, the closest to our Sun.
But even if we were able to build a massive spacecraft with today's experimental—but feasible—propulsion technology, it will still take thousand of years to reach Alpha Centauri. Using nuclear explosions—like the ones proposed in the Orion project—would be more efficient than rockets, achieving a maximum of 60 kilometers per second. That's still a whopping 21,849 years and a couple months.
Using ion thrusters—which use electrostatic or electromagnetic force to accelerate ions that in turn push the spacecraft forward—would only reduce that amount marginally. Even theoretical technology—like nuclear pulse propulsion, with speeds up to 15,000 kilometers per second—won't cut it. And that's assuming we can find a way for these engines to last all that time. And let's not even get into the resources and engineering needed to create a vessel capable of sustaining life for such a long period of time.
All to reach a stupid red dwarf with no planets to explore. We may as well not go, really. You know, let's just save Earth from our own destruction and colonize Mars or Titan or Europa (if the aliens let us do that.)
Our ignorance is our only hope
It gets even worse. Our current understanding of physics—which says that nothing can travel faster than light—basically establishes that we will never be able to achieve space travel in a way that is meaningful to Humanity. In other words, even if we are able to discover a propulsion method that could get a spacecraft close to the speed of light, it will still take hundred of years to reach an star system with planets similar to Earth. By the time the news get back to us, we all will be dead.
And that's precisely the key to our only hope to reach the stars: Our ignorance. As much as we have advanced, we are still clueless about many things. Physicists are still struggling to understand the Universe, discovering new stellar events that we can't explain, and trying to make sense of it all, looking for that perfect theory that will make everything fit together.
That fact is that, since we don't know how everything works, there still may be something that opens the way to faster-than-light space travel. Discovering the unknown—like physicists have been doing since the Greeks—and harnessing new math and theories into new technology is our only way to spread through the Universe in a way that makes sense to Humanity as a whole. You know, like Star Trek or Battlestar Galactica or Star Wars: Travel across the Universe in hours or days, not in centuries or millennia.
One of those yet-to-be-unraveled things is the Big Bang, the origin of the Universe itself. Our origin, the final question that we have been trying to answer since we came out of the cave and looked up the night sky. We still don't know exactly what happened, but the observation of the Universe from Earth and space probes have caused some physicists to propose many different models. One of these models says that, during the initial inflation period of the Universe, space-time expanded faster than light. If this turns out to be the case, it would make possible the creation of warp drives.
Yes, the warp drives.
Warp drives were first proposed in a logical way by Mexican physicist Miguel Alcubierre. He theorized that, instead of moving something faster than the speed of light—which is not possible under Einstein's relativity theory—we could move the space-time around it faster than the speed of light itself. The spacecraft will be inside a warp bubble, a flat space that will be moved by the expansion of the space behind it and the contraction of space in front of it. The spacecraft won't move faster than light, but the bubble will. Inside the bubble, everything would be normal.
A way to understand the effect, as Marc Millis—former head of the Breakthrough Propulsion Physics Project at NASA's Glenn Research Center—explains, is to look at the way a toy boat reacts in the tub when you put some detergent behind it. The bubbles will expand the space behind the boat, impulsing it forward. In the same way, a spaceship with a warp drive would be able to do the same thing.
But while there have been already experiments in the laboratory that suggest that this may indeed be possible, we are still far, far away from developing the technology that would make warp drives a reality. To start with, the amount of energy necessary to bend space like this is way beyond anything we can produce today. Some scientists, however, suggest that antimatter may be the fuel that will make this possible.
Again, there are a lot of question marks surrounding antimatter, but this is precisely part of our only hope: Somewhere, still hiding, is the breakthrough that will make interstellar travel possible. The possibility is still there.
So call me an optimist if you have to. It may be all this sun shining in New York right now. Or maybe it is because I saw Star Trek yesterday (and it was as good as I hoped it to be and then some more.) The fact is that I'm convinced that interstellar travel will happen. You and I will probably not see it, but if Humanity can survive self-annihilation, I'm sure we will achieve it.
No, "will we reach the stars?" is not the question to answer. We will. The more important question is why do we need to go?
The answer to this is the reason why we have celebrated humans in space all this week, now coming to its end. As I said when we started Get Me Off This Rock, space exploration is the most epic and most important adventure Humanity has ever embarked upon. When we travel to space we are opening the way to the preservation of Humanity. We are trying to contact other civilizations. We are trying to answer the biggest questions of them all: Who are we? Why are we here? How did we get here? Are we alone in this rock we call Earth?
But there is more. A lot more. Ultimately, the most important thing will not be getting the answers to these eternal questions. The most important thing will be the process of reaching for the stars. Because if we manage to get there, it would mean that we managed to survive as a species. That is the only way we can develop the engineering and the resources needed to build something like the Enterprise. Survive self-destruction, solve the problems we have here, collaborate, work as species, not as countries or corporations.
That's what space exploration and interstellar travel is all about. Only if we manage to go beyond our petty fights and stupid wars, only if we work together towards a better future, we will be able to go where no one has gone before. And be back to tell about it before dinner gets cold. | 0.876734 | 3.664295 |
In the last 33 years, Carolyn Porco has had a hand in some of NASA's highest profile missions. She was an integral part of the Voyager imaging team, then the public face for the Cassini mission. Now, she and her colleagues are now laying the groundwork for a mission to Enceladus, with the goal of finding life.
"We have reasons now to believe that our very best chances of finding extraterrestrial life in our lifetimes – and almost certainly, if it is there at all, a second genesis of life – is the ocean of Enceladus," Porco said in an email interview with Popular Mechanics.
"It is why there are those of us who want NASA to return there as soon as possible with the kind of instrumentation that could say for sure, one way or another, if life has gotten started there. It could turn out to be as dead as a doornail, but at Enceladus we have the chance to answer this question now. So what are we waiting for?"
The origins of the potentially revelatory mission go back quite a way. In 2005, Cassini confirmed that Saturn's tiny moon had geyser activity. There had been inklings before, especially during the Voyager mission, but Cassini was able to actually find real evidence of an undersea ocean that could be habitable. It's a possible birthplace for life, kept liquid by the moon's daily tidal distortion, caused by its eccentric orbit and its changing distance from Saturn.
"We knew for decades of Enceladus' spatial coincidence with the huge, diffuse, donut-shaped ring of tiny smoke-sized icy particles known as the E ring," Porco says. "And of course Voyager found it was a moon that showed the effects of internal activity. Very surprising for such a small moon. So, soon after the Voyager Saturn flybys were over, it was proposed that there might be geysers of water erupting from the surface, creating that E ring."
Porco became part of the Voyager mission during the Saturn flybys in 1980 and 81. As a graduate student at CalTech, she'd already studied the interaction between Saturn's rings and the moons nearby. "There were so many new findings that the Voyager imaging team couldn't keep up with it all." She wound up working many of them into her dissertation.
By the time that Voyager 2 flew by Uranus in 1986, Porco was brought on to the Voyager team full time, tasked with studying the planet's newly discovered ring system. She continued on to similar work with Neptune, revealing the relationships between planets and their rings and moons in unprecedented detail.
By the early 1990s, she found, along with fellow researcher Mark Marley (now at Ames Research Center in California), that internal oscillations within Saturn can give rise to certain features of the planet's ring system without requiring interactions with orbiting moons. It was an unknown phenomena at the time, but a finding that was ultimately confirmed by Cassini.
"There's nothing in this world like being the first to discover some fundamental fact of nature," she said. "It's profoundly satisfying."
When Cassini was finally given the green light as a NASA mission, Porco was named the imaging lead. But space is big, and despite a launch in 1997 Cassini didn't arrive near its destination until 2004. In the meantime, Porco took on the challenge of engineering a lunar burial.
Eugene Shoemaker—an astronomer who focused much of his work on asteroids and the early chronology of the solar system— would have been an Apollo astronaut, but was sidelined by Addison's disease which left him earthbound. Porco helped make sure that, after Shoemaker died in 1997, he got to go to the moon after all.
"Gene went on to do many important things in the study of the solar system, but this Apollo story was legend in my business," she said. "So, when I learned that he had died–which was impossibly sad for those of us who idolized him–and that his body was to be cremated, the first thought that came to my mind was, 'Let's send him to the Moon!'" His ashes were carried to the moon on the Lunar Propector mission, along with an epigraph designed and created by Porco.
Porco has strong opinions on the future of the space program. NASA is no stranger to changing priorities. As administration's change, so do the agency's goals, handed down from on high. It's not a situation Porco is particularly fond of . "[It's] not the way to run a space program." And while she's cautiously optimistic of private space companies, she has her doubts. "I am uneasy about having scientific exploration depend on profit-making companies."
"To me, there will always be need for governments to support the largest, most daring and most scientifically significant projects," she says. "So, the best possible future requires both enterprises."
But those are big, sweeping changes and in the near term, there's the matter of NASA's scientific exploration goals. Of course she wants the Enceladus mission and a proposal is currently being drafted up, with the hopes that it can gain the same kind of traction as the Europa mission. Both, after all, are a quest for life in our own backyard, not to mention there's a lot of evidence to suggest that Enceladus is not that different from what we know here on Earth.
"We have found evidence for hydrothermal activity of the type that powers the Lost City hydrothermal region and its biota on the floor of the Atlantic," she says. "We also know Enceladus' ocean has a salinity comparable to the Earth's oceans, and an alkalinity that is consistent with hydrothermal activity."
In a pinch (or as a bonus), she'd also love to see a mission to Neptune, "a fascinating planet very unlike Jupiter and Saturn. Neptune has been neglected since 1989. It deserves a mission that is Cassini in scope, and it's time we return," she says.
But whatever the specifics of her next project, each new mission is the culmination of decades worth of fascination and hard work.
"I was drawn to astronomy by a teenage existential quest," she says. "Around 13, I was deep into wondering about the meaning of life, and what I was doing here. I turned to religion, but that did nothing for me."
"I got to wondering where was here. So, I began studying astronomy and became enthralled by what I learned. By the time I finished high school, I knew I wanted to become an astronomer. By the time I finished college, I knew I wanted to be part of the American space program. And that's exactly what I did." | 0.829596 | 3.65836 |
What you are looking at above is proof that we are truly living in the 21st century: an image of a robot taking a selfie. To celebrate its tenth year conducting research on the surface of Mars, the NASA Exploration Rover “Opportunity” took a picture of itself, completely smothered in Martian dust.
Don’t let its grungy looks fool you, Opportunity has been highly functional and deserves to celebrate. The robot has been operational for ten years on a mission that was only designed to last for three months. Opportunity has been a rather successful interplanetary geologist, discovering chemical compositions indicating that Mars used to have a vast salty sea. Opportunity has been an inspiration to millions of people including myself, relaying back gorgeous panoramic images that are sure to instill a sense of wonder. So here’s to you, Opportunity.
To celebrate, I present a brief timeline of some important parts of Martian history:
- ~4.6 Billion years ago: Mars forms, along with many other planets in our solar system. It’s widely believed that Mars formed through the collision of planetesimals: rocks that attract other rocks through gravity and accrete more and more mass until a planet is formed.
- ~2000 BC: Ancient Egyptians take note of the back and forth movement, known as retrograde motion, of Mars in the night sky. The ancient Greeks noticed this movement as well, for the word planet comes from the Greek word for “Wanderer.”
- 1609 AD: Gallileo Galilei is the first person to observe Mars through a telescope. Fifty years later, Christian Huygens observes Mars and takes precise notes of its surface features and is able to deduct its rotational period to within an hour of its actual value.
- 1784 AD: Sir William Herschel deducts that because of the similarities between Mars and the Earth, there must be intelligent life on Mars. This inspires The War of the Worlds by H.G. Wells, as well as a century of (for the most part, terrible) “attack from space” genre movies.
- June 19, 1976 AD: NASA’s Viking 1 becomes the first probe to successfully land on the surface of Mars, sending back detailed color images of the expansive Martian surface.
- 2004 AD: The Mars rovers Spirit and Opportunity touch down on Mars. One of my favorite things about these rovers is the method that they used to land. Landing the rovers was one of the greatest engineering feats of the 21st century. The process incorporated rockets, parachutes, and giant protective airbags that bounce the rovers like a ball to slow them down from 12,000 mph to practically 0 mph in six minutes. You have to watch this video; it’s nothing short of incredible.
- 2013 AD: Water is found bound to other elements in Martian soil by NASA’s “Curiosity” rover. This officially confirms suspicions that Mars has liquid water on its surface as evidenced by satellite photographs.
- 2014 AD: Observers note that a comet will come ten times closer to Mars than any comet has ever been to the Earth. It will be closer to Mars than the moon is to the Earth and will give astronomers a rare chance of seeing interstellar bodies closely interact. | 0.900998 | 3.009315 |
Why is it so hard to detect dark matter? | Feature Tech
For nearly a century, scientists have counted on the existence of dark matter, a non-luminous material that allows them to justify many of the phenomena in astronomical observations that they observe, but can’t explain.
Many theories and astrophysical calculations need dark matter to be present but scientists have never, ever been able to detect it. Why is this ‘black cat’ so elusive?
Let’s start with the known knowns, and the known unknowns. It’s widely agreed that all the tangible ‘stuff’ you see around you – cats, people, planets, stars, and galaxies – represents about 5 percent of the ‘stuff’ in the universe. A baffling 95 percent is dark, either in the form of dark matter, about 27%, and dark energy, about 68%.
If there is so much dark matter out there, how come it hasn’t been detected yet?
Euronews put that question to René Laureijs, Project Scientist for ESA’s Euclid mission:
“We have seen evidence for dark matter through many astronomical observations. We think it’s a particle but we have never detected this particle and the reason for this is that we think that dark matter is a substance that does not interact at all with normal matter and, also, does not give light or any other electromagnetic radiation. That makes it extremely difficult to detect it,” he says.
Euclid is a space telescope that is due for launch in 2020 and will observe the movement of galaxies in unprecedented ways in order to track the interaction of dark matter with ordinary matter like stars. So it’s not aiming to directly ‘see’ dark matter, but to do a better job of grasping how it functions. The mission also investigates dark energy and how it plays a role in accelerating the expansion of the Universe.
Meanwhile here on planet Earth, the particle physics community, always up for a challenge, are trying their hardest catch a glimpse of this ‘black cat’ as it scampers across the dark room. Using big particle accelerators, like CERN’s Large Hadron Collider, they generate proton collisions in the hope of detecting a ‘new’ or unknown force, which could be then proven to be dark matter.
They also try to directly spot dark matter if it’s picked up by one of their detectors, kept down low, underground in the LNGS, or up high, attached to the International Space Station. And they also hunt for particles that would be produced when dark matter interacts with itself or with another particle. So far, they’ve found nothing, but they’re convinced they will be able to grab the black cat one of these days.
If they do get a hold it, it still may not be enough. “Each one of these (techniques) by itself is not enough to discover dark matter. You need more than one to really pin down what dark matter is and to confirm a discovery”, explains Doglioni, a member of the ATLAS Collaboration at CERN and Associate Senior Lecturer at Sweden’s Lund University.
Different branches within the scientific community collaborate in order to find what could be considered the Holy Grail in astronomy. However, each specialist takes their own approach.
“There are conferences discussing how to detect dark matter. People are exchanging their experiences through these conferences although the way you detect it, for instance, if you look at particle interactions it’s a different community than people who try to observe dark matter like us astronomers. There is an overlap but there are large communities working independently from each other to detect dark matter,” explains Euclid scientist René Laureijs.
It might be a matter of decades before we get a true glimpse of dark matter. But the cat-hunting scientists are convinced they’ll get their hands on that moggy. “It could be that dark matter is very difficult to find because it’s very rare and that we haven’t found it because there’s not enough data,” says Doglioni.
The answer is to run the LHC for another two decades, and in the meantime prepare plans for newer accelerators. They also put their faith in their equipment: “We’re also counting on technology getting better,” she told Euronews. “In 50 years’ time we’ll have technologies that will allow us to go forward, even though it seems difficult. But I think we’ll get there, yes.” | 0.828222 | 3.672036 |
Artist’s impression of a ‘supergiant fast X-ray transient’. Image credit: ESA Click to enlarge
ESA’s Integral gamma-ray observatory has discovered a new, highly populated class of X-ray fast “transient” binary stars, undetected in previous observations.
With this discovery, Integral confirms how much it is contributing to revealing a whole hidden Universe.
The new class of double star systems is characterised by a very compact object that produces highly energetic, recurrent and fast-growing X-ray outbursts, and a very luminous “supergiant” companion.
The compact object can be an accreting body such as a black hole, a neutron star or a pulsar. Scientists have called such class of objects “supergiant fast X-ray transients”. “Transients” are systems which display periods of enhanced X-ray emission.
Before the launch of Integral, only a dozen X-ray binary stars containing supergiants had been detected. Actually, scientists thought that such high-mass X-ray systems were very rare, assuming that only a few of them would exist at once since stars in supergiant phase have a very short lifetime.
However, Integral’s data combined with other X-ray satellite observations indicate that transient supergiant X-ray binary systems are probably much more abundant in our Galaxy than previously thought.
In particular, Integral is showing that such “supergiant fast X-ray transients”, characterised by fast outbursts and supergiant companions, form a wide class that lies hidden throughout the Galaxy.
Due to the transitory nature, in most cases these systems were not detected by other observatories because they lacked the combination of sensitivity, continuous coverage and wide field of view of Integral.
They show short outbursts with very fast rising times – reaching the peak of the flare in only a few tens of minutes – and typically lasting a few hours only. This makes the main difference with most other observed transient X-ray binary systems, which display longer outbursts, lasting typically a few weeks up to months.
In the latter case, the long duration of the outburst is consistent with a “viscous” mass exchange between the star and an accreting compact object.
In “supergiant fast X-ray transients”, associated with highly luminous supergiant stars, the short duration of the outburst seems to point to a different and peculiar mass exchange mechanism between the two bodies.
This may have something to do with the way the strong radiative winds, typical of highly massive stars, feed the compact object with stellar material.
Scientists are now thinking about the reasons for such short outbursts. It could be due to the supergiant donor ejecting material in a non-continuous way. For example, a clumpy and intrinsically variable nature of a supergiant”s radiative winds may give rise to sudden episodes of increased accretion rate, leading to the fast X-ray flares.
Alternatively, the flow of material transported by the wind may become, for reasons not very well understood, very turbulent and irregular when falling into the enormous gravitational potential of the compact object.
“In any case, we are pretty confident that the fast outbursts are associated to the mass transfer mode from the supergiant star to the compact object,” says Ignacio Negueruela, lead author of the results, from the University of Alicante, Spain.
“We believe that the short outbursts cannot be related to the nature of the compact companion, as we observed fast outbursts in cases where the compact objects were very different – black holes, slow X-ray pulsars or fast X-ray pulsars.”
Studying sources such as “supergiant fast X-ray transients”, and understanding the reasons for their behaviour, is very important to increase our knowledge of accretion processes of compact stellar objects. Furthermore, it is providing valuable insight into the evolution paths that lead to the formation of high-mass X-ray binary systems.
Original Source: ESA Portal | 0.880509 | 4.005054 |
A small asteroid has been orbiting Earth for 3 years, astronomers say. Meet our newest minimoon.
Tumbling through Earth’s increasingly crowded orbit are about 5,000 satellites, half a million pieces of human-made debris and only one confirmed natural object: the moon. Now, astronomers working out of the University of Arizona’s Steward Observatory think they may have discovered a second natural satellite — or at least a temporary one.
Meet 2020 CD3, Earth’s newest possible “minimoon.”
BIG NEWS (thread 1/3). Earth has a new temporarily captured object/Possible mini-moon called 2020 CD3. On the night of Feb. 15, my Catalina Sky Survey teammate Teddy Pruyne and I found a 20th magnitude object. Here are the discovery images. pic.twitter.com/zLkXyGAkZlFebruary 26, 2020
A minimoon, also known as a temporarily captured object, is a space rock that gets caught in Earth’s orbit for several months or years before shooting off into the distant solar system again (or burning up in our planet’s atmosphere).
While astronomers suspect there is at least one minimoon circling Earth at any given time, these tiny satellites are rarely discovered, likely because of their relatively small size. Until now, only one confirmed minimoon has ever been detected: a 3–foot-wide (0.9 meters) asteroid called 2006 RH120, which orbited Earth for 18 months in 2006 and 2007.
Now, there may be a second. Kacper Wierzchos, a senior research specialist for the NASA and University of Arizona-funded Catalina Sky Survey, announced the discovery of a new temporarily captured object via Twitter yesterday (Feb. 25). The object appears to measure between 6.2 and 11.5 feet (1.9 to 3.5 m) in diameter and has a surface brightness typical of carbon-rich asteroids, Wierzchos wrote.
According to an orbital model by amateur astrophysicist and San Francisco high school physics teacher Tony Dunn, the potential minimoon has likely been trapped by Earth’s gravity for about three years now and could make its exit in April 2020, resuming its regularly scheduled journey around the sun.
Here’s an animated GIF of our new mini-moon 2020 CD3, discovered by @WierzchosKacper. Rotating frame keeps the Earth/Sun line stationary. Orbital elements courtesy of IUA MPEC. https://t.co/dok3jn3G9hhttps://t.co/x1DXWLq2vm pic.twitter.com/O3eRaOIYjBFebruary 26, 2020
In a perfect universe, our departing minimoon would fly off and become trapped by the moon’s gravity, creating an even rarer class of object: a moonmoon. Sadly, moonmoons remain only theoretical, and our possible new minimoon comes with some caveats of its own. While the object’s existence has since been confirmed by several other observatories, further analysis is required to say for certain that the object is an extraterrestrial rock and not a large shard of space junk. Hopefully, we’ll have an answer before April. | 0.882635 | 3.130684 |
Astronomy Object of the Month: 2019, December
First detection of gamma-ray burst afterglow in very-high-energy gamma light
After a decade-long search, scientists have for the first time detected a gamma-ray burst in very-
high-energy gamma light. This discovery was made in July 2018 by the H.E.S.S. collaboration
using the huge 28-m telescope of the
array in Namibia. Surprisingly, this Gamma-ray burst, an extremely energetic flash following a
cosmological cataclysm, was found to emit very-high-energy gamma-rays long after the initial explosion.
Extremely energetic cosmic explosions generate gamma-ray bursts (GRB), typically lasting for only a few tens of seconds. They are the most luminous explosions in the universe. The burst is followed by a longer lasting afterglow mostly in the optical and X-ray spectral regions whose intensity decreases rapidly. The prompt high energy gamma-ray emission is mostly composed of photons several hundred thousands to millions of times more energetic than visible light, that can only be observed by satellite-based instruments. Whilst these space-borne observatories have detected a few photons with even higher energies, the question if very-high-energy (VHE) gamma radiation (at least 100 billion times more energetic than visible light and only detectable with ground-based telescopes) is emitted, has remained unanswered until now.
On 20 July 2018, the Fermi Gamma-Ray Burst Monitor and a few seconds later the Swift Burst Alert Telescope notified the world of a gamma-ray burst, GRB 180720B. Immediately after the alert, several observatories turned to look at this position in the sky.
For H.E.S.S. (High Energy Stereoscopic System), this location became visible only 10 hours later. Nevertheless, the H.E.S.S. team decided to search for a very-high-energy afterglow of the burst. After having looked for a very-high-energy signature of these events for more than a decade, the efforts by the collaboration now bore fruit.
A signature has now been detected with the large H.E.S.S. telescope that is especially suited for such observations. The data collected during two hours from 10 to 12 hours after the gamma-ray burst showed a new point-like gamma-ray source at the position of the burst. While the detection of GRBs at these very-high-energies had long been anticipated, the discovery many hours after the initial event, deep in the afterglow phase, came as a real surprise. The discovery of the first GRB to be detected at such very-high-photon energies is reported in a publication by the H.E.S.S. collaboration et al., in the journal 'Nature' on Nov. 20, 2019.
A team of researchers from 5 Polish scientific institutions took part in the discovery, including the University of Warsaw, Jagiellonian University, CAMK PAN, UMK and IFJ PAN. Poland participates in the works of the H.E.S.S. Observatory since 2005. It is worth noting that the large telescope used in the present discovery was also built with our participation. The announcement of the discovery in Nature was accompanied by a parallel presentation of a similar discovery made independently for another gamma-ray burst by the MAGIC observatory, with the participation of Polish researchers from the University of Lodz.
Original publication: Abdalla, H., Adam, R., Aharonian, F. et al.: A very-high-energy component deep in the γ-ray burst afterglow, Nature, 575, 464–467 (2019).
Presented results are a part of research conducted at the Department of High Energy Astrophysics and Department of Stellar and Extragalactic Astronomy of the Jagiellonian University’s Astronomical Observatory. A group of researchers from the JU Astronomical Observatory: Marek Jamrozy, Michał Ostrowski, Łukasz Stawarz and PhD student Angel Priyana Noel participate in the works of the H.E.S.S. observatory.
M. Ostrowski [at] oa.uj.edu.pl | 0.829624 | 3.836613 |
Gravitational collapse happens when the density of the matter is so high that the force of gravity overcomes the other fundamental forces that keep matter together.
At the core of the black hole is the singularity. A point in space-time where the density of a mass becomes infinite. This point is so massive that it bends the whole space-time around it which curvature so deep even the light can't escape it. Yes , the light, which doesn't actually have any mass isn't actually prevented from escaping the black hole due gravity itself, but the space itself being so twisted that the light is unable to find it's way out of there.
While scientists are just starting to think about the ways how we could find the miniscule black hole that might be circling the Sun at the edge of the solar system another black hole has been found. What makes it remarkable is that it's the closest one found so far. The scientists who found it said (I kid you not) it's just 1000 light years away.
It's one of those regular sized ones. Not the supermassive kind that can be found at the center of the galaxy or the small, primordial one like the suspected one in our own system.
Not only do black holes defy common sense and understanding they also defy the laws of physics. They are the only non-quantum sized objects we know that don't abide with the classical physics. Sure, one could argue about the size of singularity and it's relative size to anything at the quantum level. But still, unlike the individual quantum particle that doesn't have any effect on the macro scale the effects of the black holes are definitely measurable even in the cosmic scale.
Isn't it amazing that sun is almost exactly 400 times further from earth than moon and the moon is also 400 times smaller? What are the odds of that happening.
Over the billions of years of these objects existence, it's actually 100. Billions years ago when the moon formed it started to orbit our planet at much closer distance. Over the years it has slowly been distancing from us so that currently it just happens to be at around that 1/400 times the distance of sun away from us.
There was yet another supermoon earlier this week. Lately these occurrences have been widely marketed around the media giving them each some obscure unique name as if mere super- preposition wouldn't be enough.
So there have been planets that have been reclassified, planets that, if the theories hold true, have been destroyed or hurled out of the solar system and theoretical planets to explain anomalies in the behaviour of other celestial objects. After all those, we are left with the eight planets we know of today.
There are however unexplained behaviour of different objects in our solar system that suggest there might be more planets to be found.
In addition to actual objects that have just been demoted from planet status there has been multiple supposed planets astronomers have been trying to locate throughout history.
Vulcan was a speculated planet that was expected to reside between Mercury and the Sun. The perturbations in Mercury's orbit suggested there should be something there. These anomalies were however later explained by Einstein's theory of general relativity.
Everybody remembers Pluto's demotion to dwarf planet in 2006. This reclassification was triggered by the discovery of Eris, an object far out beyond Pluto's orbit that was found to be 27% more massive than Pluto. So either it had to be the tenth planet, or Pluto shouldn't classify as planer either.
I hope you are sitting down firmly as I'm about to tell you how fast you are actually going around just sitting there in place.
First of all, your on the surface of this planet, rotating around it's axis. The rotation takes you around the circumference of the planet in one day. To accomplish that, we are spinning around at around 1700km/h (or 0,5km/s). | 0.904011 | 3.739801 |
When in ca. 100 CE Plutarch wrote a treatise entitled Why are the days named after the planets reckoned in a different order from the actual order?, it can be deduced that
- in Rome the seven-day week had supplanted the eight-day week based on market days,
- it was commonly understood the seven days were named for the classical planets in a geocentric universe, i.e., not directly after the deities after whom they were named, and
- the days were not sequenced in their astronomical order: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon.
Plutarch's treatise is no longer extant, but we do know the answer: the order follows the astrological planetary hours. Each day of the week is named for the planet ruling its first hour.
The rest is pure arithmetic. Twenty-four hours ruled by seven planets leaves a remainder of three, so beginning with the day of the Sun, the next day is three planets to the right in the list, the Moon's day, and so on.
When after increased contact with the Roman Empire Germanic tribes adopted and adapted the seven-day week, they remythologized the names into more local deities. Whether this twist on the interpretatio germanica included Sunna, a sun goddess, feminine because the Germanic word for sun is that grammatical gender, or was simply a translation of the Latin cannot be determined. Appparently there was no readily available deity to corresponding to Saturn/Chronos, so his name remained for Saturday.
All this occurred long before West Germanic literacy and can only be inferred from Old Saxon, Old High German, and Old English.
...meanwhile in sixth century Portugal
For its own use, the Latin church had adopted the simple numbers of Genesis 1, except the first day was the Lord's day, Dominica, Monday–Friday bore numbers 2–6, and Saturday was the biblical sabbatum. This would not have been so much a reaction to pagan names as it was to assure a distinctly Christian shape to the week, beginning with the prime celebration of the Lord's Day.
The Eastern Church followed a similar pattern, adding Παρασκευή (Paraskeví) for Friday, the "Day of Preparation" for the Jewish Sabbath, on which Jesus of Nazareth was crucified. This "five numbers and the Bible" scheme is still how Greeks name the days of the week, and it influenced Slavic names as well. (Not all names: Monday, e.g., Slovak pondelok, means literally "day after no work," which should be universally adopted.)
In sixth century Portugal, St. Martin of Braga (ca. 520–580) objected to the daily dose of paganism in secular Latin and Romance languages, insisting that not only the days of the week be renamed according to ecclesiastical nomenclature, but that the planets be renamed as well. In the latter endeavor he failed to convince, but to this day, if you're in Lisbon and want to do something on Tuesday, you do it on "Thirdday": terça-feira.
...and now to seventh century England
Sources written in Old English begin to appear in the seventh century, at roughly the same time as Anglo-Saxon Britain was being christianized. These two cultural phenomena are, of course, connected, with much of Old English literature written under the aegis of the Church. Scholars have struggled for centuries to characterize the belief system, if indeed there was one, of pre-Christian Anglo-Saxons, but place names suggest veneration, if not an organized cult, for Woden, Þunor, Tiw, and Frig, i.e., our Wednesday, Thursday, Tuesday, and Friday deities. There is no extant literature from Anglo-Saxon pagans themselves, and what remnants appear are often blended with folklore. Various early kings even claimed Woden or Thor as original ancestors without any concomitant claim of their divinity.
The absence of such sources — plus a relative wealth of sermons and other occasional works in Old English — does, however, make answering your question easier: while there are sources condemning veneration of trees or watercourses as pagan practices, there were no churchmen demanding that the days of the week be renamed according to the Christian numbering. So the Venerable Bede could muse in the eighth century — without the slightest polemic — about the Germanic and presumed pagan origin of the name for the supreme feast of the Christian liturgical year: Easter.
...and a thousand years later
To find an Anglophone equivalent of Martin of Braga, you have to wait for George Fox and the seventeenth century Quakers, who not only numbered the days of the week to avoid any reference to Germanic paganism, but also the months, especially those named for Roman deities or emperors. One Quaker writer enlivened that polemic in 1751, when England finally relented to switching to that "popish" innovation, the Gregorian calendar. This practice continues today, at least in formal contexts, for some more conservative Quaker groups. | 0.804685 | 3.031689 |
X-ray Studies of Interstellar and Intergalactic Dust
(click here for PDF)
Dust grain composition, sizes, and spatial distribution can be directly measured with high resolution X-ray imaging and spectroscopy. Dust in the foreground of bright point sources will scatter X-rays through small angles, producing a diffuse `halo' image. The scattering cross-section is most sensitive to large dust grains, which are typically missed in UV, optical, and infrared studies. The dust-to-gas mass ratio and elemental constituents of dust grains can also be determined from X-ray spectroscopy. I demonstrate how a Bayesian analysis of the scattering halo around Cyg X-3 yields a grain size distribution and mass ratio that does not match properties typically assumed of Galactic dust. Finally, I will discuss the prospects for using quasars to measure the cosmic density of dust grains in intergalactic space.
Interstellar Chemistry with X-rays
X-ray spectroscopy can reveal the presence and abundance of heavy elements in space. Many of these — including magnesium, silicon, iron, and oxygen — are widely suspected to be the main constituents of interstellar dust. I will describe experiments that directly probe the composition of dust grains along the line of sight to luminous X-ray sources.
X-ray Scattering from Intergalactic Dust
I explore the possibility of detecting large grey dust in the intergalactic medium. This poster presentation won a Chambliss Astronomy Achievement Award.
Every day two tons of cosmic dust rain down upon the surface of the Earth. In this session we will explain how you can go hunting for space rocks in your own back yard. We will explore the phenomenon of micrometeorites and their journey from space to your flower bed.
Listen here at the 365 Days Astronomy Podcast website
We will explore the history and legacy of the most publicly known yet misunderstood astronomical object. We’ll be interviewing people on the streets of New York City to highlight common questions and misconceptions about Black Holes.
Listen here at the 365 Days of Astronomy Podcast website
An archive of select poster and presentation slides.
Light echo from star V838
(NASA/ESA/H E Bond) | 0.818265 | 3.522313 |
The dwarf planet Makemake, discovered in 2005, is cold, dark and remote. It sits in the Kuiper Belt beyond Neptune, orbiting the sun at a distance almost 46 times farther away than Earth and completing an orbit once every 310 Earth-years. Recent observation by the Hubble Space Telescope, however, has revealed that Makemake is not as lonely as it once appeared: it has a moon.
Finding a Dark Moon
Until this new discovery, scientists believed Makemake was the only one of the four officially recognized dwarf planets in the Kuiper belt (Pluto, Haumea, Makemake and Eris) without a moon - the fifth official dwarf planet, Ceres, is closer to Earth and also moonless. However, there were some inconsistencies in prior measurements of Makemake’s light and heat. Observations from the Spitzer and Herschel space telescopes revealed warm, dark areas on Makemake’s otherwise bright, cold surface. However, Makemake’s apparently mottled surface would not make sense with a normally rotating dwarf planet unless it was spinning with one of its poles facing directly toward Earth, a fairly unlikely situation. The “dark moon hypothesis” offered a simpler explanation: a charcoal-black moon orbiting Makemake. “Imagine that the dark material isn’t on Makemake’s surface… it’s in orbit!” image analysis lead and paper coauthor Alex Parker tweeted. “If the moon is very dark, it accounts for most previous thermal measurements!”
Makemake is the second-farthest away of the official dwarf planets (Eris is the farthest) and the second-brightest (after Pluto). While it may seem strange that astronomers had been able to see moons around farther and dimmer planets while missing Makemake’s moon, the reality is that this moon, informally called MK2, was very good at remaining hidden.
MK2 is over 1300 times dimmer and much smaller than Makemake, and its orbit appears to be edge-on to Earth, so we don’t see it circling Makemake, only oscillating back and forth. Looking for it is like looking for a firefly flitting back and forth across a spotlight. If you watch it long enough and are lucky enough to look at the right time, as this team of astronomers did, the firefly might look obvious (in Parker’s words, “not actually that faint”), but it was easy to miss before.
Part of a team from the Southwest Research Institute in Boulder, Colorado, Parker was the first to notice Makemake’s moon in data from the Hubble Space Telescope. At first, he
thought someone else must have already seen it. Just to be sure, he asked collaborator and team leader Marc Buie, “Has anyone seen the moon in the Makemake data?” When Buie replied, “There’s a moon in the Makemake data?” they knew they’d made a major discovery.
The Moon in the Data
It is unclear where exactly the moon came from or why its surface is black. More observations of MK2 from Hubble will help astronomers determine whether its orbit is circular or elliptical, which will provide clues to its origin. If MK2’s orbit is elongated, it was probably simply captured in Makemake’s gravity as it floated by. Many smaller Kuiper Belt Objects have dark surfaces like MK2. This is often because they are too small and their gravity too weak to keep bright ices (like the ones that cover Makemake) in place.
However, MK2’s darkness could be due to constant interactions with the escaping atmospheric gases streaming off Makemake: like the top of a hearth blackened with ash, it could have accumulated compounds from Makemake’s past atmosphere. If MK2’s orbit is circular, as preliminary estimates indicate, the moon may be merely debris from a collision between Makemake and another Kuiper Belt Object. If MK2 was created by an enormous crash between two Kuiper Belt Objects, according to the paper, “The apparent ubiquity of trans-Neptunian dwarf planet satellites further supports the idea that giant collisions are a near-universal fixture in the histories of these distant worlds.” If all of the dwarf planets have satellites (moons), that may mean that Kuiper Belt Objects are often subjected to huge impacts.
The New, Improved Makemake System
While MK2 does create questions about the Makemake system and the Kuiper Belt, it will also provide answers. According to Parker, "The discovery of this moon has given us an
opportunity to study Makemake in far greater detail than we ever would have been able to without the companion."
Makemake is sometimes referred to as “Pluto’s little sister” because of their similarities: both are dwarf planets, both have surfaces coated in methane ice, and both have temperatures that can drop to -400 degrees Fahrenheit. The discovery that Makemake has a moon adds yet another similarity to Pluto. When Pluto’s largest moon, Charon, was discovered in 1978, it led to enormous new insights about Pluto itself, including that it was hundreds of times lighter than was originally estimated. “That's the kind of transformative measurement that having a satellite can enable,” Parker said: MK2 will almost definitely lead to a fundamental change in how we view the dwarf planet Makemake.
Alex Parker. (Credit: Source.)
Looking at how MK2 orbits Makemake will allow scientists to calculate the system’s mass and probe its inner composition. As Caltech’s Mike Brown, a member of the team that discovered Makemake in 2005, said, “The wide range of densities of the dwarf planets is one of the most interesting mysteries out there. But we still have so few objects that each one adds a critical part of the story.” Small worlds like Makemake display a variety of internal compositions: they can contain rock and water ice, as well as other, more “exotic” ices and compounds. Since MK2 will allow scientists to tell Makemake’s density and thus the densities of the materials it’s made of, it provides a new clue about the family of dwarf planets.
The James Webb Space Telescope, scheduled to launch in 2018, will be able to conclusively test the dark moon hypothesis. Even before then, though, information about Makemake and its moon will continue to accumulate from new Hubble observations, teaching us about the outskirts of our solar system. “This new discovery opens a new chapter in comparative planetology in the outer solar system,” Buie said, and it will add to our understanding of the many worlds around us. | 0.847193 | 3.923152 |
Black holes are invisible to the naked eye, have no locally detectable features, and even light can’t escape them. And yet, their influence on their surrounding environment makes them the perfect laboratory for testing physics under extreme conditions. In particular, they offer astronomers a chance to test Einstein’s Theory of General Relativity, which postulates that the curvature of space-time is altered by the presence of a gravity.
Thanks to a team of astronomers led by the European Southern Observatory (ESO), the closest black hole has just been found! Using the ESO’s La Silla Observatory in Chile, the team found this black hole in a triple system located just 1000 light-years from Earth in the Telescopium constellation. Known as HR 6819, this system can be seen with the naked eye and could one of many “quiet” black holes that are out there.
In what is surely the biggest news since the hunt for exoplanets began, NASA announced today the discovery of a system of seven exoplanets orbiting the nearby star of TRAPPIST-1. Discovered by a team of astronomers using data from the TRAPPIST telescope in Chile and the Spitzer Space Telescope, this find is especially exciting since all of these planets are believed to be Earth-sized and terrestrial (i.e. rocky).
But most exciting of all is the fact that three of these rocky exoplanets orbit within the star’s habitable zone (aka. “Goldilocks Zone”). This means, in effect, that these planets are capable of having liquid water on their surfaces and could therefore support life. As far as extra-solar planet discoveries go, this is without precedent, and the discovery heralds a new age in the search for life beyond our Solar System.
The team made their observations of this star system – which is located about 39 light years from Earth in the direction of the Aquarius constellation – from September to December 2015. This discovery was immediately followed-up using several ground-based telescopes, which included including the ESO’s Very Large Telescope, and the Spitzer Space Telescope.
