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NASA's Swift Finds Most Distant Gamma-ray Burst Yet
On April 29, 2009, a five-second-long burst of gamma rays from the constellation Canes Venatici triggered the Burst Alert Telescope on NASA's Swift satellite. As with most gamma-ray bursts, this one -- now designated GRB 090429B -- heralded the death of a star some 30 times the sun's mass and the likely birth of a new black hole.
"What's important about this event isn't so much the 'what' but the 'where,'" said Neil Gehrels, lead scientist for Swift at NASA's Goddard Space Flight Center in Greenbelt, Md. "GRB 090429B exploded at the cosmic frontier, among some of the earliest stars to form in our universe."
Among the first 500 gamma-ray bursts detected by Swift is GRB 090429B, currently the farthest explosion ever detected and a candidate for the most distant object in the universe. (Credit: NASA Goddard/Swift)
Because light moves at finite speed, looking farther into the universe means looking back in time. GRB 090429B gives astronomers a glimpse of the cosmos as it appeared some 520 million years after the universe began.
Now, after two years of painstaking analysis, astronomers studying the afterglow of the explosion say they're confident that the blast was the farthest explosion yet identified -- and at a distance of 13.14 billion light-years, a contender for the most distant object now known.
Swift's discoveries continue to push the cosmic frontier deeper back in time. A gamma-ray burst detected on Sept. 4, 2005, was shown to be 12.77 billion light-years away. Until the new study dethroned it, GRB 090423, which was detected just six days before the current record-holder, reigned with a distance of about 13.04 billion light-years.
This video shows an animation of a gamma-ray burst. Gamma-ray bursts that are longer than two seconds are caused by the detonation of a rapidly rotating massive star at the end of its life on the main sequence. Jets of particles and gamma radiation are emitted in opposite directions from the stellar core as the star collapses. In this model, a narrow beam of gamma rays is emitted, followed by a wider beam of gamma rays. (Credit: NASA Goddard/Swift/Cruz deWilde)
Gamma-ray bursts are the universe's most luminous explosions, emitting more energy in a few seconds than our sun will during its energy-producing lifetime. Most occur when massive stars run out of nuclear fuel. When such a star runs out of fuel, its core collapses and likely forms a black hole surrounded by a dense hot disk of gas. Somehow, the black hole diverts part of the infalling matter into a pair of high-energy particle jets that tear through the collapsing star.
The jets move so fast -- upwards of 99.9 percent the speed of light -- that collisions within them produce gamma rays. When the jets breach the star's surface, a gamma-ray burst is born. The jet continues on, later striking gas beyond the star to produce afterglows.
The afterglow of GRB 090429B (red dot, center) stands out in the in this optical and infrared composite from Gemini Observatory images. The red color results from the absence of visible light, which has been absorbed by hydrogen gas in the distant universe. Credit: Gemini Observatory/AURA/Andrew Levan (Univ. of Warwick, UK) › Larger image
This is the view of GRB 090429B from Swift's X-Ray Telescope, which imaged the burst less than 107 seconds after the gamma-ray trigger. Credit: NASA/Swift/Stefan Immler › Larger image
"Catching these afterglows before they fade out is the key to determining distances for the bursts," Gehrels said. "Swift is designed to detect the bursts, rapidly locate them, and communicate the position to astronomers around the world." Once word gets out, the race is on to record as much information from the fading afterglow as possible.
In certain colors, the brightness of a distant object shows a characteristic drop caused by intervening gas clouds. The farther away the object is, the longer the wavelength where this sudden fade-out begins. Exploiting this effect gives astronomers a quick estimate of the blast's "redshift" -- a color shift toward the less energetic red end of the electromagnetic spectrum that indicates distance.
The Gemini-North Telescope in Hawaii captured optical and infrared images of GRB 090429B's quickly fading afterglow within about three hours of Swift's detection. “Gemini was the right telescope, in the right place, at the right time," said lead researcher Antonino Cucchiara at the University of California, Berkeley. "The data from Gemini was instrumental in allowing us to reach the conclusion that the object is likely the most distant GRB ever seen."
The team combined the Gemini images with wider-field images from the United Kingdom Infrared Telescope, which is also located on Mauna Kea in Hawaii, to narrow estimates of the object's redshift.
Announcing the finding at the American Astronomical Society meeting in Boston on Wednesday, May 25, the team reported a redshift of 9.4 for GRB 090429B. Other researchers have made claims for galaxies at comparable or even larger redshifts, with uncertain distance estimates, and the burst joins them as a candidate for the most distant object known.
Studies by NASA's Hubble Space Telescope and the Very Large Telescope in Chile were unable to locate any other object at the burst location once its afterglow had faded away, which means that the burst's host galaxy is so distant that it couldn’t be seen with the best existing telescopes. "Because of this, and the information provided by the Swift satellite, our confidence is extremely high that this event happened very, very early in the history of our universe,” Cucchiara said.
Swift, launched in November 2004, is managed by Goddard. It was built and is being operated in collaboration with Penn State University, University Park, Pa., the Los Alamos National Laboratory in New Mexico, and General Dynamics of Gilbert, Ariz., in the U.S. International collaborators include the University of Leicester and Mullard Space Sciences Laboratory in the United Kingdom, Brera Observatory and the Italian Space Agency in Italy, and additional partners in Germany and Japan. | 0.8946 | 3.887128 |
Astronomers say they have been stunned by the amount of energy released in a star explosion on the far side of our galaxy, 50,000 light-years away.
The position of SGR1806-20 in a radio image of the sky - 50,000 light-years away
The flash of radiation on 27 December was so powerful that it bounced off the Moon and lit up the Earth's atmosphere.
The blast occurred on the surface of an exotic kind of star - a super-magnetic neutron star called SGR 1806-20.
If the explosion had been within just 10 light-years, Earth could have suffered a mass extinction, it is said.
"We figure that it's probably the biggest explosion observed by humans within our galaxy since Johannes Kepler saw his supernova in 1604," Dr Rob Fender, of Southampton University, UK, told the BBC News website.
One calculation has the giant flare on SGR 1806-20 unleashing about 10,000 trillion trillion trillion watts.
"This is a once-in-a-lifetime event. We have observed an object only 20km across, on the other side of our galaxy, releasing more energy in a 10th of a second than the Sun emits in 100,000 years," said Dr Fender.
The event overwhelmed detectors on space-borne telescopes, such as the recently launched Swift observatory.
This facility was put above the Earth to detect and analyse gamma-ray bursts - very intense but fleeting flashes of radiation.
The giant flare it and other instruments caught in December has left scientists scrambling for superlatives.
Twenty institutes from around the world have joined the investigation and two teams are to report their findings in a forthcoming issue of the journal Nature.
Swift moved quickly to track down the source of the gamma-rays
The light detected from the giant flare was far brighter in gamma-rays than visible light or X-rays.