Data from these surveys confirmed the existence of two of these planets, and revealed five more – making this the largest find around a single star in exoplanet-hunting history. Relying on the Spitzer data, Dr. Gillon and his team were also able to obtain precise information on the planets using the transit method. By measuring the periodic dips in TRAPPIST-1’s luminosity (from the planet’s passing in front of it), they were able to measure their sizes, masses and densities.
This is especially important when studying exoplanets. Not only does it allow scientists to make accurate assessments of a planet’s composition (i.e. whether or not its rocky, icy, or gaseous), it is key in determining whether or not a planet could be habitable. It was also the first time in which accurate constraints were placed upon the masses and radii of exoplanets using this method.
A follow-up survey was then mounted with NASA’s Hubble Space Telescope to study the three innermost planets and look for signs of hydrogen and helium – the chemical signatures that would indicate if the planets were gas giants. Hubble detected no evidence of hydrogen and helium atmospheres, which only strengthened the case for these planets being rocky in nature.
Another exciting aspect of all this is that these seven exoplanets – which are some of the best candidates for habitability – are near enough to Earth to be studies closely. As Michael Gillon, lead author of the paper and the principal investigator of the TRAPPIST exoplanet survey at the University of Liege, said in a NASA press release:
“The seven wonders of TRAPPIST-1 are the first Earth-size planets that have been found orbiting this kind of star. It is also the best target yet for studying the atmospheres of potentially habitable, Earth-size worlds.”
Nikole Lewis, the co-leader of the Hubble study and an astronomer at the Space Telescope Science Institute, was also on hand at the NASA press briefing where the findings were announced. There, she shared information that was obtained by the Hubble Space Telescope. And as she explained, of the three worlds that are in the habitable zone – TRAPPIST-1e, f, and g – all experience conditions that are very similar to what we experience here on Earth.
TRAPPIST-1e is the innermost of the three exoplanets. It is very close in size to Earth, and receives about the same amount of light as Earth does – which means temperatures are likely to be very close to Earth’s as well. TRAPPIST-1f, meanwhile, is a potentially-water rich world that is also likely to be the same size as Earth. It has a 9-day orbit, and receives about the same amount of sunlight as Mars.
The outermost of the habitable zone planets is Trappist 1g. With a radius that is 13% larger than that of Earth, it is the largest planet in the system, and receives about the same amount of light as a body positioned between Mars and the Asteroid Belt would. Between these three exoplanets, and the four others in the system, astronomers now have a multiple candidates within the same star system to study what potentially-habitable worlds might look like.
During the course of the NASA press briefing, Dr. Gillon stressed why the discovery of this system is a major boon for astronomers and planetary scientists. Not only is this the first time that so many exoplanets have been discovered around the same star, but the fact that it is a red dwarf – a class of small, cooler, dimmer stars – is especially encouraging.
Compared to other classes, red dwarfs (aka. M-class stars) are the most frequent type of star in the Universe – making up an estimated 70% of stars in our galaxy alone. On top of that, the TRAPPIST-1 system is rather unique. As Gillon explained, the planets are in close enough proximity that they gravitationally interact with one another. Their proximity would also make for some excellent viewing opportunities for a person standing on the surface of one of them.
“The planets are close enough to each other,” he said, “that if you were on the surface of one, you would have a wonderful view of the others. You would see them not as we see Venus or Mars from Earth (as bright stars), but as we see the Moon. They would be as large or larger than the Moon.”
In the coming weeks and months, NASA plans to follow-up on this system of planets even more. At the moment, the Kepler space telescope is studying the system, conducting measurements of minuscule changes in the star’s brightness due to transiting planets. Operating as the K2 mission, the spacecraft’s observations will allow astronomers to refine the properties of the known planets, as well as search for additional planets in the system.
In the meantime, Dr. Gillon and his team will be using ground-based telescopes to search 1000 of the nearest ultra-cool dwarf stars to see if they too have multi-planet systems. Nikole Lewis indicated that Hubble will be conducting further observations of TRAPPIST-1 in order to obtain information about the planets’ atmospheres.
These studies will determine what gases make up the atmospheres, but will also be looking for tell-tale signs of those that indicate the presence of organic life – i.e. methane, ozone, oxygen, etc.
“The TRAPPIST-1 system provides one of the best opportunities in the next decade to study the atmospheres around Earth-size planets,” she said. “Not only will these studies let us know if any of these planets have the kind of atmospheres that are conducive to life, they will also tell us much about the formation and evolution processes of the surface – which are also key factors in determining habitability.”
The Spitzer Space Telescope will also be trained on this system in order to obtain follow-up information on the planets’ atmospheres. Besides looking for biological indicators (such as oxygen gas, ozone and methane), it will also be trying to determine the greenhouse gas content of the atmospheres – which will help put further constrains on the surface temperatures of the planets.
On top of that, next-generation missions – like the James Webb Telescope – are expected to play a vital role in learning more about this system. As Sara Seager – a professor of planetary science and physics at MIT – explained in the course of the briefing, the discovery of a system with multiple potentially-habitable planets was a giant, accelerated leap forward in the hunt for life beyond our Solar System.
“Goldilocks has several sisters,” as she put it. “An amazing system like this one lets us know there are many more life-bearing worlds out there. This star system is a veritable laboratory for studying stars orbiting very cool, very dim stars. We get to test many theories about these worlds, being tidally-locked and amount of radiation coming from host star.”
Thomas Zurbuchen – the associate administrator of NASA’s Science Mission Directorate – was also on hand at the briefing. In addition to expressing how this was a first for NASA and exoplanet-hunters everywhere, he also expressed how exciting it was in the context of searching for life beyond our Solar System:
“This discovery could be a significant piece in the puzzle of finding habitable environments, places that are conducive to life. Answering the question ‘are we alone’ is a top science priority and finding so many planets like these for the first time in the habitable zone is a remarkable step forward toward that goal.”
In 2015, the All-Sky Automated Survey for Supernovae (aka. ASAS-SN, or Assassin) detected something rather brilliant in a distant galaxy. At the time, it was thought that the event (named ASASSN-15lh) was a superluminous supernova – an extremely bright explosion caused by a massive star reaching the end of its lifepsan. This event was thought to be brightest supernova ever witnessed, being twice as bright as the previous record-holder.
But new observations provided by an international team of astronomers have provided an alternative explanation that is even more exciting. Relying on data from several observatories – including the NASA/ESA Hubble Space Telescope – they have proposed that the source was a star being ripped apart by a rapidly spinning black hole, an event which is even more rare than a superluminous supernova.
According to the ASAS-SN’s findings – which were published in January of 2016 in Science – the superluminous light source appeared in a galaxy roughly 4 billion light-years from Earth. The luminous source was twice as bright as the brightest superluminous supernova observed to date, and its peak luminosity was 20 times brighter than the total light output of the entire Milky Way.
What seemed odd about it was the fact that the superluminous event appeared within a massive, red (i.e. “quiescent”) galaxy, where star formation has largely ceased. This was in contrast to most super-luminous supernovae that have been observed in the past, which are typically located in blue, star-forming dwarf galaxies. In addition, the star (which is Sun-like in size) is not nearly massive enough to become an extreme supernova.
With information from these facilities, they arrived at a much different conclusion. As Dr. Leloudas explained in a Hubble press release:
“We observed the source for 10 months following the event and have concluded that the explanation is unlikely to lie with an extraordinary bright supernova. Our results indicate that the event was probably caused by a rapidly spinning supermassive black hole as it destroyed a low-mass star.”
The process is colloquially known as “spaghettification”, where an object is ripped apart by the extreme tidal forces of a black hole. In this case, the team postulated that the star drifted too close to the supermassive black hole (SMBH) at the center of the distant galaxy. The resulting heat and the shocks created by colliding debris led to a massive burst of light – which was mistakenly believed to be a very bright supernova.
Multiple lines of evidence support this theory. As they explain in their paper, this included the fact that over the ten-months that they observed it, the star went through three distinct spectroscopic phases. This included a period of substanial re-brightening, where the star emitted a burst of UV light that accorded with a sudden increase in its temperature.
Combined with the unlikely location and the mass of the star, this all pointed towards tidal disruption rather than a massive supernova event. But as Dr. Leloudas admits, they cannot be certain of this just yet. “Even with all the collected data we cannot say with 100% certainty that the ASASSN-15lh event was a tidal disruption event.” he said. “But it is by far the most likely explanation.”
As always, additional observations are necessary before anyone can say for sure what caused this record-breaking luminous event. But in the meantime, the mere fact that something so rare was witnessed should be enough to cause some serious excitement! Speaking of which, be sure to check out the simulation videos (above and below) to see what such an event would look like:
For years, astronomers have been observing Proxima Centauri, hoping to see if this red dwarf has a planet or system of planets around it. As the closest stellar neighbor to our Solar System, a planet here would also be our closest planetary neighbor, which would present unique opportunities for research and exploration.
So there was much excitement when, earlier this month, an unnamed source claimed that the ESO had spotted an Earth-sized planet orbiting within the star’s habitable zone. And after weeks of speculation, with anticipation reaching its boiling point, the ESO has confirmed that they have found a rocky exoplanet around Proxima Centauri – known as Proxima b.
Located just 4.25 light years from our Solar System, Proxima Centauri is a red dwarf star that is often considered to be part of a trinary star system – with Alpha Centauri A and B. For some time, astronomers at the ESO have been observing Proxima Centauri, primarily with telescopes at the La Silla Observatory in Chile.
Their interest in this star was partly due to recent research that has shown how other red dwarf stars have planets orbiting them. These include, but are not limited to, TRAPPIST-1, which was shown to have three exoplanets with sizes similar to Earth last year; and Gliese 581, which was shown to have at least three exoplanets in 2007.
The ESO also confirmed that the planet is potentially terrestrial in nature (i.e. rocky), similar in size and mass to Earth, and orbits its star with an orbital period of 11 days. But best of all are the indications that surface temperatures and conditions are likely suitable for the existence of liquid water.
It’s discovery was thanks to the Pale Red Dot campaign, a name which reflects Carl Sagan’s famous reference to the Earth as a “pale blue dot”. As part of this campaign, a team of astronomers led by Guillem Anglada-Escudé – from Queen Mary University of London – have been observing Proxima Centauri for signs of wobble (i.e. the Radial Velocity Method).
After combing the Pale Red Dot data with earlier observations made by the ESO and other observatories, they noted that Proxima Centauri was indeed moving. With a regular period of 11.2 days, the star would vary between approaching Earth at a speed of 5 km an hour (3.1 mph), and then receding from Earth at the same speed.
This was certainly an exciting result, as it indicated a change in the star’s radial velocity that was consistent with the existence of a planet. Further analysis showed that the planet had a mass at least 1.3 times that of Earth, and that it orbited the star at a distance of about 7 million km (4.35 million mi) – only 5% of the Earth’s distance from the Sun.
The discovery of the planet was made possible by the La Silla’s regular observation of the star, which took place star between mid-January and April of 2016, using the 3.6-meter telescope‘s HARPS spectrograph. Other telescopes around the world conducted simultaneous observation in order to confirm the results.
One such observatory was the San Pedro de Atacama Celestial Explorations Observatory in Chile, which relied on its ASH2 telescope to monitor the changing brightness of the star during the campaign. This was essential, as red dwarfs like Proxima Centauri are active stars, and can vary in ways that would mimic the presence of the planet.
Guillem Anglada-Escudé described the excitement of the past few months in an ESO press release:
“I kept checking the consistency of the signal every single day during the 60 nights of the Pale Red Dot campaign. The first 10 were promising, the first 20 were consistent with expectations, and at 30 days the result was pretty much definitive, so we started drafting the paper!”
Two separate papers discuss the habitability of Proxima b and its climate, both of which will be appearing soon on the Institute of Space Sciences (ICE) website. These papers describe the research team’s findings and outline their conclusions on how the existence of liquid water cannot be ruled out, and discuss where it is likely to be distributed.
Though there has been plenty of excitement thanks to words like “Earth-like”, “habitable zone”, and “liquid water” being thrown around, some clarifications need to be made. For instance, Proxima b’s rotation, the strong radiation it receives from its star, and its formation history mean that its climate is sure to be very different from Earth’s.
For instance, as is indicated in the two papers, Proxima b is not likely to have seasons, and water may only be present in the sunniest regions of the planet. Where those sunny regions are located depends entirely on the planet’s rotation. If, for example, it has a synchronous rotation with its star, water will only be present on the sun-facing side. If it has a 3:2 resoncance rotation, then water is likely to exist only in the planet’s tropical belt.
In any case, the discovery of this planet will open the door to further observations, using both existing instruments and the next-generation of space telescopes. And as Anglada-Escudé states, Proxima Centauri is also likely to become the focal point in the search for extra-terrestrial life in the coming years.
“Many exoplanets have been found and many more will be found, but searching for the closest potential Earth-analogue and succeeding has been the experience of a lifetime for all of us,” he said. “Many people’s stories and efforts have converged on this discovery. The result is also a tribute to all of them. The search for life on Proxima b comes next…”
As we noted in a previous article on the subject, Project Starshot is currently developing a nanocraft that will use a laser-driven sail to make the journey to Alpha Centauri in 20 years time. But a mission to Proxima Centuari would take even less time (19.45 years at the same speed), and could study this newly-found exoplanet up-close.
One can only hope they are planning on altering their destination to take advantage of this discovery. And one can only imagine what they might find if and when they get to Proxima b!
For years, exoplanet hunters have been busy searching for planets that are similar to Earth. And when earlier this month, an unnamed source indicated that the European Southern Observatory (ESO) had done just that – i.e. spotted a terrestrial planet orbiting within the star’s habitable zone – the response was predictably intense.
The unnamed source also indicated that the ESO would be confirming this news by the end of August. At the time, the ESO offered no comment. But on the morning of Monday, August 22nd, the ESO broke its silence and announced that it will be holding a press conference this Wednesday, August 24th.
No mention was made as to the subject of the press conference or who would be in attendance. However, it is safe to assume at this point that it’s main purpose will be to address the burning question that’s on everyone’s mind: is there an Earth-analog planet orbiting the nearest star to our own?
For years, the ESO has been studying Proxima Centauri using the La Silla Observatory’s High Accuracy Radial velocity Planet Searcher (HARPS). It was this same observatory that reported the discovery of a planet around Alpha Centauri B back in 2012 – which was the “closest planet to Earth” at the time – which has since been cast into doubt.
Relying on a technique known as the Radial Velocity (or Doppler) Method, they have been monitoring this star for signs of movement. Essentially, as planets orbit a star, they exert a gravitational influence of their own which causes the star to move in a small orbit around the system’s center of mass.
Ordinarily, a star would require multiple exoplanets, or a planet of significant size (i.e. a Super-Jupiter) in order for the signs to be visible. In the case of terrestrial planets, which are much smaller than gas giants, the effect on a star’s orbit would be rather negligible. But given that Proxima Centauri is the closest star system to Earth – at a distance of 4.25 light years – the odds of discerning its radial velocity are significantly better.
According to the source cited by the German weekly Der Speigel, which was the first to report the story, the unconfirmed exoplanet is not only believed to be “Earth-like” (in the sense that it is a rocky body) but also orbits within it’s stars habitable zone (i.e. “Goldilocks Zone”).
Because of this, it would be possible for this planet to have liquid water on its surface, and an atmosphere capable of supporting life. However, we won’t know any of this for certain until we can direct the next-generation of telescopes – like the James Webb Space Telescope or Transiting Exoplanet Survey Satellite (TESS) – to study it more thoroughly.
This is certainly an exciting development, as confirmation will mean that there is planet similar to Earth that is within our reach. Given time and the development of more advanced propulsion systems, we might even be able to mount a mission there to study it up close!
The press conference will start at 1 p.m. Central European Time (CET) – 1 p.m. EDT/10 a.m. PDT. And you bet that we will be reporting on the results shortly thereafter! Stay tuned!
The hunt for exoplanets has been heating up in recent years. Since it began its mission in 2009, over four thousand exoplanet candidates have been discovered by the Kepler mission, several hundred of which have been confirmed to be “Earth-like” (i.e. terrestrial). And of these, some 216 planets have been shown to be both terrestrial and located within their parent star’s habitable zone (aka. “Goldilocks zone”).
But in what may prove to be the most exciting find to date, the German weekly Der Spiegel announced recently that astronomers have discovered an Earth-like planet orbiting Proxima Centauri, just 4.25 light-years away. Yes, in what is an apparent trifecta, this newly-discovered exoplanet is Earth-like, orbits within its sun’s habitable zone, and is within our reach. But is this too good to be true?
For over a century, astronomers have known about Proxima Centauri and believed that it is likely to be part of a trinary star system (along with Alpha Centauri A and B). Located just 0.237 ± 0.011 light years from the binary pair, this low-mass red dwarf star is also 0.12 light years (~7590 AUs) closer to Earth, making it the closest star system to our own.
In the past, the Kepler mission has revealed several Earth-like exoplanets that were deemed to be likely habitable. And recently, an international team of researchers narrowed the number of potentially-habitable exoplanets in the Kepler catalog down to the 20 that are most likely to support life. However, in just about all cases, these planets are hundreds (if not thousands) of light years away from Earth.
Knowing that there is a habitable planet that a mission from Earth could reach within our own lifetimes is nothing short of amazing! But of course, there is reason to be cautiously optimistic. Citing anonymous sources, the magazine stated:
“The still nameless planet is believed to be Earth-like and orbits at a distance to Proxima Centauri that could allow it to have liquid water on its surface — an important requirement for the emergence of life. Never before have scientists discovered a second Earth that is so close by.”
In addition, they claim that the discovery was made by the European Southern Observatory (ESO) using the La Silla Observatory‘s reflecting telescope. Coincidentally, it was this same observatory that announced the discovery of Alpha Centauri Bb back in 2012, which was also declared to be “the closest exoplanet to Earth”. Unfortunately, subsequent analysis cast doubt on its existence, claiming it was a spurious artifact of the data analysis.
However, according to Der Spiegel’s unnamed source – whom they claim was involved with the La Silla team that made the find – this latest discovery is the real deal, and was the result of intensive work. “Finding small celestial bodies is a lot of hard work,” the source was quoted as saying. “We were moving at the technically feasible limit of measurement.”
The article goes on to state that the European Southern Observatory (ESO) will be announcing the finding at the end of August. But according to numerous sources, in response to a request for comment by AFP, ESO spokesman Richard Hook refused to confirm or deny the discovery of an exoplanet around Proxima Centauri. “We are not making any comment,” he is reported as saying.
This craft, they claim, will be able to reach speeds of up to 20% the speed of light. At this speed, it will able to traverse the 4.37 light years that lie between Earth and Alpha Centauri in just 20 years. But with the possible discovery of an Earth-like planet orbiting Proxima Centauri, which lies even closer, they may want to rethink that objective.
As Professor Phillip Lubin – a professor at the University of California, Santa Barbara, the brains behind Project Starshot, and a key advisor to NASA’s DEEP-IN program – told Universe Today via email:
“The discovery of possible planet around Proxima Centauri is very exciting. It makes the case of visiting nearby stellar systems even more compelling, though we know there are many exoplanets around other nearby stars and it is very likely that the Alpha Centauri system will also have planets.”
Naturally, there is the desire (especially amongst exoplanet enthusiasts) to interpret the ESO’s refusal to comment either way as a sort of tacit confirmation. And knowing that industry professionals are excited it about it does lend an air of legitimacy. But of course, assuming anything at this point would be premature.
If the statements made by the unnamed source, and quoted by Der Speigel, are to be taken at face value, then confirmation (or denial) will be coming shortly. In the meantime, we’ll all just need to be patient. Still, you have to admit, it’s an exciting prospect: an Earth-like planet that’s actually within reach! And with a mission that could make it there within our own lifetimes. This is the stuff good science fiction is made of, you know.
If you think that breaking all the rules is cool, then you’ll appreciate one of the latest observations submitted by the Danish 1.54 meter telescope housed at ESO’s La Silla Observatory in Chile. In this thought-provoking image, you’ll see what kind of mayhem occurs when stars are forged within an interstellar nebula.
Towards the center of the Milky Way in the direction of the constellation of Sagittarius, and approximately 5000 light-years from our solar system, an expansive cloud of gas and dust await. By comparison with other nebulae in the region, this small patch of cosmic fog known as NGC 6559 isn’t as splashy as its nearby companion nebula – the Lagoon (Messier 8). Maybe you’ve seen it with your own eyes and maybe you haven’t. Either way, it is now coming to light for all of us in this incredible image.
Comprised of mainly hydrogen, this ethereal mist is the perfect breeding ground for stellar creation. As areas contained within the cloud gather enough matter, they collapse upon themselves to form new stars. These neophyte stellar objects then energize the surrounding hydrogen gas which remains around them, releasing huge amounts of high energy ultraviolet light. However, it doesn’t stop there. The hydrogen atoms then merge into the mix, creating helium atoms whose energy causes the stars to shine. Brilliant? You bet. The gas then re-emits the energy and something amazing happens… an emission nebula is created.
This zoom starts with a broad view of the Milky Way. We head in towards the centre, where stars and the pink regions marking star formation nurseries are concentrated. We see the huge gas cloud of the Lagoon Nebula (Messier 8) but finally settle on the smaller nebula NGC 6559. The colourful closing image comes from the Danish 1.54-metre telescope located at ESO’s La Silla Observatory in Chile. Credit: ESO/Nick Risinger (skysurvey.org)/S. Guisard. Music: movetwo
In the center of the image, you can see the vibrant red ribbon of the emission nebula, but that’s not the only thing contained within NGC 6559. Here swarms of solid dust particles also exist. Consisting of tiny bits of heavier elements, such as carbon, iron and silicon, these minute “mirrors” scatter the light in multiple directions. This action causes NGC 6559 to be something more than it first appears to be… now it is also a reflection nebula. It appears to be blue thanks to the magic of a principle known as Rayleigh scattering – where the light is projected more efficiently in shorter wavelengths.
Don’t stop there. NGC 6559 has a dark side, too. Contained within the cloud are sectors where dust totally obscures the light being projected behind them. In the image, these appear as bruises and dark veins seen to the bottom left-hand side and right-hand side. In order to observe what they cloak, astronomers require the use of longer wavelengths of light – ones which wouldn’t be absorbed. If you look closely, you’ll also see a myriad of saffron stars, their coloration and magnitude also effected by the maelstrom of dust.
It’s an incredible portrait of the bedlam which exists inside this very unusual interstellar cloud…
Zoom into the Pipe Nebula by using the zoom slider, or pan around the image by using the arrow icons on the toolbar or by click-dragging the image. You can also zoom into a particular area by double-clicking on your area of interest. Image credit: ESO. Zoomify by John Williams.
Images like this of the Pipe Nebula from the European Southern Observatory’s La Silla Observatory help me dream about the grandeur of the night sky and the richness of the star lanes that make up the Milky Way. | 0.936281 | 3.856843 |
NASA/JPL-Caltech/Space Science Institute/A. Bader (Lancaster University).Composite of a true colour image of Saturn, observed by Cassini in 2016, overlaid with a false colour representation of the ultraviolet aurora in the northern hemisphere as observed on 20 August 2017.
Lancaster researchers are busy analysing some of the final data sent back from the Cassini spacecraft which has been in orbit around Saturn for more than 13 years until the end of its mission in September 2017.
For the last leg of its journey, Cassini was put on a particularly daring orbit passing between Saturn and its rings which brought it closer to Saturn than ever before. This allowed scientists to obtain images of Saturn's ultraviolet auroras in unprecedented resolution. The new observations are detailed in two new studies published in Geophysical Research Letters and JGR: Space Physics.
Saturn's auroras are generated by the interaction of the solar wind, a stream of energetic particles emitted by the Sun, with Saturn's rapidly rotating magnetic field. They are located in the planet's polar regions and known to be highly dynamic, often pulsating and flashing as different dynamic processes occur in the planet's plasma environment.
Lancaster PhD student and lead author of the research Alexander Bader said: "Surprisingly many questions revolving around Saturn's auroras remain unanswered, even after the outstanding success of the Cassini mission.
"This last set of close-up images gives us unique highly detailed views of the small-scale structures which couldn't be discerned in previous observations by Cassini or the Hubble Space Telescope. We have some ideas about what their origin could be, but there is still a lot of analysis to be done."
Satellite imagery alone will hardly be enough to unravel the aurora's mysteries – the energetic particles causing the bright lightshows around Saturn's poles originate far away from the planet's surface where magnetic field lines twist and clouds of plasma interact with one another. When located in the right region, Cassini was sometimes embedded in the particle stream connecting the auroras to the magnetosphere.
First analysis of the spacecraft's particle measurements recorded during these times showed that Saturn's auroras, like Jupiter's, are generated by much more energetic particles than Earth's. However, the underlying physical mechanisms appear to show similarities between all the three.
Even though Cassini's mission is over, the data it provided remains full of surprises and will continue to help researchers understand the workings of giant planet auroras, especially in combination with Juno observations of Jupiter's magnetosphere.
Quelle: Lancaster University | 0.804096 | 3.947219 |
- Analyzing data from the Fermi Gamma-ray Space Telescope, researchers find hints of dark matter.
- The scientists looked to spot a correlation between gravitational lensing and gamma rays.
- Future release of data can pinpoint whether the dark matter is really responsible for observed effects.
By comparing data derived from gravitational lensing and gamma ray observations by the Fermi Gamma-ray Space Telescope, a study showed that certain regions of the sky emit more gamma rays. While the main cause of this phenomenon may be supermassive black holes, the researchers think that some of the emissions may be because of dark matter. It’s a so-far-undetected substance that supposedly takes up as much as 27% of all matter in the Universe, with dark energy taking up another 68% (as per NASA).
The study builds on nine years of gamma-ray data from the Large Area Telescope (LAT) that’s part of the Fermi space observatory, and was carried out by Simone Ammazzalorso at the University of Turin in Italy, Daniel Gruen at Stanford University in California, and colleagues.
The data from the telescope previously pinpointed many individual gamma-ray sources, like the remains of supernova explosions or jets of ionized matter called blazars created from accretion of material by supermassive black holes.
While many sources were located, some of the radiation that was detected by the LAT could not be traced. To investigate this, Ammazzalorso and the team of researchers compared gamma-ray background data with the first-year data from the Dark Energy Survey, carried out by the Dark Energy Camera on the Victor Blanco 4-m Telescope in Chile, which took optical snapshots of 40 million galaxies.
The research team was trying to figure out if there’s a correlation between the location of gravitational lenses and gamma ray photons. Gravitational lensing measures the distribution of the Universe’s matter by utilizing an effect predicted by Einstein. The effect takes place when light traveling to Earth from a distant object is distorted by the gravitational pull of the matter on the way.
The Difference Between Quasars, Blazars, Pulsars and Radio Galaxies
Comparing two sets of data, the scientists realized that regions of the sky with more matter were also responsible for emitting more gamma rays. On the flip side, the regions that were less dense produced fewer gamma rays.
Specifically, the researchers observed this relationship holding at at high energies and small angular scales, as reports Physics World. Blazars were likely the cause of these kinds of gamma ray emissions, according to the physicists.
The scientists spotted a weaker version of this kind of emission at larger angular scales. This other source of the gamma rays was likely dark matter, thinks Francesca Calore, an astroparticle physicist at Annecy-le-Vieux Theoretical Physics Lab in France, who wrote a commentary for the new paper.
“This result is exciting as it marks one of the few hints at the existence of dark matter via indirect detection methods, and it opens up new possibilities for probing dark matter particle models,” said Calore.
She warned that there is still a chance the noticed correlation could be due to blazars, which are still not completely understood.
New data that will be released from the Dark Energy Survey, including 100 million galaxies, as well as other upcoming sky research like the Legacy Survey of Space and Time at the Vera Rubin Observatory in Chile should shed more light on the matter.
“With deeper redshift coverage and a better angular resolution, future instruments will enable scientists to better understand the sources behind the universe’s gamma-ray glow and, potentially, uncover the nature of dark matter,” Calore stated.
Check out the new study in Physical Review Letters.
This article was originally posted on Big Think | 0.875401 | 4.156216 |
Asteroid mining: The race for space riches
There's gold in them thar asteroids – also iron, nickel, copper and, most valuable of all, water. According to the proponents of asteroid mining, these space rocks are a virtual El Dorado in the sky with more obtainable minerals in the largest three in our solar system than on the entire Earth. The question is, where exactly is all this mineral wealth and how do you get it without going broke in the process?
There's something of an international race to the asteroids underway at the moment, with countries from the United States to Luxembourg backing missions. On the surface it seems like a two-tier race – NASA and ESA are sending giant spacecraft and even manned missions, while private firms are concentrating on tiny probes that look like scale models. But while these approaches to asteroid exploration are very different, they are far from mutually exclusive.
Before we examine these exploration plans, let's look at the asteroids and why anyone would be interested in spending billions to visit a far flung rock.
Asteroids are the debris from the formation of the Solar System, when a vast ring of gas and dust condensed to form the Sun and a surrounding disc that became a collection of planetoids that crashed together over millions of years to create the planets and moons.
The asteroids are concentrated in the famous asteroid belt between Mars and Jupiter, where the gravitational pull of the latter prevented them from forming a planet, slinging some of them into the inner Solar System, while others migrated in from beyond Pluto.
Italian priest and astronomer Giuseppe Piazzi first spied Ceres in 1801, and this is cited as the first asteroid discovered (though these days Ceres is classified as a dwarf planet). By the 20th century the asteroids were recognized as a potential treasure trove and Russian space pioneer Konstantin Tsiolkovsky speculated that asteroids might be laden with gold, platinum, and diamonds.
This was a romantic notion, but Tsiolkovsky wasn't too far off. Studies indicate that an asteroid 1,000 m (3,280 ft) across could yield about 100,000 tons of platinum – which already has miners in South Africa worried because we only mine a measly 130 tons of the metal on Earth each year.
By the 1950s, asteroid miners were a common trope in science fiction. Robert Heinlein depicted them as repeating the gold rushes of the 19th century, with grizzled prospectors in clapped-out spaceships hunting for uranium instead of gold.
In 1976, Cornell University physicist Gerard K. O'Neil published The High Frontier: Human Colonies in Space, where he outlined his ideas for building giant colonies with tens of millions of people in them. Built mostly from lunar materials, these colonies would eventually use the asteroids for raw materials such as silica, carbon, hydrogen, nitrogen, and even petrochemicals, as well as metals in quantities far beyond anything available on Earth.
Modern would-be miners also see rich pickings in the asteroids, though initially the likes of Planetary Resources and Deep Space Industries (DSI) are not going after gold or platinum or uranium, but plain, ordinary water.
This is the economics of asteroid mining. Even after almost 60 years, space travel is still horribly expensive. In a recent court case involving the theft of lunar samples recovered by the Apollo 17 mission in 1972, a US federal judge determined that the Apollo Moon rocks are worth US$50,800 per gram due to the immense costs of going to the Moon and bringing the rocks back to Earth. At that price, even if asteroids were made of flawless blue-white diamonds, it might not be worth going after them.
Today, the price of getting into orbit has dropped, but not as much as was hoped. The cost of reaching geosynchronous orbit stands at about US$27,063 per kg (2.2 lb), so the economics of asteroid mining are still daunting.
This is why asteroid mining companies are focusing on near-Earth asteroids. These are asteroids that have been thrown out of their regular orbit by the gravity of Jupiter and now make eccentric passages through the inner solar system. Reaching these and returning to Earth with your plunder takes less propellant than going to the asteroid belt.
It also seems logical to try to avoid the costs of bringing materials back to Earth and concentrate on things that space missions need, but are expensive to bring from Earth. In the case of Deep Space industries and Planetary Resources, this is water, which is vital for space travelers, but costs US$10,000 per liter to send to the ISS. If the a near-Earth asteroid could be turned into a cheaper source, the water could be used for drinking and bathing, as well as split into hydrogen and oxygen for use as fuel. In addition, acting as a space-based supplier for the International Space Station or satellites could form the basis for a new orbital economy.
In the long run, many would-be asteroid miners see this new space economy as the real bonanza. Returning asteroid materials to Earth, even in refined form, is expensive. It may even unsettle Earthlings by reminding them of unpleasant science fiction novels where asteroids are deliberately fired at Earth, hitting with the force of large H-bombs.
It might be more profitable and safer to leave the asteroid products in space and use them there by means of 3D printing and other advanced production methods. Why go to the trouble of sending steel and copper back to Earth when they could be used to build satellites or space stations or more mining equipment?
But even that is a very large leap in a field where even the most basic of infrastructure needs to be built. It's one thing for NASA to build an entire space travel system from scratch and put a man on the Moon in less than a decade. It's quite another for a private company to do the same in order to stake a claim on Ceres. Private companies need to keep money coming in and the lights on while making sure investors are happy – or at least not too nervous. Companies need to reduce the costs of working in space and find a way to make it pay off in the short term.
One way to do this is to develop technology for mining and prospecting that can be repurposed for use on Earth. Call it the Teflon and Tang option, named after NASA's PR offensive in the 1970s to sell itself on the grounds of all the spinoffs it produced (though neither Teflon nor Tang were among them).
Currently, the main asteroid mining firms are concerned less with recovering minerals from asteroids than they are with remote prospecting to identify which asteroids are promising targets for exploitation and what they might contain.
Planetary Resources bases much of its surveying strategy on its Arkyd satellites. These are a series of platforms that act as technology demonstrators, culminating in the Arkyd 100, which is a small orbital telescope designed to hunt for and identify prospective asteroids. Eventually, the company hopes to have a constellation of these satellites in orbit and, if successful, they'll be joined by the Arkyd 200, a deep space probe for rendezvousing with asteroids for close observation, and Arkyd 300, which would act in swarms for detailed prospecting.
It's a bold plan, but it doesn't answer the question of how to pay the bills, so Planetary Resources has decided that when it deploys its Arkyd 100 constellation, one of its first missions will be to turn around and look at the Earth. Called Ceres, this program will allow Earthbound customers in industries such as oil, gas and agriculture to hire the constellation of 10 satellites to make detailed twice-daily observations using infrared and hyperspectral sensors.
Deep Space Industries (DSI) is another firm that hopes to achieve success by starting small, keeping things cheap and going for short-term goals, but is also faced with the problem of making that first profitable step. Satellite propellants may be worth US$25 million a ton to send into orbit and replacing them with space-based equivalents is tempting, but with DSI estimating that its first satellites will cost US$20 million, that's a pretty wide margin to span.
Like Planetary Resources, DSI is planning on repurposing some of its technology for non-mining efforts. One of the company's major efforts is Prospector-1, which is an asteroid lander mission that will "only" cost something in the neighborhood of US$10 million. Since Prospector-1 isn't due to launch for a decade and there are bills to pay, DSI is offering the platform to other companies to develop their own low-cost missions.
DSI's other approach is to partner with the government of Luxembourg. Under this agreement, DSI will establish a new headquarters in the country and the Luxembourg space program, (LuxIMPULSE) will co-fund R&D projects beginning with DSI's Prospector-X technology demonstrator satellite. This low-Earth orbit minisatellite is designed to prove the practicality of DSI's technology for deep space missions to seek out, survey, and mine asteroids for water and minerals.
Mixing it with the big boys
But the question remains, what chance do these tiny private companies have? For all their ambitions, the missions being planned by the likes of Planetary Resources and DSI look like student projects compared to the efforts of NASA and other space agencies. Are these entrepreneurs out of their league?
In one sense, the answer is yes. Where the private ventures work in budgets of millions, NASA's OSIRIS-REx mission alone cost almost a billion dollars and uses a spacecraft the size of a truck. If all goes well, it will return the first samples from the asteroid Bennu by 2023, as well as providing a detailed study of the asteroid's composition and other properties. All this will be much more, and long before, anything the private companies can deliver.
But OSIRIS-REx's mission isn't about space mining. Its purpose is mainly pure science, and the samples coming back to Earth have as much to do with asteroid mining as the Apollo mission samples did with lunar mining. They might produce useful information, but they're not directly concerned with commercial exploitation.
OSIRIS-REx is designed to carry out many different functions with a suite of instruments for everything from infrared spectronomy to cosmic ray analysis. Such deep space probes are built with a high-degree of survivability to protect the investment, so they have redundant systems and shielding.
But that doesn't mean the information brought back by OSIRIS-REx will be of no use to asteroid miners. An interesting aspect of this is one of the probe's secondary mission objectives – to study asteroid deflection. Bennu is wider than the Empire State Building is tall and the asteroid has a slight chance of impacting the Earth in the future, so NASA is studying what it would take to deflect it from its present trajectory. It's an important question not only from the viewpoint of planetary security, but for asteroid miners, who will certainly need such a capability.
This ability to redirect asteroid also has a more immediate purpose. One of NASA's flagship projects is the manned Orion space capsule, which is designed for deep-space missions, but is currently lacking any plausible destination. One way to solve this is the space agency's proposed Asteroid Redirect Mission.
If it can be funded, it will launch a robotic spacecraft in December 2020 that will not only rendezvous with a near-Earth asteroid, but capture it with a huge tarp and ferry it back to cislunar orbit using a solar-electric propulsion system similar to the one on the Dawn mission.
After the boulder has been placed into lunar orbit in the mid-2020s, NASA will launch an Orion spacecraft with two astronauts aboard on a 25-day mission to rendezvous with the asteroid fragment for study and collecting samples. Not only will this provide new insights into the asteroids, but NASA regards the mission as a rehearsal for an eventual manned mission to Mars.
These and other missions, such as the US-European Asteroid Impact and Deflection mission (AIDA), put asteroids high on the list of space destinations in the 21st century, though for many different reasons. Some are going for pure science, some to stave off earthly disaster and some to mine. One day these missions might even include colonists bound for the asteroid belt.
At present the planned missions fit into two distinct categories with different priorities and different approaches. Space agencies like NASA are answerable to governments and taxpayers while asteroid miners take their orders from stockholders and customers. Space agencies have larger budgets, much broader mandates, and carry out missions that could have an impact on national security or prestige. In addition, they tend to be very risk adverse because a major disaster could throw a wet blanket on future projects for decades.
On the other hand, private miners work on shoestring budgets, have very specific goals, and, though they are driven by a need to stay in the black, they are more likely to take on risk. Mistakes will be made, but others will learn from them and the commercial imperative may drive space exploration forward faster and in unforeseen ways.
Rather than a gold rush, asteroid mining might be more aptly compared to oil and gas exploration, where pure geological research spills over into the hunt for new drilling fields. If asteroid mining does prove to be viable in coming decades, it will be on the back of lessons learned from both government and private missions. Only time and the balance sheet will tell. | 0.856397 | 3.446198 |
Astronomers have identified the smallest known black hole. The puny object weighs only 3.8 times the Sun’s mass and spans just 24 kilometres across.
The black hole is believed to have formed from the collapse of a massive star when it ran out of fuel.
Astronomers are not sure what the smallest possible mass is for black holes formed this way, but they estimate that it is somewhere between 1.7 and 2.7 times the Sun’s mass. Less massive objects are expected to collapse into dense neutron stars instead of black holes.
“This black hole is really pushing the limits,” says Nikolai Shaposhnikov of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, US, who carried out the study with Lev Titarchuk, also of Goddard. “For many years, astronomers have wanted to know the smallest possible size of a black hole, and this little guy is a big step toward answering that question.”
The black hole they studied is part of a binary system called XTE J1650-500, where the black hole and an ordinary star orbit around each other. Gas stolen from the ordinary star heats up and emits X-rays as it spirals into the black hole.
As in other similar systems, the intensity of the X-rays rises and falls in a semi-regular way, producing what are known as quasi-periodic oscillations (QPOs). The reason for this is still debated, but some scientists say it is due to gas repeatedly piling up near the black hole and then getting swallowed.
Regardless of how they are produced, the frequency of the QPOs appears to be closely related to the black hole mass. Shaposhnikov and Titarchuk have previously used this relationship to calculate the mass of three other black holes that had already been weighed using well-established techniques and found good agreement between the different approaches.
Now, the two have used the Rossi X-ray Timing Explorer satellite (RXTE) to study QPOs from XTE J1650-500. They calculate the black hole weighs 3.8 times the Sun’s mass, with an uncertainty of 0.5 times the Sun’s mass. The next smallest black hole with a well-measured mass is called GRO 1655-40. It weighs about 6.3 times the Sun’s mass.
Exotic black holes
Even smaller black holes may have been produced in the violence of the universe’s earliest moments. Some of these primordial black holes could be microscopic, but so far none of the exotic black holes have been detected.
There is also a chance that microscopic black holes could be created in the Large Hadron Collider particle accelerator due to begin operating in 2008. But these black holes should evaporate with a flash of radiation in a fraction of a second.
At the other extreme are black holes with billions of times the mass of the Sun that reside at the centres of some galaxies. The heaviest known weighs as much as 18 billion Suns. By contrast, the black hole at the centre of our Milky Way galaxy weighs about 4 million Suns and is about 20 million kilometres across.
A black hole’s size is defined by a boundary called its event horizon. Anything that passes closer to the black hole’s centre than the event horizon – including light – is doomed to be swallowed by the black hole.
The new results were presented on Monday at a meeting of the American Astronomical Society’s High-Energy Astrophysics Division in Los Angeles, California, US. | 0.874233 | 3.934111 |
Ralph McNutt’s contributions to interstellar mission studies are long-term and ongoing. We’ve looked at the Innovative Interstellar Explorer concept he has been studying at the Applied Physics Laboratory (Johns Hopkins), but IIE itself rose out of earlier design studies for a spacecraft that would penetrate the heliopause to reach true interstellar space. One possibility for that earlier probe was a ‘Sun-diver’ maneuver, a close pass by the Sun to gain a gravitational slingshot effect, followed by an additional kick from an onboard booster.
The thinking a few years back was to reach 1000 AU in less than fifty years, but Innovative Interstellar Explorer has lost the Sun-diver maneuver and focuses on a more realistic 200 AU, as part of a NASA Vision Mission study that contemplates a gravitational assist at Jupiter and the use of radioisotope electric propulsion. IIE is subject to the same funding constraints as any other mission of this nature but it’s well worth perusing its specs on the site, for McNutt is both scientist and visionary, a man who looks beyond the ‘lifetime of a researcher’ limit for mission duration.
That has taken him into interesting intellectual terrain, writing in a study for NASA’s now defunct Institute for Advanced Concepts of a future technology that could reach speeds of 200 AU per year. That’s fast enough to get you to Epsilon Eridani in 3500 years, approximately the lifetime of the Egyptian empire. Writes McNutt:
“A more robust propulsion system that enabled a similar trajectory toward higher declination stars such as Alpha Centauri could make the corresponding shorter crossing in a correspondingly shorter time of ~1400 years, the time that some buildings have been maintained, e.g., Hagia Sophia in Constantinople and the Pantheon in Rome. Though far from ideal, the stars would be within our reach.”
Human Expeditions to the Gas Giants and Beyond
Given these musings, where does McNutt stand on human exploration of the Solar System itself? We learn the answer in an interesting piece that has just appeared in the Johns Hopkins APL Technical Digest where, writing with Jerry Horsewood and Douglas Fiehler, he notes the sharp constraint that radiation exposure places upon mission designers. We know we can reach the outer Solar System — our unmanned probes continue to demonstrate the capability — but humans in deep space have to cope with solar energetic particles from the Sun (SEPs) and galactic cosmic rays (GCRs). That means getting to the destination quickly.
The article looks at optimized trajectories to Callisto, Enceladus, Miranda, Triton and Pluto, five expeditions that each demand one-way flight times of no more than two years, with a total mission time of five years. Solar energetic particles can be shielded against, but running the numbers on galactic cosmic rays shows they would require a huge mass penalty for shielding. To approximate the shielding effect of the Earth’s atmosphere would involve a shield massing thousands of tons. Limiting flight times seems the only solution.
To make this happen, McNutt envisions a nuclear electric propulsion system with an overall power level of 100 MWe, with the electricity generated by the nuclear reactor being used to power up the plasma stream that propels the vehicle. The Neptune mission, targeted for a 2075 launch, would achieve 197.5 kilometers per second with a thrust time of 1.2 years — compare that to the 16.2 kilometers per second New Horizons is currently managing on its trajectory to Pluto/Charon. And the trajectories of these five fast missions are themselves interesting:
The striking point for all of these trajectories, and especially for the three outermost targets, is the lack of curvature. To date, planetary transfer trajectories make use of near-Hohmann-transfer orbits (minimum-energy solutions), albeit sometimes with intermediate planetary gravity assists. Propulsive maneuvers typically are used for gravitational capture at the target, rather than slowing down from faster-than-required transfer orbits. The “straight” trajectories are driven by the requirement of a fixed transit time; without the interplanetary deceleration period before reaching the target planet, the spacecraft in each case would escape from the solar system.
Demands of the Journey
It’s the radiation constraint that pushes our propulsion technologies well past current capabilities, shortening acceptable trip times and demanding speeds that in our current context are almost surreal. Back in 1968, Clarke and Kubrick’s 2001: A Space Odyssey sent the ‘Discovery 1’ mission to Jupiter without evident regard for radiation shielding, and young optimists like me in the audience assumed that the outer planets would be within reach some time in the early 21st Century. Now we’re talking about putting together a set of missions that vaguely resemble Clarke and Kubrick’s a century later than the film had supposed.
Interestingly, by McNutt’s calculations, these expeditions would be mounted in a vehicle offering a habitable volume about twice that of the spaceship in 2001 if we assume a crew of ten (a crew of six is also considered in the paper). And if 2001 didn’t concern itself with enroute radiation, another thing it didn’t dwell on was the method for constructing the interplanetary craft. To build such a vehicle, we’ll need something like the extremely heavy lift launch vehicles (EHLLVs), or ‘Supernovas,’ that were originally studied in the 1960s. McNutt discusses lifting a thousand tons to low-Earth orbit with each launch for assembly of the outer system spacecraft in space. The study envisions 30 Supernova launches for the five expeditions.
Costs of an International Venture
All of this adds up to huge costs, some $4 trillion, which compares to a US GDP of $13 trillion in 2006 and a world GDP in the same year of $48 trillion. The five expeditions to the outer planets would clearly demand an international initiative, one that would cost 1.5 times the U.S. cost of World War II in 2006 dollars. From the study’s summary:
A 5-year round-trip mission will require ~10 t per person of expendable supplies with a likely crew of at least six people and an extremely reliable vehicle with an extremely dedicated and stable crew. Infrastructure capable of putting tens of thousands of metric tons of materials into LEO will be required as well. Such a project is potentially achievable at the cost of at least 10% of the current world GDP. With current investment in human space activity in the United States, even with growth projected on the basis of the growth of the overall U.S. economy, a dedicated, international effort will likely be required if the entire solar system is to have an initial reconnaissance by human crews by the beginning of the 22nd century.
Getting a human presence to the outer planets by the end of the century is going to be tough even if we assume the propulsion advances that can achieve 200 kilometers per second — or in the case of Pluto/Charon, over 300 kilometers per second. But this is exactly the kind of study we need to place our current technology in context. We can’t assume anything about future breakthroughs. We can only define the problems we face so that in that context, future work may produce solutions that can lower travel times and costs to acceptable levels.
The report is McNutt, Horsewood and Fiehler, “Human Missions Throughout the Solar System: Requirements and Implementations,” available online. McNutt’s Phase I and II studies for the NASA Institute for Advanced Concepts are still available on the NIAC site. | 0.903837 | 3.808437 |
It’s staggering how much our view of the Solar System has changed over the past few decades. The system I grew up with seemed a stable place. The planets were in well-defined orbits out to Pluto and, even if it were always possible another might be found, it surely couldn’t pose any great surprise in that great emptiness that was the outer system. But today we routinely track trans-Neptunian objects with diameters over 500 kilometers — about 50 of these have now been found, and some 122 TNOs at least 300 kilometers in diameter. We know about well over a thousand objects in that ring of early system debris called the Kuiper Belt.
It’s an increasingly messy place, this outer Solar System, and it has its own terminology. We have centaurs and plutinos, resonance objects, cubewanos, scattered disk objects (SDOs), Neptune trojans, damocloids, apollos and, perhaps, inner Oort cloud objects.
Nope, this isn’t the Solar System I grew up with, and every new discovery adds to the enchantment. Its burgeoning population of outer objects tells us much about its history, assuming we can make the right deductions from what we see. Orbital trajectories are a kind of history written in motion. The reason that a belt of objects beyond Neptune was first suspected was that Jupiter-family comets have orbital inclinations too low to be consistent with an origin in the Oort Cloud, that spherical cloud of comets thought to stretch a light year or more from the Sun. Advances in CCD technology soon made it possible to track down Kuiper Belt objects, and it’s now believed that 100,000 KBOs with diameters larger than 100 kilometers could exist, and perhaps as many as 800 million objects with diameters larger than five kilometers.
Image: Views of the Kuiper Belt and the Oort Cloud. Credit: Donald K. Yeoman/NASA/JPL.
The Outer System Poker Game
All of which is intriguing in its own right, but sometimes it takes a wild card to drive the story forward. That wild card came in the form of Sedna, discovered in 2003 by Mike Brown (Caltech). Brown has been ruminating over the discovery on his Mike Brown’s Planets site, where he notes the fact that the orbit of every object in the Solar System can be explained, at least in principle, by interactions with the known planets. Every object except Sedna:
Seven years ago, the moment I first calculated the odd orbit of Sedna and realized it never came anywhere close to any of the planets, it instantly became clear that we astronomers had been missing something all along. Either something large once passed through the outer parts of our solar system and is now long gone, or something large still lurks in a distant corner out there and we haven’t found it yet.
The possibilities are fascinating, one being the existence of an unknown planet of approximately Earth’s size at roughly 60 AU. Another possibility: A star that passed close to the Solar System at some point in the remote past, perhaps as close as 500 or 600 AU. In both cases, gravitational interactions would have interfered with what would otherwise have been a routine Kuiper Belt object, kicking it into its present orbit. Brown pegs the chances of a rogue star encounter at around one percent, but in any case, finding the culprit star would be impossible. The Sun has orbited the Milky Way 18 times in our Solar System’s history. “Everything is now so mixed up,” he adds, “that there is no way to know for sure what was where back when.”
The View from a Cluster
The third possibility? A kick from not one passing star but from many relatively nearby stars, a kick dating back to the Sun’s presence in the cluster in which the Sun was born. Brown’s description of the process and the place in which it might have occurred is worth repeating:
In the cluster of stars in which the sun might have been born there would have been thousands or even tens to hundreds of thousands of stars in this same volume, all held together by the gravitational pull of the massive amounts of gas between the still-forming stars. I firmly believe that the view from the inside of one of these clusters must be one of the most awesome sights in the universe, but I suspect no life form has ever seen it, because it is so short-lived that there might not even be time to make solid planets, much less evolve life.
A striking view indeed, and the poets among us can muse on its transience. Brown continues:
For as the still-forming stars finally pull in enough of the gas to become massive enough to ignite their nuclear-fusion-powered cores they quickly blow the remaining gas holding everything together away and then drift off solitary into interstellar space. Today we have no way of ever finding our solar siblings again. And, while we see these processes occurring out in space as other stars are being born, we really have no way to see back 4.5 billion years ago and see this happening as the sun itself formed.
But Sedna may help, because its orbit should be a record of what was going on when the Sun and our Solar System were in their infancy, a key to unlocking a 4.5 billion year old puzzle. The problem is that with only a single object of this kind, we wouldn’t have enough information on which to build the bigger picture, which is why researchers like Brown continue to look for other Sednas. It’s also why numerous other theories have sprung up, including the possibility that Sedna once orbited a different star and is actually an extra-solar dwarf planet. Or (an old favorite) that a brown dwarf somewhere in the Oort Cloud could have given it its nudge.
Of Dust and the Disk
All this reminds me of Mark Kuchner’s work on Kuiper Belt dust. Kuchner (NASA GSFC) has been running supercomputer simulations tracking the interactions of dust grains, and points to the Kuiper Belt as not only the home of countless small objects, but of dust and debris that model, though in a much older and developed way, the debris disks around Vega and Fomalhaut. At stake is how dust travels through the Solar System, affected by the solar wind and pushed by sunlight, not to mention the effects of collisions between icy grains themselves.
Kuchner’s team has been able to create infrared simulations of the Solar System as it might be seen from another star, using models of dust generation that could reflect what the condition of the Kuiper Belt was in a series of time frames going back in steps to 15 million years ago. The simulations show that a broad dusty disk like today’s collapses into a dense ring as we go back in time, producing something similar to the rings we’ve found around other stars. But today’s belt is still active. “[E}ven in the present-day solar system,” says Christopher Stark (Carnegie Institution for Science), “collisions play an important role in the Kuiper Belt’s structure.”
Interestingly for our model of dust in the outer system, Neptune’s gravitational effects push nearby particles into preferred orbits, creating a clear zone near the planet and dust enhancements that precede and follow it around the Sun. Kuchner calls this ‘carving a little gap in the dust.’ Our picture of dust in planetary systems is developing, but it’s worth noting how much work we have to do to anticipate the effects of dust on fast-moving spacecraft as we push past the heliopause and into true interstellar space. And Sedna’s odd orbit reminds us how much awaits discovery in our own systems’ furthest reaches. | 0.857277 | 3.877385 |
The telescope was built to spot black holes and other distant and dark stellar objects. This is the first time the spacecraft has trained its eyes on our own sun. It's a kind of out-there idea hatched in the early days of the mission, when scientists realized NuStar's powerful instruments might be able to see new details in our star. Because NuStar senses x-rays, they could turn it toward the sun without hurting the instruments.
NuStar already has given insights into temperature fluctuations above sunspots. It may also be able to capture theorized nanoflares in action. Nanoflares are small-scale solar flares, and they could help to explain the curious difference between the hot temperatures of the corona and the cooler temperatures of the sun's surface below.
The probe may even be able to spot axions at the core of the sun. If so, NuStar could confirm the existence of the ever-elusive dark matter, which makes up a majority of the universe but has never been seen before.
Via Boing Boing. | 0.890259 | 3.287649 |
Astronomers with the European Southern Observatory (ESO) have found a black hole that’s the nearest such object but discovered, simply 1,000 light-years away—shut sufficient to be seen with the unaided eye. It’s a part of a triple star system, dubbed HR 6819, and the ESO scientists consider different members of this class of methods might additionally harbor black holes that beforehand weren’t excessive precedence for black gap searches. They introduced their discovery in a new paper revealed within the journal Astronomy and Astrophysics.
Scientists suppose there are much more black holes within the Universe than now we have found up to now—most likely a whole lot of tens of millions of them, given the age of our Universe—as a result of we will not observe them straight; we are able to merely infer their presence by their impact on surrounding matter. A black hole’s gravitational results can affect the orbits of close by stars, for instance, or infalling matter can type an accretion disk of scorching gasoline quickly orbiting the black hole, emitting highly effective X-rays. Or an unlucky star will get too near a black gap and be torn aside for its hassle, with the infalling remnants additionally accelerating and heating as much as emitting X-rays into space.
However, the majority of black holes are literally quiet and, therefore, very troublesome to detect. This newest discovery affords helpful clues about the place at the very least among the really dark black holes is likely to be hiding. “One won’t ever get sufficient telescope time to do an intensive search like that on all objects,” ESO scientist Thomas Rivinius, a co-author on the paper, instructed Ars. “What it’s essential to do is a staged strategy that can assist you in establishing candidates, then skinny out the candidate’s record, and solely then have a detailed and detailed have a look at the remaining ones. Understanding what to search for ought to put us in a greater place to seek out them.” | 0.851311 | 3.808254 |
Although spring has officially been with us now for just over a week, we can still partake of many of the bright stars of the wintertime season. At around 9 p.m. local time, over toward the west and south our early evening sky is still strewn with brilliant constellations and outstanding deep-sky objects.
Interestingly two of these star patterns, mighty Orion, the hunter and Gemini, the twins rise together. Both are oblong in shape, though Gemini is somewhat longer and thinner; it contains far fewer bright stars compared to neighboring Orion, and Gemini does not contain a distinctive line of stars in the middle to match Orion’s three-star belt. Both figures are tilted as they ascend in the eastern sky, elevated at the ends toward the Milky Way that lies between them.
Gemini is positioned farther to the north than most of the other winter constellations and seems to drop behind the rest as they climb high into the sky, passing more or less overhead when at their highest, bringing up the rear of the westward march across the sky along with Orion’s two dogs. In fact, even though they are generally considered to be a wintertime star pattern, we might consider Gemini to belong more to early spring.
There they are, standing upright, high up in the western evening sky: the Gemini twins.
The heads of the twins are the bright stars Pollux (yellowish; 17th-brightest star in the sky) and Castor (white; a bit dimmer than Pollux). Castor is famous in the annals of binary stars as the pair whose mutual revolution was first made known. It was the British astronomer William Herschel who provided in the year 1803 that the two stars of Castor are united by the bond of their attraction. And in fact, Castor is actually a system of six stars, forming one of the most remarkable examples of a multiple-star system in the heavens. With the naked eye we see only one star, but just imagine, in that one speck of light we actually have six stars for the price of one! This sextuple star can be seen only as a double through a small telescope.
Yellowish Pollux, too, has a companion — though not a star, but a planet. It was discovered in June 2006 and was originally known as “Pollux b,” but is now called Thestias. It’s a gas giant about twice as large as Jupiter and orbits Pollux at a distance of 1.65 astronomical units — a little farther from its star than Mars is from the sun.
The stars that compose the twins’ arms and bodies are fainter than those in their heads and feet. A second-magnitude star known as Alhena marks one of Pollux’s feet. In places where light pollution hides many of the fainter stars, only Pollux, Castor and Alhena may be visible, forming a long wedge with its point aimed straight at Orion.
According to legend, Pollux and Castor hatched from an egg from their mother Leda, following her seduction by Zeus. The twins were among the heroes who sailed with Jason in the quest for the Golden Fleece. They helped save the great ship Argo from sinking during a major storm, and for this reason ancient mariners regarded Pollux and Castor as the patrons of seafarers. In Elizabethan times they were also considered the protectors of all at sea. The expression “by Jiminy” was a popular corruption of the swearing by the ancients by these patrons, as in “by Gemini.” The brothers have figured in scores of ancient folk tales. They were adventurers, warriors, and famous navigators.
A new planet!
If I were to venture a guess, I would think that Gemini was William Herschel’s favorite constellation. Not only did he make the discovery revealing Castor to be a binary star, but this musician (an organist), who made telescopes for diversion and spent much of his spare time observing the heavens, discovered a new planet in Gemini.
Herschel was observing stars in Gemini on the night of March 13, 1781, when he ran across a star that “appeared visibly larger than the rest … I suspected it to be a comet,” he wrote in his notes. By the end of August, with Gemini rising in the morning sky, the new object was visible once more. But the more astronomers studied it, the more they began to wonder if it really was a comet. For one thing, it seemed to be following a nearly circular orbit out beyond Saturn, whereas comets have highly elliptical orbits that carry them far away into the outskirts of the solar system in between each close pass by the sun.
It was Finnish mathematician Anders Lexell (1740-1784) who first confirmed that Herschel had found a new planet in the solar system; another wanderer barely visible to the naked eye and twice as remote from the sun compared to Saturn. It was the first planet to be discovered with a telescope. Following this discovery, which won him international acclaim, Herschel accepted an offer from King George III to give up his music career and to become Sir William Herschel, England’s Astronomer Royal.
Many people thought that the planet should be named Herschel as an additional honor to its discoverer. Herschel himself named it Georgium Sidus, or “George’s Star,” after the King. But astronomers ultimately decided to call it Uranus to match the classical names of the other planets. Certainly, that made more sense, otherwise our list of the planets going outbound from the sun would read this way: Mercury, Venus, Earth, Mars, Jupiter, Saturn and … George?
One of the “greatest sights”
Located just off the trailing foot of Castor, is the 35th deep-sky object that was cataloged by French astronomer, Charles Messier (1730-1817). Called Messier 35 (M35), it can just be seen with the unaided eye on dark transparent nights. In low-power binoculars it may look like a dim, fairly large unresolved interstellar cloud, but look again. Even through light-polluted suburban skies, glasses with 7X magnification reveal at least a half dozen of the cluster’s brightest stars against the whitish glow of about 200 fainter ones.
M35 has been described as a “splendid specimen” whose stars appear in curving rows, reminding one of the bursting of a skyrocket. Walter Scott Houston (1912-1993) who wrote the Deep-Sky Wonders column in Sky & Telescope magazine for nearly half a century called M35: “one of the greatest objects in the heavens; a superb object that appears as big as the Moon and fills the eyepiece with a glitter of bright stars from center to edge.”
Located less than half a degree southwest from M35 is an unusual object that brought me a brief surge of excitement, as well as to countless numbers of other amateurs over the years. In September 1985, while camping in the Adirondacks of northern New York, I was scanning the Orion-Gemini region with my 10.1″ Dobsonian telescope, looking for two famous periodic comets, Halley and Giacobini-Zinner. It was then that I stumbled across a faint, circular cloud of light, which initially appeared as a possible new comet.
The object, in fact, is the faint open star cluster NGC 2158. Indeed, if you get a chance to train a telescope on M35 and come across this small, faint patch of nebulosity a short distance away at least you won’t be making the “comet mistake” that so many others have made. On that September night back in 1985, for not a few minutes I thought I was looking at “Rao’s Comet” but after composing myself and checking a celestial handbook, I came back down to Earth. “Scotty” Houston himself fell into this trap, later calling NGC 2158 his “lasting monument to my early, somewhat careless, years of observing.”
Joe Rao serves as an instructor and guest lecturer at New York’s Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers’ Almanac and other publications. Follow us on Twitter @Spacedotcom and on Facebook | 0.925886 | 3.802642 |
This story was updated at 7:01 p.m. EST.
Thepossibility of an asteroid walloping the planet Mars this month is whetting theappetites of Earth-bound scientists, even as they further refine the spacerock's trajectory.
The spacerock in question — Asteroid2007 WD5 — is similar in size to the object that carved MeteorCrater into northern Arizona some 50,000 years ago and is approaching Marsat about 30,000 miles per hour (48,280 kph).
Whether theasteroid will actually hit Mars or not is still uncertain.
Such animpact, researchers said, would prove an awesome opportunity for planetary sciencesince NASA's Mars Reconnaissance Orbiter (MRO) and a flotilla of otherspacecraft are already in position to follow up any impact from orbit.
?An impactthat we could witness/follow-up with MRO would be truly spectacular, and couldtell us much about the hidden subsurface that could help direct a search forlife or life-related molecules,? said John Rummel, NASA's senior scientist forastrobiology at the agency's Washington, D.C., headquarters.
Observationsof the asteroid between Dec. 29 and Jan. 2 allowed astronomers to slightlylower the space rock's odds of striking Mars to about 3.6 percent (down from3.9), giving the object a 1 in 28 chance of hitting the planet, according to Tuesdayreport from NASA's Near Earth-Object program office at the Jet PropulsionLaboratory in Pasadena, Calif.
Moreobservations may further reduce the asteroid's impact chances to nil, NEOofficials said. The space rock's refined course stems from observations byastronomers at New Mexico Tech's Magdalena Ridge Observatory.
But if WD5does smack into Mars, some astronomers have a fair idea of what havoc it mayspawn. The likely strike zone would be near the equator, but to the north ofthe current position of NASA's Opportunity rover at Victoria Crater, NASA officialshave said.
MarkBoslough, a collision dynamics expert at New Mexico's Sandia NationalLaboratory, said the atmosphere at Mars' surface is similar to that of Earth atan altitude of 12 miles (20 km). Some space rocks that target Earth explodeunder the pressure created as they stream into our atmosphere. But they tendnot to explode until much below the 12-mile mark.
"Sothis won't be an airburst," Boslough said. "It will either hit theground intact and make a single crater, or break up and generate a cluster ofcraters."
Thecollision, were it to occur, could also create a visible dust plume as ejectais lofted high into the martian atmosphere, he said.
Theresulting crater could reach more than a half-mile (0.8-km) in diameter, orabout the size of the Opportunity rover's Victoria home, NASA added.
Boslough'sbreak-up scenario is reminiscent of CometP/Shoemaker-Levy 9, which broke into more than 20 fragments as it nearedJupiter in 1994, then repeatedly pummeled the gas giant over the course of six days.The resulting impact scars were visible to telescopes on Earth, in orbit andNASA's Galileo probe, which was en route to Jupiter at the time of the collision.
LikeGalileo at Jupiter, NASA's MRO probe and its High-Resolution Imaging Experiment(HiRISE) camera would be in prime position for a martian collision. With itsability to resolve objects three feet (one meter) across, HiRISE as been billedas the most powerful camera ever sent to study Mars.
?If theasteroid hits Mars, we?ll get a great look at the crater within a few days ofimpact,? said HiRISE principal investigator Alfred McEwen of the University ofArizona?s Lunar and Planetary Laboratory in Tucson.
SPACE.com Staff Writer Tariq Malik contributed to thisreport from New York City.
- VIDEO: Mars Rover Team Ponders Mission's End
- IMAGES: Impact Craters on Earth and Beyond
- Top 10 Mars Rover Discoveries | 0.869005 | 3.298476 |
- Explain the difference between mass and weight
- Explain why falling objects on Earth are never truly in free fall
- Describe the concept of weightlessness
Mass and weight are often used interchangeably in everyday conversation. For example, our medical records often show our weight in kilograms but never in the correct units of newtons. In physics, however, there is an important distinction. Weight is the pull of Earth on an object. It depends on the distance from the center of Earth. Unlike weight, mass does not vary with location. The mass of an object is the same on Earth, in orbit, or on the surface of the Moon.
Units of Force
The equation is used to define net force in terms of mass, length, and time. As explained earlier, the SI unit of force is the newton. Since
Although almost the entire world uses the newton for the unit of force, in the United States, the most familiar unit of force is the pound (lb), where 1 N = 0.225 lb. Thus, a 225-lb person weighs 1000 N.
Weight and Gravitational Force
When an object is dropped, it accelerates toward the center of Earth. Newton’s second law says that a net force on an object is responsible for its acceleration. If air resistance is negligible, the net force on a falling object is the gravitational force, commonly called its weight , or its force due to gravity acting on an object of mass m. Weight can be denoted as a vector because it has a direction; down is, by definition, the direction of gravity, and hence, weight is a downward force. The magnitude of weight is denoted as w. Galileo was instrumental in showing that, in the absence of air resistance, all objects fall with the same acceleration g. Using Galileo’s result and Newton’s second law, we can derive an equation for weight.
Consider an object with mass m falling toward Earth. It experiences only the downward force of gravity, which is the weight . Newton’s second law says that the magnitude of the net external force on an object is We know that the acceleration of an object due to gravity is or . Substituting these into Newton’s second law gives us the following equations.
The gravitational force on a mass is its weight. We can write this in vector form, where is weight and m is mass, as
In scalar form, we can write
Since on Earth, the weight of a 1.00-kg object on Earth is 9.80 N:
When the net external force on an object is its weight, we say that it is in free fall, that is, the only force acting on the object is gravity. However, when objects on Earth fall downward, they are never truly in free fall because there is always some upward resistance force from the air acting on the object.
Acceleration due to gravity g varies slightly over the surface of Earth, so the weight of an object depends on its location and is not an intrinsic property of the object. Weight varies dramatically if we leave Earth’s surface. On the Moon, for example, acceleration due to gravity is only . A 1.0-kg mass thus has a weight of 9.8 N on Earth and only about 1.7 N on the Moon.
The broadest definition of weight in this sense is that the weight of an object is the gravitational force on it from the nearest large body, such as Earth, the Moon, or the Sun. This is the most common and useful definition of weight in physics. It differs dramatically, however, from the definition of weight used by NASA and the popular media in relation to space travel and exploration. When they speak of “weightlessness” and “microgravity,” they are referring to the phenomenon we call “free fall” in physics. We use the preceding definition of weight, force due to gravity acting on an object of mass m, and we make careful distinctions between free fall and actual weightlessness.
Be aware that weight and mass are different physical quantities, although they are closely related. Mass is an intrinsic property of an object: It is a quantity of matter. The quantity or amount of matter of an object is determined by the numbers of atoms and molecules of various types it contains. Because these numbers do not vary, in Newtonian physics, mass does not vary; therefore, its response to an applied force does not vary. In contrast, weight is the gravitational force acting on an object, so it does vary depending on gravity. For example, a person closer to the center of Earth, at a low elevation such as New Orleans, weighs slightly more than a person who is located in the higher elevation of Denver, even though they may have the same mass.
It is tempting to equate mass to weight, because most of our examples take place on Earth, where the weight of an object varies only a little with the location of the object. In addition, it is difficult to count and identify all of the atoms and molecules in an object, so mass is rarely determined in this manner. If we consider situations in which is a constant on Earth, we see that weight is directly proportional to mass m, since that is, the more massive an object is, the more it weighs. Operationally, the masses of objects are determined by comparison with the standard kilogram, as we discussed in Units and Measurement. But by comparing an object on Earth with one on the Moon, we can easily see a variation in weight but not in mass. For instance, on Earth, a 5.0-kg object weighs 49 N; on the Moon, where g is , the object weighs 8.4 N. However, the mass of the object is still 5.0 kg on the Moon.
Clearing a Field A farmer is lifting some moderately heavy rocks from a field to plant crops. He lifts a stone that weighs 40.0 lb. (about 180 N). What force does he apply if the stone accelerates at a rate of
Strategy We were given the weight of the stone, which we use in finding the net force on the stone. However, we also need to know its mass to apply Newton’s second law, so we must apply the equation for weight, , to determine the mass.
Solution No forces act in the horizontal direction, so we can concentrate on vertical forces, as shown in the following free-body diagram. We label the acceleration to the side; technically, it is not part of the free-body diagram, but it helps to remind us that the object accelerates upward (so the net force is upward).
Significance To apply Newton’s second law as the primary equation in solving a problem, we sometimes have to rely on other equations, such as the one for weight or one of the kinematic equations, to complete the solution.
Can you avoid the boulder field and land safely just before your fuel runs out, as Neil Armstrong did in 1969? This version of the classic video game accurately simulates the real motion of the lunar lander, with the correct mass, thrust, fuel consumption rate, and lunar gravity. The real lunar lander is hard to control. | 0.828413 | 3.925159 |
If you could only see gamma-rays, photons with up to a billion or more times the energy of visible light, the Moon would be brighter than the Sun! That startling notion underlies this novel image of the Moon, based on data collected by the Fermi Gamma-ray Space Telescope’s Large Area Telescope (LAT) instrument during its first seven years of operation (2008-2015). Fermi’s gamma-ray vision doesn’t distinguish details on the lunar surface, but a gamma-ray glow consistent with the Moon’s size and position is clearly found at the center of the false color map. The brightest pixels correspond to the most significant detections of lunar gamma-rays. Why is the gamma-ray Moon so bright? High-energy charged particles streaming through the Solar System known as cosmic rays constantly bombard the lunar surface, unprotected by a magnetic field, generating the gamma-ray glow. Because the cosmic rays come from all sides, the gamma-ray Moon is always full and does not go through phases. The first gamma-ray image of the Moon was captured by the EGRET instrument onboard the Compton Gamma-ray Observatory, launched 25 years ago. | 0.880698 | 3.672371 |
Crescent ♐ Sagittarius
Moon phase on 18 January 2088 Sunday is Waning Crescent, 24 days old Moon is in Scorpio.Share this page: twitter facebook linkedin
Previous main lunar phase is the Last Quarter before 2 days on 15 January 2088 at 15:13.
Moon rises after midnight to early morning and sets in the afternoon. It is visible in the early morning low to the east.
Lunar disc appears visually 9.8% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1768" and ∠1950".
Next Full Moon is the Snow Moon of February 2088 after 19 days on 6 February 2088 at 21:33.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 24 days old. Earth's natural satellite is moving from the second to the final part of current synodic month. This is lunation 1088 of Meeus index or 2041 from Brown series.
Length of current 1088 lunation is 29 days, 17 hours and 56 minutes. It is 2 hours and 25 minutes longer than next lunation 1089 length.
Length of current synodic month is 5 hours and 12 minutes longer than the mean length of synodic month, but it is still 1 hour and 51 minutes shorter, compared to 21st century longest.
This lunation true anomaly is ∠208.8°. At the beginning of next synodic month true anomaly will be ∠241.2°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
Moon is reaching point of apogee on this date at 17:28, this is 11 days after last perigee on 6 January 2088 at 19:17 in ♊ Gemini. Lunar orbit is starting to get closer, while the Moon is moving inward the Earth for 16 days ahead, until it will get to the point of next perigee on 3 February 2088 at 18:12 in ♊ Gemini.
This apogee Moon is 405 230 km (251 798 mi) away from Earth. It is 178 km farther than the mean apogee distance, but it is still 1 479 km closer than the farthest apogee of 21st century.
1 day after its ascending node on 17 January 2088 at 02:46 in ♏ Scorpio, the Moon is following the northern part of its orbit for the next 12 days, until it will cross the ecliptic from North to South in descending node on 31 January 2088 at 03:49 in ♉ Taurus.
1 day after beginning of current draconic month in ♏ Scorpio, the Moon is moving from the beginning to the first part of it.
11 days after previous North standstill on 6 January 2088 at 13:10 in ♊ Gemini, when Moon has reached northern declination of ∠20.031°. Next day the lunar orbit moves southward to face South declination of ∠-19.974° in the next southern standstill on 20 January 2088 at 07:04 in ♐ Sagittarius.
After 5 days on 23 January 2088 at 19:38 in ♑ Capricorn, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.83659 | 3.179235 |
NASA's space snowman reveals secrets: few craters, no water
This Jan. 1, 2019 image from NASA shows Arrokoth, the farthest, most primitive object in the Solar System ever to be visited by a spacecraft. Astronomers reported Thursday, Feb. 13, 2020 that this pristine, primordial cosmic body photographed by the New Horizons probe is relatively smooth with far fewer craters than expected. (NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Roman Tkachenko via AP)
Marcia Dunn, The Associated Press
Published Thursday, February 13, 2020 2:42PM EST
CAPE CANAVERAL, Fla. - NASA's space snowman is revealing fresh secrets from its home far beyond Pluto.
More than a year after its close encounter with the snowman-shaped object, the New Horizons spacecraft is still sending back data from more than 4 billion miles (6.4 billion kilometres) away.
“The data rate is painfully slow from so far away,” said Will Grundy of Lowell Observatory in Flagstaff, Arizona, one of the lead authors.
Astronomers reported Thursday that this pristine, primordial cosmic body now called Arrokoth - the most distant object ever explored - is relatively smooth with far fewer craters than expected. It's also entirely ultrared, or highly reflective, which is commonplace in the faraway Twilight Zone of our solar system known as the the Kuiper Belt.
Grundy said in an email that to the human eye, Arrokoth would look less red and more dark brown, sort of like molasses. The reddish colour is indicative of organic molecules.
While frozen methane is present, no water has yet been found on the body, which is an estimated 22 miles (36 kilometres) long tip to tip. At a news conference Thursday in Seattle, New Horizons' chief scientist Alan Stern of Southwest Research Institute said its size was roughly that of the city.
As for the snowman shape, it's not nearly as flat on the backside as previously thought. Neither the small nor big sphere is fully round, but far from the flatter pancake shape scientists reported a year ago. The research team likened the somewhat flattened spherical forms to the shape of M&Ms.
No rings or satellites have been found. The light cratering suggests Arrokoth dates back to the formation of the solar system 4.5 billion years ago. It likely was created by a slow, gentle merger between two separate objects that possibly were an orbiting pair. The resulting fused body is considered a contact binary.
This kind of slow-motion hookup likely arose from collapsing clouds in the solar nebula, as opposed to intense collisions theorized to form these planetesimals, or little orbiting bodies.
New Horizons flew past Arrokoth on Jan. 1, 2019, more than three years after the spacecraft visited Pluto. Originally nicknamed Ultima Thule, the object received its official name in November; Arrokoth means sky in the language of the Native American Powhatan people.
Launched in 2006, the spacecraft is now 316 million miles (509 million kilometres) beyond Arrokoth. The research team is looking for other potential targets to investigate. Powerful ground telescopes still under construction will help survey this part of the sky.
Emerging technology will enable scientists to develop a mission that could put a spacecraft in orbit around Pluto, 3 billion miles (5 billion kilometres) away, according to Stern. After a few years, that same spacecraft could be sent even deeper into the Kuiper Belt to check out other dwarf planets and objects, he said.
The New Horizons scientists reported their latest findings at the annual meeting of the American Association for the Advancement of Science, as well as in three separate papers in the journal Science.
David Jewitt of the University of California, Los Angeles, who was not involved in the studies, said a flyby mission like New Horizons, where encounters last just a few days, is hardly ideal.
“For future missions, we need to be able to send spacecraft to the Kuiper Belt and keep them there” in orbit around objects, Jewitt wrote in a companion piece in Science. That would allow “these intriguing bodies to be studied in stunning geological and geophysical detail,” he noted.
The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute's Department of Science Education. The AP is solely responsible for all content. | 0.88393 | 3.397604 |
March Equinox: Equal Day and Night (nearly).
March Equinox in the Northern hemisphere is on Wednesday, 20 March 2019, 21:58 GMT (figures 1 & 2).
Figure 1. On the equinox the Earth's axis is perpendicular to the Sun's rays. Equinoxes occur because the axis of the Earth's spin, its polar axis is tilted at an angle of 23.5° to the plane of its orbit around the Sun (not to scale).
Figure 2. Equinoxes and solstices mark the beginning of astronomical seasons. The equinoxes start spring and autumn, while solstices mark the beginning of summer and winter.
In March, the Sun is travelling northwards across the equator.
On 21st March there will be a full Moon, known as the Worm Moon (figure 3) and it is usually considered the last Full Moon of winter. It is also called Lenten Moon, Crow Moon, Crust Moon, Chaste Moon, Sugar Moon, and Sap Moon. It marks the end of winter, and the start of spring and the Full Moon is named after the earthworms that emerge at this time of year. Sap Moon or Sugar Moon mark the time for harvesting maple syrup from maple tree saps. Another name is Crust Moon, after the crust which forms on top of snow as it melts and refreezes. Chaste Moon refers to the purity of the spring season, while Crow Moon signifies that crows appear at the end of winter. Lentenis derived from Germanic languages and means spring, and has also given name to the Christian lent period before the Easter celebrations.
Figure 3. Worm Moon.
Close approach of the Moon and Jupiter: 27th March will see these two bodies pass within 1°52' of each other. The Moon will be 21 days old. Visible in the morning sky, becoming accessible at approximately 02:54, when they rise 7° above the South East horizon. They will reach highest point in the sky at 05:32, 15° above the South horizon. They will be lost to dawn twilight at about 05:41, 15° above the South horizon. They may be difficult to observe because they will appear no higher than 15° above the horizon.
They will be too widely separated to fit within the field of view of a telescope, however, they should be visible to the naked eye or through a pair of binoculars (figure 4 & 5). On 27th March the distance of the Moon and Jupiter from Earth will be:
Moon = 0.0026 Astronomical Units (AU’s) = 241 800 miles
Jupiter = 5 AU’s = 465 000 000 miles
Figure 4. Moon and Jupiter close approach.
Figure 5. Jupiter visible to the naked eye as a tiny star-like object (circled) just below the moon (top).
WARNING: Never attempt to view through binoculars, telescope or any optical aid an object close to the Sun. Also, never attempt to view the Sun unaided, doing so may result in immediate and permanent blindness. Always use astronomical approved viewing equipment.
The Stellarium software will assist greatly in locating objects in the sky.
Physicist - Nuclear Fusion & Astrophysics. | 0.842711 | 3.472069 |
In the beginning, there was a big bang. And then, around 100,000 years later, helium and hydrogen combined for the first time to create a molecule called helium hydride. For the first time in history scientists have detected helium hydride, offering a direct connection to the earliest days of the universe.
While it may not present the photo opportunities of a black hole, helium hydride has been crucial in the formation of the known universe. When it was first forming, there wasn’t much of a universe yet and it was all extremely hot, with helium and hydrogen constantly bumping into each other. Only when helium hydride started forming could the universe cool down and expand. Later, cooled helium would interact with helium hydride and create molecular hydrogen, a crucial ingredient in the development of stars.
That’s been the longtime theory, at least. But this theory, which tracks the very earliest moments of chemistry in history, has been unproven until now.
“The lack of evidence of the very existence of helium hydride in interstellar space was a dilemma for astronomy for decades,” says Rolf Guesten of the Max Planck Institute for Radio Astronomy, in Bonn, Germany, and lead author of the paper, in a press statement.
The dilemma was solved by NASA’s Stratospheric Observatory for Infrared Astronomy, or SOFIA. The world’s largest airborne observatory, SOFIA is an 80/20 partnership of NASA and the German Aerospace Center (DLR). It’s an airplane—an extensively modified Boeing 747SP aircraft carrying a 2.7-meter (106 inch) reflecting telescope.