Research teams say the event can be traced to the magnetar SGR 1806-20.
This remarkable super-dense object is a neutron star - it is composed entirely of neutrons and is the remnant collapsed core of a once giant star.
Now, though, this remnant is just 20km across and spins so fast it completes one revolution every 7.5 seconds.
"It has this super-strong magnetic field and this produces some kind of structure which has undergone a rearrangement - it's an event that is sometimes characterised as a 'star-quake', a neutron star equivalent of an earthquake," explained Dr Fender.
"It's the only possible way we can think of releasing so much energy."
SGR 1806-20 is sited in the southern constellation Sagittarius. Its distance puts it beyond the centre of the Milky Way and a safe distance from Earth.
"Had this happened within 10 light-years of us, it would have severely damaged our atmosphere and would possibly have triggered a mass extinction," said Dr Bryan Gaensler, of the Harvard-Smithsonian Center for Astrophysics, who is the lead author on one of the forthcoming Nature papers.
"Fortunately there are no magnetars anywhere near us."
The initial burst of high-energy radiation subsided quickly but there continues to be an afterglow at longer radio wavelengths.
This radio emission persists as the shockwave from the explosion moves out through space, ploughing through nearby gas and exciting matter to extraordinary energies.
"We may go on observing this radio source for much of this year," Dr Fender said.
This work is being done at several centres around the globe, including at the UK's Multi-Element Radio-Linked Interferometer Network (Merlin) and the Joint Institute for VLBI (Very Long Baseline for Interferometry) in Europe - both large networks of linked radio telescopes. | 0.866905 | 3.766122 |
A Very Bright Idea: Venus, Saturn, Jupiter Show Off
With apologies to Tinker, Evers and Chance, April features a cosmic double-play combination: Venus to Saturn to Jupiter.
The nights of April start with Venus ready to play. Find Venus by looking west at dusk. This effervescent planet has a negative fourth magnitude (ultra-bright) glow, making it the brightest object aside from the sun and the moon. It shimmies below the lovely ladies of Pleiades (Messier 45) on the evening of April 11.
Forget television and steal a moment for yourself April 19 and 20: The sliver of a new moon dances below Venus on April 19, and a slightly larger sliver dances above Venus the next night.
When evening falls, Saturn is high in the southeastern sky, loitering between the constellations Leo and Cancer. The ringed planet — and enjoy those rings now — has lots of night ahead. It crosses the meridian about 10 p.m. and sets about 5 a.m. early in the month. Later in the month, it sets about 4 a.m.
Saturn is zero magnitude, which means it is visible even from welllighted urban locations. Those magnificent rings are wide open now and, from our perspective, they will begin to shut. The rings will appear edge-on, invisible to us, in 2009.
Early-morning sky gazers will enjoy finding Jupiter. The large, gaseous planet rises in the east-southeast well after midnight and can be seen high in the south at dawn now. This negative second magnitude (very bright) object is snuggled to the west of Sagittarius and south of Ophiuchus.
If you see streaks of meteors crossing the heavens in mid-April, you’re watching the Lyrid meteors. These meteors are likely to be viewed between April 16 and 25. There are not very many of them, and they peak April 22, when it is dark in Europe and it will be afternoon here. Nevertheless, try looking.
April 5 — Astronomer Marc Pound discusses “The Story of the Horsehead” at the University of Maryland Observatory’s open house in College Park. See the heavens through a telescope afterward, weather permitting. 8 p.m. Information: 301-405-6555; www.astro.
April 7 — Learn about telescopes at Family Day at the National Air and Space Museum’s Steven F. Udvar-Hazy Center in Chantilly, near Dulles Airport. 10 a.m. to 3 p.m. Admission is free; parking is $12. Information: www.nasm.si.edu/udvarhazy; 202-633-1000.
April 14 — Frank Summers, astrophysicist with the Space Telescope Science Institute, on “From Simulation to Visualization: Astrophysics Goes Hollywood” at the National Capital Astronomers meeting at the University of Maryland Observatory, College Park. 7:30 p.m. Information: www.capitalastronomers.org.
April 17 — Elizabeth P. Turtle, planetary scientist at Johns Hopkins University, presents a lecture, “Exploring the Surface of Titan With Cassini-Huygens,” at 8 p.m. at the Lockheed Martin IMAX Theater, National Air and Space Museum. Beforehand, attend a free showing of the film “Cosmic Voyage” at 6:30 p.m. and meet the lecturer at 7:30 p.m. Information: 202-633-1000; www.nasm.si.edu.
April 20 — Astronomer Lisa Winter on “The Milky Way: A Tour of Our Galaxy,” at the University of Maryland Observatory’s open house in College Park. 8 p.m. Information: 301-405-6555; www. astro.umd.edu/openhouse.
April 21 — Find out how America’s native peoples used the heavens in a special joint presentation with the National Museum of the American Indian at “Explore the Universe,” a Family Day event, at the National Air and Space Museum. 10 a.m. to 3 p.m., with another session at 1 p.m. at the American Indian museum. Information: 202633-1000; www.nasm.si.edu.
April 21 — Astronomy Day, hosted by the Northern Virginia Astronomy Club, at Sky Meadows State Park near Paris, Va. Enjoy solar observing through safe filters, and after sundown, peek through telescopes for the stars and planets. 3 to 11 p.m., rain or shine. Parking fee. Information: www.novac.com. | 0.889248 | 3.168141 |
This is the home page of the KELT-South telescope. It is for use by members of the public interested in the KELT project, and for scientists who want to learn more about the details of KELT. For a basic description of what KELT-South is and does, see the link above, About KELT-South.
For information about the twin telescope of KELT-South in the northern hemisphere, see the website of KELT-North.
Major KELT-South Planet discovery – KELT-11b
KELT-11b is the latest discovery from KELT-South. It is extraordinarily inflated, with a mass one fifth that of Jupiter but a size almost 40% larger, so the bulk density is below 0.1 grams per cc.
The star is extremely bright at V=8, and the star is also fairly evolved onto the subgiant branch. This is the brightest transit host in the southern hemisphere and the 6th brightest transiting system known. The planet is in a P=4.73 day orbit, and it’s low density gives it an extremely large projected atmospheric scale height of 2700 km. This is an excellent target for transmission spectroscopy.
More KELT-South Exoplanets: KELT-14b and KELT-15b
Our next KELT-South discoveries are a pair of hot Jupiters, one which (KELT-14b) is a simultaneous discovery along with the SuperWASP project. This paper is led by Joey Rodriguez, recently graduated from Vanderbilt, and headed to a postdoctoral position at Harvard-Smithsonian CfA.