For decades, astronomers searched the cosmos for the type of molecule that was the first to form after the Big Bang. Now, the combination of helium and hydrogen — called helium hydride — has finally been found in the present-day universe. Details: https://t.co/nwxY4T51XO pic.twitter.com/PdceRPPTsH
— SOFIAtelescope (@SOFIAtelescope) April 17, 2019
Helium hydride has long presented challenges to scientists. In the late 1970s, while studying a planetary nebula called NGC 702, a growing suspicion formed that it could be a cradle for this earliest of molecules. But nothing, not even space telescopes, could clear the noise of the nebula for the specific signal of helium hydride.
So scientists turned to SOFIA. The plane flies at 45,000 feet, above the interfering layers of the Earth’s atmosphere. While it can’t get as close to objects in space as the Hubble, it does have one serious advantage—it can come back to Earth. That means scientists can make adjustments based on why they are searching the skies.
“We’re able to change instruments and install the latest technology,” says Naseem Rangwala SOFIA deputy project scientist. “This flexibility allows us to improve observations and respond to the most pressing questions that scientists want answered.”
One of those instruments is known as the German Receiver at Terahertz Frequencies, or GREAT. Scientists were able to alter GREAT by adding a channel specifically geared towards helium hydride. Similar to a radio receiver, GREAT was able to tune into the frequencies generated by helium hydride molecules.
“It was so exciting to be there, seeing helium hydride for the first time in the data,” said Guesten. “This brings a long search to a happy ending and eliminates doubts about our understanding of the underlying chemistry of the early universe.”
Originally posted on Popular Mechanics | 0.871044 | 3.916748 |
Astronomers gathered among the stone-carved heads of Easter Island on Sunday to witness a total eclipse of the Sun. Meanwhile, 720 km away in space, ESA’s Proba-2 was focused on the same target.
The microsatellite’s orbit fell outside the path of totality, so only a partial eclipse was seen – but it was still a valuable scientific opportunity.
This eclipse was actually Proba-2’s second. The first occurred on 15 January, while it was being commissioned. This time around, the satellite, equipped with a quartet of scientific instruments focused on the Sun and space weather, was fully operational.
SWAP: observing beyond the visible
As a US eclipse expedition studied the fine structures of the Sun’s corona in visible light, Proba-2’s SWAP telescope provided views of the same features at extreme ultraviolet (EUV) wavelengths.
“SWAP’s EUV perspective helps track magnetic structures from their origin on the solar surface to locations high above,” said Dan Seaton of the Royal Observatory of Belgium (ROB), which operates SWAP.
“And because SWAP is sensitive to one type of coronal emission – from highly ionised atoms – its results help astronomers to differentiate the eclipse’s various sources of light to characterise the processes involved.
“SWAP's observations were coordinated as part of a larger, international scientific campaign. For example, Proba-2 pointed away from the Sun just before and after the eclipse to contribute to a composite super-wide-field image of the EUV corona, searching for apparent voids in the corona that remain dimly understood.
Astronomers will combine SWAP imagery with observations from the ground as well as images from other satellites such as Japan’s Hinode and NASA’s Solar Dynamics Observatory.”
LYRA: gathering extinction curves
Proba-2’s second Sun-watching instrument, LYRA, gathered ‘extinction curves’ as the Moon gradually obscured the Sun.
“The Sun’s illumination is not uniform,” explained Marie Dominque of ROB. “LYRA is a radiometer recording overall solar radiation so doesn’t produce any image.
“However, we want to know how the light is distributed, and how the signal changes as we approach the Sun’s edge. This is called ‘limb darkening’ – or ‘limb brightening’ in this case, since in the shortest two of our four observing wavelengths we see more brightness, not less.”
LYRA results will be reviewed against SWAP imagery, she added: “In a couple of channels during January’s eclipse we didn’t pick up the expected v-shaped curves as the Moon moved in and out. It turned out to be a sign of active regions on the Sun.”
DSLP and TPMU: probing ionosphere hole
Proba-2’s other pair of instruments investigated the eclipse’s effects. Incoming solar radiation ionises upper layers of Earth’s atmosphere, giving rise to the electrically charged ‘ionosphere’. But when the shadow of an eclipse falls on Earth an effective hole is formed in the local ionosphere.
DSLP and TPMU chart plasma variations within the ionosphere. They performed a special set of measurements.
“This event gave us a useful opportunity to study the ionospheric response to solar radiation changes,” said Stepan Stverak of the Czech Astronomical Institute.
“The DSLP worked in a burst mode to gather ionospheric properties during the eclipse, for comparison to the unperturbed ionosphere surveyed before and afterwards.”
Results are also being checked against those of French Demeter microsatellite, flying a previous generation of ESA plasma sensors. | 0.817838 | 3.885253 |
Astrobiology – the study and search for life beyond Earth – is the umbrella discipline for the work of the SETI Institute. Astrobiology encompasses a wide range of study areas, including astronomy, geology, biology, and sociology. It is succinctly encapsulated by the so-called Drake Equation. The latter, devised more than five decades ago by astronomer Frank Drake, is an scheme for estimating the number of communicating societies elsewhere in the Milky Way galaxy. Even though this famous formulation was intended to guide the search for extraterrestrial intelligence, it turns out to also describe the other research areas pursued by our scientists. In particular, what sorts of worlds might be amenable to life, how might life arise, and where might we find it? These considerations spur much of the Institute’s work, where nearly 100 scientists and staff are investigating topics in astrobiology. Much of this effort is focused on the nearby worlds of our solar system: could there once have been life on Mars, and might it still be there? What about biology in the oceans and lakes of the various moons of Jupiter and Saturn? There are more than a half-dozen nearby locales that seem to have the requirements for life. The Institute’s purview also extends beyond the solar system. These include efforts to find planets around other stars using both the Kepler spacecraft and the groundbased Gemini Planet Imager. The Institute also uses the Allen Telescope Array to search for signals coming from other parts of the galaxy that would betray the presence of intelligence. In addition, the Institute investigates such fundamental subject areas as the nature of asteroids and meteors, which could be important delivery systems for the ingredients necessary for biology, as well as interspecies communication and the chemical signatures of life that might be found in the atmospheres of exoplanets. It is often opined that the next two decades will witness the first discovery of extraterrestrial life, either microbial biology or signals from intelligence. The SETI Institute is uniquely positioned to be the first to make this discovery. | 0.908081 | 3.201748 |
The Brightest Quasar From the Early Universe Shines Like 600 Trillion Suns
It wasn’t until 800 million years after The Big Bang that the universe’s first light sources emerged. Those ancient, brilliant, energy-dense objects are unfathomably old, and catching sight of one of them is very rare indeed. But thanks to a stunning stellar coincidence, scientists presenting at the 233rd meeting of the American Astronomical Society this week say they have glimpsed one — and it’s the brightest we’ve ever seen.
A 12.8 billion-year-old quasar — a galaxy with a supermassive black hole in its center that expels high-energy particles — recently appeared to astronomers as a galaxy 6 billion light years away serendipitously aligned with it. This coincidence allowed the quasar’s light to pass through the gravitational distortions of a closer galaxy and into the telescopes of astronomers on Earth.
"We knew immediately that this is a special object in term of its brightness.
The Hubble Space Telescope snapped some images of the quasar, which was given the unceremonious moniker J043947.08+163415.7 despite being 700 million times the size of the sun and 600 trillion times as bright. The bending and magnifying phenomenon caused by the galaxy — called gravitational lensing — is what allowed the astronomers to observe the quasar, determining it’s the brightest one humans have ever observed from the very early universe.
The international team behind the discovery, led by University of Arizona Professor of Astronomy Xiaohui Fan, Ph.D., presented its findings at AAS in Seattle, Washington on Wednesday. Fan says that he and his collaborators knew from the beginning that they were on to something big, but they didn’t initially recognize just how unique this discovery really was.
“As soon as we were able to measure the distance, we knew immediately that this is a special object in term of its brightness,” he tells Inverse, “but it took us a bit longer to figure out that it was gravitationally lensed.”
If it hadn’t been for the lensing effect, which both magnified the quasar’s light by a factor of 50 and redirected it toward Earth, astronomers would have missed the quasar altogether. Even to a high-resolution telescope like the Hubble Space Telescope, the light from the quasar would have appeared extremely dim after traveling 12.8 billion light years. Even as the lensing effect made the quasar appear brighter, a sighting like this one needs ample eyes on it to confirm what’s going on. And that it did!
" We didn’t expect we could see an object this bright this early in the universe.
In addition to Hubble, an international network of telescopes collaborated to confirm this finding, including the Gemini Observatory, the James Clerk Maxwell Telescope, the United Kingdom Infra-Red Telescope (UKIRT), the W.M. Keck Observatory, and the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1).
“We didn’t expect we could see an object this bright this early in the universe. And the key reason is the lensing effect that boosted the quasar brightness,” says Fan. “This is the first such lensed object discovered in the early universe, even though theory has predicted that it should exist for about 20 years.”
“So the discovery of this object is actually a very nice confirmation of our theory,” he adds.
The team determined the quasar’s age and distance, Fan explains, by measuring the redshift of the wavelength of emissions from hot gas in the quasar. After identifying the signature of gases emitted by the quasar — which included hydrogen and ionized carbon and magnesium — the team was able to measure how much their expected emissions had been shifted by their journey through space. This analysis told the tale of a supermassive black hole 700 million times the size of the sun — and as bright as 600 trillion suns.
The research currently appears as a preprint paper on arXiv, but it will be published in an upcoming issue of the Astrophysical Journal Letters.
The team’s next steps will paint a fuller picture of the quasar and its surroundings.
We are doing a lot of further observations, including a better spectrum that could have high sensitivity to probe the intergalactic gas, and an image that is even sharper than Hubble (using the Atacama Large Millimeter Array) that will study the environment of the supermassive black hole that is powering this quasar,” says Fan. | 0.880689 | 3.831114 |
The asymmetry of biological molecules may have come from space, say French scientists.
So-called chiral molecules, including amino acids and sugars, can exist in two forms which are mirror images of each other. However, here on Earth, they exist in only one form, either left-handed or right-handed.
For instance, the amino acids that make up proteins only exist in one of their two enantiomeric forms, the left-handed form. On the other hand, the sugars present in the DNA of living organisms are solely right-handed. The phenomeon is known as homochirality.
In a study, the team reproduced the conditions found in interstellar space and found that there, too, biological molecules tend towards one form or the other.
One theory is that life originated from a mixture containing 50 percent of one type and 50 percent of the other, and that homochirality progressively emerged during the course of evolution.
Another is that asymmetry leading to homochirality preceded the appearance of life and was of cosmic origin. This is supported by the predominance of left-handed molecules in certain amino acids extracted from primitive meteorites.
The researchers first reproduced analogs of interstellar and cometary ices in the laboratory. Using the DESIRS beamline at the SOLEIL synchrotron facility, the ices were subjected to circularly polarized ultraviolet radiation, reckoned to mimic the conditions encountered in some space environments.
When the ices were warmed up, an organic residue was produced – and tests showed a bias towards one particular handedness comparable to that measured in primitive meteorites.
The result, they say, reinforces the hypothesis that the origin of homochirality is prebiotic and interstellar. According to their scenario, the asymettry of life’s molecules is derived from the delivery of extraterrestrial organic material. This material may even have formed outside the solar system, they say. | 0.809778 | 3.366625 |
In his groundbreaking Cosmos, now nearly 40 years old, Carl Sagan speculated at length about life beyond the Earth. He even whisked us off on a journey through the galaxy in his ship of the imagination, letting us peer at the “Book of Worlds,” which catalogued dozens of habitable exoplanets.
This was amazing stuff in 1980, but in the four decades since, Carl Sagan has been proven partially correct. We now know that the cosmos is brimming with exoplanets, just as he imagined all those years ago. Nevertheless, the grandest stuff hasn’t yet been demonstrated. After a systematic search for decades, no signs of extraterrestrial life, let alone extraterrestrial intelligence, have been detected.
The failure of the radio signals never particularly bothered me. Many of the exoplanets discovered, even the ones that are potentially habitable, are hundreds or even thousands of light years away. Even at the speed of light, the signals would take hundreds of years to reach us, and even then, we would detect them only if they were beamed directly at us. When we consider that we’ve been sending out signals into space through our radio and TV broadcasts for less than a century, we get the idea of the nature of the problem.
Instead, the more damning indictment about extraterrestrial life has been the absence of any chemical detection suggesting the presence of life. One of the most fascinating things about the universe is that we can tell what something is made of by seeing how it absorbs light. Carl Sagan, as ever, explains it well.
So why haven’t we heard any news of exoplanets with atmospheres containing water vapor, oxygen, nitrogen, or some other substance that might suggest that life is there? Maybe there just hasn’t been enough time to gather all the data, or our instruments aren’t yet adequate to detect something so fine. Exoplanets don’t give off light on their own, after all, and detecting their reflected light from such a distance is daunting.
Even so, the list of habitable exoplanets seems rather small, and only one, Kepler 452-b, has been discovered orbiting an actual sun-like star. The other potentially habitable exoplanets (that is, planets which are in the habitable zone of their star, where they have a temperature where liquid water can exist) mostly orbit red dwarf stars.
That’s important, because life might not be able to come about without a certain level of ultraviolet light. As early as Cosmos, Carl Sagan was talking about this – that ultraviolet light from the sun and lightning in the atmosphere potentially brought the molecules of life together on the early Earth.
Red dwarf stars give off much less ultraviolet light than the sun does, because they emit far less energy. The sun, it turns out, isn’t an average star after all. It’s larger and brighter than about 88% of the stars in the universe! The implication here is that, while Carl Sagan was right when he noted that “the stuff of life is common throughout the cosmos,” the energy sources needed to do the work of assembling it in the right way, and under the right conditions, might be much rarer.
Some scientists are now describing an “abiogenesis zone,” where it isn’t enough for exoplanets to simply be in a “habitable zone” where liquid water can exist. Instead, they also need to be in a place where they receive enough energy to kickstart the chemical reactions that lead to life. If true, that would reduce the number of potentially habitable exoplanets even further. The scientists behind the “abiogenesis zone” theory created a chart, showing that, of all the potentially habitable exoplanets discovered so far, only a scant few examples fall in the “abiogenesis zone.”
So, are we alone after all? Is the earth truly a freakish planet?
It’s still a giant universe. Just because of the sheer size of the cosmos, it’s still far more unlikely that Earth is the only inhabited planet, or even that we’re the only civilization. There are certainly more than a few habitable exoplanets in the “abiogenesis zone” out there. We’ve only begun to look. Nevertheless, their comparative rarity does raise some troubling questions, not the least of which is that we’re still very ignorant.
We need to do more and we’ll undoubtedly get better at this thing. When the James Webb Space Telescope launches in 2021, a lot of questions should begin getting answered – and more opportunities will be open for you to make a name for yourself.
The search for habitable exoplanets and extreterrestrial life is one of the prime grounds where glory might be won. You want your name to last through the ages? Whoever is first to discover life on another world is going to be immortalized forever, no matter what kind of life it is. A single bacterium on a planet beyond our own would be one of the biggest scientific breakthroughs in history. Astronomy is one of the few scientific fields available where amateurs can still make a big impact. In many respects, the hunt for habitable exoplanets now resembles what archaeology was back when Heinrich Schliemann began his search for Troy. Professional scholars at the time scoffed at Schliemann’s theories, but he’s the one who reaped the glory. The search for extraterrestrial life, though obviously even harder, is similar.
All my life, I’ve loved space – maybe not like Carl Sagan did, but I’ve loved it nevertheless. I’ve thought more about life lately, and its seeming rarity in the universe has made me contemplate it still more often. As I’ve left my 20s and entered my 30s, that feeling of youthful invincibility has eroded. I know now I don’t have all the time in the world. The days pass quickly and you don’t get them back. Tomorrow always looks like it will come, but sometime, it won’t. Eventually, even the stars will die. What do you do in that time? Think of all those graves you drive by on the highway. Do you eventually fade in with them, anonymously? Can you make the kind of impact that Carl Sagan made? There might be such a way.
Amateur astronomers have been hunting for habitable exoplanets for a long time. There are even practical guides to doing it. Apart from your other work, it’s something you should consider, as I strongly am. Is it delusional? Quite possibly. But 19th century scholars said the same about the work Schliemann was doing. Some of the work of Carl Sagan was scoffed at.
There’s more than one road to glory. Each field has its own chance of success. Even if you do something great, you might not be remembered. If you discover extraterrestrial life, you surely will be. Even if you don’t, if you discover habitable exoplanets that go on to some other kind of notoriety, your name will be in contention. It’s worth a try, right? Carl Sagan would certainly encourage you.
While you’re at it, be nice to me for giving you these ideas by reading Stumped. | 0.835027 | 3.885166 |
Crescent ♑ Capricorn
Moon phase on 25 October 2093 Sunday is Waxing Crescent, 5 days young Moon is in Capricorn.Share this page: twitter facebook linkedin
Previous main lunar phase is the New Moon before 5 days on 20 October 2093 at 07:33.
Moon rises in the morning and sets in the evening. It is visible toward the southwest in early evening.
Moon is passing about ∠10° of ♑ Capricorn tropical zodiac sector.
Lunar disc appears visually 1.8% wider than solar disc. Moon and Sun apparent angular diameters are ∠1966" and ∠1930".
Next Full Moon is the Beaver Moon of November 2093 after 8 days on 3 November 2093 at 06:46.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 5 days young. Earth's natural satellite is moving from the beginning to the first part of current synodic month. This is lunation 1160 of Meeus index or 2113 from Brown series.
Length of current 1160 lunation is 29 days, 12 hours and 24 minutes. It is 34 minutes longer than next lunation 1161 length.
Length of current synodic month is 20 minutes shorter than the mean length of synodic month, but it is still 5 hours and 49 minutes longer, compared to 21st century shortest.
This lunation true anomaly is ∠284.3°. At the beginning of next synodic month true anomaly will be ∠314.2°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
12 days after point of apogee on 13 October 2093 at 02:43 in ♋ Cancer. The lunar orbit is getting closer, while the Moon is moving inward the Earth. It will keep this direction for the next day, until it get to the point of next perigee on 26 October 2093 at 10:39 in ♑ Capricorn.
Moon is 364 559 km (226 526 mi) away from Earth on this date. Moon moves closer next day until perigee, when Earth-Moon distance will reach 370 030 km (229 926 mi).
12 days after its ascending node on 12 October 2093 at 13:29 in ♋ Cancer, the Moon is following the northern part of its orbit for the next day, until it will cross the ecliptic from North to South in descending node on 26 October 2093 at 05:22 in ♑ Capricorn.
12 days after beginning of current draconic month in ♋ Cancer, the Moon is moving from the beginning to the first part of it.
At 15:11 on this date the Moon is meeting its South standstill point, when it will reach southern declination of ∠-22.213°. Next 13 days the lunar orbit will move in opposite northward direction to face North declination of ∠22.330° in its northern standstill point on 8 November 2093 at 02:08 in ♋ Cancer.
After 8 days on 3 November 2093 at 06:46 in ♉ Taurus, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.848363 | 3.082242 |
Developing a rover to examine and observe the barren surface of Mars is quite difficult, but designing a robot to analyze the depths of the ocean of distant moons is completely arduous.
Researchers believe that satellites with water bodies such as Enceladus, Saturn’s Moon, or Jupiter’s Europa, have the perfect conditions for discovering alien life in the Solar System. Although future Mars expeditions may reveal fossils of ancient life forms aged billions of years, living organisms could have survived and still exist in the oceans of volcanically active moons.
The pursue of extraterrestrial life in other cosmic bodies’ oceans is charged with problems, especially since any probe has to navigate by itself beneath ice layers that could be up to 19 kilometers (12 miles) thick, through no signal could permeate.
However, NASA has now built its first aquatic rover which can submerge upside down under the ocean of ice, and it is scheduled to begin the first testings in the Antarctic Ocean.
The rover has been dubbed ‘Bruie,’ which stands for Buoyant Rover for Under-Ice Exploration. It has been created and built by NASA’s Jet Propulsion Laboratory (JPL) located in Pasadena and been sent to Antarctica for testing.
Exploring the Ice Oceans of Distant Worlds
Kevin Hand, a JPL chief scientist on the Bruie program, says that Europa and Enceladus are the best options to search and find life. He explains that the ice shells above these oceans serve as a window into what’s underneath, and the chemistry of the ice could aid in the attempts to find life withing those water bodies.
“On Earth, the ice covering our polar oceans serves a similar role, and our team is interested in what is happening where the water meets the ice,” he added.
The rover is three feet long and is geared with two steady wheels to clutch on the underside of the ice cover. It can capture images and gather data of the crucial area where water and ice melt, known as the ‘ice-water interface.’
“We’ve found that life often lives at interfaces, both the sea bottom and the ice-water interface at the top,” said lead engineer Andy Klesh.
The majority of underwater vehicles have a difficult time examining this particular region because ocean currents might make them collide, or they would lose power by maintaining the same position. Even so, Bruie utilizes buoyancy to remain fastened against the ice and is resistant to most currents.
The vehicle can power down as well, powering on again to make measurements, which means it could stay for months under the ice, examining the place’s conditions.
In the following weeks, researchers will perforate the ice and send the attached rover down into the water to test its network of gadgets, including its duo array of high-definition live cameras. The probe will also be equipped with numerous tools that will measure parameters associated with life, such as dissolved oxygen, the salinity of the water, pressure, and temperature.
The development of Bruie will continue, so it will manage several months at once under the ice, remotely navigate without a fasten, and observe the ocean at increased depths. | 0.80806 | 3.724878 |
The brilliant planet Jupiter made its closest approach to the planet Earth in April this year and remains a fantastic sight to behold especially in telescopes above 4” aperture.
Roman observers named Jupiter after the patron deity of the Roman state following Greek mythology, which associated it with the supreme god, Zeus.
Astronomers soon recognized Jupiter as the largest planet in the solar system long before any spacecraft provided detailed exploration. The planet’s massive size 88,846 miles(142,984Kms) at the equator holds 2.5 times the mass of all the other planets combined. This makes Jupiter the most dominant body in the solar system after the Sun. The planet’s volume is so great that 1,321 Earths could fit inside of it.
Jupiter is a magnificent example of a gas giant planet. It has no solid surface and is composed of a small rocky core enveloped in a shell of metallic hydrogen, which is surrounded by liquid hydrogen, which in turn is surrounded by a blanket of hydrogen gas. By count of atoms, the atmosphere is 90% hydrogen and 10% helium, this is compositionally more similar to brown dwarfs and small stars.
So, it’s not difficult see why many astronomers wondered whether it should be considered a king-sized planet or a failed star.
As the solar system condensed out of interstellar gas and dust, Jupiter acquired most of the matter that was not ejected into interstellar space and did not fall inward to form the Sun. But although Jupiter is large as planets go, it would need to be about 75 times its current mass to ignite nuclear fusion in its core and become a star. Had it had this requisite mass it would have become a star in visible light and we would today inhabit a binary or double star system, with two suns in our sky; something which is very common throughout our Milky Way galaxy.
We of course would undoubtedly think this would be a natural and beautiful experience but you could end up with a lifetime of sleepless nights: more likely life might never have evolved on Earth because the temperatures would have been to high and the atmospheric characteristics all wrong. Life may have existed Jim, “but not as we know it” (Star Trek).
Now astronomers have found other stars orbited by planets with masses far greater than Jupiter’s.
What about sub-stellar brown dwarfs?
Our largest planet doesn’t come close to these “almost stars”. Astronomers define brown dwarfs as bodies with at least 13 times Jupiter’s mass. At this point, a hydrogen isotope called deuterium can undergo fusion early in a brown dwarf’s life.
So, the reality is that while Jupiter is a planetary giant, its mass falls far short of the mark to consider it a failed star.
I’m off to the mountains of southern Spain to observe Jupiter under dark skies and at a higher altitude, With my trusty 8” Newtonian reflector and my 4.25” apochromatic triplet refractor I’m looking to see the N & South Equatorial belts, the N & S Temperate zones, the Great Red Spot (a great anticyclonic storm bigger than the Earth), maybe a White Oval and the Galilean satellites, Io, Europa, Ganymede and Callisto, mmmh and some nice tapas and Rioja!
El Beadlo FRAS | 0.886914 | 3.714823 |
The sky is filled with “magnifying glasses” that allow astronomers to study very distant objects barely visible with even the largest existing telescopes.
Using NASA’s Hubble Space Telescope, an international group of astronomers, including three from UC Santa Barbara, has found that one of these lenses — a massive galaxy within a cluster of galaxies that gravitationally bends and magnifies light — has created four separate images of the same distant supernova.
The scientists’ findings appear in a March 6 special issue of the journal Science, marking the centennial of Albert Einstein’s general theory of relativity. Einstein’s theory predicts that concentrations of mass in the universe will bend light like a lens, magnifying objects behind the mass when seen from Earth — exactly what the astronomers found in their new images.
“With four perspectives, you can actually measure the difference in the light paths,” explained co-author Kasper Schmidt, a postdoctoral fellow in UCSB’s Department of Physics. “You can think of these time-variable source images of the supernova as trains. Each leaves the station at the same time but arrives at different times because the ‘routes’ and the ‘landscape’ they travel through are not the same.”
When light from a background object passes by a mass, such as an individual galaxy or a cluster of galaxies, the light is bent. However, when the background object is almost exactly behind the mass, “strong lensing” smears extended objects (like galaxies) into an “Einstein ring” surrounding the lensing galaxy or cluster of galaxies.
Strong lensing of small, pointlike objects often produces multiple images. When the alignment of the source and lens is ideal, images are seen in a formation dubbed the Einstein cross, which will help astronomers refine their estimates of the amount and distribution of dark matter in the lensing galaxy and cluster. Dark matter cannot be seen directly but is believed to make up most of the universe’s mass.
“The locations of the images of the supernova tell us something about the ‘landscape’ the light is traveling through,” said co-author Curtis McCully, a postdoctoral researcher who has a joint appointment with UCSB’s Department of Physics and the Las Cumbres Observatory Global Telescope Network. “The shape of the landscape coupled with the difference in the arrival times — which we expect to be a few days to a few months for the four images we discovered — allows us to infer how far the light traveled. That lets us compare the size of the universe 5 billion years ago to the size of the universe today, so we can measure how fast the universe is expanding.”
The scientists have nicknamed the distant supernova Refsdal in honor of Sjur Refsdal, the late Norwegian astrophysicist and pioneer of gravitational lensing studies. The supernova is located about 9.3 billion light years away (redshift = 1.5), near the edge of the observable universe, while the lensing galaxy is about 5 billion light years (redshift = 0.5) from Earth. The galaxy that is splitting the light from the supernova into an Einstein cross is part of a large cluster, called MACS J1149.6+2223, which has been known for more than 10 years.
Although astronomers have discovered dozens of multiply imaged galaxies and quasars, they have never seen a stellar explosion resolved into several images. In 2009, astronomers reported that the MACS J1149.6+2223 cluster created the largest known image of a spiral galaxy ever seen through a gravitational lens. The new supernova is located in one of that galaxy’s spiral arms, which also appears in multiple images in the foreground lensing cluster. The supernova, however, is split into four images by a red elliptical galaxy within the cluster.
“These gravitational lenses are like a natural magnifying glass. It’s like having a much bigger telescope,” said lead author Patrick Kelly, a postdoctoral scholar at UC Berkeley. “We can get magnifications of up to 100 times by looking through these galaxy clusters.”
Given the peculiar nature of gravitational lensing, astronomers predict that they will have an opportunity for a supernova replay in the next 10 years. This is because light can take various paths around and through a gravitational lens, arriving at Earth at different times. Computer modeling of this lensing cluster shows that the researchers missed opportunities to see the exploding star 50 and again 10 years ago, but images of the explosion will likely repeat in the next decade.
“What we’ve found tells us something about the gravitational potential, which we can link to the basic equation of the universe and the expansion rate of the universe,” said Schmidt. “This relates to the big bang model as we believe it is right now. In that sense, it’s a very essential and fundamental quantity that we can estimate from this discovery. At least that’s our goal.”
Tucker Jones, a postdoctoral fellow in UCSB’s Department of Physics, is another co-author. | 0.869281 | 4.04277 |
The galaxy M61 has done it again: it’s produced another supernova, the eighth such event since 1926. That makes this lovely face-on spiral galaxy in the Virgo cluster one of the most prolific supernova producers of the past century.
The supernova, cataloged as SN2020jfo, was discovered on May 6, 2020 at the Zwicky Transient Facility at Palomar Observatory near San Diego. Upon discovery, the exploding star was magnitude 14.7. It’s since brightened to about 14.3. To see it visually requires at least a 10″ telescope, but it is relatively easy to take a snapshot with an astronomy camera and a much smaller scope. I took the 20x10s stack of images at the top with an 85mm Tele Vue refractor, an 0.8x focal reducer, and an inexpensive ZWO ASI290MM camera.
One of the more prominent members of the Virgo cluster, Messier 61 is a lovely barred spiral with winding arms knotted with star-forming nebula and clouds of blue-white stars. It’s a starburst galaxy, one wracked with prodigious star formation which explains why so many supernovae have been seen here. With lots of massive, fast-burning young stars forming, it’s inevitable that they reach their spectacular end as a Type II supernova during which the star, as it runs out of fuel, collapses and snaps back in a spectacular explosion. It releases as much energy in a few weeks as our Sun releases in its entire 10 billion year life span.
M61 is about the same size as our Milky Way and lies about 52 million light years away, so the progenitor star detonated when Earth was in the Eocene period back when Australia and Antarctica were still connected and most of the planet was covered in lush forest.
And since astronomy is not just a matter of contemplating space but also time, keep in mind that the light from thousands more supernovae from M61 are on the way to us now, events to be detected by generations of Earth-bound astronomers yet to be born.Share This: | 0.87019 | 3.42252 |
No one ever pretended outer space is a hospitable place. There’s the hard vacuum, the lethal cold and the ever-present risk of even a small meteor hit. And then there’s the way the human body seems to revolt at the very idea of being there.
No sooner do astronauts arrive in space than up to 40% of them begin throwing up. Most of them adjust soon enough, but they may continue to feel dizzy and fatigued all the same. There’s also back pain, calcium loss, muscle atrophy, nasal congestion, accelerated heart rate and increased blood pressure—all a result of the skeletal and circulatory systems trying to adjust to zero gravity. Longer term damage may include distorted cell growth—also a result of zero-g—and DNA changes caused by cosmic radiation, leading to an increased risk of cancer and other diseases.
But how much of all that can you blame exclusively on space? Some people just have weaker bones than others; some are predisposed to hypertension or cancer. Separating heredity from environment isn’t easy even when the environment you’re talking about is a decidedly extreme one. Serendipity, however, has now provided a perfect way to begin investigating the mystery, in the form of Scott and Mark Kelly, identical twins who just happen to be astronauts.
The Kellys have already achieved national and even global renown—Mark for his four shuttle missions and his cumulative 54 days in space, not to mention his high-profile devotion to his wife, former Congresswoman Gabrielle Giffords, as she continues to recover from the 2011 assassination attempt that nearly took her life; and Scott for his two shuttle flights, including a six-month stay aboard the International Space Station (ISS). Mark has since retired from NASA, but Scott is still flying, set for a full-year aboard the ISS, beginning in March 2015. And that has provided NASA with an unprecedented opportunity to run a nifty experiment.
In anticipation of the time Scott will spend aloft, NASA’s Human Research Program—a division of the space agency that studies space biology and safety—has begun requesting ideas from biologists and other researchers for comparison tests that can be conducted on the two men, both during and after the year-long mission. The name of the project—Differential Effects on Homozygous Twin Astronauts Associated with Differences in Exposure to Spaceflight Factors—is just the kind of scientific mouthful you’d expect, but it also frames perfectly just how valuable twins can be to scientists trying to understand the human body. The genetic software of identical twins matches perfectly, which means that most differences in how they age and the illnesses they do or don’t develop are attributable to environmental factors or life experiences. That makes the Kellys priceless lab subjects.
“This is a once-in-a-space-program opportunity,” said John Charles, chief of the Human Research Program’s International Science Office, in a statement that accompanied the announcement of the project. “The mission of the HRP is to reduce the risk to astronauts during long-duration space flight. In typical investigations, we usually have a specific outcome in mind and are goal-oriented. In this case, the slate is essentially blank. I am anxious to see what proposals we receive from the scientific community.”
(MORE: Beijing, We Have a Space Program)
Some of the experiments are obvious. Blood samples will be taken of both men at the same intervals during the course of the year. Saliva samples and cheek swabs may be collected too and psychological and fitness tests may be conducted—though exactly what those last two will involve has yet to be determined. Follow-up tests after Scott comes home will be carried out as well—for years and perhaps even for the remainder of the brothers’ lives.
The Kellys aren’t perfect subjects: the time Mark has already spent in space muddies the study up a little since he’s been exposed to the same exotic physical environment Scott has. The ideal subjects would be a twin who is flying in space and one who has never left the planet. But after Scott’s return he will have amassed 540 days in space, or precisely 10 times Mark’s total, which ought to be a big enough difference to give the findings real credibility.
(MORE: What It’s Like to Go to Mars)
Whatever results the study yields will have more than theoretical implications. A year in orbit seems like a lot, but it’s only a fraction of the time an eventual Mars trip would take—with its outbound and inbound legs of at least eight months each, not to mention a long stay on the Martian surface. That mission, in turn, would be nothing compared to a long-imagined trip to Jupiter’s moon Europa, with its globe-girdling ocean that could be home to life. On the same day NASA announced the Kelly experiment, it also released a paper in the Journal Astrobiology, outlining the goals for a Europa mission.
Neither trip is coming in the near future; at the moment, NASA doesn’t even have a way to launch its own astronauts to low-Earth orbit. But for the U.S., China and other countries, deep space colonization does remain a long-term—if distant—goal. Making sure we can survive the trip is a vital first step. | 0.871771 | 3.325789 |
The QuasiUniversal Intergalactic Denomination, or QUID, is the new currency ofinter-planetary travelers. It was designed for the foreign exchange companyTravelex by scientists from Britain's National Space Centre and the University of Leicester.
The design intent is that QUIDs must withstand the rigors ofspace travel – no sharp edges and no chemicals that could hurt space tourists.
"Noneof the existing payment systems we use on earth – like cash, credit or debitcards – could be used in space," said Professor George Fraser from the University of Leicester. "Anything with sharp edges, like coins, would be a risk toastronauts while the chips and magnetic strips used in our cards on Earth wouldbe damaged beyond repair by cosmic radiation."
The QUID (see photo)is made from a space-qualified polymer – PTFE (polytetrafluoroethylene). Thismaterial is widely used by space agencies because of its durability andversatility. Earthlings know it better as "teflon," and arewell-aware of its resistance to high temperatures and corrosive materials.(Merchants will like the ease with which QUIDs slide out of consumer's pockets.)
The rounded edges of the QUID make it safer, and alsoencompass the eight planets orbiting a sun which are part of the design. Eachof the orbiting planets contain a serial number; taken together, these numberswill give each QUID disc a unique code to prevent counterfeiting.
What's a QUID worth? The current exchange rate for the newcurrency is £6.25 to the QUID (or US$12.50 or about 8.68 Euros).
Hopefully, as we travel further from Earth and spreadthroughout the galaxy, people will not confuse the QUID with the"quid" – a slang term for the British pound sterling, possiblyderiving from the location of the Royal mint at Quidhampton, Wiltshire, England.
Science fiction fans are probably more used to terms likethe ubiquitous "credit." Here's a sample of more interesting futurecurrency names:
"Authority pays the same for ice now as thirty yearsago. And that's not okay. Worse yet, Authority scrip doesn't buy what it usedto. I remember when Hong Kong Luna dollars swapped even for Authority dollars.Now it takes three Authority dollars to match one HKL dollar..."
"...Mr. Icholtz brought out his wallet and begancounting out skins. 'Very little publicity will be attached to this at first.But eventually--' He offered Hnatt the stack of brown, wrinkled, truffle-skinswhich served as tender in the Sol system..."
(Read more about the truffle skins)
Readers are encouraged to contributemore examples.
(This Science Fiction in the News story used withpermission of Technovelgy.com – where science meetsfiction)
- Future of Flight: Space Tourism,Investment and Technology
- LookingBack on 50 Years of Spaceflight
- VIDEO:Future Fashion?s Past | 0.868911 | 3.122721 |
We are all, quite literally, made of star dust. Many of the chemicals that compose our planet and our bodies were formed directly by stars. Now, a new study using observations by NASA's Spitzer Space Telescope reports for the first time that silica - one of the most common minerals found on Earth - is formed when massive stars explode.
Look around you right now and there's a good chance you will see silica (silicon dioxide, SiO2) in some form. A major component of many types of rocks on Earth, silica is used in industrial sand-and-gravel mixtures to make concrete for sidewalks, roads and buildings. One form of silica, quartz, is a major component of sand found on beaches along the U.S. coasts. Silica is a key ingredient in glass, including plate glass for windows, as well as fiberglass. Most of the silicon used in electronic devices comes from silica.
In total, silica makes up about 60 percent of Earth's crust. Its widespread presence on Earth is no surprise, as silica dust has been found throughout the universe and in meteorites that predate our solar system. One known source of cosmic dust is AGB stars, or stars with about the mass of the Sun that are running out of fuel and puff up to many times their original size to form a red giant star. (AGB stars are one type of red giant star.) But silica is not a major component of AGB star dust, and observations had not made it clear if these stars could be the primary producer of silica dust observed throughout the universe.
The new study reports the detection of silica in two supernova remnants, called Cassiopeia A and G54.1+0.3. A supernova is a star much more massive than the Sun that runs out of the fuel that burns in its core, causing it to collapse on itself. The rapid in-fall of matter creates an intense explosion that can fuse atoms together to create "heavy" elements, like sulfur, calcium and silicon.
To identify silica in Cassiopeia A and G54.1+0.3, the team used archival data from Spitzer's IRS instrument and a technique called spectroscopy, which takes light and reveals the individual wavelengths that compose it. (You can observe this effect when sunlight passes through a glass prism and produces a rainbow: The different colors are the individual wavelengths of light that are typically blended together and invisible to the naked eye.)
Chemical elements and molecules each emit very specific wavelengths of light, meaning they each have a distinct spectral "fingerprint" that high-precision spectrographs can identify. In order to discover the spectral fingerprint of a given molecule, researchers often rely on models (typically done with computers) that re-create the molecule's physical properties. Running a simulation with those models then reveals the molecule's spectral fingerprint.
But physical factors can subtly influence the wavelengths that molecules emit. Such was the case with Cassiopeia A. Although the spectroscopy data of Cassiopeia A showed wavelengths close to what would be expected from silica, researchers could not match the data with any particular element or molecule.
Jeonghee Rho, an astronomer at the SETI Institute in Mountain View, California, and the lead author on the new paper, thought that perhaps the shape of the silica grains could be the source of the discrepancy, because existing silica models assumed the grains were perfectly spherical.
She began building models that included some grains with nonspherical shapes. It was only when she completed a model that assumed all the grains were not spherical but, rather, football-shaped that the model "really clearly produced the same spectral feature we see in the Spitzer data," Rho said.
Rho and her coauthors on the paper then found the same feature in a second supernova remnant, G54.1+0.3. The elongated grains may tell scientists something about the exact processes that formed the silica.
The authors also combined the observations of the two supernova remnants from Spitzer with observations from the European Space Agency's Herschel Space Observatory in order to measure the amount of silica produced by each explosion. Herschel detects different wavelengths of infrared light than Spitzer. The researchers looked at the entire span of wavelengths provided by both observatories and identified the wavelength at which the dust has its peak brightness. That information can be used to measure the temperature of dust, and both brightness and temperature are necessary in order to measure the mass. The new work implies that the silica produced by supernovas over time was significant enough to contribute to dust throughout the universe, including the dust that ultimately came together to form our home planet.
The study was published on Oct. 24, 2018, in the Monthly Notices of the Royal Astronomical Society, and it confirms that every time we gaze through a window, walk down the sidewalk or set foot on a pebbly beach, we are interacting with a material made by exploding stars that burned billions of years ago.
NASA's Herschel Project Office is based at NASA's Jet Propulsion Laboratory in Pasadena, California. The NASA Herschel Science Center, part of IPAC, supports the U.S. astronomical community. Caltech manages JPL for NASA.
The JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena, California. Spacecraft operations are based at Lockheed Martin Space in Littleton, Colorado. Data are archived at the Infrared Science Archive housed at IPAC at Caltech.