First KELT-South Exoplanet Discovery: KELT-10b
KELT-10b is the first exoplanet discovered by the KELT-South telescope. It is a hot sub-Jupiter at 68% of Jupiter, but 40% larger, so it is very inflated. This discovery is led by Rudi Kuhn, who is currently a staff scientist at SAAO working on SALT. KELT-10b is a great example of what we want the KELT project to deliver, since the host star is bright at V=10.7, and an orbital period of just over 4 days.
A new KELT-North discovery – KELT-8b
Another KELT-North planet – KELT-7b
KELT-7b is a great discovery. It is another inflated hot Jupiter, this one in a 2.73-day orbit. It is the fifth most massive, fifth hottest, and the ninth brightest star known to host a transiting planet. See the paper, led by our KELT collaborator Allyson Bieryla.
Recently, Vanderbilt graduate student Joey Rodriguez paid a maintenance visit to KELT-South. While there, he worked with SAAO technician Willie Koorts to lubricate the roof mechanism for the KELT-South building. They needed a simple and effective lubrication option, and Willie found an excellent homemade solution. Check it out:
Newest KELT Discovery – KELT-6b
Announcing KELT-6b, a transiting Saturn-mass exoplanet in a 7.9-day orbit. This is the smallest planet yet discovered by KELT, and also the one with the longest period. Its host star is especially metal-poor, and is a near-twin of the host star of exoplanet HD209458b, one of the best-studies transiting exoplanets.
KELT Software Release – TAPIR
TAPIR is a free software package for scheduling observations of transit candidates. Developed by KELT collaborator Eric Jensen at Swarthmore College, it allows a survey to upload a list of potential transit candidates to an online portal, and all those interested in observing the candidates can log in, set a variety of observing constraints, and see all candidates that fulfill those constraints.
An example of this would be for an observer to log in, select their observing location and time zone, and see all upcoming transit events for the uploaded candidates for the next several nights. The observer can filter for candidates that will be above a given airmass through the entire transit, for candidates with expected depths larger than a given value, or for candidates with an internal priority ranking above some level. There are many other ways the observer can customize their requirements.
What makes this package unique and powerful are the extensive options for time-sensitive flexibility and customization. Most software tools for planning observations allow the observer to generally check object observability, but TAPIR addresses the time-sensitive requirements for transit observing with unprecedented power. It allows each observer to customize their requirements, and to do so in one step for the entire uploaded dataset. It serves as a many-to-many conduit, allowing any number of independent observers to check their ability to observe any number of potential transits.
New KELT discovery!
Announcing KELT-3b, a hot Jupiter transiting a V=9.8 star in a 2.703 day orbit. With this discovery, 2 of the 20 brightest transiting planets are KELT discoveries. That number will keep going up.
On June 13, 2012, the KELT project announced its first major discoveries. KELT-North has discovered two new companions to bright stars.
- KELT-1b is a 27 M_J, 1.1 R_J transiting brown dwarf in a 1.2 day orbit around a V=10.7 F5 star. It is the shortest period and brightest transiting brown dwarf discovered, and is only the second definitively inflated brown dwarf known. KELT-1b: A Strongly Irradiated, Highly Inflated, Short Period, 27 Jupiter-mass Companion Transiting a mid-F Star
- KELT-2Ab is a 1.5 M_J, 1.3 R_J mildly inflated hot Jupiter in a 4.1 day orbit around a slightly evolved V=8.77 F7 star. It is the ninth brightest transiting planet, and the third-brightest one discovered by a ground-based survey. The evolutionary state of the star means that this exoplanet has one of the best measured ages of any known exoplanet. The host star also has a common proper motion M-dwarf binary companion (KELT-2B) that may be the cause of KELT-2Ab’s orbital location. KELT-2Ab: A Hot Jupiter Transiting the Bright (V=8.77) Primary Star of a Binary System
Both of these discoveries are extremely exciting, and are exactly what KELT was built to do. These two discoveries come from the KELT-North telescope, which has been operating longer than KELT-South and so if further along with its search. We also have several more interesting targets from both telescopes that we are working to confirm and hopefully publish over the next year.
Below is a model of the transit of KELT-1b across its host star.
Here is an animation showing the gradual buildup of the KELT-2 lightcurve:
The video shows the brightness of the host star plotted over time, with the data folding back on itself ever 4 days, 2 hours, 43 minutes, and 50 seconds, which is how long the planet takes to orbit the star. Each white point is a measurement of the star’s brightness, and the red points are the average of the white points in time. The dip in the middle is the starlight being blocked by the planet.
The music in the video is “Orbital” by Josh Ritter, from the album “So Runs the World Away”. Used with permission.
Here is a cool video of the KELT-South telescope in operation over the course of one night in Sutherland, South Africa:
If you have any questions about the project or this webpage, please contact Joshua Pepper: | 0.853639 | 3.476647 |
NASA’s newest Mars probe, called MAVEN, has successfully entered its designated orbit around the "red planet." Scientists will use its sophisticated instruments to try to learn what happened to the atmosphere Mars had a few billion years ago.
After a 10-month, 711-million kilometer journey, MAVEN’s thrusters slowed it down to enter into orbit Sunday around Mars.
MAVEN, which stands for ‘Mars Atmosphere and Volatile Evolution Mission’, will try to find answers to two simple questions: “Where did the water go? Where did the carbon dioxide go?”
MAVEN principal investigator Bruce Jakosky says scientists now know that Mars once had a much denser atmosphere, but it changed significantly over the last few billion years when most of its gases disappeared into space. What they still don’t know is how and why that happened.
“We are trying to understand what the cause of that climate change has been, and we are looking at the role that escape to space may have played in removing the atmosphere, and changing the atmosphere,” he said.
Implications of study
MAVEN will be exploring the top layers of what’s left of the Martian atmosphere, because scientists think that charged particles emitted by the sun, the so-called “solar wind”, may have been responsible for slowly stripping away the atmospheric gasses, including water vapor.
Learning about how Mars lost its water is key to understanding if the planet most like Earth in the solar system ever could have supported life.
It will take five weeks for the spacecraft to deploy its booms, get calibrated and be ready for work, before beginning the one-year mission which carries a price tag of $671 million.
Right now, NASA’s engineers are still celebrating the fact that so far the mission went without a glitch.
“It really is an amazing amount of work that the team did to make it look so smooth tonight," he said. "It is kind of cliched, people walk around going 'it is not rocket science', well sometimes it is rocket science.”
MAVEN has joined two American and one European spacecraft orbiting the Red Planet, together with three rovers still operating on its surface. In two days, India’s first Mars explorer should enter its orbit where it will also conduct atmospheric measurements.
Maven is NASA's 21st shot at Mars and the first since the Curiosity rover landed on the red planet in 2012.
Just this month, Curiosity arrived at its prime science target, a mountain named Sharp, ripe for drilling. The Opportunity rover is also still active a decade after landing.