For more information about Herschel and Spitzer, visit:
News Media ContactCalla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.
Director of Communications, SETI Institute | 0.91677 | 3.999675 |
To mark Halloween, NASA has released an image of a cloud of gas and dust which looks like a celestial pumpkin. The image was created with data captured by the Spitzer Space Telescope.
A massive star, known as an O-type star and about 15 to 20 times heavier than the Sun, is likely responsible for sculpting this cosmic pumpkin.
A recent study of the region suggests that the powerful outflow of radiation and particles from the star likely swept the surrounding dust and gas outward, creating deep gouges in this cloud, which is known as a nebula.
Spitzer, which detects infrared light, saw the star glowing like a candle at the centre of a hollowed-out pumpkin. The study's authors have nicknamed the structure the "Jack-o’-lantern Nebula."
A plethora of objects in the universe emit infrared light, often as heat, so objects tend to radiate more infrared light the warmer they are.
Invisible to the human eye, three wavelengths of infrared light compose the multicolour image of the nebula seen here.
Green and red represent light emitted primarily by dust radiating at different temperatures, though some stars radiate prominently in these wavelengths as well.
The combination of green and red in the image creates yellow hues. Blue represents a wavelength mostly emitted, in this image, by stars and some very hot regions of the nebula, while white regions indicate where the objects are bright in all three colours.
The O-type star appears as a white spot in the centre of a red dust shell near the centre of the scooped-out region.
A high-contrast version of the same image makes the red wavelength more pronounced. Together, the red and green wavelengths create an orange hue.
The picture highlights contours in the dust as well as the densest regions of the nebula, which appear brightest.
The data used to create this image was collected during Spitzer’s "cold mission," which ran between 2004 and 2009. | 0.826262 | 3.748833 |
Suppose you’re an astronomer trying to detect fiendishly subtle ripples in space-time sent from objects made of exotic matter. How would you do it?
How about with a GPS system? That’s the idea behind NANOGrav, the North American Nanohertz Observatory for Gravitational Waves.
NANOGrav acts as a kind of GPS, but rather than a fleet of global positioning satellites orbiting Earth, the project uses an array of 54 pulsars orbiting the galaxy. And instead of locating your position on Earth, NANOGrav uses the pulsar radio signals to look for tiny shifts in the position of our planet in space.
“Imagine a sphere containing these pulsars being squeezed and stretched by gravitational waves,” says UWM physics professor Xavier Siemens. As gravitational waves disturb the space-time in this sphere, which spans hundreds of light-years, NANOGrav should detect tiny variations in the signals from the pulsars.
“That’s one of the beautiful parts of this experiment,” says Siemens, the principal investigator on a $14.5 million, five-year grant to establish and operate the NANOGrav Physics Frontiers Center. “Nature has built an important part of the apparatus for us, and we get that for free.”
Although the successful LIGO project provides one method of finding gravitational waves, NANOGrav lets scientists study gravitational wave frequencies inaccessible with other discovery methods. By observing low-frequency gravitational waves, NANOGrav could provide information on phenomenon like super-massive black hole binaries or gravitational wave echoes from the earliest stages of the universe.
NANOGrav is sifting through radio waves collected by the gigantic Arecibo Observatory in Puerto Rico and the Robert C. Byrd Green Bank Telescope in West Virginia, looking for signs of these fantastically huge gravitational waves.
As with LIGO, the NANOGrav scientists hope to discover something that could disrupt conventional physics wisdom, such as cosmic strings. Although considered outlandish by some scientists, they are a theoretical artifact from the universe’s rapid expansion during an infinitesimal moment after the Big Bang. | 0.821835 | 3.80847 |
September 21, 2011
Twenty Six NASA science spacecraft have been added to the list of available satellites.
All of these spacecraft are currently operating and providing a wealth of scientific information
to the world. As future spacecraft are placed into low Earth orbit, they will be added as well.
Note that these spacecraft are not nearly as large as the ISS and as such, will be not be as bright and will
be challenging to see. We recommend that you allow at least 5 minutes outside before the sighting for your eyes
to adjust to the darkness prior to an attempt to view any of these spacecraft.
As for now, the following spacecraft are listed:
ACRIMSAT : ACRIMSAT is the latest in a series of long-term
solar-monitoring missions, utilizing the proven Active Cavity Radiometer Irradiance Monitor III (ACRIM III) instrument.
ADEOS-II : The ADEOS-II (SeaWinds)
scatterometer is a specialized microwave radar that measures near-surface wind velocity (both speed and direction)
under all weather and cloud conditions over Earth's oceans. This is a twin sister to the QuikSCAT sensor and flies
on the Japanese ADEOS-II Spacecraft to provide similar observations beyond the QuikSCAT mission.
AIM : Aeronomy of Ice in the Mesosphere (AIM) is a mission
to determine the causes of the highest altitude clouds in the Earth's atmosphere.
Aqua : Aqua will obtain precise atmosphere and ocean
measurements to understand their role in Earth's climate and its variations. Aqua carries six state-of-the-art instruments
to observe the Earth's oceans, atmosphere, land, ice and snow covers, and vegetation.
Aquarius : Aquarius is a focused satellite
mission to measure global sea surface salinity (SSS). By measuring SSS over the globe with such unprecedented precision,
Aquarius will answer long-standing questions about how our oceans respond to climate change and the water cycle.
CALIPSO : The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations
(CALIPSO) spacecraft was developed to help scientists answer significant questions and provide new
information about the effects of clouds and aerosols (airborne particles) on changes in the Earth's climate
CloudSat : CloudSat uses advanced radar to "slice" through clouds to see their vertical structure, providing a
completely new observational capability from space.
EO-1 : Earth Observing-1 (EO-1) is an advanced land-imaging mission that will demonstrate new instruments and spacecraft
systems. EO-1 will validate technologies contributing to the significant reduction in cost of follow-on Landsat missions.
GALEX : The Galaxy Evolution Explorer (GALEX) is an
orbiting space telescope that observes galaxies in ultraviolet light.
GRACE-1 and GRACE-2 : The GRACE mission is to accurately map variations in the Earth's gravity field. The GRACE mission
has two identical spacecraft flying about 220 kilometers apart in a polar orbit 500 kilometers above the Earth.
Hinode : Hinode (formerly known as Solar-B) is a highly sophisticated observational satellite equipped with three
advanced solar telescopes.
HST : The Hubble Space Telescope (HST) is a telescope that
orbits Earth. Its position above the atmosphere, which distorts and blocks the light that reaches our planet,
gives it a view of the universe that typically far surpasses that of ground-based telescopes.
Jason-1 and Jason-2 : Jason-1 is an
oceanography mission to monitor global ocean circulation, improve global climate predictions, and monitor events such
as El Nino conditions and ocean eddies. The Jason-2 satellite is an international Earth observation satellite mission
that continues the sea surface height measurements begun in 1992 by the joint NASA/CNES TOPEX/Poseidon mission and
followed by the NASA/CNES Jason-1 mission.
LandSat-7 : Landsat 7 systematically provides well-calibrated,
multispectral, moderate resolution, substantially cloud-free, Sun-lit digital images of the Earth's continental
and coastal areas with global coverage on a seasonal basis.
ORBVIEW-2 : The ORBVIEW-2 (SeaStar)
satellite carries the SeaWiFS instrument which is designed to monitor the color of the world's oceans.
Various ocean colors indicate the presence of different types and quantities of marine phytoplankton,
which play a role in the exchange of critical elements and gases between the atmosphere and oceans.
QuikSCAT : The QuikSCAT mission is intended
to record sea-surface wind speed and direction data under all weather and cloud conditions over Earth's oceans.
RHESSI : The Reuven Ramaty High Energy Solar
Spectroscope Imager (RHESSI) scientific objective is to understand solar impulsive energy release, particale
acceleration, and particle and energy transport.
RXTE : The Rossi X-ray Timing Explorer (RXTE)
is a satellite that observes the fast-moving, high-energy worlds of black holes, neutron stars,
X-ray pulsars and bursts of X-rays that light up the sky and then disappear forever.
SORCE : The Solar Radiation and Climate
Experiment (SORCE) is a NASA-sponsored satellite mission that will provide state-of-the-art measurements of
incoming x-ray, ultraviolet, visible, near-infrared, and total solar radiation.
Suzaku : Suzaku, formerly known as NeXT,
is Japan's fifth X-ray astronomy mission, and was developed at the Institute of Space and Astronautical Science
of Japan Aerospace Exploration Agency (ISAS/JAXA) in collaboration with U.S. (NASA/GSFC, MIT) and
Swift : The Swift Gamma Ray Burst Explorer is a
first-of-its-kind multi-wavelength observatory dedicated to the study of gamma-ray burst (GRB) science.
Its three instruments work together to observe GRBs and afterglows in the gamma-ray, X-ray, ultraviolet,
and optical wavebands.
Terra : Terra (formerly EOS AM-1) is the
flagship satellite of NASA's Earth observing systems. Terra is the first EOS (Earth Observing System) platform
and provides global data on the state of the atmosphere, land, and oceans, as well as their interactions with
solar radiation and with one another.
TIMED : The Thermosphere, Ionosphere, Mesosphere
Energetics and Dynamics (TIMED) spacecraft explores the Earth's Mesosphere and Lower Thermosphere (60-180
kilometers up), the least explored and understood region of our atmosphere.
TRMM : The Tropical Rainfall Measuring
Mission (TRMM) is a joint mission between NASA and the National Space Development Agency (NASDA) of Japan.
TRMM is particularly devoted to determining rainfall in the tropics and subtropics of the Earth. | 0.853409 | 3.283124 |
William Herschel was a German astronomer and musician who rose to fame when he discovered the planet, Uranus. He was born in Germany as Friedrich Wilhelm Herschel as the son of Anna Moritzen and Issak Herschel.
His father was a military musician and young Friedrich played in the same band in his early years. In 1759, he left the band to become a musician before becoming an organist.
Introduction to Astronomy
Herschel was not an astronomer by profession but he had a significant interest in the workings of space and the vast confines of the universe. In the year 1772, his sister Caroline moved to England to live with him and train as a singer.
During this time, Friedrich’s interest grew in astronomy and he rented a small telescope. Gradually he learned how to care for the observational objects and polishing and grinding his own mirrors.
The Discovery of Uranus
On the night of March 13th, 1781 Herschel spotted a small object that appeared to be moving over the course of several nights. At first, he thought that it was a comet.
But after further observation, he confirmed that it was a planet. He lobbied to have it named ‘Georgium Sidus’ after King George III.
Eventually, it was named ‘Uranus’ after the Greek god of the sky. Because of his discovery, the king knighted him and named him court astronomer. Because of the increase in pension, he was able to quit music and focus fully on his pursuit of astronomy.
William Herschel Facts
William Herschel was subsequently elected as a member of the Royal Society. He was presented with the copy of Charles Messier’s ‘Catalog of Nebulae and Star Clusters’ and that pique his interest even more.
He began to delve into the exploration of the stars even more. From October 1783, he began doing a sky survey of his own. Eventually, by standing long hours peering through his telescope, he examined the entire patch of the Great Britain sky.
William Herschel Discovered
Over the course of 20 years, Herschel observed 2,500 nebulae and star clusters and recorded them in the ‘General Catalogue of Nebulae’.
This catalog eventually expanded and of the 7,840 nebulae and clusters in the catalog today, 4,630 were discovered by Herschel and his son.
He also observed and discovered several moons around Uranus including Titania and Oberon. In the year 1800, William Herschel performed a simple experiment determining the temperature of different colors of sunlight passing through a prism.
He used his measurements to deduce a presence of what is now known as infrared radiation. He was the one that proposed the name ‘asteroids’ to large objects discovered in 1801.
The Contribution of His Sister, Caroline
Caroline Herschel, his sister, moved to England to live with him and advance her musical career. Instead, she served as Herschel’s assistant until her death. She was the first woman who discovered the first comet.
After that, she discovered eight others. She also discovered several other deep sky objects and ultimately became the first woman who was given a paid scientific position. She also received an honorary membership from the Royal Society. | 0.885497 | 3.314163 |
New phase of water could dominate the interiors of Uranus and Neptune : phys.org: by Lisa Zyga
Structure of superionic ice in (left) the bcc phase and (right) the newly discovered and more stable fcc phase. Credit: Hugh F. Wilson, et al. ©2013 American Physical Society
Read more at: http://phys.org/news/2013-04-phase-dominate-interiors-uranus-neptune.html/
Although superionic ice doesn’t exist under normal conditions on Earth, the high pressures and temperatures where it is thought to exist are very similar to the predicted conditions in the interiors of Uranus and Neptune.
“Uranus and Neptune are called ice giants because their interiors consist primarily of water, along with ammonia and methane,” Wilson said. “Since the pressure and temperature conditions of the predicted new phase just happen to line up with the pressure and temperature conditions of the interiors of these planets, our new fcc superionic phase may very well be the single most prevalent component of these planets.”
The researchers predict that understanding superionic ice—particularly the stable fcc phase—will offer insight into these ice giants.
“Uranus and Neptune remain very poorly understood at this stage, and their interiors are deeply mysterious,” Wilson said. “The observations we have are very limited—every other planet in the solar system we’ve visited multiple times, but Uranus and Neptune we’ve just done brief flybys with Voyager 2. What we do know is that they have bizarre non-axisymmetric non-dipolar magnetic fields, totally unlike any other planet in our solar system. We also know that they’re extremely similar in mass, density and composition, yet somehow fundamentally different, because Neptune has a significant internal heat source and Uranus hardly emits any heat at all.”
It’s possible that the predicted bcc-to-fcc phase transition may explain the planets’ unusual magnetic fields, although more research is needed in this area.
“Our results imply that Uranus’s and Neptune’s interiors are a bit denser and have an electrical conductivity that is slightly reduced compared to previous models,” Militzer added.
Understanding Uranus and Neptune’s interiors could have implications far beyond our solar system, as well.
“One thing we’re learning from the Kepler mission is that Uranus-like or Neptune-like exoplanets are extremely common,” Wilson said. “They appear to be more common than Jupiter-like gas giants. So understanding our local ice giants is important, because they’re an archetypal example for a huge class of planets out there in the universe.” | 0.849185 | 3.705953 |
Researchers from Yale University claim to have found stronger evidence to confirm that galaxies with little or no dark matter do really exist.
Dark matter is a mysterious, hypothetical form of matter, thought to dominate the makeup of galaxies. It is believed to account for about 85 per cent of the matter in the known Universe.
Scientists also believe that dark matter is possibly composed of some elusive subatomic particles, such as axions, that are yet to be discovered by scientists.
About two years ago, Yale researchers discovered a weird galaxy, dubbed NGC 1052-DF2 (or DF2), which seems to contain almost no dark matter. It was the first time that any such galaxy had been found in the Universe.
While many scientists praised the finding at the time, some also raised doubts about the accuracy of the results.
Now, Yale researchers have come up with two new studies, whose results confirm that their initial observations about NGC 1052-DF2 were correct.
In the first study, researchers took more precise measurements of DF2 using the Keck Cosmic Web Imager installed on W. M. Keck Observatory. With these measurements, the team found that the globular clusters present within DF2 were moving at a speed that matched well with the mass of the DF2's normal matter. The clusters would have moved at much faster speeds had there been dark matter within the galaxy.
In the second study, the researchers discovered another galaxy with very little or no dark matter. It was spotted using the Keck Observatory's Low Resolution Imaging Spectrometer and was labelled NGC 1052-DF4 (or DF4) by the research team.
According to scientists, these two galaxies can be classified as ultra-diffuse galaxies (UDGs), which are similar to the Milky Way in terms of size, but have between 100 to 1000 times fewer stars. Because of that, they appear translucent and are difficult to observe in the Universe.
The new observations suggest that there could be more such galaxies in the Universe.
Yale researchers are currently conducting a wide-area survey using the Dragonfly Telephoto Array in a bid to identify more UGDs. They also plan to examine potential candidates using the Keck telescopes.
The detailed findings of the studies are published in The Astrophysical Journal Letters.
Your questions on supporting remote and home working answered
China has built a new spacecraft able to carry six astronauts to space
Join us for the first part of our virtual event series
Huawei warns that any disruption in its 5G participation in UK could do a 'disservice' to the country
A number of MPs have indicated the decision to deploy Hauwei could be overturned
Emails contain large amounts of critical business data, usually stored in archives for compliance and legacy purposes | 0.838817 | 3.854757 |
Astronomers have spotted the fastest moving stellar corpse to date – and it appears to be headed straight out of our galaxy.
A team from the US National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico, and the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, US, clocked the dead star at 1100 kilometres per second.
The object, called B1508+55, is a rotating neutron star, or pulsar. It is the superdense core of a massive star that exploded as a supernova about 2.5 million years ago. The explosion seems to have ejected the pulsar with such force that it will eventually escape the Milky Way entirely, says team member Shami Chatterjee, an astronomer with NRAO and CfA.
However, current simulations of supernovae have never produced such breakneck speeds. In the models, the newly formed neutron star starts out fast but soon slows down when material from the outer layers of the exploded star crashes back onto it. In 2004, the first 3D model of a supernova found that the blast could send a neutron star flying at about 200 kilometres per second – nearly six times slower than the new record holder.
“I think everyone believes that supernova explosions do in nature provide these [higher] kick velocities,” Chatterjee told New Scientist. “It’s just that our simulations are not quite there yet.”
The researchers watched this pulsar for two years with the Very Long Baseline Array – a collection of 10 radio-telescopes scattered from Hawaii to the US Virgin Islands. They determined the pulsar lies 7700 light years away and gauged its speed by observing how its position on the sky changed in that time.
From this, they traced its route backwards to its likely birthplace 2.5 million years ago in a region full of huge stars in the constellation Cygnus. The stars are so massive that they will eventually blow up as supernovae, potentially spawning other speedy stellar corpses.
Journal reference: Astrophysical Journal Letters (vol 630, p L61) | 0.844167 | 3.589678 |
Rhett Allain reports: Bob Riggle is 80 years old and he has a car. This car has a 2,500 horsepower engine mounted in the rear. But what happens when you have this much power? Yes, you can see in the video that there are two events. First, the car does a “wheelie” and second the car rolls over.
Fortunately no one was injured, but at least this is a great opportunity for a physics lesson.
Center of Mass and Wheelies
There are some forces acting on this car so let’s start with a diagram.
There are essentially three forces on the car in this case.
- The gravitational force pulls down. We can model this force as though it was only pulling down at one point. We call this point the center of mass (technically, it would be the center of gravity—but on the surface of the Earth these two points are at the same place).
- There is the force that the ground pushes up on the car. Since the car is not accelerating in the vertical direction, this ground force must be equal to the gravitational force.
- The friction force pushes on the tire at the point of contact with the ground. This force pushes the car in the direction that it is accelerating.
But how does this car stay tilted up like that? Shouldn’t the gravitational force make it fall back down? Clearly, it doesn’t. Perhaps the best way to understand this wheelie is to consider fake forces. We normally consider forces as interactions between objects (between the ground and the car or between the Earth and the car). However, it’s sometimes useful to create other forces that are due to accelerations. Now, these are fake forces in that they are not a real interaction. But as viewed in an accelerating reference frame (like inside the car), it is as though there is this real acceleration force.
Since the car accelerates to the left (in the above diagram), the fake force is to the right and keeps the car in wheelie up position.
But what about torque? If you want to rotate an object, you need torque. One expression for torque would be (this is just the scalar form—for simplicity):
In this expression, F is the force, r is the distance from the point of rotation to the point where the force is applied and θ is the angle between these two things. For the total torque about the wheel, it’s really just the torque due to the gravitational force and the torque due to the fake force.
If you put the engine in the front of the car (where it usually is) then the center of mass moves closer to the front. This means the gravitational torque will be much larger (since r is larger). If you get the center of mass closer to the back wheel, the torque from the fake force doesn’t need to be as high to get a wheelie. Read the rest of this entry »
LAUREL, Md. — Nola Taylor Redd reports: With less than 24 hours to go before NASA’s New Horizons probe makes its close flyby of Pluto, scientists are already learning more about the dwarf planet than ever before, including the fact that it is bigger than previously thought.
New Horizons’ latest views of Pluto have shown the dwarf planet to be 1,473 miles (2,370 kilometers) across, making it the largest body in the icy Kuiper Belt at the edge of the solar system. The observations also confirmed the presence of a polar ice cap on Pluto, and measured three of the dwarf planet’s moons.
“Pluto is not disappointing,” said principal investigator Alan Stern, of the Southwest Research Institute in Boulder, Colorado, during a NASA briefing here today (July 13).
As New Horizons closes in, the spacecraft made the most precise measurements to date of Pluto’s size using methods similar to those employed by NASA’s Voyager spacecraft. The new diameter of the dwarf planet makes it larger than fellow Kuiper Belt denizen Eris, which is 1,445 miles (2,326 km) in diameter.
Previous estimates for the size of Pluto had put its radius at 1,430 miles (2,301 km). But Pluto now stands as the undisputed king of the Kuiper Belt.
“This settles the debate about the largest object in the Kuiper Belt,” Stern said. Read the rest of this entry »
Isabella Steger reports: Hong Kong’s legislature is expected to vote down a proposal that would let the public directly elect the city’s chief executive in 2017 — but only from a prescreened slate of candidates. The showdown follows city-wide protests and a year and a half of efforts by Hong Kong’s leaders to sell the Beijing-backed election plan. Here are five things to know about the vote.
1. The Legislature Will Vote This Week
The proposal currently on the table will be put to a vote this Wednesday and Thursday. This is arguably the most critical of five stages in the election overhaul blueprint, laid down by Beijing and in accordance with the Basic Law, Hong Kong’s mini-constitution
2. Pro-Democracy Lawmakers Oppose the Package
The package lays out the rules for electing Hong Kong’s chief executive in 2017 within a framework formulated by Chinese authorities, in which all candidates must be nominated by a 1,200-member committee that is heavily pro-Beijing. After slight tweaks announced in April, the opposition maintains that the system is not democratic enough to allow one of their own candidates to stand.
3. The Plan Is Not Likely to Pass
27 pro-democracy lawmakers — who control a little more than one-third of the city’s legislature –say they will vote against the package, as has one lawmaker who isn’t part of the opposition camp. Read the rest of this entry »
PopMech Editors: Say hello to the shortest lunar eclipse of the century. These stunning photos capture the blood moon as captured over Colorado, China, and New Zealand. For more, check out our original post on the early morning event.
Undocking coverage lasts from 6:15 p.m. to 7:30 p.m. EDT, while landing coverage is scheduled to run from 9 p.m. to 11 p.m. EDT
Mike Wall reports: NASA will test-fire the booster of its Space Launch System (SLS) megarocket today at 11:30 a.m. EDT (1530 GMT), and three astronauts will return to Earth from the International Space Station in the evening. You can watch the space action live on Space.com, courtesy of NASA TV.
“What’s impressive about this test is, when ignited, the booster will be operating at about 3.6 million pounds of thrust, or 22 million horsepower. This test firing is critical to enable validation of our design.”
— Alex Priskos, manager of the SLS Boosters Office at NASA’s Marshall Space Flight Center in Huntsville, Alabama
The SLS rocket booster test takes place at the facilities of aerospace firm Orbital ATK in Promontory, Utah, with webcast coverage beginning at 11 a.m. EDT (1500 GMT). There will be no spaceflight involved: Engineers will fire the 177-foot-long (54 meters) booster for two minutes on the ground, in a horizontal configuration.
“What’s impressive about this test is, when ignited, the booster will be operating at about 3.6 million pounds of thrust, or 22 million horsepower,” Alex Priskos, manager of the SLS Boosters Office at NASA’s Marshall Space Flight Center in Huntsville, Alabama, said in a statement. “This test firing is critical to enable validation of our design.”
Another booster test is planned for early 2016, NASA officials said.
The SLS will incorporate two of the five-segment boosters, as well as four RS-25 engines, on its first two flights, which will be capable of lofting 70 metric tons of payload to low-Earth orbit (LEO). NASA intends to scale the rocket up to deliver 130 metric tons to LEO, to enable manned missions to faraway destinations such as Mars. The first SLS flight is currently scheduled for 2018.
This evening, NASA astronaut Barry “Butch” Wilmore and Russian cosmonauts Alexander Samokutyaev and Elena Serova will wrap up their nearly six-month-long mission aboard the International Space Station and come back down to Earth. Read the rest of this entry »
The gift from Robert and Renee Belfer was announced as the institution celebrates its 50th anniversary this year.
An exhibition titled “A Roman Villa – The Belfer Collection” showcasing approximately 100 of the objects will be on view at The Israel Museum from June 5 through Nov. 21.
The collection is “one of the most important private holdings of antiquities anywhere,” museum Director James Snyder said in a telephone interview from Jerusalem…Read more
Je Suis Charlie Hashtag Makes Media History
The “Je Suis Charlie” hashtag has become one of the most popular in the history of Twitter as people around the world showed their solidarity for the victims of the Paris outrage.
At its height the tag was tweeted at a rate of 6,500 times a minute and featured in 3.4 million tweets in just one 24 hour period.
The phrase is in reference to the Charlie Hebdo magazine where 12 people were slaughtered when Islamist terrorists stormed their offices in Paris on Wednesday sparking a series of attacks lasting three days.
STICKIN’ IT TO THE MAN: ‘I refuse to comply with the requirements of my illegal detention under house arrest. The bracelet with some effort has been cut off with kitchen scissors’Posted: January 5, 2015
Putin Critic Alexei Navalny Defies House Arrest
Navalny received suspended sentence on 30 December for embezzling money but was not released from house arrest
Kremlin critic Alexei Navalny said on Monday he would no longer comply with the terms of his house arrest and had cut off his monitoring tag.
Navalny, who led mass protests against Vladimir Putin three years ago, was handed a suspended sentence on 30 December after being found guilty of embezzling money in a trial that led to his brother being jailed on similar charges.
“It is stupid to brag, but I am the first person in the history of Russian courts to be sitting under house arrest after the verdict.”
He was placed under house arrest almost a year ago during the investigation but said in a blog that he was perhaps the only person in Russian legal history to be kept under house arrest after being sentenced.
He said he should have been released after sentencing in late December but instead was being held pending the publication of the verdict on 15 January – a situation that even the police did not know how to deal with. Read the rest of this entry »
Public discontent in Hong Kong is at its highest for years
AFP reports: Thousands are expected to take part in a major pro-government rally in Hong Kong Sunday to counter a civil disobedience campaign that has pledged to paralyse the city in a push for electoral reform.
Public discontent in Hong Kong is at its highest for years, with concern over perceived interference from Beijing and growing divisions over how its leader should be chosen in 2017 under political reforms.
“We want to let the world know that we want peace, we want democracy, but please, do not threaten us, do not try to turn this place into a place of violence.”
— Alliance co-founder Robert Chow
Pro-democracy campaigners from the Occupy Central group have pledged to mobilise protesters to take over some of the busiest thoroughfares of the financial hub if public nomination of candidates is ruled out by the authorities.
FLASHBACK 2012: SCMP’s Benjamin Garvey, who more or less live-tweeted the proceedings, tweeted this photo and message: “Cameraman was hit from behind, other cameramen lept to his defence, grabbed attacker, held him until police came.”
But the movement has been heavily criticised by Beijing and city officials as being illegal, radical and violent.
[Also see – Hong Kong Asks Beijing for Greater Democracy]
Organisers of Sunday’s rally, the Alliance for Peace and Democracy, say the silent majority of the city’s seven million residents do not support the Occupy movement.
“We want to let the world know that we want peace, we want democracy, but please, do not threaten us, do not try to turn this place into a place of violence,” alliance co-founder Robert Chow told AFP.
More than 120,000 people have signed up for the rally, which started shortly after 1:30 pm (0530 GMT), but the turnout could reach up to 200,000, the alliance said. Read the rest of this entry »
WAM TOKYO, 5th May, 2014 (WAM) — A strong earthquake with a preliminary magnitude of 6.0 on the Richter scale struck Tokyo on Monday, the Japan Meteorological Agency said. No tsunami warning was issued for the 5:18 a.m. (2018 GMT Sunday) quake, the agency said.
According to the Kuwait News Agency, KUNA, at least 17 people were injured in Tokyo and its neighbouring prefectures, according to police and fire-fighters. There was no impact on nuclear power plants in the region, operators said. All subway systems in Tokyo and some train services linking central Tokyo and other cities were temporarily suspended after the quake, but resumed later.
The focus of the tremor was 162 km underground near Izu Oshima Island in the Pacific Ocean, about 120 km south of Tokyo, the Japan Meteorological Agency was quoted as saying. Read the rest of this entry »
Serious question: Is there a good argument for a president skipping a national security meeting on a day such as this?
— Charles C. W. Cooke (@charlescwcooke) March 1, 2014
The United Nations Security Council will be holding a closed door meeting for the second consecutive day to discuss the current situation in Ukraine.
The President of the Security Council said informal consultations among council members would begin at 2 p.m. (1900 GMT) Saturday. The council also held closed door consultations on Friday at the request of Ukraine’s U.N. Ambassador Yuriy Sergeyev who referred to “the deterioration of the situation” in the Crimean Peninsula which he said “threatens the territorial integrity of Ukraine.”
Russia’s parliament on Saturday approved a motion to use the country’s military in Ukraine after a request from President Vladimir Putin. Ukraine has already accused Russia of “a military invasion and occupation” of strategic points in the Crimean peninsula, a Ukrainian territory where Russia’s Black Sea fleet is based.
At least 15 people have been killed in a trolley bus blast in Volgograd, emergency services report, only a day after a suicide bombing ripped through the city’s railway station, killing 17.
Monday, December 30
“The emergency services have reacted very swiftly. All those injured have been taken to hospitals, as their identities are being determined,” he said.
05:37 GMT: According to witness reports to ITAR-TASS, there were many students on the bus.
“There was a loud ‘pop’, then a flash, everything was enveloped in smoke,” one female witness said, describing the sudden realization.
05:34 GMT: The Investigative Committee now puts the number of injured at 15.
05:30 GMT: In describing the character of the blast, ITAR-TASS law enforcement sources have said that it appears to be a suicide attack, “judging from the body fragments characteristic of such a bombing.” | 0.88899 | 3.035106 |
Science has many scenarios for the apocalypse. Air & Space talks about one more thing – this is a supernova explosion. In the past, it was supernova explosions that were one of the causes of mass extinctions on our planet. During one such extinction, 70% of all terrestrial vertebrates died.
Betelgeuse is harmless, but other stars turning into supernovae can doom the Earth to death.
In a recent publication on The Astronomer’s Telegram, Edward Guinan and Richard Wasatonic of Villanova University reported a mysterious darkening of the bright star Betelgeuse, which makes up the right “shoulder” of the constellation Orion.
Ginan and his student Vasatonic began to observe this star in 1981, and Vasatonic continues this work since 1995. The red super giant Betelgeuse never shone as dimly as now. In terms of brightness in the starry sky, Betelgeuse occupied eighth or ninth place, but by the beginning of February it dropped to 21 or 22 places, which is why Orion looks rather strange. Since September, the temperature of this star has also fallen by about 100 degrees Celsius, and the brightness has dropped by about 25%.
The question is whether this is a prelude to a supernova explosion, or is it just a natural wobble. Located 700 light years from Earth, Betelgeuse is one of the closest stars to us from among those that may become supernovae. If it explodes, then in brightness it will almost equal the full moon. The expected explosion can occur both tomorrow and after 100 thousand years.
Supernova explosions are one of the causes of mass extinctions on Earth such as what happened 2.6 million years ago, or the Permian mass extinction that happened 252 million years ago. It was the most disastrous disaster for the terrestrial flora and fauna of that time, destroying about 96% of all marine species and 70% of all terrestrial vertebrates.
Fortunately, Betelgeuse does not pose any danger to the Earth. Whenever it explodes, its deadly radiation will spread evenly in all directions, and by the time it reaches us, the level of this radiation will be very weak, without causing any concern. But there are other supernova candidates, such as the Wolf-Rayet stars, which are much more dangerous. Some of them can emit gamma radiation streams that emit radiation in a narrow direction along the axis of rotation of the star. If the Earth is on the line of fire, the consequences will be disastrous. The most notorious example of this kind is the star WR 104, which is too far from our planet to pose a threat to it. But other, closer Wolf-Rayet stars such as the one found in the Gamma Sails system can be much more dangerous.
That is why the study of stars turning into supernovae can save our lives in the future. In the case of Betelgeuse, we will know about a bright explosion in about an hour. This will be known to us by neutrinos and gravitational waves, which will come to us before the impact reaches the surface of the star, and visible light begins to rapidly increase.
It would be nice to follow Betelgeuse this summer, when she comes too close to the Sun, and it will be impossible to observe it from the Earth. The amateur astronomer Walter Webb has one suggestion in connection with this: let our spacecraft located near Mars help us in this matter. | 0.808824 | 3.610195 |
NASA-led mission hailed a major success
Working with NASA and other partners from across the globe, scientists at the University of Central Lancashire UCLan) have played a key role in the launch of a rocket-borne camera that aims to uncover some of the mysteries surrounding the outer atmosphere, or corona, of the Sun.
The recent mission, which took place at 2:54 pm EDT May 29, 2018, has already been hailed a major success. The clarity of images returned is unprecedented and their analysis will provide scientists around the world with clues to one of the biggest questions in heliophysics – why the Sun's atmosphere, or corona, is so much hotter than its surface.
The precision instrument, called the High Resolution Coronal Imager or Hi-C for short, flew aboard a Black Brant IX sounding rocket at the White Sands Missile Range in New Mexico. The mission was led by NASA’s Marshall Space Flight Center (MSFC) in Huntsville, Alabama with partners UCLan, the Harvard-Smithsonian Center for Astrophysics, Boston and the Lockheed Martin Solar and Astrophysics Laboratory in Palo Alto, California.
"This was the third launch of Hi-C," said Amy Winebarger, principal investigator for the Hi-C mission at NASA's MSFC. "Our second launch in 2016 had an issue with the camera on-board the telescope of the instrument. So, while we gathered critical engineering data and some images, we did not get the high-quality images of the corona we were expecting. We improved the camera from the last launch and are already getting exciting data from this most recent experiment that could help explain the long-held questions about the Sun's atmosphere."
The UCLan team consisted of Professor Robert Walsh (Jeremiah Horrocks Institute), Dr Darren Ansell and Ben Watkinson (School of Engineering) who participated in field operations and science data analysis post flight. Professor Walsh commented: “We are very excited that UCLan scientists have played an important role in making the HiC rocket flight such a success.”
The telescope on Hi-C, the centrepiece of the payload weighing 210kn and measuring 3 metres long, is designed to observe a large, active region in the Sun's corona in fine detail. The instrument has been improved from the last mission with an updated camera that is expected to improve the data taken from the Sun and the images received. The duration of the space portion of the Hi-C mission provided five minutes of observation time with the telescope acquiring an image about every five seconds.
Scientists anticipate that analysis of the imaging data from Hi-C's third flight will help resolve current questions about connections between the hot and cool regions of the solar atmosphere. To meet this goal, Hi-C's launch and data collection was coordinated with the Interface Region Imaging Spectrograph (IRIS), a satellite observatory that captures images of the cooler portions of the sun’s atmosphere.
"Understanding how the Sun works is important to everyday things we do on Earth," continued Professor Walsh. "Solar flares and disruptions can interrupt radio, GPS communications and satellites that disseminate cell phone signals. By studying how the Sun releases these bursts of energy, we hope to be able to better anticipate them and, in the future, design technology better equipped to withstand these disruptions."
It is anticipated that images from the latest Hi-C mission will be available to the public by the end of the year.
Part of the team who worked on the mission | 0.827929 | 3.060546 |
Joseph N. Pelton, President, International Space Safety Foundation and Chair, IAASS Academic Committee, is addressing the issues relating to Potentially Hazardous Asteroids in a three part series. Part one is presented here:
When I explain to people that I meet everyday that I am involved with the study of space safety, the first response they make is: “Just what is space safety?” The problem is that everyone, even within the field of space safety, has their own definition. Some people think of astronaut safety. Others think about the design of safer launchers, spacecraft or satellites. Others in field of satellite telecommunications think about possible conjunction of spacecraft or space debris hazards. Yet others think about nuclear materials and toxic materials such as hypergolic fuels used in space missions which might expose people to risk. Recently, space traffic management and space situational awareness have been hot topics. Just a very few think about Near Earth Objects (NEOs), Potentially Hazardous Asteroids (PHAs) and other dangers from space such as cosmic radiation or coronal mass ejections (CMEs).
The International Space Safety Foundation (ISSF) and the International Association for the Advancement of Space Safety (IAASS) are concerned with “all of above.” We are truly concerned about these safety issues and risks and even more. The following series of 3 editorials seeks to raise awareness about physical hazards from space that are remote in terms of likelihood but potentially devastating in scope.
As Space Writer Leonard David has said about potentially hazardous asteroids in near earth orbits: “They are nasty and mean and can mess up Planet Earth big time.”
The first of these editorials is about assessing the nature and degree of risk. The second editorial is about a realistic assessment of the nature of the risk in coming decades—thus we are thus particularly looking at potential hazards that may affect the lives of people currently on Earth through the lives of our grandchildren. The third editorial is about what could or should be done about those risks to mitigate them once discovered.
So what should we do to assess just how big a risk is posed by Near Earth Objects? How can the general public start to grasp even what we are talking about? Apollo 8 Astronaut Rusty Schweickart, who for years headed the B16 Foundation, is a brilliant spokesperson on this subject, but people he has reached have generally been space scientists and perhaps a few sci-fi zealots. How can we reach a wider audience and give them a realistic view of the dangers within a scientifically accurate framework. One possible answer is the so-called Torino Scale.
At Unispace III in Torino, Italy, the assemblage agreed to adopt the Torino Scale that combined an assessment of “likelihood” with the size, kinetic force and likely degree of devastation that a wayward meteorite of varying sizes could create if it impacted our planet. Almost everyone in the world understands what the Richter Scale is and its progressive levels of impact as measured on a logarithmic scale from 1 to 10. Likewise we understand categories of hurricanes from 1 to 5. The Torino Scale for Potentially Hazardous Asteroids—also on a scale of 1 to 10—can help the general public understand that it is especially Category 8 to 10 Near Earth Asteroids that are important for us to avoid if we possibly can. We need to involve the United Nations, the general press, and major news web sites to get out the word on the Torino Scale.
This general understanding of the Torino scale can help us build consensus to invest in two important things. One would better means of space situational awareness. These enhances system would go well beyond the capabilities of NASA’s Wide Field Infra-Red Survey Explorer (WISE ) in order to provide a comprehensive and much understanding of the 20,000 to 45,000 asteroids out there could impact Earth in very unwelcome ways in coming decades, centuries or even millennia. The other investment would be to create improved systems to actual address the threat of “killer asteroids.” There have been efforts first advocated by Arthur C. Clarke that turned into NASA’s Earth Guard as well as the European Commission’s latest effort known as “NEOShield.” These programs are aimed at developing tools to deal with an asteroid that is found to be on a collision path with our planet. At this stage these are programs with extremely modest funds and with no real sense of urgency. If we discovery we have a potential scale threat that is a Number 9 or 10 on the Torino Scale and it is too late—then it will indeed be TOO LATE. The ISSF and IAASS will in future months and years be trying to raise public understanding through advancing wider knowledge of the Torino Scale. Next time we will address what are the threats we face from PHAs.
Stay tuned for the next article in this series: Clarifying Near Term Risk. | 0.826967 | 3.189721 |
First dark matter search results from Chinese underground lab hosting PandaX-I experiment
Scientists across China and the United States collaborating on the PandaX search for dark matter from an underground lab in southwestern China report results from the first stage of the experiment in a new study published in the Beijing-based journal Science China Physics, Mechanics & Astronomy.
PandaX is the first dark matter experiment in China that deploys more than one hundred kilograms of xenon as a detector; the project is designed to monitor potential collisions between xenon nucleons and weakly interactive massive particles, hypothesized candidates for dark matter.
In the new study, scientists explain, "Dark matter is a leading candidate to explain gravitational effects observed in galactic rotational curves, galaxy clusters, and large scale structure formation."
"Weakly interacting massive particles (WIMPs), a particular class of dark matter candidates, are interesting in particle physics and can be studied in colliders [and in] indirect and direct detection experiments."
If confirmed, dark matter particles would extend understanding of the fundamental building blocks of nature beyond the Standard Model of particle physics, and would provide support for theories on supersymmetry and extra dimensions of space-time.
"Direct positive detection of WIMPs using ultra-low background detectors in deep underground laboratories would provide convincing evidence of dark matter in our solar system and allow the probing of fundamental properties of WIMPs," they add in the new study.
Direct detection experiments using different technologies have produced many interesting results, but not universally confirmed evidence of weakly interacting massive particles. These results have produced much excitement across the global scientific community and call for further examination of WIMP signals through other experiments.
"In recent years, new techniques using noble liquids (xenon, argon) have shown exceptional potential due to the capability of background suppression and discrimination, and scalability to large target masses," state the PandaX collaborators. "The XENON10/100 and LUX experiments using the dual-phase technique have improved WIMP detection sensitivity by more than two orders of magnitude in a wide mass range."
China's PandaX experiment, operated at the China Jinping Underground Laboratory, uses the dual-phase xenon technique to search for both low and high mass WIMP dark matter.
The initial success of the PandaX project demonstrates China has joined the global competition at the scientific frontier marking dark matter searches.
Today more than twenty dark matter search experiments are being conducted worldwide. Many dark matter search experiments, such as the DAMA/LIBRA experiment in Italy, the CoGeNT and CDMS experiments in the US, and the German-led CRESST experiment have reported findings that could be interpreted as positive signals of dark matter in recent years.
The PandaX collaboration joins this effort with results from a dark matter search that started in May of 2014.
No dark matter signal was observed in the first PandaX-I run, which places strong constraints on all previously reported dark matter-like signals from other similar types of experiments.
The PandaX experiment to date has collected about 4 million raw events; only about ten thousand events fell into the energy region of interest for dark matter. In the quiet central part of the xenon target only 46 events were observed.
However, the data from these 46 events was consistent with signals marking background radiation, not dark matter.
PandaX stands for Particle and Astrophysical Xenon Detector. The experiment is being conducted by an international team of about 40 scientists, and led by researchers from Shanghai Jiao Tong University.
The goal of the first stage of PandaX experiment is to examine previously reported dark matter-like signals. The scale of the PandaX-I experiment is second only to that of LUX, which is currently the planet's largest dark matter experiment and is located in a South Dakota mine in the US.
To shield the Chinese experiment from cosmic rays, the PandaX detector is located at the China Jinping Underground Laboratory (CJPL), the deepest underground laboratory in the world. CJPL was developed by Tsinghua University and the Yalong River Hydropower Development Company in 2010.
link.springer.com/article/10.1 … 07/s11433-014-5598-7 | 0.897773 | 3.550047 |
You might not see it or even realize it, but Earth's magnetic field is vital in protecting life on the planet from the constant onslaught of harmful cosmic radiation and charged particles from the solar wind. Extending out from Earth's core like an invisible cocoon, the planet's geomagnetic field is also informed by the lithosphere (its crust and upper mantle). The layer is made up of magnetized rocks that produce a weak field that is difficult to detect, meaning that the exact details of Earth's magnetic field as a whole is probably much more complex than we might imagine.
That's what researchers over at the European Space Agency (ESA) are revealing in a recent three-dimensional map of the Earth's "lithospheric magnetic field", created using data from a trio of satellites collectively known as Swarm. The result is a map that does not look uniform at all, offering new clues and more questions about how our lithosphere's magnetic field has changed over the course of geological history. As one of the team's scientists, Nils Olsen from the Technical University of Denmark, explains, this is the highest resolution map of its kind:
By combining Swarm measurements with historical data from the German CHAMP [Challenging Minisatellite Payload] satellite, and using a new modelling technique, it was possible to extract the tiny magnetic signals of crustal magnetization.
This colour-coded model shows areas of weak magnetic activity shaded in blue, while areas of high magnetic activity are shown in red. One of the mysteries opened up by this new map is an area of sharp magnetic intensity around the city of Bangui in the Central African Republic, as seen in the video. Scientists theorize that it may be due to a meteorite crashing here over 540 million years ago.
The earth's ever-changing crust -- altered through volcanic activity on land and underwater -- also provides insight into the history of the planet's dynamic magnetic field as minerals in cooling magma organize themselves according to a magnetic north that can shift over time, creating 'stripes' along the ocean floor that can be seen in the model. Dhananjay Ravat from the University of Kentucky explains:
These magnetic stripes are evidence of pole reversals and analyzing the magnetic imprints of the ocean floor allows the reconstruction of past core field changes. They also help to investigate tectonic plate motions. The new map defines magnetic field features down to about 250 km and will help investigate geology and temperatures in Earth’s lithosphere.
Another mystery that the scientists are pondering is why the Earth's magnetic field is weakening in certain regions. Scientists believe that Swarm's data will help us better understand natural processes that occur inside the planet, as well as conditions in outer space that are influenced by solar activity. In any case, there's plenty to unravel as the mission continues to observe and map Earth's complex and ever-shifting magnetic field. Read more over at ESA's Swarm. | 0.80823 | 3.883663 |
Nov. 2, 2011 -- Something strange is happening on the planet Uranus. A fuzzy white spot has appeared on its frigid blue cloud tops, 1.8 billion miles from the sun, and astronomers say it's probably a giant methane storm, something unimaginable on Earth.
What do you do if you're a serious astronomer, poring over the images from the Gemini Observatory in Hawaii? You go on Facebook -- not some obscure scholarly network-- to invite amateurs to join in. (Images are being collected by an organization called the International Outer Planet Watch.)
"This is a science that's for the public," said Heidi Hammel, a planetary scientist who's studied the outer ice giants Uranus and Neptune, the seventh and eighth planets from the sun. "There is action going on right now, and you can be part of it."
When she said right now, she meant now. The first images of the storm on Uranus only came in on Thursday night, and it may only be 3-5 days before the storm fades from view. Hammel has filed a request for the Hubble telescope in Earth orbit to take a look at Uranus on a "target of opportunity" basis. If enough amateur astronomers chime in, Hubble will be diverted from other observations to turn toward Uranus before the moment passes.
"If you could look at it up close, I imagine it would look like a really tall anvil cloud," said Hammel.
It may be roughly similar in formation to a thunderstorm on Earth -- except that it's hundreds of miles across, if not more, high in Uranus' atmosphere.
Since the storm is not obscured by clouds above it, it appears 10 times brighter than the rest of the planet, report astronomers who have seen it this week. To amateurs, even with fairly large telescopes, it may show only as a faint dot. But if enough chip in, they may be able to calculate how quickly Uranus' frozen clouds are turning. Scientists say the planet rotates in just over 17 hours.
Uranus has had a tough time as planets go. It is just on the edge of visibility from Earth, appearing to the naked eye as a dim star -- if you live in a place with crystal-clear skies, far from cities. The astronomer John Flamsteed put it on a star chart as long ago as 1690, but only in 1781 did Sir William Herschel realize it was a planet, moving against the background of stars in the sky.
It takes 84 Earth years to orbit the sun once, and it's turned on its side relative to the other planets, perhaps because it was slammed -- twice, according to one computer model -- by debris as the solar system was forming. It's only been visited by one space probe, Viking 2 in 1986, which sped by on its way to Neptune and on out toward the stars.
So did Uranus have a bad day last week?
"No, it had a great day," said Hammel. "It's great when a planet that gets no respect does something really interesting." | 0.877271 | 3.50667 |
Imaging deep sky objects from a suburban driveway forces one to find ways to deal with light pollution. Light pollution is the enemy of astronomers – but in reality, there are ways around it.
Some of the most beautiful objects in the cosmos are called emission nebula. They are clouds of gas, often where new stars are being born. They give off light only in very specific wavelengths, resulting from their elemental gases being ionized in specific ways.
We can use this to our advantage by imaging through filters that only allow those wavelengths through – and therefore much less of the light pollution. By a happy accident, most light pollution exists at different wavelengths than the colors emission nebulae shine at. Even white LED streetlights are less intense at the wavelengths we’re interested in for these objects.
The problem is how to represent the light gathered through these “narrowband filters” in a visually pleasing way. Most of the Hubble photos you see use what’s called a “SHO mapping” – where the color red represents Sulfur-II emissions, green represents Hydrogen-alpha emissions, and blue represents Oxygen-III emissions. That gives you pretty pictures such as the famous “pillars of creation,” but it’s not a representation of what these objects would really look like to the eye. They are false-color images that have scientific value, and sometimes happen to be really pretty. But usually they just look green, with bloated, magenta stars.
And to the eye, these objects are beautiful in their natural state. Wouldn’t it be great if we could reconstruct a visible-light image from narrowband data? It would be like banishing light pollution from your city, or like having a telescope in the Atacama desert! Well, we can.
Yesterday, I derived a way of mapping narrowband data to RGB (red, green blue) images that uses the spectral characteristics of emission nebulae to reconstruct how they appear in visible light – just given their emissions in Sulfur-II (SII), Hydrogen-alpha (Ha), and Oxygen-III (OIII). People have tried this before; commonly, an “HOO” mapping is used to reflect the fact that Hydrogen emissions are red to the eye, and Oxygen is more or less cyan. Some more advanced imagers have also added some Hydrogen data into the blue channel, knowing that there’s actually a second Hydrogen emission line closer to blue. But few people have gone to the trouble of synthesizing each emission line from a nebula from this data, converting the wavelengths to precise RGB values, and combining them all together. I posted the details of how I derived it all on a forum called Cloudy Nights. But the final result is this:
R = 0.5*Ha + 0.5*SII G = 0.5*OIII + 0.094*Ha B = 0.295*OIII + 0.1*Ha
And, here’s my image of the Eagle Nebula created with this formula, taken from my light-polluted driveway, literally underneath a streetlight. Look for the “pillars of creation” in the middle – as they really are!
This is REALLY EXCITING – at least to me! I’ve compared this to an image taken with a 2.2-meter telescope in the Atacama desert – and although their image appears more red than mine, mine actually has more detail and what I think is more pleasing color palette. If you compare it to a true-color image taken with somewhat comparable equipment, it’s actually a pretty close match. And NO color manipulation in Photoshop was required – this image just fell out of the math naturally. This means processing my images will be a much faster process, and with nothing subjective in how they are produced. While that does take some of the “art” out of the process, the geek in me loves the fact that nature is producing art all on its own.
A guy with a PhD in optical science chimed in on the discussion where I originally posted this, and basically said “yeah, that’s close to how I’ve been doing it too, and my results look like yours.” I’m giddy that someone who understands this stuff better than me arrived at similar results on his own, just working from the physics and math of it all.
And, it makes me want to scream from the mountaintops: astrophotography can be done anywhere! I think a lot of people shy away from this hobby in part because they think they’ll never get good results where they live, and their family commitments prevent them from traveling to dark sky sites. But this image shows that even from an urban driveway, you can create images that rival huge, professional observatories in the Chilean desert. You just have to know the right tricks.
I want to write more about those tricks; every image on this site was taken from my suburban home in a “red zone” on the light pollution map, and every time I feel like I’m winning a battle against light pollution. You’re not limited to emission nebulae in suburbia – planets, the Moon, and even many distant galaxies are attainable if you know how and have the right gear. Sure, at a dark site there are objects you can image that I can’t – and you’ll get a quality image in much less time. I’ll probably never produce an APOD from my driveway, but very satisfying results happen all the time. So much is within reach from your own backyard, and that’s really exciting. | 0.808066 | 3.883973 |
The photo itself is unremarkable, and tells us nothing about Mars we didn’t know already. Yet MarCO-B’s snapshot, taken a few days after Thanksgiving, is important—the first close-up of another planet taken by a CubeSat.
Over the past 15 years, nearly a thousand of these small, cheap, modular satellites have been launched into Earth orbit to take pictures, test technology, and perform other simple tasks. The twin MarCOs, A and B, have the distinction of being the first CubeSats sent to interplanetary space. They survived the 300-million-mile journey to Mars, and half the battle was won right there.
NASA wanted to know if the briefcase-size MarCOs could handle such a long journey, then play a significant role on arrival: relaying radio signals back to Earth from the Mars Insight lander as it made its way down to the planet’s surface. The CubeSats weren’t critical to the primary mission’s success; other spacecraft were stationed in Mars orbit to capture Insight’s data in case the MarCOs failed.
NASA and the Jet Propulsion Laboratory spent just $18.5 million—a relative pittance—on the two smallsats and took only 14 months to build them. Launched with Insight on an Atlas V rocket last May, the MarCOs separated from the larger spacecraft shortly after leaving Earth orbit, and made their own way to Mars. During the cruise, JPL tested all the functions required of an interplanetary spacecraft. A new, purpose-built radio called Iris was able to communicate with the dish antennas of the Deep Space Network, a first for such a compact device. “It worked great!” enthused John Baker, JPL’s program manager for small spacecraft.
So did the onboard navigation system (which was accurate to within a few hundred meters at a distance of 90 million miles) and MarCO’s propulsion system, which squirted cold, compressed gas—the same kind used in fire extinguishers—from eight thrusters. The only glitches were blurry photos from MarCO-A’s low-cost camera, and a leaky thruster on MarCO-B, which the team was able to work around. Space radiation turned out to be no problem; the onboard computer memory suffered not a single upset.
The success of MarCO bodes well for future planetary CubeSats of increasing sophistication. Their advent will be, says Baker, “like going from the age of the mainframe to the age of the laptop.” His group is building a number of advanced CubeSats to be deployed in the vicinity of Earth and the moon from NASA’s new Space Launch System rocket when it makes its debut in 2020. Also on that test flight will be an asteroid mission called NEA Scout, which will carry the first “science-grade” camera on a planetary CubeSat. (The cheap, 1.2-megapixel cameras on the MarCOs were “a last-minute add-on,” says Baker, included to verify that the high-gain antenna had unfolded properly.)
As for the MarCOs, their mission officially ended when Insight touched down on Mars. But, says Baker, the team is considering an asteroid fly-by as an encore, and is now looking for suitable targets—if NASA gives the okay. | 0.865314 | 3.539796 |
Chaos in the Atlantis basin
This animation features the region of Atlantis Chaos on our neighbor planet Mars. It is based on a color mosaic and digital terrain model of this region from the press release from June 12th, 2014. The images were acquired by the High Resolution Stereo Camera (HRSC) on board ESA's Mars Express spacecraft. The camera is operated by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR). The animation was created by the Planetary Sciences and Remote Sensing group at Freie Universität Berlin. Systematic processing of HRSC image data is carried out at DLR Institute of Planetary Research Berlin-Adlershof.
Atlantis Chaos Animation
A myriad of terrain types are found across the Terra Sirenum region in the southern highlands of Mars. Within the Atlantis basin, a complex and rugged landscape spread across roughly 200 kilometres known as Atlantis Chaos. The Atlantis basin likely owes its existence to an asteroid impact that took place in the early history of Mars. Now, the circular profile of what could be the crater rim is barely detectable. There are several other large basins in Terra Sirenum – most likely created by asteroid impacts as well. Many scientists suspect that standing water once filled these partially connected crater depressions – the hypothetical Eridania lake, which may have covered an area of over one million square kilometres.
Image processing and the HRSC experiment on Mars Express
This movie is generated from an image mosaic, composed of 4 single HRSC images (orbits Orbits 6393, 6411, 6547 (2008/2009) und 12.724 (2014) with an average ground resolution of 15 meters per pixel. The image center lies at approximately 34° southern latitude and 183° eastern longitude. The mosaic image was combined with topography information (from stereo data of HRSC) to generate a three-dimensional landscape. Finally this landscape is recorded from different perspectives, as with a movie camera, to render a flight.
To download the raw images and dtms in GIS-ready formats, follow this link to Atlantis Chaos on the mapserver.
Animation: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO
Musik: Jason Pfaff, CC BY-NC-ND 3.0
This video (without music) is licenced under the Creative Commons Attribution-ShareAlike 3.0 IGO (CC BY-SA 3.0 IGO) licence. The user is allowed to reproduce, distribute, adapt, translate and publicly perform it, without explicit permission, provided that the content is accompanied by an acknowledgement that the source is credited as 'ESA/DLR/FU Berlin', a direct link to the licence text is provided and that it is clearly indicated if changes were made to the original content. Adaptation/translation/derivatives must be distributed under the same licence terms as this publication.
More information about ESA licence agreements
The High Resolution Stereo Camera was developed at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) and built in collaboration with partners in industry (EADS Astrium, Lewicki Microelectronic GmbH and Jena-Optronik GmbH). The science team, which is headed by principal investigator (PI) Ralf Jaumann, consists of over 52 co-investigators from 34 institutions and ten countries. | 0.861444 | 3.002603 |
This is a diagram showing the temperature profile.
Click on image for full size
Image from: Arizona Press
Jupiter's Thermosphere Temperature Profile
This is the temperature profile of Jupiter's thermosphere. The thermosphere is the other region of the atmosphere where warming takes place. On Jupiter, incoming particles from the magnetosphere play a strong role in raising the temperature of this region. The thermosphere is also warmed from the sun's ultraviolet radiation. There is no top, or thermopause, to the thermosphere.
The graph shows that the temperature goes from about 170 K (-153 degrees) to about 850 K (1100 degrees).
For a picture showing how the temperature changes in whole atmosphere, click here.
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Indian Journal of History of Science, Vol, 45, no.2, June 2010, pp. 287-297
Rahu and Katu were deployed as planetary deities in the sixth century CE immediately after the mathematical theory of eclipses was propounded by Aryabhata. Their literary credentials however go back to early Vedic times. Here our aim is to examine, in a joint mythological and astronomical-astrological (“astronomological”) context, how the textual meanings of Rahu and Ketu have evolved with time. There are clear stages in their evolutionary histories, which must be borne in mind while interpreting early references.
The legend of Rahu shows signs of internal development. Successor to the Rgvedic Svarbhanu, Rahu as eclipse-causing demon was reduced to a body-less head so that the swallowed sun or moon had an escape route. Rahu’s identification with the lunar ascending node represents an attempt to connect new scientific developments with traditional beliefs. Ketu, in contrast, was a dictionary word used to denote a variety of related phenomenon especially comets. The promotion of the head-less body as a demon represents expansion of mythology in the light of new scientific developments. Ketu was now given an additional entirely new role, creating avoidable confusion. Significantly, Ketu’s iconography represents efforts at reconciling its two disparate roles.
Key words: mathematical theory of eclipses, astrology, Vedic mythology, planetary deities, Buddhist mythology, astronomical omens, ritual
Ancient Indian perception of the moving cosmic environment two millennia ago was bipolar. Orbits of the seven geocentric planets (graha) by virtue of their predictability represented cosmic order, while phenomena like meteors, comets and eclipses which did not fit into any pattern were classified as utpata, portent or calamity. This world view is preserved in a Buddhist Sanskrit text, Sardulakarnavadana, the legend contained in which is known to have been translated in an abridged form into Chinese in 265 CE (Vaidya 199,p.xi) . As the 5th century CE came to a close, the status of eclipses was modified.
Mathematical theory of eclipses was propounded in India in 499CE by Aryabhata (born 476 CE) in his influential Siddhantic treatise simply known as Aryabhatiyam (See Ohashi 2009 for a recent review). According to this theory, solar and lunar eclipses occur when the moon is at either of its orbital nodes. These theoretical points move in a direction opposite to that of the planets and complete an orbit in the rather short period of 18.6 years. This development was immediately taken note of in astrological literature, which classified the two nodes as planets, implying that they were now amenable to mathematics. Since they were hypothetical they were dubbed shadow planets. The 6th century CE text Brihajjataka (2.2-3) by Varahamihira (died 587 CE) includes Rahu and Ketu in the list of planets, and even gives their synonyms: Tamas, Agu and Asura for Rahu; and Shikhi for Ketu (Rao 1986, p.76), which however never gained currency. The two nodes are 180 degrees apart so that specifying one fixes the other. It would thus have sufficed to include just one of them. Both were listed no doubt to bring the planetary number up to nine which was considered sacred.
If new words had been coined to designate the two nodes, matter would have rested there. But both Rahu and Ketu are terms of Vedic vintage. The term Rahu had previously been used as a proper noun and exclusively in connection with eclipse so that its deployment represents an attempt at integrating new scientific developments with ancient tradition. On the other hand Ketu was merely a common noun employed variously but never in association with eclipse. Here then was an old term which was given an entirely new identity, representing expansion of mythology in the light of new scientific developments.
It is not uncommon to see even earlier references to Rahu and Ketu being interpreted in terms of their later status. This is unfortunate, because it distorts the history of the evolution of “astronomological” thought. The new coinage is advisedly used in preference to the extant terms astronomical and astrological to avoid backdating the present differentiation into earlier times when they would have been essentially seen as one. Our aim is to investigate how the textual meanings of the terms Rahu and Ketu have evolved with time. We must keep in mind some notable features of the available source material. Most texts remained open for a long time and were contributed to by generations of authors. There is no reason to expect or demand internal self- consistency from them. The texts were often composed in metrical poetry and were meant for a select audience. Very often the meaning assigned to a particular word depends on the context in which it is used.
An important source of information on ancient India is the Mahabharata which was expanded over a long period of time to include matter that went beyond the description of the Bharata battle which it had originally set out to describe. The astronomical content of the Mahabharata is consistent with Vedic astronomy in that it marks sky positions with the help of bright stars or star groups known as naksatra. The Mahabharata is not familiar with the twelve zodiacal signs which make their appearance in post-Mauryan India in about the first century BCE at Baudha Gaya where they are depicted on the railing pillars (Kane 1975, p. 598). Given the size and the nature of the contents of the Mahabharata it is reasonable to assume that if zodiacal signs had been introduced into India when the Mahabharata text was still open they would have found their way into it. We thus conclude that the Mahabharata text had been closed by about 1st century BCE (Kochhar 2000, p.56). This is an important datum. At one place the Mahabharata (Vanaparva 188. 87-88) does say that “when the moon, the sun and Jupiter in Tisya come together in one rasi, krta age will begin”. The term rasi is used here in the general sense of a portion of sky, not in the precise sense of a zodiacal sign.
The Mahabharata does not make any reference to the week days either. There is no unanimity on the epoch when they were introduced into India. Varahamihira, already referred to, in his other works , Pancasiddhantika and Brihatsamhita, mentions week days while quoting authorities who had lived much earlier . From this it has been inferred that week days were introduced into India in the first century CE(Kane 1975, pp. 680-1). A more plausible case has been built by Markel (1991) to suggest that the week made its appearance in India only in forth century CE.
Vedic Rahu and Ketu
The Rgveda does not know of Rahu. Rgveda (5.40:5-9) describes how Svarbhanu, son of an asura, pierced the sun “through and through with darkness”. The eclipse caused great distress among observers: “All creatures looked like one who is bewildered, who knoweth not the place where he is standing”. The sun himself appealed to Atri: “Let not the oppressor with this dread, through anger, swallow me up, for I am thine, O Atri”. In response, “By his fourth sacred prayer Atri discovered Surya concealed in gloom that stayed his function”. “The Brahmana Atri, as he set the press-stones, serving the Gods with praise and adoration, established in the heavens the eye of Surya, and caused Svarbhanu’s magic arts to vanish. The Atris found the Sun again, him whom Svarbhanu of the brood of Asuras had pierced with gloom. This none besides had the power to do.” (Griffith 1896, p. 255) .The Atris were prominent contributors to the Rgveda. The whole of the fifth mandala is authored by them. The passage quoted above is mentioned and embellished at a number of places in the Vedic literature :Tandya Brahmana (4.5.2; 4.6.13; 6.6.8; 14.11. 14-15; 23.16.2), Gopatha Brahmana (8.19), Satapatha Brahmana (188.8.131.52), and Sankhayana Brahmana (24.3) ( Dikshit 1896, Vol.1, p.58; Kane 1975, pp. 241-242). What the Atris probably did was to chant mantras while the eclipse lasted. The Rgvedic description is significant. An eclipse was seen as the demon’s work in disrupting the cosmic order. Propitiation was needed to restore that order.
Dikshit (1896, Vol. 1, p. 57) while translating a passage from the Rgveda renders Svarbhanu as Rahu and goes on to give its meaning as the lunar ascending node. Similarly Kane (1975, p.569), while discussing a reference in the Maitrayani Upanisad, equates Rahu and Ketu with the ascending and descending node respectively. Svarbhanu’s career as an asura did not last long. It is not clear when and how Svarbhanu made way for Rahu, who appears for the first time, and as the sun’s enemy, in Atharvaveda (19, 9-10). Chandogya Upanisad (8.13) makes an interesting analogy: The “soul that has acquired true knowledge is said to shake off the body after casting off all evil” like “the moon becoming free from the mouth of Rahu” (Kane 1975, p.569).The Pali Buddhist sources refer to the moon and the sun freeing themselves from the clutches of Rahu by invoking Buddha’s name (Candima Sutta, Samyutta-nikaya 2.9; Suriya Sutta, Samyutta-nikaya 2.10).
Mahabharata (Bhismaparva 13.39-45) uses both Svarbhanu and Rahu as interchangeable names. Rahu is a graha, 12000 yojanas in diameter, bigger than both the moon (11000 yojanas) and the sun (10000 yojanas). Rahu had to be bigger than the sun and the moon so that it could grab them. Note that the term graha here carries the sense of a grabber and not that of a body in orbit. In course of time, the name Svarbhanu came to be de-stigmatized so much so that a son of Lord Krsna was given the name (Mani 1975, p. 778).
Atharvaveda (13.16-24) employs Ketu to mean ray of light. These nine verses are taken from Rgveda (1.50.1-9) in the same order and more or less in the same form. They are also found “in one or more other Vedic texts” (Whitney 1905, Vol.2, p.722). More typically Ketu meant combination of fire and smoke. The Atharvaveda passage (19.9.10) quoted above refers to Dhumaketu as an epithet of mrtyu [death]. It either means a comet or literally as “smoke-bannered” to the smoke rising from a funeral pyre (Whitney 1905,Vol. 2, p. 914). Atharvaveda (11.10.1-2, 7) uses Ketu in the plural, as arunah ketavah [ruddy Ketus]. Here the reference seems to be to comets or meteors. Varahamihira’s Brihatsamhita, composed in 6th century CE but containing much older material, quotes a still earlier astronomer Garga on a class of 77 comets, called Aruna, which are dark red in colour (Bhat 1981,Vol. 1, p.138).
Puranic Rahu and Ketu
If the demon Rahu devours the sun or the moon to cause an eclipse, how do they become visible again? The answer is provided by the well – known story samudramanthana (churning of ocean), described in Mahabharata, Visnupurana and elsewhere. In the story, the demon Rahu’s head is chopped off, which survives. It is the Rahu head which causes an eclipse. Since the rest of the body is missing, there is an escape route for the sun and the moon. Note that the name Rahu now belonged to the body-less head. The head-less body would remain unclaimed, till the 6th century CE; see below. Brhatsammhita (5:1-3) while narrating this story also refers to a prevalent alternative belief that Rahu is of a serpentine form with only the head and the tail. The ancient Iranian text Bundahishn talks of goshir, an eclipse-causing serpent. It is not clear whether Varahamihira is referring to the Iranian legend or an un-recorded Indian one. Al Biruni writing in the 11th century reserves the name Rahu for the dragon’s head and calls the tail Ketu (Sachau 1888, Vol. 2, p.234).There were some half-hearted attempts to relate eclipses to predictable phenomena. Thus it was speculated that an eclipse took place when five planets get together (Brihatsamhita 5.17)
Mahabharata (Adiparva 65. 11-12, 31) names Kasyapa as the father and Simhika as the mother of Rahu, who is at times designated Simihkeya after her. His three other real brothers are also mentioned, their given names, Sucandra, Candraharta and Candrapramardana, all being associated with moon. Kasyapa from another wife Danu had 34 named sons including one called Ketuman (not Ketu).Curiously the names Surya, Candramas and Svarbhanu figure in the list (Adiparva 65.22-26).These 34 demons are thus Rahu’s half brothers. This naming is an exrecise in meaningless creativity. This association may have an astronomical basis which does not seem to have been noted before. Varahamihira in his Brihatsamhita (3.7; 11.22) mentions a class of 33 comets known as Tamaskilakas (dark shafts), called children of Rahu. They were noticed by the 11th century astronomer and chronicler Al-Biruni also. Described as black, and shaped like a crow or a beheaded man or a sword, or bow and arrow, they are always in the neighbourhood of the sun and the moon. It is likely that this category include sunspots (Bhat 1981, pp.25-26). An ancient authority quoted by Varahamihira on Tamaskilaka is Garga, who figures in Mahabharata also as an astronomer and advisor ( Mani 1975, p. 280). He may well have been responsible for constructing a myth about 34 half-brothers of Rahu out of the description of Tamaskilakas. It is noteworthy that from independent considerations Garga has been place at about 100 BCE (Kane 1975, p.681), the epoch we have assigned to the closure of the Mahabharata.
Inverted astronomy in Mahabharata
The Mahabharata talks about the prevalent astronomical knowledge albeit often in an inverted manner. It will be useful to inspect the context in which these references were made.
When the two rival armies stood confronting each other, and the Bharata war looked imminent, last ditch efforts were made to avert it by appealing to the ineffectual king Dhrtarastra whose villainous sons were widely held responsible for bringing things to such a pass. To convey the enormity of the sense of impending genocide, the king was told that in anticipation of the war the natural order had already broken down. The effect was heightened by the fact that the so-called eye witness account was brought to the sightless king by his own biological father. The revered Ved Vyasa tells Dhrtarastra (Bhismaparva 3.46) as follows.
“Cows are giving birth to asses; and elephants to dogs. Sons are enjoying sexual pleasures with their mothers. Idols of gods are laughing, vomiting blood, feeling sad, and falling off their pedestals on their own. Animals are being born with three horns, four eyes, five feet, two urinary organs, and two tails. Women are giving simultaneous birth to four –five girls, who immediately start singing, dancing and laughing. Trees are flowering out of season. Lotus and water-lily are blossoming on tree tops. Even koel, peacock and parrot are making fearsome sounds. There is a downpour of blood and bones from the sky.”
The imagined weirdness of the world in anticipation of the fratricidal war was extended to the skies as well. “Arundhati well known for her devotion to her husband Vasistha has left him behind. [The reference here seems to be the star pair in Ursa Major rather than to individuals.] Dawn and the dusk look like as if they are on fire. Vyasa tells Dhrtarastra that he could not make out the difference between day and night, because the sun, moon and the stars all were burning bright throughout. This is a fearsome sign. Although it was the Kartika full moon night, the moon was not visible; its luster had given way to fire.
It is in this background that even the more-reasonable sounding descriptions of celestial phenomenon should be seen. A recurring theme is the reference at various places in the Mahabharata to Rahu, as if the occurrence of an eclipse was at par with holocaust on earth. “Rahu has seized the sun” (Bhismaparva 3.11). “Rahu is approaching the sun” (Bhismaparva 141.10).”Rahu swallowed the sun most untimely” (Salyaparva 55.10). “Rahu eclipsed the sun and the moon simultaneously” (Asvamedhaparva 76. 15, 16, 18). Meteors (ulka) and earthquakes are also similarly invoked. As part of the celestial foreboding it is stated that a very dangerous Dhumaketu has overcome the naksatra Pusya. This will bring destruction to both sides. (This ill-omen appears in the 4th century CE Buddhist text Sardulakarnavadana as well; see below).
Continuing, his listing of ill omens, Ved Vyasa tells Dhrtarastra that the sveta graha (white planet) has transgressed Citra, while the parusa graha (harsh planet) has established itself between Citra and Svati (Bhismaparva 3.11, 16). The translators have exercised their own discretion in rendering these terms. Sveta graha has been left untranslated (Sathe et al. 1985, p.39) or equated with Ketu (Ganguli 1884-1896, Book 6, p.12). Parusa graha has been identified with Rahu by one translator ( Ganguli 1884-1896, Book 6, p.12) and with Ketu by ANOTHER (Sathe et al. 1985, p.39).. The arbitrariness is obvious. As we have argued it would be anachronistic to associate Rahu and Ketu with a planet in pre-Varahamihira times.
Greek astronomical elements made their documented appearance in India in 149 CE when a Greek astro-text was translated into Sanskrit by Yavanesvara. It was versified in 269CE by Sphujidhvaja under the title Yavanajataka (Pingree, p. 1959). The versification was a significant development, because it signifies assimilation of Greco-Babylonian elements into Indian tradition. And yet, Vedic astronomical tradition remained extant even after the introduction of Yavana texts, as can be seen from passages in Sardulakarnavadana, already referred to. “Irrespective of the naksatra, when the sun or the moon is seized by Rahu, the king along with his subjects comes to pain.” “Irrespective of the naksatra when Ketu enters the moon, the neighbouring enemy king gets the upper hand.” “When Dhumaketu establishes itself in the Pusya naksatra, then defeat in enemy’s assault from all four directions is guaranteed” (Vaidya 1999, p. 374, couplets 462,463, 466). As we have already noted, Dhumaketu in Pusya as a bad omen is mentioned in the Mahabharata also. It is significant that Ketu and Dhumaketu are listed separately and along with Rahu under utpata.
Once the mathematical theory of eclipse was propounded, Rahu ceased to be an utpata; its predictability however did not remove the fear associated with it. On the other hand, Ketu as comet continued to be an utpata. Brihatsamhita assigns separate chapters to a discussion on eclipses under the heading Rahu and on comets under Ketu. Brihatsamhita does not mention Ketu in the context of eclipse. As mentioned earlier, it is Varahamihira’s other text Brihajjataka which twins Ketu with Rahu as the eclipse-causing shadow planets, introducing the concept of navagraha. Ketu was now given a brand new identity; the torso which had been lying lifeless after the detachment of the Rahu head was now resurrected and named Ketu.
We have argued that inclusion of the demon Rahu in the list of mathematically tractable planets took place after 499CE. Support for this conclusion comes from iconographic data. The “ first surviving depiction of Rahu occurs in a relief of the ‘Churning of the Ocean’ carved over the façade of the doorway of cave-temple number nineteen at Udayagiri in the Vidisha district of Madhya Pradesh, which can be dated to ca. A.D.430-450. Earliest known representations of Rahu as a member of the planetary deities are those on two stone lintels, 100cm by 20cm, originally from the villages of Nachna and Kuthara in the Panna district in the Bundelkhand region of Madhya Pradesh, most likely sculpted during the reign of the Uccakalpa king Jayanatha (r. ca. A.D.490-510)” ( Markel 1990, pp.11-13). If the assigned dates are correct, it is remarkable that Rahu’s planetization occurred within a decade of Aryabhata’s theory. Ketu as a planetary deity appears in about 600 CE or a little later, in Uttar Pradesh. In the eastern state of Orissa, Ketu was not counted in until the tenth century, which thus had only eight grahas till then (Markel 1990, p.21). One wonders whether it was from Orissa that Rahu as Yahu travelled to Burma as one of the eight nats (spirits).
Astronomical literature employs the term Rahu in connection with eclipse but in a number of ways. Aryabhata does not use either Rahu or Ketu; he and following him many others refer to a node as pata. Brahmagupta (b.598CE) in his long career displays signs of intellectual evolution. Taking a position contrary to Aryabhata, he in his Brahmasphutasiddhanta, prepared in 628 CE, expresses his faith in the demon Rahu as the cause of eclipse . Al Biruni noted this (Sachau 1888,Vol. 2, p.110). His later text, Khandakhadyaka (665 CE), however, calculates eclipses in a matter-of-fact way employing the technical term pata and without naming Rahu or Ketu (Chatterjee 1970, pp. 80-85).
The 689 CE astronomical handbook Karanaratna by Devacarya (Shukla 1979) uses Rahu to denote the eclipse shadow (2.2) as well as the ascending node (e.g.1.15). Significantly, at one place (1.13) the latter is called Rahumukha (Rahu head). A tersely written basic astronomical text will have no reason to mention Ketu. As comet, meteor or the like Ketu lay outside the scope of theory while as descending node it would be redundant once the ascending node Rahu or pata was mentioned.
In later Iranian (and Arabic) mythology the ascending node Rahu and the descending node Ketu become the head and the tail of the dragon Al –Djawzahr. Ketu as comet is not forgotten; he figures as al-Kayd (Hartner 1965). Rahu and Ketu as part of mathematical astronomy were introduced into China during the Tang dynasty (618-907CE), but with modified meaning. While Rahu was retained in the sense of the lunar ascending node, Ketu was used as a designation for lunar apogee (Niu 1995)
The imagery and iconography of Rahu and Ketu have evolved over time, with the latter having been more difficult to conceptualize. While Rahu has been well-defined since the days of the samudramanthana story, Ketu had in the sixth century CE the eclipse role thrust upon him in addition to the cometary ( and not the other way round as Neugebauer (1957, p.211) suggests).
The tradition of eclipse calculation has continued uninterrupted till relatively recent times. A copper plate inscription tells us about the grant of a village by the Kalachuri king Ratnadeva II to an astronomer , Jagannatha by name, for correctly predicting the lunar eclipse of 1128CE. He knew two Siddhantas and succeeded where other astronomers in the court failed. Hence the reward ( Mirashi 1933-34,p.161).Seven centuries later, a Pondicherry-based traditional astronomer calculated for the benefit of John Warren the lunar eclipse of 1825 May 31-June 1, with the help of shells, placed on the ground, and from tables memorized “by means of certain artificial words and syllables”. The results were remarkably accurate for the time. There was an error of +4 minutes for the beginning, -23 minutes for the middle and -52 minutes for the end (Neugebauer 1983, p.436). Traditional almanacs still use old algorithms for their planetary position calculations, but have taken to using modern methods for calculating eclipses as a concession to the greater time consciousness of the present times.
To sum up, the terms Rahu and Ketu have been continuously in use since the early Vedic times, but their meaning has not remained static. Rahu was an eclipse-causing demon whose name was confined to the severed head in the samudramanthana story. In the sixth century CE, Rahu was identified with the ascending node of lunar orbit and designated the eighth planet.
From the earliest time till the sixth century CE, Ketu was not a proper noun but a dictionary word used to denote phenomena like comets and meteors. This meaning continued later as well. But in the sixth century CE, Ketu was made into a proper noun by identifying it with the descending node of the lunar orbit and designating it the ninth planet. The headless body of the demon left behind from the samudramanthana days was retrospectively named Ketu. This evolutionary sequence needs to be kept in mind while interpreting textual references. More specifically, identification of Rahu or Ketu with a planet in a text prior to Varahamihira would be an exercise in anachronism.
I thank Yukio Ohashi, K.T.S. Sarao, B.V. Subbarayappa, K. Ramaubramaniam and Michio Yano for help and useful conversations.
(To help place an author’s work in context, date of original publication is cited in the text. For convenience, date of translation or reprint, mostly facsimile, is added.)
Bhat, M. Ramakrishna (1981) Varahamihira’s Brihat Samhita (Delhi: Motilal Banarasidass).
Chatterjee, Bina (1970) The Khandakhadyaka of Brahmagupta with the commentary of Bhattotpla, Vol. I. ( Delhi: Motilal Banarasidass).
Dikshit, Sankar Balakrishna (1896) History of Indian Astronomy (English translation by R.V. Vaidya, Pt I,1968; Pt II, 1981. New Delhi: India Meteorological Department).
Ganguli, Kisari Mohan (1884-1896) Mahabharata of Krishna-Dvaipayana Vyasa ( on-line)
Griffith, Ralph T. H. (1896 ) The Hymns of the Rgveda ( Reprint, Delhi : Motilal Banarasidass, 1973).
Hartner, W. (1965) “ Al-Djawzahar”. In :Encyclopedia of Islam,Vol.2 ( Leiden: Brill), pp.501-502.
Kane, Pandurang Vaman. (1975) History of Dharmasastra, Vol. 5 (Poona: Bhandarkar Oriental Research Institute).
Kochhar, Rajesh (2000) The Vedic People (Hyderabad: Orient Longman).
Mani, Vettam (1975) Puranic Encyclopaedia (Delhi: Motilal Banarasidass).
Ohashi, Yukio (2009) “The mathematical and observational astronomy in traditional India”. In: Science in India, Vol. 13, Pt.8 (ed. J.V. Narlikar) (New Delhi: Viva Books), pp 1-88.
Markel, Stephen (1991) “The genesis of the Indian planetary deities”. East and West, Vol. 41. pp. 173-188)
Markel, Stephen (1990): “The Imagery and Iconographic Development of the Indian Planetary Deities Rahu and Ketu”. South Asian Studies, 6:9-26.
Mirashi, V.V. (1933-34) Epigraphia India, Vol. XXII, 159-165.