All these robotic scouts are paving the way for the human explorers that NASA hopes to send in the 2030s. The space agency wants to understand as much about the red planet as possible before it sends people there, AP reported.
Some material for this report came from Reuters and AP. | 0.832862 | 3.481469 |
Looking at the Big Picture Through The Wrong End of the Telescope
This post at Bizarre Science (link via Troppo Armadillo) has prompted a little blogospheric warming over the past 24 hours. It refers to this article recently published in on the effects of supernovae on atmospheric temperature. This helpful digest of the article by Tim Patterson, author of the Bizarre Science post may be more accessible.
The story, in a nutshell is this. We all know that the Earth orbits the Sun. The Sun, in turn, orbits the centre of our galaxy the Milky Way. At least, this is the story according to the current high school science curriculum - give it another couple of hundred years, and the whole picture might have been brought up to date with General Relativity which, if you're optimistic about the progress of scientific knowledge will be as obsolete as the "little objects go round big objects" Newtonian view we're working with here. The pessimistic prospect that the whole of twentieth century astrophysics might equally well have been thrown out in favour of a theory in which the speed of light increases the further you get from the earth so that objects allegedly millions of light years away are only 6,000 light years away at most, doesn't bear thinking about. The mathematics of such a theory would make calculating a Lorenz-Fitzgerald contraction look easier than splitting the bill at a Sunday yum-cha.
So the Sun orbits the center of the galaxy, pulling the Earth and the other planets along with it. Its orbit takes it through regions of space which have a lot of stars in them (the galactic arms) and regions where there are fewer stars (the spaces between the arms). When the Earth is passing through one of the galactic arms, It gets more galactic cosmic radiation, which originates (apparently) from supernovae. A supernova is essentially the sort of big kaboom that would satisfy Marvin the Martian (remember Duck Dodgers in the twenty four and halfth Century?), although not the biggest of all possible kabooms. The biggest kaboom of all was probably the last, unless someone can come up with quite a few teratons of matter that's been otherwise unaccounted for because it's in some bizarre form that nobody has recognised yet.
At this point we can leave cosmology behind, and look at the effects of cosmic radiation from supernovae, and other (non Solar) sources, on the Earth's atmosphere. What it amounts to is this: cosmic radiation ionises aerosols (stuff suspended or "dissolved" in the atmosphere). Ionised aerosols attract water more readily than non-ionised aerosols, so clouds form more easily. Easier cloud formation means more cloud formation, and clouds relect light; in technical jargon, clouds increase the Earth's albedo, which means that if you have a lot of cloud cover over long periods, the atmosphere should, generally speaking, get cooler. So when the Earth is in one of the galactic arms, you get more exposure to galactic cosmic rays, which means more cloud cover which means lower global temperatures. And when the Earth is out in the galactic boondocks, you get less exposure to galactic cosmic rays, which means less cloud cover, which means higher global temperatures.
The authors of the article, Dr. Jan Veizer and Dr. Nir J. Shaviv, were able to show a 135 million year cycle of temperature increases and decreases. The evidence for the cycle came from analysing the fossilised remains of shellfish: lest this be taken as an invitation to Luddite skepticism its worth specifying that the analysis measured the concentration or relative quantity of Oxygen-18 in the fossilised shellfish. Let's assume, for the time being that the amount of oxygen with an atomic weight of 18 in a shellfish fossil reflects changes in global temperature. I doubt that reinforcing this by saying that I consider this perfectly plausible is going to work somehow: habitual irony has serious drawbacks when you're trying to make a serious statement for a change. Perhaps I should say that I don't consider it any less plausible than the accepted view that the speed of light is a physical constant that doesn't vary with distance from the Earth.
The case for galactic cosmic radiation as a driver of climate change, at least on geological timescales is largely made by statistical inference. Essentially, the authors are arguing that it's very likely that much of the climatic variation over the past 545 million years has been due to supernova activity, with only a 1.2% chance that the explanation is something else. In essence, arguing that the temperature cycle studied by Veizer and Shaviv was caused by something other than galactic cosmic radiation would be a little like backing a 100 to 1 outsider at Eagle Farm. That might be a sensible bet if the horse's name was Fine Cotton, but that's not the point of the analogy.
Does this finding shoot another big hole in the scientific basis for the Kyoto protocol? Veizer and Shaviv sound a couple of cautionary notes for anyone who wants to leap to this conclusion:
In summary, we find that with none of the CO2 reconstructions can the doubling effect of CO2 on low-latitude sea temperatures be larger than ~1.9 °C, with the expected value being closer to 0.5 °C. These results differ somewhat from the predictions of the general circulation models (GCMs) (IPCC, 2001), which typically imply a CO2 doubling effect of ~1.5–5.5 °C global warming, but they are consistent with alternative lower estimates of 0.6–1.6 °C (Lindzen, 1997).
As a qualifier, one should note that global temperature changes should exceed the tropical ones because the largest temperature variations are in the high-latitude regions for which we do not have any isotope record. A review of GCMs (IPCC, 2001) shows that the globally averaged warming from CO2 is expected to be typically 1.5 times larger than that of the tropical temperatures, and our model uncertainty limits should therefore be modified accordingly. [my emphasis]
As a final qualification, we emphasize that our conclusion about the dominance of the CRF over climate variability is valid only on multimillion year time scales. At shorter time scales, other climatic factors may play an important role, but note that many authors (see previous references) suggest a decisive role for the celestial driver also on multi-millennial to less than annual time scales. [my emphasis again]
Once again, it looks like the global warming debate hasn't been settled, despite the optimistic expectations of the global warming skeptics. At times like these, I like to remind myself that not only did the Montreal Accord finally get up, but according to the evidence that's now starting to emerge, the bloody thing worked. | 0.894242 | 3.589274 |
With its dense and hydrocarbon-rich atmosphere, Titan has been a subject of interest for many decades. And with the success of the Cassini-Huygens mission, which began exploring Saturn and its system of moons back in 2004, there are many proposals on the table for follow-up missions that would explore the surface of Titan and its methane seas in greater depth.
The challenges that this presents have led to some rather novel ideas, ranging from balloons and landers to floating drones and submarines. But it is the proposal for a “Dragonfly” drone by researchers at NASA’s JHUAPL that seems particularly adventurous. This eight-bladed drone would be capable of vertical-takeoff and landing (VTOL), enabling it to explore both the atmosphere and the surface of Titan in the coming decades.
The mission concept was proposed by a science team led by Elizabeth Turtle, a planetary scientist from NASA’s Johns Hopkins University Applied Physics Laboratory (JHUAPL). Back in February, the concept was presented at the “Planetary Science Vision 2050 Workshop” – which took place at NASA’s headquarters in Washington, DC – and again in late March at the 48th Lunar and Planetary Science Conference in The Woodlands, Texas.