Neugebauer, Otto (1957) “Notes on Al-Kaid”. J. Amer. Oriental Soc., 77, 211-215.
Neugebauer, Otto (1983) Astronomy and History : Selected Essays ( New York : Springer-Verlag).
Rao , Bangalore Suryanarain (1986) Varahamihira’s Brihat Jataka ( Delhi : Motilal Banarasidass, Reprint 2008).
Sachau, Edward C. (1888) AlBeruni’s India, ( 2 vols reprinted as one , Delhi : Atlantic Publishers)
Sathe, Shriram: Deshmukh, Vijaya; and Joshi Prabhakar ( 1983) Bhartiya Yuddha: Astronomical References ( Pune : Shri Babasaheb Apte Smarak Samiti).
Shukla, Kripa Shankar (1979) Karana-Ratna of Devacarya ( Lucknow : Lucknow University).
Vaidya, P. K. (ed.) (1999) Divyavadana ( Darbhanga: Mithila Institute).
Whitney, William Dwight (1905) Atharva-veda-samhita, 2 vols. (Cambridge, USA: Harvard University).
Yano, Michio (2003)”Calendars, astronomy and astrology” .Blackwell Companion to Hinduism (ed.:Cavin Flood)( Oxford: Blackwell) | 0.870827 | 3.132724 |
According to NASA, Saturn has a seriously thicc relative about 700 light-years away, in the constellation Virgo. Somehow, the fact this is Saturn’s lookalike isn’t even close to the coolest thing about this exoplanet.
Using the space agency’s Hubble and Spitzer space telescopes, scientists analyzed the atmosphere of this strange world, called WASP-39b. Though it’s similar to Saturn in terms of mass, researchers have recently discovered evidence that WASP-39b contains roughly three times as much water as its famous cousin. The researchers’ findings have been published in The Astronomical Journal.
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By observing the starlight that penetrates through the planet’s atmosphere, researchers found WASP-39b’s atmosphere traps a lot of water vapor. They posit the planet was formed farther away from its star and wallopped by icy objects along the way.
“This spectrum is thus far the most beautiful example we have of what a clear exoplanet atmosphere looks like,” the study’s lead investigator Hannah Wakeford, an astronomer the Space Telescope Science Institute in Baltimore, Maryland, says in a statement.
WASP-39b is considered a “hot Saturn” by astronomers. Though it’s similar in mass to the gas giant in our solar system, it’s located 20 times closer to its host star — WASP-39 — than Earth is to our sun. It’s also tidally locked, meaning one side of the planet is always facing its sun. That side of the planet can get as hot as 1,430 degrees Fahrenheit (776.7 degrees Celsius).
Even though it’s super far away, this watery world can help scientists better understand the way planets in our solar system may have formed.
“WASP-39b shows exoplanets can have much different compositions than those of our solar system,” the study’s co-author David Sing of the University of Exeter in Devon said in a statement. “Hopefully this diversity we see in exoplanets will give us clues in figuring out all the different ways a planet can form and evolve.”
Next-generation telescopes like James Webb will help demystify exoplanets like WASP-39b and allow scientists to peer into these strange worlds with unprecedented clarity. Of course, that all depends on when James Webb gets off the ground, as NASA already pushed the launch from October 2018 to spring 2019.
NASA, you know what you have to do. Don’t leave us hanging. | 0.873462 | 3.779786 |
Apr 22, 2013
Could the dolerite structures in Tasmania be electrical formations?
The Island of Tasmania in the south of Australia is one of the most provocative spots on Earth. The remarkable diversity of plant life and the unique animals found nowhere else have provided scientists of every stripe with near-ideal conditions for study. The ecology is isolated, with little incursion from transplanted animals, although the rats that stowed away on early ships and the cats that were subsequently imported to kill the rats have had a dramatic (and sometime devastating) impact on the native animals.
Cradle Mountain might qualify as another example of the mysterious stone monoliths that are found on every continent (and under the sea). Unlike other Australian formations that are composed entirely of sandstone and a loose conglomerate of quartzite, sandstone, seashells and a collection of whatever minerals are found in the surrounding area, Cradle Mountain is a solid chunk of dolerite, or congealed basalt lava.
Tasmania illustrates violent geologic activity that took place “millions of years ago” according to conventional models. The mountainous uplifts, the deep, steep-sided gorges, the “needles” of stone that rise out of the ocean around its circumference and the many crater lakes found in the interior are said to be the remains of volcanic eruptions due to the movement of tectonic plates. Indeed, lava flows that buried valleys and snuffed-out jungles and forests are easy to see. The difficulty with the observation is that the features appear to be exceptionally fresh rather than extremely ancient. How do sharp needles of stone and vertical cliffs enclosing flat-bottomed channels come to exist through the slow process of erosion?
As most geologists propose, the erosive action of wind and rain tends to “melt” rock formations because rainwater is a weak form of carbonic acid and wind carries grains of dust that grind away at the stone over eons of time. Sharp points become blunted mounds; vertical walls become gently sloping hills, while river valleys mature from canyons into shallow meanders in a broad flood plain. It is counter-intuitive, therefore, to find youthful topography in a location that should have matured into old age millennia ago.
Cradle Mountain, in particular, is crowned with rock formations that seem to defy the elemental forces that are attempting to dissolve its very structure. Upright columns of dolerite stand like Easter Island statues in the rain. As standard mineralogical studies seem to indicate, basaltic lavas are often found eroded into columnar forms with a tendency to split into vertical fractures. On mountain peaks that are exposed to alternate freezing and thawing, the rainwater supposedly seeps into cracks in the stone where it freezes and expands, forcing the rock apart into slabs. Or, water finds the path of least resistance in the stone, carving vertical cracks ever deeper until, eventually, the rock falls apart.
In a Picture of the Day about the tepuis of Amazonia, it was noted that on many of the summits rock formations that look more like abstract sculpture gardens are abundant. Stone points, thickets of tubular palisades and upraised, columnar “hands” with multiple fingers demonstrate that weathering cannot be the primary cause. How does erosion leave behind stacked stone towers with many layers, sharp edges, mushroom-shaped caps and fine detail? Figures such as those should have softened long ago. Cradle Mountain is crowned with an incredible number of similar oddities. The mountain, itself, resembles the South American massifs so closely that they could be cousins.
Dove Lake is one of many such “crater lakes” that can be found in the region. It is a bowl-shaped lake, very deep, scooped out of the bedrock. Around the lake are vertical cliffs that seem to indicate that Dove Lake is actually the bottom of a larger crater that is several kilometers in diameter. Lake Willis is another bowl-shaped lake located high above Dove Lake. Its overflow runs down into Dove Lake as a spectacular waterfall. Crater Lake, Lake Lilla and others are similar in shape. A particularly interesting detail is that these lakes appear to have been created by a kind of shotgun blast from space. They are clustered together, have nearly identical morphology and are “punched” into the strata, leaving it visible as multiple layers.
How did the Australian landforms come to be? If what has been taught since Lyell and Agassiz is correct, they were formed by glaciers, volcanism, erosion and other slow, steady, predictable forces that are supposed to be occurring invisibly all around us all the time. But if the Electric Universe hypothesis of planetary scarring is correct, they might have been created in an instant and in the recent past. | 0.804685 | 3.048842 |
A research team led by astronomers from the University of Tokyo and the National Astronomical Observatory of Japan (NAOJ) has discovered that inclined orbits may be typical rather than rare for exoplanetary systems — those outside of our solar system. Their measurements of the angles between the axes of the star’s rotation (stellar rotational axis) and the planet’s orbit (planetary orbital axis) of exoplanets HAT-P-11b and XO-4b demonstrate that these exoplanets’ orbits are highly tilted. This is the first time that scientists have measured the angle for a small planet like HAT-P-11 b. The new findings provide important observational indicators for testing different theoretical models of how the orbits of planetary systems have evolved.
Since the discovery of the first exoplanet in 1995, scientists have identified more than 500 exoplanets, planets outside of our solar system, nearly all of which are giant planets. Most of these giant exoplanets closely orbit their host stars, unlike our solar system’s giant planets, like Jupiter, that orbit the Sun from a distance. Accepted theories propose that these giant planets originally formed from abundant planet-forming materials far from their host stars and then migrated to their current close locations. Different migration processes have been suggested to explain close-in giant exoplanets.
Disk-planet interaction models of migration focus on interactions between the planet and its protoplanetary disk, the disk from which it originally formed. Sometimes these interactions between the protoplanetary disk and the forming planet result in forces that make the planet fall toward the central star. This model predicts that the spin axis of the star and the orbital axis of the planet will be in alignment with each other.
Planet-planet interaction models of migration have focused on mutual scatterings among giant planets. Migration can occur from planet scattering, when multiple planets scatter during the creation of two or more giant planets within the protoplanetary disk. While some of the planets scatter from the system, the innermost one may establish a final orbit very close to the central star. Another planet-planet interaction scenario, Kozai migration, postulates that the long-term gravitational interaction between an inner giant planet and another celestial object such as a companion star or an outer giant planet over time may alter the planet’s orbit, moving an inner planet closer to the central star. Planet-planet migration interactions, including planet-planet scattering and Kozai migration, could produce an inclined orbit between the planet and the stellar axis.
Overall, the inclination of the orbital axes of close-in planets relative to the host stars’ spin axes emerges as a very important observational basis for supporting or refuting migration models upon which theories of orbital evolution center. A research group led by astronomers from the University of Tokyo and NAOJ concentrated their observations with the Subaru Telescope on investigating these inclinations for two systems known to have planets: HAT-P-11 and XO-4. The group measured the Rossiter-McLaughlin (hereafter, RM) effect of the systems and found evidence that their orbital axes incline relative to the spin axes of their host stars.
The RM effect refers to apparent irregularities in the radial velocity or speed of a celestial object in the observer’s line of sight during planetary transits. Unlike the spectral lines that are generally symmetrical in measures of radial velocity, those with the RM effect deviate into an asymmetrical pattern (see Figure 1). Such apparent variation in radial velocity during a transit reveals the sky-projected angle between the stellar spin axis and planetary orbital axis. Subaru Telescope has participated in previous discoveries of the RM effect, which scientists have investigated for approximately thirty-five exoplanetary systems thus far.
In January 2010, a research team led by the current team’s astronomers from the University of Tokyo and the National Astronomical Observatory of Japan used the Subaru Telescope to observe the planetary system XO-4, which lies 960 light years away from Earth in the Lynx region. The system’s planet is about 1.3 times as massive as Jupiter and has a circular orbit of 4.13 days. Their detection of the RM effect showed that the orbital axis of the planet XO-4 b tilts to the spin axis of the host star. Only the Subaru Telescope has measured the RM effect for this system so far.
In May and July 2010, the current research team conducted targeted observations of the HAT-P-11 exoplanetary system, which lies 130 light years away from the Earth toward the constellation Cygnus. The Neptune-sized planet HAT-P-11 b orbits its host star in a non-circular (eccentric) orbit of 4.89 days and is among the smallest exoplanets ever discovered. Until this research, scientists had only detected the RM effect for giant planets. The detection of the RM effect for smaller-sized planets is challenging because the signal of the RM effect is proportional to the size of the planet; the smaller the transiting planet, the fainter the signal.
;The team took advantage of the enormous light-collecting power of the Subaru Telescope’s 8.2m mirror as well as the precision of its High Dispersion Spectrograph. Their observations not only resulted it the first detection of the RM effect for a smaller Neptune-sized exoplanet but also provided evidence that the orbital axis of the planet inclines to the stellar spin axis by approximately 103 degrees in the sky. A research group in the U.S. used the Keck Telescope and made independent observations of the RM effect of the same system in May and August 2010; their results were similar to those from the University of Tokyo/NAOJ team’s May and July 2010 observations.
The current team’s observations of the RM effect for the planetary systems HAT-P-11 and XO-4 have shown that they have planetary orbits highly tilted to the spin axes of their host stars. The latest observational results about these systems, including those obtained independently of the findings reported here, suggest that such highly inclined planetary orbits may commonly exist in the universe. The planet-planet scenario of migration, whether caused by planet-planet scattering or Kozai migration, rather than the planet-disk scenario could account for their migration to the present locations.
However, measurements of the RM effect for individual systems cannot decisively discriminate between the migration scenarios. Statistical analysis can help scientists determine which, if any, process of migration is responsible for the highly inclined orbits of giant planets. Since different migration models predict different distributions of the angle between the stellar axis and planetary orbit, developing a large sample of the RM effect enables scientists to support the most plausible migration process. Inclusion of the measurements of the RM effect for such a small-sized planet as HAT-P-11 b in the sample will play an important role in discussions of planetary migration scenarios.
Many research groups are planning to make observations of the RM effect with telescopes around the world. The current team and the Subaru Telescope will play an integral role in investigations to come. Continuous observations of transiting exoplanetary systems will contribute to an understanding of the formation and migration history of planetary systems in the near future. | 0.933628 | 4.059052 |
We’re on the cusp of exciting developments in exoplanet detection, as yesterday’s post about the Near Earths in the AlphaCen Region (NEAR) effort makes clear. Adapting and extending the VISIR instrument at the European Southern Observatory’s Very Large Telescope in Chile, NEAR has seen first light and wrapped up its first observing run of Centauri A and B. What it finds should have interesting ramifications, for its infrared detection capabilities won’t find anything smaller than twice the size of Earth, meaning a habitable zone discovery might rule out a smaller, more Earth-like world, while a null result leaves that possibility open.
The NEAR effort relies on a coronagraph that screens out as much as possible of the light of individual stars while looking for the thermal signature of a planet. An internal coronagraph is one way to block out starlight (the upcoming WFIRST — Wide Field Infrared Survey Telescope — mission will carry a coronagraph within the telescope), but starshade concepts are also in play for the future. Here we separate the space telescope from the large, flat shade making up a separate spacecraft.
Image: Shown here as a potential mission for pairing with the James Webb Space Telescope but likewise applicable to WFIRST, a starshade is a separate spacecraft that blocks out light from the parent star, allowing the exoplanet under scrutiny to be revealed. Credit: University of Colorado/Northrup Grumman.
I’ve been fascinated with starshades ever since learning of the concept through Webster Cash’s work at the University of Colorado Boulder, and discussing with him the possibility of actually imaging distant exoplanets sharply enough to make out weather patterns and continents. But before we get to anything that ambitious, we have to clear the early hurdles, which are numerous. One of them, a big one, is the problem of distance and spacecraft orientation.
Consider: What NASA is looking at right now through its Exoplanet Exploration Program (ExEP) in an effort known as S5 is a pair of spacecraft separated by 20,000 to 40,000 kilometers, using a shade 26 meters in diameter. These numbers aren’t chosen arbitrarily — they mesh with the WFIRST telescope and its 2.4-meter diameter primary mirror, to be launched in the mid-2020s, although a recent report notes that the work is ‘relevant for any roughly 2.4-m space telescope operating at L2.’ As I mentioned above, WFIRST will carry its own coronagraph, but because a starshade is a separate spacecraft, one could join WFIRST in space by the end of the 2020s.
Ashley Baldwin has written extensively about starshades for Centauri Dreams, as a search in the archives will reveal (but start with WFIRST: The Starshade Option). Any consideration of starshades notes the problems to be solved here, as JPL engineer Michael Bottom explains in terms of his work on starshade feasibility for ExEP:
“The distances we’re talking about for the starshade technology are kind of hard to imagine. If the starshade were scaled down to the size of a drink coaster, the telescope would be the size of a pencil eraser and they’d be separated by about 60 miles [100 kilometers]. Now imagine those two objects are free-floating in space. They’re both experiencing these little tugs and nudges from gravity and other forces, and over that distance we’re trying to keep them both precisely aligned to within about 2 millimeters.”
Image: Three views of a starshade. Credit: NASA / Exoplanet Exploration Program.
The S5 team has been working on the technology gaps that have to be closed to allow such a mission to fly given the demands of formation sensing and control. Bottom has come up with a computer program that addresses the issue of spacecraft drifting out of alignment. As discussed in the recent ExoTAC Report on Starshade S5 Milestone #4 Review (‘Milestone #4’ refers to lateral formation sensing and control of the starshade position), a telescope modeled on WFIRST would see the pattern of starlight as it bent around the starshade, a subtle pattern of light and dark that would flag drift down to an inch and less at these distances.
Using algorithms developed by JPL colleague Thibault Flinois, Bottom’s program can sense when the firing of starshade thrusters is needed to return to proper alignment, making this delicate formation flying feasible through automated sensors and thruster controls. It’s also heartening to learn that Bottom and Flinois can demonstrate meeting the alignment demands of larger starshades for future missions, positioned fully 74,000 kilometers from the telescope.
NASA’s starshade technologies became more tightly focused starting in 2016 through a proposal from the ExEP, which anticipated bringing the concept to Technical Readiness Level 5; this is the S5 effort. To put that in context, here is NASA’s overview of what TRL 5 means:
Once the proof-of-concept technology is ready, the technology advances to TRL 4. During TRL 4, multiple component pieces are tested with one another. TRL 5 is a continuation of TRL 4, however, a technology that is at 5 is identified as a breadboard technology and must undergo more rigorous testing than technology that is only at TRL 4. Simulations should be run in environments that are as close to realistic as possible. Once the testing of TRL 5 is complete, a technology may advance to TRL 6. A TRL 6 technology has a fully functional prototype or representational model.
Image: Starshade technology gaps. Credit: NASA / Exoplanet Exploration Program.
There is so much to be analyzed in the starshade concept, from optimal starlight suppression to the stability of the starshade shape and its accuracy in deployment and necessary maneuvering. All of that has to take place within the framework of the above formation sensing and control issues. But Bottom and Flinois’ work has clearly moved the ball. From the report:
Overall, the ExoTAC believes that Milestone #4 has been fully met and congratulates the entire team on their excellent efforts to advance the technology readiness levels of the elements in the S5 activity. Precision lateral control over thousands of kilometers is an unprecedented requirement, and essential for starshade operation. Achieving this first of fifteen S5 Milestones serves as a confidence builder for the entire S5 activity.
We also note that by virtue of the successful achievement of Milestone #4, the Exoplanet Exploration Program’s Technology Gap List item S-3 on “Lateral Formation Sensing” is Retired.
For more on the NASA starshade work, see Starshade Technology Development. | 0.833692 | 3.828707 |
Petrologic investigations of martian rocks have been accomplished by mineralogical, geochemical, and textural analyses from Mars rovers (with geologic context provided by orbiters), and by laboratory analyses of martian meteorites. Igneous rocks are primarily lavas and volcaniclastic rocks of basaltic composition, and ultramafic cumulates; alkaline rocks are common in ancient terranes and tholeiitic rocks occur in younger terranes, suggesting global magmatic evolution. Relatively uncommon feldspathic rocks represent the ultimate fractionation products, and granitic rocks are unknown. Sedimentary rocks are of both clastic (mudstone, sandstone, conglomerate, all containing significant igneous detritus) and chemical (evaporitic sulfate and less common carbonate) origin. High-silica sediments formed by hydrothermal activity. Sediments on Mars formed from different protoliths and were weathered under different environmental conditions from terrestrial sediments. Metamorphic rocks have only been inferred from orbital remote-sensing measurements. Metabasalt and serpentinite have mineral assemblages consistent with those predicted from low-pressure phase equilibria and likely formed in geothermal systems. Shock effects are common in martian meteorites, and impact breccias are probably widespread in the planet’s crustal rocks. The martian rock cycle during early periods was similar in many respects to that of Earth. However, without plate tectonics Mars did not experience the thermal metamorphism and flux melting associated with subduction, nor deposition in subsided basins and rapid erosion resulting from tectonic uplift. The rock cycle during more recent time has been truncated by desiccation of the planet’s surface and a lower geothermal gradient in its interior. The petrology of Mars is intriguingly different from Earth, but the tried-and-true methods of petrography and geochemistry are clearly translatable to another world.
When the American Mineralogist published its first issue a century ago, the notion of irrigation canals on Mars constructed by sentient beings was just falling out of favor, and no geologist contemplated the likelihood of ever studying martian rocks. Even in the modern spacecraft era, martian petrology has proved to be challenging. Nonetheless, significant progress has been made in determining the mineral identities and modal proportions, rock textures, and geochemical compositions that are necessary to characterize the petrology of the martian crust.
Mars rovers have, so far, analyzed rocks from four surface sites. Rover instruments can provide substantial information required for in situ petrologic characterization, but with significant limitations. Some minerals have been identified by visible/near-infrared reflectance spectroscopy (e.g., Bell et al. 2008), but commonly only one spectrally dominant mineral at a time, and complete mineral assemblages remain elusive. The thermal infrared emission spectra of minerals add linearly, so coexisting phases can be deconvolved (e.g., Ruff et al. 2008), provided they have diagnostic spectra and are sufficiently abundant. Spectroscopy from orbiting spacecraft has also been an effective mineralogic tool (e.g., Bibring et al. 2006; Christensen et al. 2008; Murchie et al. 2009; Carter and Poulet 2013; Ehlmann and Edwards 2014), but with the same limitations. Other techniques using instruments on rovers have provided more specific mineral determinations. Mössbauer spectra have allowed the identification of some Fe-bearing phases (e.g., Morris and Klingelhöfer 2008). X-ray diffraction shows great promise (e.g., Vaniman et al. 2014), but only a few rocks have been analyzed so far. Microscopic imagers provide textural information (e.g., Herkenhoff et al. 2008; Blaney et al. 2014), although many rock surfaces are weathered or coated with dust. Geochemical analyses of major and minor elements in rocks are carried out by α-particle X-ray spectrometers (APXS) (e.g., Gellert et al. 2006; Schmidt et al. 2014), but measurements can be compromised by dust contamination.
Martian meteorites (McSween and Treiman 1998; McSween 2008) allow more complete petrologic investigations, although the locations on Mars from which they came (and thus geologic contexts) are unknown. The times when they were launched from Mars by impacts are estimated by summing their cosmic-ray exposure ages, which measure the time spent in space, and their terrestrial ages, also determined from cosmogenic nuclides. The launch ages form clusters that usually consist of a single lithology (Fig. 1), suggesting that each cluster represents a different sampling site on Mars, and non-clustered meteorites may represent additional sites. The meteorites thus sample many more locations than have been visited by rovers. However, the meteorites are biased compositionally and chronologically, probably because young, coherent igneous rocks are most likely to survive launch during impacts, so they are not representative of the whole martian crust (McSween et al. 2009).
Despite these caveats, some firm conclusions about martian petrology are emerging. Data from remote-sensing and martian meteorites indicate that the planet’s crust is dominated by basalt and related ultramafic rocks. Ancient sedimentary rocks, both clastic and chemical, have become the focus of rover exploration, spurred in part by the search for evidence of liquid water and, by extension, extraterrestrial life. Thermally metamorphosed rocks have only been identified from orbital spectroscopy, although many meteorites have been metamorphosed by shock. This paper synthesizes what we have learned about martian petrology and reveals gaps in knowledge that will hopefully be filled by the time of the next centennial.
Sources of petrologic data
Mars Pathfinder first analyzed rocks on the martian surface. The APXS-analyzed rocks had andesitic compositions (Rieder et al. 1997; McSween et al. 1999; recalibrated by Brückner et al. 2008; Foley et al. 2008), although alteration of rock surfaces likely accounts for their silica-rich nature. Because of this compositional uncertainty, we will not base any conclusions on these rocks.
The Mars Exploration Rovers (MER) Spirit and Opportunity landed in Gusev Crater and Meridiani Planum, respectively. Each rover carried an APXS for geochemistry, a miniature thermal emission spectrometer (MiniTES) and Mössbauer spectrometer (MB) for mineralogy, a panoramic camera (PanCam) with color filters and microscopic imager (MI) for imaging texture, and a rock abrasion tool (RAT) for brushing or griding rock surfaces. Spirit operated for six years, analyzing basalts on the floor of Gusev Crater and altered volcanic and volcaniclastic rocks in the Columbia Hills and at Home Plate (Squyres et al. 2004a, 2006a, 2007). Opportunity has operated for 10 years (and is still in operation at this writing), traversing >40 km and characterizing sedimentary rocks exposed in progressively larger craters (Squyres et al. 2004b, 2006b, 2009, 2012). Opportunity also analyzed one igneous sample, Bounce Rock (presumably ejecta from a distant crater), that resembled martian meteorites (Zipfel et al. 2011).
The Mars Science Laboratory (MSL) Curiosity rover landed in Gale Crater in 2011. Its instruments include an APXS, a laser-induced breakdown spectrometer (ChemCam) for element detection and textural imaging of rocks a few meters away, a powder X-ray diffractometer (CheMin) for mineralogy, a panoramic camera (MastCam) and a microscopic imager (MAHLI) for studying textures, mass spectrometers and gas chromatographs (SAM) capable of analyzing organic molecules and stable isotopes, and a rock-sampling device for brushing rock surfaces, scooping or drilling samples, and delivering them to CheMin and SAM. Curiosity has operated for more than one year (at this writing), working its way across the floor of Gale Crater, and has arrived at the base of an interior peak (informally called Mt. Sharp) of exposed strata. During its traverse, it has analyzed various sedimentary and igneous rocks (Blaney et al. 2014; Grotzinger et al. 2014; Sautter et al. 2014a; Schmidt et al. 2014; Stolper et al. 2013).
APXS measurements sample only the outer few tens of micrometers and thus are susceptable to dust contamination. MER and MSL APXS data vary in quality, depending on the extent to which the analyzed rock surfaces contained adhering dust. In this paper, I have attempted to use the best available APXS analyses, relying on data published in scientific literature. Additional data are archived in the NASA Planetary Data System, but are not plotted here. ChemCam data are normally reported as element ratios, and many elements are not analyzed; these data are useful for mineral identification but not for bulk-rock chemistry.
Remote sensing by orbiters does not provide sufficient data for petrologic characterization, but is very useful in identifying critical minerals used to develop geologic context. For some rock compositions, orbital spectroscopy provides the only data available. I will make reference to global geochemical maps by the γ-ray spectrometer (GRS) (Boynton et al. 2008) on Mars Odyssey, thermal emission spectrometer (TES) data (Christensen et al. 2008) from Mars Global Surveyor, and visible/near-infrared spectrometry from the Observatoire pour la Mineralogie, l’Eau, les Glaces et l’Activite (OMEGA) (Bibring et al. 2006) on Mars Express and from the compact reconnaissance imaging spectrometer (CRISM) (Murchie et al. 2009) on Mars Reconnaissance Orbiter.
Meteorites from Mars are recognized by the composition of trapped martian atmospheric gas in impact-melted glasses, distinctive bulk oxygen isotopic compositions, and Fe/Mn ratios in pyroxenes (McSween 1984). Shergottites are subdivided into basaltic, olivine-phyric, and lherzolitic varieties, corresponding to basalt, basalt with olivine megacrysts, and olivine-pyroxene cumulate, respectively. Nakhlites and chassignites are cumulates of augite and olivine, respectively, and ALH 84001 is an orthopyroxene cumulate. A new variety, augite basalt, has so far only been described in abstracts. NWA 7034 and other samples paired with it (NWA 7475, 7533, 7906, 7907, 8114) are the only sedimentary rocks—regolith breccias—in the martian meteorite collection. Compilations of the petrology and geochemistry of martian meteorites are given by Lodders (1998), McSween and Treiman (1998), Treiman (2005), Bridges and Warren (2006), and McSween and McLennan (2013).
Petrology of martian igneous rocks
Geochemical analyses of surface rocks by MER APXS (tabulated by Brückner et al. 2008) and of martian meteorites indicate that Mars is dominated by igneous rocks with basaltic compositions and products of limited fractional crystallization (McSween et al. 2009) (Fig. 2). GRS global maps of silica abundance (Boynton et al. 2008) are consistent with this finding (GRS boxes in Fig. 2). The andesitic composition determined for Mars Pathfinder rocks is illustrated in Figure 2, although this is likely an altered composition as no abrasion of surface rinds prior to measurement was possible.
Distinguishing volcanic, volcaniclastic, and sedimentary float rocks on Mars is not always obvious, as the textural features normally attributed to these rock classes may not be visible at the scale of rover observations. This debate extends to interpretations of orbital data as well (Ehlmann and Edwards 2014). Moreover, alteration overprints on igneous rocks can further complicate their identification. The reader should note that some misclassifications may occur in the following igneous rock descriptions.
Rocks analyzed by rovers
Gusev Crater has become the most thoroughly studied igneous province on Mars. Basalts encountered by the Spirit rover on the Gusev plains are float. Although a large volcano, Apollinaris Patera, of comparable age to the basaltic plains is located north of Gusev Crater, putative flow paths through a breach in the crater wall would require lavas to flow uphill, so a local magma source beneath the crater is favored (Lang et al. 2010). Petrologically related volcanic rocks occur mostly as float on the Columbia Hills, sitting on older outcrops of altered igneous rocks (Squyres et al. 2006a).
Basaltic rocks in Gusev (McSween et al. 2004, 2006a) are highly oxidized, mildly alkaline (McSween et al. 2006b), and generally silica undersaturated (Fig. 3), as reflected in the abundance of olivine (up to 20–30%). The modal mineralogies of Gusev volcanic rocks have been determined from modeling Mössbauer data for Fe-bearing minerals combined with CIPW norms calculated from APXS bulk chemistry for other minerals (McSween et al. 2008). Modes for Humphrey (basalt), Irvine (basalt), Wishstone (tephrite), and Backstay (trachybasalt) are illustrated in Figure 4. The textures of these lavas are porphyritic or aphanitic (Figs. 5a and 5b) and sometimes vesicular (Fig. 5c). Bedded volcaniclastic rocks occur at Home Plate (Squyres et al. 2007).
As in Gusev, the igneous rocks encountered in Gale Crater by the Curiosity rover are float. Some controversy exists about whether some are fine-grained volcanic rocks or first-generation sedimentary rocks; these lithologies also constitute most of the clasts in conglomerates. Their source is undetermined, perhaps transported from the crater walls or thrown in as ejecta (Schmidt et al. 2014).
APXS analyses of aphanitic volcanic rocks analyzed in Gale are strongly alkaline (Fig. 3), with volcanic compositions that include hawaiite (Bathurst_Inlet) and mugearite (Jake_M) (Stolper et al. 2013; Schmidt et al. 2014), as well as other compositions (Grotzinger et al. 2015). These rocks are characterized by especially high contents of K and Fe. The CIPW normative mineralogies of Bathurst_Inlet and Jake_M contain orthoclase, and Jake_M contains nepheline (Fig. 4). ChemCam analyses have distinguished fine-grained monzonitic rocks with elongated feldspar phenocrysts (Fig. 5d) and coarse-grained, granular dioritic rocks (Sautter et al. 2014a, 2014b). The coarse-grained rocks contain augite, sodic plagioclase, and orthoclase, although no modes or norms have been reported.
Highly fractionated (felsic) rocks are uncommon on Mars. Earlier reports of widespread andesites, based on TES thermal emission spectra, are now reinterpreted as partly altered basalt (e.g., Michalski et al. 2005). Spectroscopic searches for quartz, easily identified in TES data, have been unsuccessful; a lone detection of quartzofeldspathic rocks (Bandfield et al. 2004) has been reinterpreted as altered amorphous silica rocks (Ehlmann et al. 2009). A GRS-derived global silicon map shows abundances ranging from 18–23 wt%, corresponding to 39–50 wt% SiO2 (Boynton et al. 2008). This silica range overlaps those of basaltic rocks analyzed in Gusev and of martian meteorites (see below), and suggests no exposures of rocks more felsic than basaltic andesite occur anywhere, at least at the coarse (~450 km) GRS spatial resolution. However, at finer resolution one dacite flow has been identified from TES spectra (Christensen et al. 2005), and feldspathic rocks have been noted from CRISM and OMEGA spectra (Carter and Poulet 2013; Wray et al. 2013) and encountered by the Curiosity rover as noted above (Sautter et al. 2014a). Monzonite clasts occur in a martian meteorite breccia as well (Humayun et al. 2013).
The specific locations on Mars from which martian meteorites derive are unknown. However, several young rayed craters have been found in the Tharsis and Elysium volcanic regions and appear to be plausible launch sites for these meteorites (Tornabene et al. 2006).
Shergottites are basalts and gabbros formed from subalkaline magmas. Their compositions are distinct from those of Gusev rocks (Figs. 2 and 3). Basaltic shergottites (e.g., Stolper and McSween 1979; Rubin et al. 2000) are composed of pigeonite, augite, plagioclase (transformed into maskelynite by shock), and accessory Fe-Ti oxides, phosphates, zircon, baddelyite, and ferrosilite (sometimes decomposed to silica and fayalite) (Fig. 6a). Pyroxenes have Mg-rich cores, interpreted as entrained cumulus grains, with Fe-rich overgrowths. Olivine-phyric shergottites (e.g., Goodrich 2003; Greshake et al. 2004) contain those same phases, plus olivine megacrysts (5–28%) (Fig. 6b). The megacrysts in olivine-phyric shergottites have been variously interpreted as xenocrysts, phenocrysts, or antecrysts. Lherzolitic shergottites (e.g., McSween et al. 1979; Usui et al. 2010) are composed of olivine, orthopyroxene, augite, maskelynite, and chromite. The “lherzolitic” term is probably a misnomer, because mineral proportions vary widely in these heterogeneous rocks, and are hard to quantify from thin sections. As more lherzolitic shergottites have been found, characterization suggests that they may be more properly classified as olivine gabbros; some sections consist of olivine poikilitically enclosed by pyroxene, and other sections of the same meteorites are gabbroic.
Shergottites can be either enriched or depleted in incompatible trace elements, and enriched shergottites contain more radiogenic Sr and Nd isotopes (e.g., Symes et al. 2008). These geochemical characteristics are illustrated in Figure 7a, where meteorites with high-La/Yb ratios are enriched, and ɛ143Nd decreases with enrichment. The enriched shergottites are also more highly oxidized than depleted shergottites (e.g., Wadhwa 2001; Herd et al. 2002) (Fig. 7b). The depleted shergottites are interpreted to reflect the compositions of their mantle source; it is unclear whether the enriched shergottites represent melts of metasomatized mantle or magmas that have assimilated crust. Although the shergottites are nearly anhydrous, several lines of evidence suggest that their parent magmas were hydrous and lost water during ascent or eruption (e.g., McSween et al. 2001; McCubbin et al. 2012).
Two other martian meteorite types, nakhlites (e.g., Day et al. 2006; Treiman and Irving 2008) and chassignites (e.g., Johnson et al. 1991; Beck et al. 2006), are clinopyroxenites and dunites, respectively, and their cumulus augites and olivines (Fig. 6c) crystallized from mildly alkaline, dry parent basaltic magmas. Nakhlites consist of augite (70–80%), olivine (9–17%), and mesostasis (8–20%) containing Fe-Ti oxides, sulfides, and sprays of sodic plagioclase and K-feldspar (Treiman 2005). Their textures are dominated by elongate, aligned augite crystals. The cores of the olivines are xenocrysts (Goodrich et al. 2013). The nakhlites have been interpreted to have formed in a single thick flow or sill, and they can be placed in approximate stratigraphic order based on petrographic differences related to cooling rate and thermal annealing (e.g., Mikouchi et al. 2003); however, this interpretation does not take into account complexities in the internal dynamics of flows. Most nakhlites have experienced minor aqueous alteration, which produced iddingsite and other alteration phases (Hallis and Taylor 2011). Chassignites consist of olivine (90–92%), augite (3–5%), feldspar (2%), and chromite (2–5%), with accessory Fe-Ti oxides, sulfides, and phosphate. Their textures are dominated by subhedral olivine crystals, sometimes poikilitically enclosed by augite. The petrologic relationship between nakhlites and chassignites is unclear, but they have the same crystallization and Mars ejection ages.
The newly recognized augite basalts (Agee et al. 2014) consist of augite and plagioclase with minor olivine and oxides. The compositions of NWA 7635 and 8159 are shown in Figure 2. They are chemically similar to nakhlite intercumulus melt, but trace element and age differences preclude them being basalts complementary to the nakhlite suite (Herd et al. 2014).
ALH 84001 (Mittlefehldt 1994), famous for its purported evidence for martian life (McKay et al. 1996), is an orthopyroxene cumulate (Fig. 6d). It has been brecciated and annealed, and zoned Mg-Ca-Fe carbonate globules were precipitated in fractures by fluids. Its basaltic parent magma was isotopically similar to shergottites (Lapen et al. 2010).
NWA 7034 (Agee et al. 2013), NWA 7533 (Humayun et al. 2013), and other paired meteorites (i.e., stones that were part of the same pre-atmospheric meteoroid) are sedimentary breccias (as described below), composed partly of igneous clasts. The igneous lithologies include basalt, mugearite, and trachyandesite (Santos et al. 2013, who prefer volcanic terminology), or gabbro, monzonite, and norite (Humayun et al. 2013, who prefer plutonic terminology). Textures range from subophitic to granoblastic. These rocks are alkaline and resemble the igneous lithologies in Gusev and Gale craters (the bulk composition of NWA 7034 is shown in Fig. 2). Igneous minerals identified include plagioclase (38%), low-Ca pyroxene (25%), clinopyroxenes (pigeonite and augite, 18%), Fe-Ti oxides (10%), alkali feldspars (sanidine and anorthoclase, 5%), apatite (4%), and trace zircon and pyrite.
The compositions of olivines and pyroxenes in martian meteorites are generally more ferroan than in terrestrial basalts, and plagioclase tends to be more sodic: the ranges for olivine, pyroxene, and plagioclase, respectively, are Fo66–79, En32–77, and An39–70 in shergottites, Fo15–42, En37–62, and An23–40 in nakhlites, and Fo68–80, En49–56, and An30–80 in chassignites (Treiman 2005; Bridges and Warren 2006). Mars rocks analyzed by rovers have similar mineral compositions: normative olivine, pyroxene, and plagioclase compositions from Gusev rocks are Fo42–73, En44–64, and An16–47 (McSween et al. 2008). These differences in martian and terrestrial mineral compositions reflect bulk compositional differences between the planets. Bulk martian meteorites are rather Al-poor and P-rich, leading to late crystallization of plagioclase and to abundant phosphates. Feldspars (and Al) are more abundant in Gusev rocks than in the meteorites, but phosphates are abundant in both.
Trace element patterns in bulk martian meteorites are shown as a spider diagram in Figure 8. All these meteorites show depletions in Rb and K, which are highly incompatible, but not in adjacent incompatible elements. These alkali elements are soluble in aqueous fluids, although Ba, Sr, and U are as well and do not show consistent depletions. Nakhlites are enriched in incompatible trace elements and, unlike the shergottites, they show depletions in Zr and Hf. These elements are also depleted in terrestrial basalts affected by fluids and suggest alteration of the nakhlite source region. Trace elements are not normally analyzed by APXS (exceptions are Zn, Br, and Ni in Gusev rocks, as well as Ge in Gale rocks), so systematic comparisons with meteorite data are not yet possible. However, orbital average GRS measurements of K and Th (Taylor et al. 2006) are consistent with the highest values in shergottites. ChemCam on the Curiosity rover has measured Li, Rb, Sr, and Ba in individual minerals (Ollila et al. 2014), but bulk-rock data cannot be determined from these analyses.
Geochronology and petrogenesis
The igneous rocks analyzed in Gusev and Gale Craters are older (early Hesperian, ~3.65 Ga and <~3.7 Ga, respectively), based on crater counting (Parker et al. 2010; Thomson et al. 2011) than most martian meteorites (Nyquist et al. 2001; Righter et al. 2014): shergottite ages are 170–475 Ma (late Amazonian), nakhlites/chassignites are ~1.3 Ga (middle Amazonian), and the newly recognized augite basalts are ~2.4 Ga (early Amazonian). The orthopyroxenite ALH 84001 is much older, ~4.1 Ga (Noachian) (Lapen et al. 2010), and zircons in the NWA 7533 breccia give ages of ~4.4 and ~1.4 Ga (Humayun et al. 2013; Yin et al. 2014), the former corresponding to Pre-Noachian time. Although an ancient age (~4.5 Ga) has been suggested for shergottites (Bouvier et al. 2008) based on Pb-Pb chronology, most workers (e.g., Nyquist et al. 2001; Borg and Drake 2005; Symes et al. 2008; Shafer et al. 2010) accept younger, typically concordant ages indicated by other radioisotope systems such as 87Rb-87Sr, 147Sm-143Nd, 176Lu-176Hf, and 40Ar-39Ar.
The Y-980459 olivine-phyric shergottite and several basaltic rocks (Humphrey and Fastball) in Gusev Crater are thought to represent primary magma compositions. Phase equilibria experiments indicate that these rock compositions represent multiply saturated magmas with olivine + orthopyroxene ± spinel at 1.0–1.2 GPa, corresponding to depths of 85–100 km (Musselwhite et al. 2006; Monders et al. 2007; Filiberto et al. 2010). This mineral assemblage is predicted as a partial melting residue for the Mars upper mantle. Other shergottites have fractionated compositions and contain some cumulus phases, and their crystallization paths have been determined by experiments (Stolper and McSween 1979; McCoy and Lofgren 1999). MELTS models indicate that the tephrites and trachybasalts in Gusev Crater (Fig. 2) could have been produced by fractionation of hydrous Gusev basalt (Humphrey) magma at varying pressures (McSween et al. 2006b; Udry et al. 2014a). Alternatively, Schmidt and McCoy (2010) suggested a two-stage melting model, in which tephrites and trachybasalts were generated first, followed by melting of the depleted source to form Humphrey-like basalts. The highly alkaline mugearite in Gale crater could also have formed by fractionation of hydrous magma at high pressure (Stolper et al. 2013) and may require a metasomatized mantle source (Schmidt et al. 2014).
Not as much is known about the origin of nakhlite and chassignite magmas, because of the difficulty in determining parent magma compositions of these cumulate rocks. Attempts to estimate their parent magmas have been based on trapped melt inclusions (e.g., Johnson et al. 1991; Stockstill et al. 2005; Goodrich et al. 2013), with experiments or MELTS modeling to determine their crystallization paths. Some nakhlite melt inclusions are K-rich and can fractionate to produce alkaline magmas (Goodrich et al. 2013). An estimated parental melt composition for Chassigny is also similar to those of Gusev basalts (Filiberto 2008).
The difference in rock compositions (alkaline vs. tholeiitic) between old rocks on the martian surface and young martian meteorites is striking and suggests global magmatic evolution through time. However, Noachian rocks have not been definitely sampled. Several explanations for this difference in composition have been offered, including melting and fractionation at different pressures (Baratoux et al. 2011), under different redox conditions (Tuff et al. 2013), or with different water contents (Balta and McSween 2013).
Petrology of martian sedimentary rocks
The martian crust contains a rich variety of sedimentary rocks, including both clastic rocks (sandstone and siltstone, shale and mudstone, and conglomerate) and chemically deposited rocks (mostly evaporitic sulfate, and some carbonate). The clastic rocks differ fundamentally from most terrestrial sediments, in that they are derived from basalt, rather than from felsic rocks like those that dominate the Earth’s continental crust (McLennan and Grotzinger 2008). Clay-bearing rocks and sulfates have been studied mostly from orbital OMEGA and CRISM spectra (e.g., Murchie et al. 2009). Correlation of crustal age with mineralogy has led to a mineral-based timeline for Mars (Bibring et al. 2006), defined by an early warm and wet (or alternatively cold and intermittently wet) period characterized by clay formation, followed by a period of increased aridity conducive to the deposition of Ca-, Mg-, and Fe-bearing sulfates, and succeeded by the current cold and dry period dominated by the formation of iron oxides. These periods were also marked by fluids with varying pH. Meridiani rocks analyzed by the Opportunity rover formed during the middle (acidic) period (Hurowitz et al. 2006), but after a long trek to Endeavor crater that rover has now encountered subjacent clay-bearing strata (Arvidson et al. 2014) formed under neutral to slightly basic pH conditions.
The molar A-CNK-FM diagram, where A = Al2O3, CNK = CaO + Na2O + K2O, and FM = FeOTotal + MgO (Fig. 9), provides a means of quantifying chemical changes in rocks and estimating alteration mineralogy. This diagram is especially useful for sediments derived from basaltic rocks, and has been applied to martian sedimentary rocks (e.g., Hurowitz and McLennan 2007). Analyzed sedimentary rock compositions from Meridiani and Gale and altered rocks from Gusev plot fairly close to this face of the projection, so this diagram provides a reasonably accurate representation of their geochemistry. The compositions of sedimentary rocks are very similar to basalt at the same locations, pointing to their igneous provenance and lack of chemical changes during weathering. The rocks in Figure 9 form a nearly linear array, with some dispersion resulting from mixing of sulfate or clay. The resulting trend is notably unlike terrestrial basaltic sedimentary rock compositions, which extend toward the A-FM side. This linear trend has been interpreted to reflect dissolution of olivine under acidic weathering conditions (Hurowitz and McLennan 2007) or physical sorting of olivine and other minerals during transport (McGlynn et al. 2012). However, the Opportunity rover has recently found evidence of leaching processes in some altered martian rocks (Arvidson et al. 2014). Also indicated on Figure 9 are the approximate compositions of minerals in the basaltic protolith and some common sedimentary minerals. Most of these rocks plot between clay and sulfate, although detrital igneous minerals are important constituents.
Rocks analyzed by rovers
The best-characterized martian sedimentary sequence is the late Noachian to early Hesperian-age Burns formation, analyzed in Meridiani by the Opportunity rover. Three facies, representing eolian dunes, sand sheets, and subaqueous interdune sands were recognized in Endurance Crater (Fig. 10) by Grotzinger et al. (2005). Three facies can be recognized from sedimentary structures and textures (Figs. 11a and 11b), including festoon cross-bedding, planar stratification, ripples, and a deflation surface. Burns Formation rocks are impure evaporitic sandstones, composed of altered siliciclastic materials of basaltic origin, cemented by evaporitic precipitates. Diagenetic overprints (McLennan et al. 2005) resulting from a fluctuating water table include the formation of hematite-rich concretions (“blueberries”), soft sediment deformation, and crystal molds from dissolution of a soluble evaporate mineral. Weakly indurated strata with similar stratigraphy were encountered in subsequently visited larger craters in Meridiani (Squyres et al. 2009, 2012).
The mineral assemblage of Meridiani sandstones was modeled by fitting chemical (APXS) and mineralogical (Mössbauer) trends (Clark et al. 2005). A derived mineral assemblage for Merdiani rocks, consisting mostly of subequal amounts of sulfate, silica, and igneous detritus (feldspar and pyroxene), is illustrated in Figure 12.
Another way to assess the mineralogy of sandstones is by comparison with unconsolidated sand (soil). Soil mineralogy for Mars has been estimated by modeling Mössbauer data to determine the proportions of Fe-bearing minerals, combined with normative mineralogy calculated from APXS chemistry and the abundance of alteration minerals determined from Mini-TES spectra (McSween et al. 2010). Sediments at both Gusev and Meridiani are mixtures of unaltered basaltic minerals (70–83%) plus silica, Fe-oxides, clay, sulfate, and chloride, collectively interpreted as an altered component unrelated to the detrital basaltic debris. Similarly, X-ray diffraction analysis of Rocknest sand at Gale indicated a composition of 74% basaltic minerals (plagioclase, olivine, pyroxene, oxides) with minor alteration phases and ~25% amorphous material (Bish et al. 2013).
Once Opportunity reached Endevour Crater (Squyres et al. 2012), it encountered fine-grained layered rocks containing spherules (“newberries,” compositionally distinct from blueberries and possibly formed by impact), and overlain by impact breccias. These rocks occur stratigraphically below Burns formation rocks that characterize Meridiani Planum. The older (Noachian) rocks are cut by gypsum veins and contain clay minerals (Arvidson et al. 2014). Orbital CRISM spectra (Wray et al. 2009) had earlier shown the presence of smectite, best matched by nontronite. PanCam spectra suggest that the clay forms thin veneers on the rocks and is not a depositional phase. APXS-measured chemistry for these rocks is not noticeably different from rocks at other locations, although several rocks have elevated Al (Fig. 9), possibly reflecting clay formed by nearly isochemical alteration.
Many rocks analyzed by the Spirit rover in the Columbia Hills of Gusev Crater are sedimentary or volcaniclastic. Because of considerable chemical diversity and structural complexity, these rocks have not been studied as extensively as the Meridiani rocks (McLennan and Grotzinger 2008). The rocks are generally basalt-derived detritus, cemented by sulfate and silica. A few rocks containing significant amounts of carbonate (Morris et al. 2010) have been discovered. The rock Comanche, interpreted as an olivine cumulate, is estimated to contain 26% secondary Mg-Fe carbonate, as well as amorphous material of unknown origin (Fig. 12), based on modeling Mini-TES, Mössbauer, and APXS spectra. Rocks at Home Plate, a layered butte, are altered pyroclastic rocks, succeeded by cross-bedded sandstones that may consist of reworked pyroclastic materials (Squyres et al. 2007). Some of the layered rocks contain up to 90% silica, with elevated Ti, and are interpreted to have been leached by hydrothermal fluids (Squyres et al. 2008).
Sedimentary rocks in Gale crater have been analyzed by the Curiosity rover, and exploration is ongoing. The early Hesperian Yellowknife Bay formation (Grotzinger et al. 2014) is a coarsening-upward succession of mudstone to sandstone (Figs. 10 and 11c). A K-Ar age for the mudstone is 4.21 ± 0.35 Ga (Farley et al. 2014), confirming the antiquity of the detrital crater rim component of this rock. The Yellowknife Bay rocks are laminated to massive. Mudstone facies, in particular, contain various diagenetic features, including concretions (Stack et al. 2014) and mineralized fractures (Siebach et al. 2014), that suggest active precipitation in the depositional environment. Diagenetic phases, such as Ca-sulfate veins, crosscut both fine- and coarse-grained lithologies, indicating emplacement during later diagenesis. The bulk chemistry of Yellowknife Bay rocks (McLennan et al. 2014) is broadly similar to sedimentary rocks in Gusev and Meridiani (Fig. 2), reflecting their basaltic provenance with no evidence for chemical fractionation. Contents of Fe are highly variable, and sandstones of the Glenelg member (Fig. 10) are Fe-cemented (Blaney et al. 2014). Unlike the Burns Formation, in which the basaltic protolith was altered before deposition and was cemented with sulfate, the basaltic detritus in Gale sedimentary rocks was not appreciably chemically weathered and the rocks contain very few chemical precipitates. Alteration of these rocks occurred during diagenesis of water-saturated sediment rather than by weathering in the sediment source region (Grotzinger et al. 2015). The modal mineralogy of Sheepbed mudstone, the stratigraphically lowest member of the Yellowknife Bay formation, was determined by X-ray diffraction (Vaniman et al. 2014). The rock is a disequilibrium assemblage of basaltic minerals, with smectitic clay, amorphous material (including allophane-like material), and other alteration minerals (Fig. 12).
As Curiosity continued its traverse to Gale’s central mountain (Mt. Sharp), it obtained analyses of the Windjana sandstone. Its composition is alkaline, like the Gale igneous rocks, and its modal mineralogy (Fig. 12) has a high proportion of detrital igneous minerals (Grotzinger et al. 2015). Conglomerates (Fig. 11d) have also been encountered during Curiosity’s traverse (Williams et al. 2013).
Missing from the rocks analyzed so far by Mars rovers are massively layered MgFe-, and Ca-sulfates, layered Al- and FeMg-phyllosilicates, and chloride deposits, all observed in remote sensing data (e.g., Bibring et al. 2006; Murchie et al. 2009; Osterloo et al. 2010). Although sulfate cements and veins occur in Gusev and Gale sedimentary rocks, these differ petrologically from the massive evaporitic deposits.
The only martian sedimentary meteorites studied so far are the paired samples NWA 7034 and NWA 7533. The bulk composition of NWA 7034 is similar to igneous rocks in Gusev Crater (Fig. 2). These regolith samples are polymict breccias (Fig. 13), composed of igneous detritus (described above) and impact-melted clasts in a fine-grained matrix partly altered by aqueous processes (Muttik et al. 2014). Some large “pebbles” have breccia-within-breccia textures, and their rounded outlines suggest that they were transported sedimentary rocks (McCubbin et al. 2014). These pebbles contain metamict zircons that give ages of ~1.4 Ga (Yin et al. 2014), much younger than the ~4.4 Ga (Pre-Noachian) ages of zircons in the igneous clasts (Humayun et al. 2013; Yin et al. 2014), and suggest that the host breccia was assembled after 1.4 Ga.
Petrology of martian metamorphic rocks
Most martian meteorites have suffered shock metamorphism to varying degrees, although the nakhlites show minimum shock effects. Shock in basaltic shergottites has transformed plagioclase into diaplectic glass (maskelynite), and veins of impact melt crosscut some meteorites (Stöffler et al. 1986). Impact-melt pockets may also contain high-pressure polymorphs—stishovite and post-stishovite (from tridymite) and hollandite (from plagioclase) (El Goresy et al. 2004). Atmospheric gas implanted into pockets of impact melt in shergottites provides the most persuasive evidence that these meteorites are from Mars (Bogard and Johnson 1983).
Olivine megacrysts in many olivine-phyric shergottites are stained brown, which is attributed to shock oxidation (Ostertag et al. 1984). The olivine-phyric shergottite Tissint is the most severely shocked martian meteorite. It contains a wide variety of high-pressure polymorphs in melt pockets, including ringwoodite (from olivine), akimotoite, majorite, and silicate perovskite (from pyroxene), lingunite (from plagioclase), tuite (from merrillite), and stishovite (from tridymite) (Baziotis et al. 2013). These phases correspond to localized shock conditions of ~25 GPa and ~2000 °C.
ALH84001 has also been highly shocked (Treiman 1998; Greenwood and McSween 2001), and some of the features originally attributed to martian life apparently resulted from impact vaporization and condensation (Bradley et al. 1996; Golden et al. 2004). The NWA 7034 and NWA 7533 regolith breccias contain significant amounts of impact melts, some clast-laden (Humayun et al. 2013) and some completely melted (Udry et al. 2014b). Shock effects may be widespread in martian rocks; however, these effects are more common in lunar meteorites than in returned lunar samples. On Mars breccias are ubiquitous, and Newsom et al. (2015) identified possible shatter cones, impact spherules, and other evidence suggestive of impact melting at Gale crater.
Thermal or hydrothermal metamorphism
Thermal or hydrothermal metamorphism was most likely to have occurred in ancient (Noachian) rocks, because radiogenic heat production was five times greater than the present-day value (Hahn et al. 2011). Before exploring Mars for metamorphic rocks, it would be helpful to predict likely diagnostic mineral assemblages. The Noachian gradient has been estimated at ~12 °C/km (McSween et al. 2014) based on the GRS-measured abundances of radiogenic heat-producing elements (U, Th, K) in the present crust and correction for radioactive decay over time (Hahn et al. 2011). This gradient is likely to be a lower limit, as gradients estimated from other constraints on Noachian heat flow range from 14–20 °C/km (McSween et al. 2014, and references therein). These gradients in the crust of Mars, where pressure increases less rapidly with depth than on Earth, would produce temperatures and pressures corresponding to the following low-grade metamorphic facies: zeolite, prehnite-actinolite, and pumpellyite-actinolite.
Based on the inference that the crust of Mars is basaltic, we can predict the mineralogy of low-grade metabasalts from molar ACF diagrams, where A = Al2O3 + Fe2O3 – Na2O – K2O, C = CaO – 3.3 P2O5, and F = MgO + FeO + MnO (Fig. 14). The compositions of basaltic rocks for which we have complete major element analyses (martian meteorites, and basalts from Gusev and Gale) are projected onto this diagram (McSween et al. 2014). The three triangles show predicted mineral assemblages for the various facies. The diagnostic assemblages for most of these metabasalts are chlorite + actinolite + one of the following: laumontite, prehnite, or pumpellyite. Olivine-phyric and lherzolitic shergottites plotting outside of the triangles defined by those minerals would contain chlorite + actinolite + serpentine or talc. In addition, sodic plagioclase (albite) or analcime, and possibly silica could occur. Ultramafic rocks at these metamorphic grades should produce serpentine, or talc + magnesite, depending on fluid composition.
Of the diagnostic metamorphic minerals for metabasalts suggested by these plots, only prehnite, chlorite, and analcime have been positively identified in CRISM and OMEGA spectra (Ehlmann et al. 2009; Carter et al. 2013), although unspecified zeolite spectra could include laumontite, and pumpellyite has been suggested based on radiative transfer modeling (Poulet et al. 2008). The apparent absence of actinolite in the spectra is perplexing; however, we do not know the chemical compositions of martian metabasalts, so there is no certainty that they should contain enough actinolite to be detected spectrally. Additionally, TES spectral deconvolutions in the best-studied Noachian terrane (Nili Fossae) indicated the presence of albite (Milam et al. 2010), and silica, analcime, and Fe,Mg smectite have been recognized from visible/near-infrared spectra (Elhmann et al. 2009). The spectra of ultramafic rocks in Nili Fossae indicate either serpentine, magnesite, and possibly talc (Ehlmann et al. 2008, 2009, 2010; Viviano et al. 2013), as predicted for this metamorphic grade.
Some metamorphic rocks in Nili Fossae were excavated by impacts, suggesting that metamorphism occurred in the subsurface at depths of perhaps 5–8 km, as inferred from crater diameter/depth relations. Noachian geothermal gradients based solely on heat-producing radioactive elements are not high enough to produce the observed mineral assemblages at these depths, so additional heat supplied by geothermal sources seems likely (Ehlmann et al. 2011; McSween et al. 2014). Impact craters on Earth commonly develop hydrothermal systems, and hydrothermal metamorphism could have produced these martian rocks.
In addition to Nili Fossae, metamorphic minerals have also been identified in other Noachian terrains, especially in excavated rocks in the central peaks and ejecta blankets of craters. A global spectroscopic survey (Carter et al. 2013) reported 85 occurrences of prehnite, 268 of chlorite, 94 of serpentine or talc, 152 of unspecified zeolites, and 5 of epidote (the latter indicating greenschist facies conditions).
Martian rock cycles
The rock cycle (Fig. 15, top) has proven to be a convenient, albeit simplified way to relate igneous, sedimentary, and metamorphic rocks on Earth. The terrestrial version does not include shock metamorphism, but that has been added here because impact processes have played such an important role in altering rocks on Mars. The absence of plate tectonics, and in particular subduction, on Mars prevents cycling of crustal rocks back into the mantle, the subsidence of depositional basins, as well as flux melting that produces felsic magmatism. The lack of uplift resulting from plate collisions also limits erosion to produce sediments.
Two hypothesized martian rock cycles, representing different ages, are illustrated at the bottom of Figure 15. In Noachian and early Hesperian time, igneous processes were important, as inferred from the NWA 7034 and ALH 84001 meteorites and seen in volcanic rocks in Gusev and Gale Craters. Chemical and physical weathering of surface rocks produced sediments, which were transported and deposited by flowing (probably intermittent) water, as evidenced in Meridiani and Gale rocks. Chemical alteration and precipitation of evaporative salts may have followed different pathways during the Noachian and Hesperian periods, however, depending on a change in the pH of aqueous fluids from near-neutral to acidic (McLennan and Grotzinger 2008). Groundwater-driven diagenesis and hydrothermal activity further altered igneous and sedimentary rocks. Burial of surface rocks by subsequent volcanism or the deposition of sediments or impact ejecta over time exposed subsurface rocks to increased pressure and temperature (perhaps aided by hydrothermal cells), causing metamorphism. Continuing impacts may have caused shock metamorphism in any of these materials. Although impacts certainly produced some melts, these were not on the scale of subduction zone magmatism and differed compositionally (impact melts tend to represent complete, rather than partial melting, and form from mafic crustal rather than ultramafic mantle sources).
During Amazonian time, the martian rock cycle was likely truncated substantially. Volcanism has continued, but has become localized in a few provinces like Tharsis and Elysium. The absence of surface water means that sediments were produced by physical weathering (including impacts) and transported and deposited primarily by winds. Few fluids were available to promote diagenesis or metamorphism. It is unclear to what extent modern sediments (soils) can be lithified into sedimentary rocks. Earlier-formed sedimentary rocks, as well as igneous rocks, have continued to suffer shock metamorphism, but the low-geothermal gradient in modern Mars probably precludes thermal metamorphism, at least in the accessible crust.
Geochemical, mineralogical, and textural analyses of rocks by rovers, coupled with laboratory studies of martian meteorites and inferences from orbital remote sensing data, have provided information with which the rocks of Mars can be characterized. The petrology of Mars is intriguingly different from that of our own planet, but the application of tried-and-true petrographic and geochemical methods has been instrumental in the geologic exploration of another world.
The martian crust is composed mostly of igneous rocks of basaltic composition, along with ultramafic cumulates. Ancient basaltic rocks analyzed by Mars rovers and sampled by one meteorite are more alkaline than young martian meteorites. Further evidence of and explanation for this apparent magmatic evolution over time is needed.
Source regions were compositionally distinct, and magmas derived from them have inherited differences in trace element patterns, radiogenic isotopic compositions, and oxidation states. The extent of mantle heterogeneity, as well as the possible magmatic assimilation of crust, are open questions.
Fractional crystallization of basaltic parent magmas at different depths, likely with varying water contents, produced trachyte, trachybasalt, hawaiite, and mugearite melts, as well as cumulate pyroxenites and dunites. Felsic (silica-rich) igneous rocks are unknown, but feldspar-rich rocks occur locally. Magma fractionation has produced different suites of rocks than on Earth.
Sedimentary clastic rocks range from ancient clay-rich mudstone to sandstone and conglomerate, derived from basaltic protoliths and retaining significant igneous detritus and similar bulk compositions. Volcaniclastic rocks are also common. Chemical rocks include evaporative sulfate and carbonate, and sulfates, silica, and Fe oxides are common cements. What factors, in addition to distinct protoliths, have controlled the nature of surface materials on Mars requires further exploration.
Depositional, diagenetic, and hydrothermal processes in martian rocks have terrestrial analogs, but evolving global environmental conditions (from wetter, neutral-pH, to drier, acidic, and finally to desiccated, highly oxidized) have produced distinctive sedimentary rocks and altered igneous rocks. Although the broad picture seems clear, the transitions between environments are confusing.
Shock metamorphism has affected most martian meteorites. Although the effects of impacts are likely to have been pervasive in rocks on Mars, only breccias have been clearly documented from spacecraft data.
Hydrothermally altered or metamorphosed rocks have been inferred from diagnostic minerals in orbital spectra, consistent with predictions from phase equilibria in metabasalt and serpentinite. Until metamorphic rocks are analyzed from the ground or as meteorites, metamorphic processes on Mars will remain speculative.
The martian rock cycle during Noachian and early Hesperian time was similar in some respects to that of Earth. However, the absence of plate tectonics precluded high-pressure metamorphism and flux melting associated with subduction, as well as sedimentary deposition in subsided basins and rapid erosion resulting from tectonic uplift. The Amazonian rock cycle can hardly be called that, as recent geologic activity on Mars has been limited.
I thank Bethany Ehlmann, Linda Kah, and Jeff Taylor for constructive reviews. This work was partly supported by NASA Cosmochemistry grant NNX13AH86G and Cornell University Mars Exploration Rovers subcontract 39361-6446. | 0.870294 | 3.950926 |
New Astronomy Book Sheds Light on Ever-Expanding Universe
Top astronomers all over the world have had a working understanding for about a century that the universe is continually expanding. But recent discoveries have had astronomers double-checking their facts. This is because according to recent research, the current universe is expanding 9% faster than the early universe. This is faster than first predicted. And you can read about these findings in an article published by Astronomy Magazine.
These findings, which seem to be valid, have caused some controversy among scientists, though. This research, which was conducted from the Hubble Space Telescope, is in direct conflict with the European Space Agency’s Planck spacecraft studies of the early universe and how it would continue to expand. The European Space Agency’s Planck spacecraft studies suggest that as the universe expands in the future, it will follow the same pattern as it always has.
Dark Matter and Dark Energy
Dark matter and dark energy, which have been theorized about for some time now, seem to be one of the unpredictable variables that partially explain the accelerated expansion of the universe. However, most dark matter, which scientists have only caught glimpses of, is too small to reflect light and therefore cannot be seen, even with the Hubble Space Telescope. And the existence of dark energy has never actually been established for certain.
And while all of this new information is fascinating, this kind of science isn’t as easy to follow as television shows like “Star Trek” or the “Big Bang Theory.” In fact, even if you read the article in Astronomy Magazine (which is written for laymen), you may walk away scratching your head. This is because astronomers don’t use the words “Star,” “Planet,” and “Galaxy” so much as they use the words “Cepheid,”“Magellanic Cloud,” “Type Ia Supernova,” “Neutrinos,” and “Dark Radiation.”
So to fully appreciate even the simplest explanation of how the universe is expanding, you will need a glossary of astronomy. This is a book that is set up like a dictionary, with entries that define astronomy terms and also explain the concepts of astronomy, cosmology, and their sub-disciplines. An astronomy glossary can turn you from a stargazer into a person who has a concept of how the universe works.
One such glossary, Astroglossary: Revised Edition, compiled by the late G. Cyr, is one of the most comprehensive and easily understood astronomy reference books on the market today. It is an invaluable resource which includes all of the critical terms needed to understand modern astronomy, and at the same time gives any reader a deeper appreciation of the universe.
In fact, using this glossary as a resource is the first step to fully comprehending new findings of the universe. Whether you are reading an article in a scientific magazine or watching a television program about how the universe is developing, you will be able to absorb much more information if you have the Astroglossary on hand. Knowing critical terms while you educate yourself about the wonders of the universe will also help you better understand how infinitely beautiful, awesome, and ever-expanding it is. | 0.83327 | 3.63131 |
How we do laboratory work on exoplanet atmospheres is an interesting challenge. We’ve worked up models of the early Earth’s atmosphere and conducted well-known experiments on them. Still within our own system, we’ve looked at worlds like Mars and Titan and, with a good read on their atmospheric chemistry, can reproduce an atmosphere within the laboratory with a fair degree of accuracy.
In the realm of exoplanets, we’re in the early stages of atmosphere characterization. We’re getting good results from transmission spectroscopy, which analyzes the light from a star as it filters through a planetary atmosphere during a transit. But thus far, the method has mostly been applied to gas giants. Getting down to the realm of rocky worlds is the next step, one that will be aided by space-based assets like the James Webb Space Telescope. Can lab work also help?
Probing the Atmosphere of a ‘Super-Earth’
Worlds smaller than gas giants are plentiful. Indeed, ‘super-Earths’ are the most common planets we’ve found outside our own Solar System. Larger than the Earth but smaller than Neptune, they present us with a challenge because we have no nearby examples to help us project what we might find. That leaves us with computer modeling to simulate possible targets of observation and, in the lab, experimentation to see which mixture produces what result.
At Johns Hopkins University, Sarah Hörst has been conducting experimental work that varies possible exoplanet atmospheres, working with different levels of carbon dioxide, hydrogen and water vapor, along with helium, carbon monoxide, methane and nitrogen. Hörst and team adjust the percentages of these gases, which they mix in a chamber and heat. The gaseous mixture is passed through a plasma discharge that initiates chemical reactions within the chamber.
The research team used JHU’s Planetary Haze Research chamber (PHAZER) to conduct the experiments. A key issue is how to choose atmospheric compositions that would be likely to be found on super-Earths, as the paper on this work explains:
Atmospheres in chemical equilibrium under a variety of expected super-Earth and mini-Neptune conditions can contain abundant H2O, CO, CO2, N2, H2 and/or CH4, various combinations of which may have a distinct complement of photochemically produced hazes, such as ‘tholins’ and complex organics in the low-temperature, H2-rich cases, and sulphuric acid in the high-metallicity, CO2/H2O-rich cases. Warm atmospheres outgassed from a silicate composition can also be dominated by H2O and CO2. We therefore chose to focus on a representative sample of gas mixtures that are based on equilibrium compositions for 100×, 1,000× and 10,000× solar metallicity over a range of temperatures from 300–600 K at an atmospheric pressure of 1 mbar.
Image: This is Figure 2 in the paper. Caption: Due to the large variety of gases used for the experiments, this schematic provides a general idea of the setup. The details varied depending on the gases used, with attention paid to the solubility of gases in liquid water, condensation temperatures and gas purity. Credit: Sarah Hörst/JHU.
At issue is the question of haze, solid particles suspended in gas that can make it difficult to gauge the spectral fingerprints that identify individual gases. You might recall the clear upper atmosphere scientists found at the ‘hot Saturn’ WASP-39b (see Probing a ‘Hot Saturn’). Using transmission spectroscopy on this world, much larger than a super-Earth, Hannah Wakeford’s team at STscI found clear evidence of water vapor, and a surprising amount of it.
It was the fact that WASP-39b’s upper atmosphere is apparently free of clouds that allowed such detailed study of the atmospheric constituents. When we’re dealing with planets with haze, our ability to read these signs is more problematic. Learning more about the kinds of atmospheres likely to be hazy should help us refine our target list for future observatories.
Hörst’s laboratory work probes the production of haze, as the scientist explains:
“The energy breaks up the gas molecules that we start with. They react with each other and make new things and sometimes they’ll make a solid particle [creating haze] and sometimes they won’t,” Hörst said. “The fundamental question for this paper was: Which of these gas mixtures – which of these atmospheres – will we expect to be hazy?”
Two of the atmospheres in which water was dominant turned out to produce a large amount of haze, an indication that haze is not solely the result of interactions in methane chemistry. From the paper:
The two experiments with the highest production rates had the two highest CH4 concentrations, but the one with the third highest production rate (10,000× at 600 K) had no CH4 at all, demonstrating that there are multiple pathways for organic haze formation and that CH4 is not necessarily required. In the case of the experiment with no CH4, the gas mixture had CO, which provided a source of carbon in place of CH4. However, it is important to note that the production rates are not simply a function of carbon abundance, C/O, C/H or C/N ratios in the initial gas mixtures. This result also demonstrates the need for experimental investigations to develop a robust theory of haze formation in planetary atmospheres.
The researchers found a wide variation in particle color as a function of metallicity. The color of particles produced in the haze turns out to have an effect on the amount of heat it traps. Such findings may have implications for astrobiology, when we consider that primitive layers of haze could shield life in its early stages, preventing energetic photons from reaching the surface.
This work is in its early stages, as the paper makes clear:
Although models of atmospheric photochemistry and haze optical properties provide good first estimates, they are incomplete and biased due to the relatively small phase space spanned by the Solar System atmospheres on which they are based. Laboratory production of exoplanet hazes is a crucial next step in our ability to properly characterize these planetary atmospheres. These experimental simulations of atmospheric chemistry and haze formation relevant to super-Earth and mini-Neptune atmospheres show that atmospheric characterization efforts for cool (T < 800 K) super-Earth- and mini-Neptune-type exoplanets will encounter planets with a wide variety of haze production rates.
The paper also reminds us that hazes will have an effect on reflected light, which will have a bearing on future direct imaging of exoplanets. Lab work like this is part of building the toolsets we’ll need for probing rocky worlds around nearby stars in search of biosignatures. My assumption is that in the early going, we are going to see a lot of ambiguous results, with atmospheres with potential biosignatures being likewise capable of interpretation through abiotic means. Homing in on the most likely targets and understanding the chemistry at play will give us the best chance for success when looking at worlds so unlike any in our own system.
The paper is Hörst et al., “Haze production rates in super-Earth and mini-Neptune atmosphere experiments,” Nature Astronomy 5 March 2018 (abstract). | 0.894583 | 3.962106 |
|A set of maps illustrating the planetary bodies of the Solar System. Click on the planet or moon to view the maps. Top rows: real-color photos, bottom rows: our maps. (The surface of Venus and Titan is not visible due to the thick cloud cover or fog.)
PLUTO AND CHARON (2016)
|Note: The aliens depicted on the maps are creatures of imagination. The only known living things In the Solar System can be found on the Earth. Life and traces of life are sought by space probes on Mars, Europa and Titan, with no success so far. Life, as diverse as ours, is likely to be found only on planets in other solar systems in the future, with a surface temperature similar to that on the Earth.
In the framework of the program Europlanet 2012, six Solar System bodies are mapped by planetary scientists and graphic artists on spectacular map pages. This is the first project, in which such detailed, hand-drawn lunar and planetary maps are created for children, in the most spoken languages of Europe. The maps, prepared according to the latest data from space probes, are accompanied by this website where background information can be found in a form understandable for children. The topics covered here are compiled with the help of the children’s questions asked about the maps.
The map series was prepared with the support of ICA Commission on Planetary Cartography. Editor of the series is Henrik Hargitai, planetologist. The graphic artists who created the maps in the visual language of children were selected from the best children’s book illustrators of Hungary: András Baranyai (Venus), Csilla Gévai (Europa), László Herbszt (the Moon), Csilla Kőszeghy (Mars), Panka Pásztohy (TItan) and Dóri Sirály (Io).
Supporters: Europlanet 2012 Outreach Funding Scheme, Paris Observatory, International Cartographic Association Commission on Planetary Cartography
Published by Eötvös Loránd Tudományegyetem. Budapest, 2014.
Explanations for the online texts in the descriptions
General descriptions of parameters
- Body type: Planet or moon. Planets orbit the Sun, moons orbit a planet. One side of moons generally always face its planet (tidally locked).
- Body composition: Rocky bodies are made of silicate rocks (example Earth), icy bodies are made of rock-H2O ice mixture but their surface usually contains the lighter part of the mixture, ice (example: Europa). In these worlds mountains and plains are made of rock-hard ice. Icy bodies occur only in the colder Outer Solar System.
- Atmosphere: atmospheres only occur if the gravity (and size) of the body is sufficient to hold gas molecules. It is easier to hold a gas molecule if it is colder.
- Liquid: liquids may be water in the inner Solar System or methane-ethane-nitrogen in the Outer Solar System. Liquids only occur where there is an atmosphere that produces air pressure. If air pressure is too low, water molecules evaporate/sublimate. If temperature is too low, liquids freeze. If temperature is too high, liquids evaporate. Water may exist underground.
- Endogenic features: Features produced by forces in the interior of the planet. Volcanism requires molten interior. Heat is provided from planetary formation (impact / accretion heat) or the irreversible decay of radioactive elements. Small bodies cool quicker than large bodies, so volcanism is found only on larger planets. An exception is if the interior is continuously heated. This happens inside moons on elliptic orbits where tidal forces produce interior heat (Io). Tectonic forces produce fractures during earthquakes. This requires movements within the planet, also driven by internal heat. Volcanoes grow upward by adding more lava but may collapse and produce crater-like caldera.
- Exogenic features: Features produced by processes on the surface or atmosphere. Includes aeolian (wind), fluvial (river), lacustrine (lake), oceanic features and their deposits.
- Cosmogenic features: Features produced by impacting bodies (smaller craters and larger impact basins). Younger craters have radial rays (produced by ejected materials)
- Common features: The most common feature is craters. Most craters formed after the Solar System formed and still had many small bodies in space. Craters, however, are rare on surfaces that are resurfaced recently, because resurfacing removes or buries craters. Resurfacing processes include volcanic plains, fluvial erosion and sedimentation, and subduction by plate tectonics.
- Rare features: Rare features are unique to a planet. They may be remnants of older times.
- Life limiting parameter: Life should be able to grow and reproduce. Life may be limited by below freezing or above boiling temperatures, lack of atmosphere, lack of water, lack of magnetosphere (too much radiation).
Shapes of geologic features
- Circular: usually an impact crater, rarely volcanic caldera
- Linear (straight): negative: tectonic fracture, positive: dune, ridge or mountain
- Sinuous: river or lava channel
- Lobate: water rich impact crater ejecta, glacier, landslide
- Radial: impact crater ray
- Concentric: impact crater ring
(MAP: use http://countrymovers.elte.hu/countrymovers.html for Earth map or Google map).
- Body type: planet
- Body composition: rocky
- Atmosphere: just right
- Liquid: water
- Endogenic features: volcanoes, faults, plate tectonics
- Exogenic features: rivers, lakes, dunes, floodplains, deltas, glaciers
- Cosmogenic features: 100+ impact craters, many buried or eroded
- Common features: oceans, mountains, plains, rivers
- Rare features: glaciers etc.
- Life limiting parameter: where it is too dry (no liquid water – deserts), too cold (no liquid water – Antarctica)
Size comparison of the highest mountains on Earth and Olympus Mons on Mars | 0.867282 | 3.320213 |
In November of 2018, the NASA Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) lander set down on Mars. Shortly thereafter, it began preparing for its science operations, which would consist of studying Mars’ seismology and its heat flow for the sake of learning how this planet – and all the other terrestrial planets in the Solar System (like Earth) – formed and evolved over time.
With science operations well-underway, InSight has been “listening” to Mars to see what it can learn about its interior structure and composition. A few weeks ago, mission controllers discovered that the lander’s Seismic Experiment for Interior Structure (SEIS) instrument detected its strongest seismic signal (aka. a “marsquake”) to date. This faint quake could reveal much about the Red Planet and how it came to be.
The faint seismic signal, detected by the lander’s Seismic Experiment for Interior Structure (SEIS) instrument, was recorded on April 6th, or the 128th Martian day (Sol 128) since the lander touched down. This is the first recorded seismic signal that appears to have originated from inside the planet, as opposed to being caused by something like wind.
NASA scientists are now examining the SEIS data to determine the exact cause of the signal, which may have originated from inside Mars or been caused by a meteorite crashing into the planet’s surface and sending ripples through the mantle. On Earth, seismic activity (aka. “earthquakes”) are the result of action between tectonic plates, particularly along fault lines.
While Mars and the Moon do not have tectonic plates, they still experience quakes, which are largely the result of the continual heating and cooling of their surfaces. This causes expansion and contraction, which eventually results in stress strong enough to break the crust. While the new seismic event was too small to provide solid data on the Martian interior, it is giving the mission team an idea of how seismic activity on Mars works.
For instance, the faint nature of this event is similar to those measured by the Apollo astronauts during the late 1960s and early 1970s. Beginning with Apollo 11, NASA astronauts installed a total of five seismometers on the lunar surface that measured thousands of moonquakes between 1969 and 1977. The data obtained by these sensors allowed scientists to learn a great deal about the Moon’s interior structure and composition.
In this respect, InSight is carrying on in a tradition that began with the Apollo missions. As Renee Weber, a planetary scientist at NASA’s Marshall Space Flight Center, explained in a recent NASA press release:
“We thought Mars was probably going to be somewhere between Earth and the Moon [in terms of seismic activity]. It’s still very early in the mission, but it’s looking a bit more Moon-like than Earth-like.”
Unlike Earth’s surface, which is constantly quivering from seismic noise created by the planet’s oceans and weather, the Martian surface is extremely quiet. This allows SEIS, which was provided by France’s National Center for Space Studies (CNES) and built by the French National Higher Institute of Aeronautics and Space (ISAE) in Toulouse, to pick up faint rumbles that would go unnoticed on Earth.
As Lori Glaze, the Planetary Science Division director at NASA Headquarters, said:
“The Martian Sol 128 event is exciting because its size and longer duration fit the profile of moonquakes detected on the lunar surface during the Apollo missions.”
InSight’s SEIS, which it placed on the surface in December of 2018, is allowing scientists to gather similar data about Mars. And much like how composition data on the Moon allowed scientists to hypothesize that the Earth-Moon system has a common origin (the Giant Impact Theory), it is hoped that this data will shed light on how the rocky planets of our Solar System formed.
This is the fourth seismic signal detected by the InSight lander, the previous three having taken place on March 14th (Sol 105), April 10th (Sol 132) and April 11th (Sol 133), respectively. However, these signals were even fainter than the one detected on April 6th which makes them even more ambiguous as far as their origins are concerned. Here too, the team will continue studying them to try to learn more.
Regardless of what caused the April 6th signal, its detection is an exciting milestone for the team. As Philippe Lognonné, the SEIS team lead at the Institut de Physique du Globe de Paris (IPGP) in France, said:
“We’ve been waiting months for a signal like this. It’s so exciting to finally have proof that Mars is still seismically active. We’re looking forward to sharing detailed results once we’ve had a chance to analyze them.”
From the four events recorded since December, the SEIS team has indicated that the instrument has surpassed their expectations in terms of sensitivity. “We are delighted about this first achievement and are eager to make many similar measurements with SEIS in the years to come,” said Charles Yana, the SEIS mission operations manager at CNES.
The lander continues to study the planet’s interior from its spot in Elysium Planitia, a plain near Mars’ equator. At present, mission controllers are still trying to figure out how to dislodge the Heat and Physical Properties Package (HP3) heat probe, which became stuck in buried rock back in February while trying to hammer itself into the ground to measure the temperatures there.
Be sure to check out this recording of the seismic event, courtesy of NASA JPL and the SEIS team: | 0.840445 | 3.921442 |
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