Such a mission, as Turtle explained to Universe Today via email, is both timely and necessary. Not only would it build on many recent developments in robotic explorers (such as the Curiosity rover and the Cassini orbiter); but on Titan, there is simply no shortage of opportunities for scientific research. As she put it:
“Titan’s an ocean world with a unique twist, which is the rich and complex organic chemistry occurring in its atmosphere and on its surface. This combination makes Titan a particularly good target for studying planetary habitability. One of the big questions about the development of life is how chemical interactions led to biological processes. Titan’s been doing experiments in prebiotic chemistry for millions of years – timescales that are impossible to reproduce in the lab – and the results of these experiments are there to be collected.”
Their proposal is based in part on previous Decadal Surveys, such as the Campaign Strategy Working Group (CSWG) on Prebiotic Chemistry in the Outer Solar System. This survey emphasized that a mobile aerial vehicle (i.e an airship or a balloon) would well-suited to exploring Titan. Not only is Titan the only known body other than Earth that has a dense, nitrogen-rich atmosphere – four times as dense as Earth’s – but it’s gravity is also about 1/7th that of Earth’s.
However, balloons and airships would be unable to study Titan’s methane lakes, which are one of the most exciting draws as far as research into prebiotic chemistry goes. What’s more, an aerial vehicle would not be able to conduct in-situ chemical analysis of the surface, much like what the Mars Exploration Rovers (Spirit, Opportunity and Curiosity) have been doing on Mars.
As such, Turtle and her colleagues began looking for a proposal that represented the best of both worlds – i.e. an aerial platform and a lander. This was the genesis of the Dragonfly concept.
“Several different methods have been considered for in-situ aerial exploration of Titan (helicopters, different types of balloons, airplanes),” said Turtle. “Dragonfly takes advantage of the recent developments in multi-rotor aircraft to provide aerial mobility for a lander with a sophisticated payload. Because Dragonfly would be able to travel long distances – a few tens of kilometers at a time, and up to a few hundred kilometers over the course of the mission – it would be possible to make measurements at multiple sites with very different geologic histories.”
The mission is also in keeping with concepts that Turtle and her colleagues – which includes Ralph Lorenz (also from JHUAPL), Melissa Trainer of the Goddard Space Flight Center, and Jason Barnes of University of Idaho – have been exploring for years. In the past, they proposed a mission concept that would combine a Montgolfière-style balloon with a Pathfinder-like lander. Whereas the balloon would explore Titan from a low altitude, the lander would explore the surface up close.
By the 48th Lunar and Planetary Science Conference, they had officially unveiled their “Dragonfly” concept, which called for a qaudcopter to conduct both aerial and surface studies. This four-rotor vehicle, it was argued, would be able to take advantage of Titan’s thick atmosphere and low gravity to obtain samples and determine surface compositions in multiple geological settings.
In its latest iteration, the Dragonfly incorporates eight rotors (two positioned at each of its four corners) to achieve and maintain flight. Much like the Curiosity and upcoming Mars 2020 rovers, the Dragonfly would be powered by a Multimission Radioisotope Thermoelectric Generator (MMRTG). This system uses the heat generated by decaying plutonium-238 to generate electricity, and can keep a robotic mission going for years.
This design, says Turtle, would offer scientists the ideal in-situ platform for studying Titan’s environment:
“Dragonfly would be able to measure compositional details of different surface materials, which would show how far organic chemistry has progressed in different environments. These measurements could also reveal chemical signatures of water-based life (like that on Earth) or even hydrocarbon-based life, if either were present on Titan. Dragonfly would also study Titan’s atmosphere, surface, and sub-surface to understand current geologic activity, how materials are transported, and the possibility of exchange of organic material between the surface and the interior water ocean.”
This concept incorporates a lot of recent advances in technology, which include modern control electronics and advances in commercial unmanned aerial vehicle (UAV) designs. On top of that, the Dragonfly would do away with chemically-powered retrorockets and could power-up between flights, giving it a potentially much longer lifespan.
“And now is the perfect time,” says Turtle, “because we can build on what we’ve learned from the Cassini-Huygens mission to take the next steps in Titan exploration.”
Currently, NASA’s Jet Propulsion Laboratory is developing a similar concept. Known as the Mars Helicopter “Scout”, for use on Mars, this aerial drone is expected to be launched aboard the Mars 2020 mission. In this case, the design calls for two coaxial counter-rotating rotors, which would provide the best thrust-to-weight ratio in Mars’ thin atmosphere.
This sort of VTOL platform could become the mainstay in the coming decades, wherever long-term missions that involve bodies that have atmospheres are called for. Between Mars and Titan, such aerial drones could hop from one area to the next, obtaining samples for in-situ analysis and combining surface studies with atmospheric readings at various altitudes to get a more complete picture of the planet. | 0.898092 | 3.81947 |
A Portion of the Large Magellanic Cloud Taken by the Hubble TelescopeESA/NASA/HubbleOn Wednesday, an international team of scientists announced they had found the most convincing evidence yet that dark matter exists.
Dark matter makes up at least a quarter of our universe. It's the invisible stuff that holds our stars, galaxies, and clusters of galaxies together. The problem is, no one has ever been able to prove that it exists.
The latest results are not conclusive, but they provide better evidence than any previous experiments, MIT astrophysicist Samuel Ting said in a news conference. We are closer than ever to one of the secrets of the universe.
It all started in 1933 when Fritz Zwicky noticed something weird in a distant galaxy.
Zwicky, from the California Institute of Technology, noted a discrepancy between the mass of visible matter and the calculated mass of a galaxy cluster called the Cosizema cluster.
He calculated that the cluster had 400 times more mass than it should have had, based on what he saw with a telescope.
Zwicky also noticed that motion of the galaxies in the clusters was much too fast to be held together from the gravitational attraction created by visible matter alone.
The stars and galaxies would fly apart if there weren't some extra mass creating a gravitational effect that kept them together.
Zwicky theorized that there must be some invisible "dark matter" to explain his observations.
It took many many decades, however, for the world to warm up to Zwicky's theory. That's because dark matter is just that — dark. The mysterious substance does not emit or absorb light, or other forms of electromagnetic waves.
So finding concrete evidence of the elusive substance is incredibly difficult.
Although dark matter cannot be seen or touched, we can measure its gravitational effects.
Mass is measured by its gravitational effects on celestial bodies. The more massive something is, the stronger its gravitational pull. Gravity is the glue that holds our solar system, galaxies, and clusters of galaxies together.
Scientists know the mass of visible matter, like stars, dust, and gas, and that this mass would not create a strong enough gravitational attraction to keep stars and galaxies together. Thus, without the gravitational interactions created by some invisible mass, which we have named "dark matter," galaxies would fly apart as they whip around.
Dark matter is potentially made of very tiny, not-yet-identified particles.
Most cosmologists accept that dark matter is made of subatomic particles. But no one knows what those particles are.
The theory is that dark matter particles are everywhere, whipping in between stars and surrounding our milky way in a giant halo.
The next breakthrough was in 1950, courtesy of physicist Vera Rubin.
Vera Rubin, then a graduate student at Cornell University, saw that bodies at the furthest edges of galaxies didn't move more slowly than those at the center, as Newton's laws said they should.
She theorized that there must be something in the outskirts of galaxies that was causing these objects to move faster than expected. It had to be dark matter.
In 1973, two Princeton professors realized they needed dark matter to complete their model of the universe.
Every time Princeton physicists Jeremiah Ostriker and Jim Peebles tried to replicate the Milky Way using what scientists knew about our home galaxy, they failed. The simulations suggested there was more mass in the universe than accounted for.
Without this extra mass, the computer would spit out pictures of blobs or random shapes. Something crucial was missing.
The simulations suggested there was more mass in the universe than accounted for — this brought them back to the theory of dark matter.
The professors knew that if they added more matter — a LOT more matter — they could generate enough gravity to hold their model together.
They knew about Fritz Zwicky's observations 40 years earlier, so Ostriker and Peebles sat down at their computer and added dark matter to their model. It worked.
Vera Rubin popped back into the picture in the 1970s, offering more tantalizing evidence that we live in a sea of dark matter.
In 1978, building further on Zwicky's theory, Rubin and instrument maker Kent Ford found that single galaxies, not just clusters, had more mass than was visible.
Over the past decades, most scientists have been convinced that dark matter exists, although they have still not found any direct evidence of it.
The hunt continues to this day, using large particle colliders as well as underground and space-based detectors.
Particle detectors housed in a mine in North Yorkshire failed to shed light on how the universe is made.
Starting in 1987, a group of scientists from the United Kingdom used particle detectors located 3,600 feet underground in Boulby mine to learn more about dark matter.
The project wrapped up in 1997 with no conclusive results.
A telescope buried under the Antarctic Ice in 2010 has yielded similarly disappointing results, so far.
The IceCube detector at the South Pole records interactions of subatomic particles called neutrinos. Understanding the origins of these particles could reveal more information about dark matter.
So far, scientists have not detected any neutrinos that come from space.
Large particle colliders haven't produced any concrete evidence either.
Experiments at CERN's Large Hadron Collider, for example, try to produce dark matter particles by smashing other particles together.
Physicists could detect their existence from the amount of energy "missing" after a collision.
In 2008, a Russian-European spacecraft found the most compelling evidence yet that dark matter exists.
The PAMELA satellite, operated by Russia, Italy, Germany, and Sweden, detected an excess of positrons, the antimatter counterpart of electrons. The extra positrons, scientists believed, could be the result of two dark matter particles colliding and decaying, which would be indirect evidence that dark matter exists.
There was just one problem. If the positrons were originating from a larger dark matter particle, scientists would also expect the number of positrons to drop off at an energy level exceeding the maximum possible mass of dark matter particles. But they didn't see that.
The most convincing evidence that dark matter exists comes from a particle physics detector that was fixed to the outside of the International Space Station two years ago.
For the last two years, scientists have been collecting information about cosmic rays — charged particles flying around our universe — from an instrument on the International Space Station called the Alpha Magnetic Spectrometer.
The detector records the kinds of particles that pass through it, as well as their mass, speed, and direction of travel.
On April 3, 2013, scientists announced that they found the same excess of positrons as PAMELA had found a few years earlier. The difference is that this experiment is more precise than any previous experiment.
"AMS is the first experiment to measure to 1 percent accuracy in space," Nobel laureate Samuel Ting said in a statement released by CERN. "It is this level of precision that will allow us to tell whether our current positron observation has a dark matter or pulsar origin."
This latest news is exciting, but we shouldn't jump to conclusions. There could be another, simpler explanation for the excess of positrons.
The positrons could be the result of dark matter particles colliding and destroying each other.
There could also be a more mundane answer. They might just come from pulsars, collapsed stars that spew out charged particles as they rotate.
The good news is that scientists are more determined than ever to find the source of this antimatter signal. The AMS will continue to record data on the International Space Station, so every day we get closer to an answer.
And so, dark matter still remains one of the great mysteries of science.
"What we have shown today only represents less than 10 percent of the data," Ting said. With enough time, "there's no question we are going to solve this problem" he added.
Finding evidence of dark matter will provide us with a greater understanding of the nature of our universe.
Not all science is so complicated. | 0.868845 | 4.047849 |
Behold a star from the second generation of generation of stars after the Big Bang, something scientists have been seeking for a while. Its unique make-up may prove that our galaxy developed by cannibalizing dwarf galaxies.
In the dwarf galaxy Sculptor, this star is made out of the same material as the oldest stars in the Milky Way. The Harvard Center for Astrophysics found this beauty, and a press release explains:
"This star likely is almost as old as the universe itself," said astronomer Anna Frebel of the Harvard-Smithsonian Center for Astrophysics, lead author of the Nature paper reporting the finding.
Dwarf galaxies are small galaxies with just a few billion stars, compared to hundreds of billions in the Milky Way. In the "bottom-up model" of galaxy formation, large galaxies attained their size over billions of years by absorbing their smaller neighbors.
"If you watched a time-lapse movie of our galaxy, you would see a swarm of dwarf galaxies buzzing around it like bees around a beehive," explained Frebel. "Over time, those galaxies smashed together and mingled their stars to make one large galaxy - the Milky Way."
If dwarf galaxies are indeed the building blocks of larger galaxies, then the same kinds of stars should be found in both kinds of galaxies, especially in the case of old, "metal-poor" stars. To astronomers, "metals" are chemical elements heavier than hydrogen or helium. Because they are products of stellar evolution, metals were rare in the early Universe, and so old stars tend to be metal-poor.
Old stars in the Milky Way's halo can be extremely metal-poor, with metal abundances 100,000 times poorer than in the Sun, which is a typical younger, metal-rich star. Surveys over the past decade have failed to turn up any such extremely metal-poor stars in dwarf galaxies, however.
"The Milky Way seemed to have stars that were much more primitive than any of the stars in any of the dwarf galaxies," says co-author Josh Simon of the Observatories of the Carnegie Institution. "If dwarf galaxies were the original components of the Milky Way, then it's hard to understand why they wouldn't have similar stars."
The team suspected that the methods used to find metal-poor stars in dwarf galaxies were biased in a way that caused the surveys to miss the most metal-poor stars. Team member Evan Kirby, a Caltech astronomer, developed a method to estimate the metal abundances of large numbers of stars at a time, making it possible to efficiently search for the most metal-poor stars in dwarf galaxies.
"This was harder than finding a needle in a haystack. We needed to find a needle in a stack of needles," said Kirby. "We sorted through hundreds of candidates to find our target."
Among stars he found in the Sculptor dwarf galaxy was one faint, 18th-magnitude speck designated S1020549. Spectroscopic measurements of the star's light with Carnegie's Magellan-Clay telescope in Las Campanas, Chile, determined it to have a metal abundance 6,000 times lower than that of the Sun; this is five times lower than any other star found so far in a dwarf galaxy.
The researchers measured S1020549's total metal abundance from elements such as magnesium, calcium, titanium, and iron. The overall abundance pattern resembles those of old Milky Way stars, lending the first observational support to the idea that these galactic stars originally formed in dwarf galaxies.
You can download a supermassive version of the image over at the link. [Harvard Center for Astrophysics] | 0.815263 | 3.977856 |
Astrophysicists Discover ‘Compact Jets’ From Neutron Star
By Kim McDonald and Linda Vu
Compact jets that shoot matter into space in a continuous stream at near the speed of light have long been assumed to be a unique feature of black holes. But these odd features of the universe may be more common than once thought.
Astrophysicists using NASA's Spitzer Space Telescope recently spotted one of these jets around a super-dense dead star, confirming for the first time that neutron stars as well as black holes can produce these fire-hose-like jets of matter. A paper detailing their surprising discovery appears in this week’s issue of the Astrophysical Journal Letters.
"For years, scientists suspected that something unique to black holes must be fueling the continuous compact jets because we only saw them coming from black hole systems,” said Simone Migliari, an astrophysicist at the University of California, San Diego’s Center for Astrophysics and Space Sciences and the lead author of the paper. “Now that Spitzer has revealed a steady jet coming from a neutron star in an X-ray binary system, we know that the jets must be fueled by something that both systems share.”
A neutron star X-ray binary system occurs when a normal star orbits a dead star that is so dense all of its atoms have collapsed into neutrons, hence the name “neutron star.” The normal star circles the neutron star the same way Earth orbits the Sun.
Migliari and his colleagues from four institutions in the U.S. and Europe used Spitzer's super sensitive infrared eyes to study a jet in one such system called 4U 0614+091. In this system, the neutron star is more than 14 times the mass of its orbiting stellar companion.
|Artist concept shows jets of
shooting out from the neutron star.
NASA/JPL-Caltech/R. Hurt (SSC)
As the smaller star travels around its dead partner, the neutron star's intense gravity picks up material leaving the smaller star’s atmosphere and creates a disk around itself. The disk of matter, or accretion disk, circles the neutron star similar to the way rings circle Saturn. According to Migliari, accretion disks and intense gravitational fields are characteristics that black holes and neutron stars in X-ray binaries share.
“Our data show that the presence of an accretion disk and an intense gravitational field may be all we need to form and fuel a compact jet,” he said.
Typically, radio telescopes are the tool of choice for observing compact jets around black holes. At radio wavelengths, astronomers can isolate the jet from everything else in the system. However, because the compact jets of a neutron star can be more than 10 times fainter than those of a black hole, using a radio telescope to observe a neutron star's jet would take many hours of observations.
With Spitzer's supersensitive infrared eyes, Migliari's team detected 4U 0614+091's faint jet in minutes. The infrared telescope also helped astronomers infer details about the jet's geometry. System 4U 0614+091 is located approximately 10,000 light years away in the constellation Orion.
Other co-authors of the paper are John Tomsick of UCSD; Thomas Maccarone, Rob Fender and David Russell of the University of Southampton, UK; Elena Gallo of UC Santa Barbara; and Gijs Nelemans of the University of Nijmegen in the Netherlands.
NASA's Jet Propulsion Laboratory manages the Spitzer Space Telescope and science operations for the mission are conducted at the Spitzer Science Center at the California Institute of Technology.
Kim McDonald, UCSD, (858) 534-7572
Whitney Clavin, NASA's Jet Propulsion Laboratory, (818) 354-4673
Simone Migliari, (858) 822-3435 or (619) 277-8468/cell | 0.893694 | 3.987185 |
October 24, 2016 – Ten thousand volunteers viewing images of Martian south polar regions have helped identify targets for closer inspection, yielding new insights about seasonal slabs of frozen carbon dioxide and erosional features known as “spiders.”
From the comfort of home, the volunteers have been exploring the surface of Mars by reviewing images from the Context Camera (CTX) on NASA’s Mars Reconnaissance Orbiter and identifying certain types of seasonal terrains near Mars’ south pole. These efforts by volunteers using the “Planet Four: Terrains” website have aided scientists who plan observations with the same orbiter’s High Resolution Imaging Science Experiment (HiRISE) camera. HiRISE photographs much less ground but in much greater detail than CTX.
Volunteers have helped identify more than 20 regions in mid-resolution images to investigate with higher resolution. “It’s heartwarming to see so many citizens of planet Earth donate their time to help study Mars,” said HiRISE Deputy Principal Investigator Candice Hansen, of the Planetary Science Institute, Tucson, Arizona. “Thanks to the discovery power of so many people, we’re using HiRISE to take images of places we might not have studied without this assistance.”
Planetary scientist Meg Schwamb, of the Gemini Observatory, Hilo, Hawaii, presented results from the first year of this citizen science project last Thursday at the annual meeting of the American Astronomical Society’s Division for Planetary Sciences and the European Planetary Science Congress, in Pasadena, California.
The type of terrain called spiders, or “araneiform” (from the Latin word for spiders), is characterized by multiple channels converging at a point, resembling a spider’s long legs. Previous studies concluded that this ground texture results from extensive sheets of ice thawing bottom-side first as the ice is warmed by the ground below it. Thawed carbon dioxide gas builds up pressure, and the gas escapes through vents in the overlying sheet of remaining ice, pulling dust with it. This process carves the channels that resemble legs of a spider.
“The trapped carbon dioxide gas that carves the spiders in the ground also breaks through the thawing ice sheet,” Schwamb said. “It lofts dust and dirt that local winds then sculpt into hundreds of thousands of dark fans that are observed from orbit. For the past decade, HiRISE has been monitoring this process on other parts of the south pole. The 20 new regions have been added to this seasonal monitoring campaign. Without the efforts of the public, we wouldn’t be able to see how these regions evolve over the spring and summer compared with other regions.”
Some of the HiRISE observations guided by the volunteers’ input confirmed “spider” terrain in areas not previously associated with carbon dioxide slab ice.
“From what we’ve learned about spider terrain elsewhere, slab ice must be involved at the locations of these new observations, even though we had no previous indication of it there,” Hansen said. “Maybe it’s related to the erodability of the terrain.”
Some of the new observations targeted with information from the volunteers confirm spiders in areas where the ground surface is made of material ejected from impact craters, blanketing an older surface. “Crater ejecta blankets are erodible. Perhaps on surfaces that are more erodable, relative to other surfaces, slab ice would not need to be present as long, or as thick, for spiders to form,” Hansen said. “We have new findings, and new questions to answer, thanks to all the help from volunteers.”
The productive volunteer participation continues, and new CTX images have been added for examining additional areas in Mars’ south polar region. Planet Four: Terrains is on a platform released by the Zooniverse, which hosts 48 projects that enlist people worldwide to contribute to discoveries in fields ranging from astronomy to zoology. For information about how to participate, visit:
With CTX, HiRISE and four other instruments, the Mars Reconnaissance Orbiter has been investigating Mars since 2006.
Malin Space Science Systems, San Diego, built and operates CTX. The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp. of Boulder, Colorado. NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project NASA’s Science Mission Directorate, Washington. Lockheed Martin Space Systems of Littleton, Colorado, built the orbiter and collaborates with JPL to operate it. | 0.868447 | 3.656867 |
The path of comet 67P/Churyumov-Gerasimenko in October 2013
This image shows the path of 4-kilometre diameter comet 67P/Churyumov-Gerasimenko, last observed on 5 October 2013 by ESO's Very Large Telescope (VLT) when the comet was around 500 million kilometres away — before it passed behind the Sun and out of view from Earth's perspective.
Viewed against a crowded star field towards the centre of the Milky Way, the comet was still so far from the Sun that the icy nucleus was not releasing any gas or dust, and appeared as a simple spot (potw1403b). As it approaches the Sun, its surface will heat up and its ices will sublimate, dragging dust out to form a tail. This image shows the star field with the track of the comet marked with a line.
The observations mark the start of a close collaboration between ESA and ESO to monitor the comet from the ground during Rosetta's encounter with 67P/CG later this year. Rosetta was launched in 2004 and aims to explore the surface of the comet, deploying a lander down onto 67P/CG to see what its surface is like.
ESO, Colin Snodgrass (Max Planck Institute for Solar System Research, Germany).
About the Image
|Release date:||20 January 2014, 10:00|
|Size:||1000 x 1000 px|
About the Object | 0.810124 | 3.118548 |
The latest news about space exploration and technologies,
astrophysics, cosmology, the universe...
Posted: Jul 21, 2017
Flashes of light on the dark matter
(Nanowerk News) A web that passes through infinite intergalactic spaces, a dense cosmic forest illuminated by very distant lights and a huge enigma to solve. These are the picturesque ingredients of a scientific research – carried out by an international team composed of researchers from the International School for Adavnced Studies (SISSA) and the Abdus Salam International Center for Theoretical Physics (ICTP) in Trieste (Italy), the Institute of Astronomy of Cambridge and the University of Washington – that adds an important element for understanding one of the fundamental components of our Universe: the dark matter.
In order to study its properties, scientists analyzed the interaction of the “cosmic web” – a network of filaments made up of gas and dark matter present in the whole Universe – with the light coming from very distant quasars and galaxies. Photons interacting with the hydrogen of the cosmic filaments create many absorption lines defined “Lyman-alpha forest”.
This microscopic interaction succeeds in revealing several important properties of the dark matter at cosmological distances. The results further support the theory of Cold Dark Matter, which is composed of particles that move very slowly. Moreover, for the first time, they highlight the incompatibility with another model, i.e. the Fuzzy Dark Matter, for which dark matter particles have larger velocities.
Although constituting an important part of our cosmos, the dark matter is not directly observable, it does not emit electromagnetic radiation and it is visible only through gravitational effects. Besides, its nature remains a deep mystery. The theories that try to explore this aspect are various.
In this research, scientists investigated two of them: the so-called Cold Dark Matter, considered a paradigm of modern cosmology, and an alternative model called Fuzzy Dark Matter (FDM), in which the dark matter is deemed composed of ultralight bosons provided with a non-negligible pressure at small scales.
To carry out their investigations, scientists examined the cosmic web by analyzing the so-called Lyman-alpha forest. The Lyman-alpha forest consists of a series of absorption lines produced by the light coming from very distant and extremely luminous sources, that passes through the intergalactic space along its way toward the earth’s telescopes. The atomic interaction of photons with the hydrogen present in the cosmic filaments is used to study the properties of the cosmos and of the dark matter at enormous distances.
Through simulations carried out with supercomputers, researchers reproduced the interaction of the light with the cosmic web. Thus they were able to infer some of the characteristics of the particles that compose the dark matter.
More in particular, evidence showed for the first time that the mass of the particles, which allegedly compose the dark matter according to the FDM model, is not consistent with the Lyman-alpha Forest observed by the Keck telescope (Hawaii, US) and the Very Large Telescope (European Southern Observatory, Chile). Basically, the study seems not to confirm the theory of the Fuzzy Dark Matter. The data, instead, support the scenario envisaged by the model of the Cold Dark Matter.
The results obtained - scientists say - are important as they allow to build new theoretical models for describing the dark matter and new hypotheses on the characteristics of the cosmos. Moreover, these results can provide useful indications for the realization of experiments in laboratories and can guide observational efforts aimed at making progress on this fascinating scientific theme. | 0.869869 | 3.772603 |
Earth (from Old English: Eorðe; Greek: Γαῖα Gaia;[n 5] Latin: Terra), otherwise known as the World (especially in geopolitics and geography),[n 6] or the Globe, is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets.
According to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earth’s gravity interacts with other objects in space, especially the Sun and the Moon, Earth’s only natural satellite. During one orbit around the Sun, Earth rotates about its axis over 365 times; thus, an Earth year is about 365.26 days long.[n 7] Earth’s axis of rotation is tilted, producing seasonal variations on the planet’s surface. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earth’s orientation on its axis, and gradually slows its rotation.
Earth’s lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earth’s surface is covered with water, mostly by its oceans. The remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earth’s polar regions are covered in ice, including the Antarctic ice sheet and the sea ice of the Arctic ice pack. Earth’s interior remains active with a solid iron inner core, a liquid outer core that generates the Earth’s magnetic field, and a convecting mantle that drives plate tectonics.
Within the first billion years of Earth’s history, life appeared in the oceans and began to affect the Earth’s atmosphere and surface, leading to the proliferation of aerobic and anaerobic organisms. Some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earth’s distance from the Sun, physical properties, and geological history have allowed life to evolve and thrive. In the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that ever lived on Earth are extinct. Estimates of the number of species on Earth today vary widely; most species have not been described. Over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival. Humans have developed diverse societies and cultures; politically, the world has about 200 sovereign states. | 0.865984 | 3.358253 |
19 Feb 2010
Queen's astronomer Professor Alan Fitzsimmons and recent PhD graduate Dr. Sam Duddy are part of an international team that has been awarded over 80 nights at the European Southern Observatory to investigate the changing spin of asteroids.
The ability of asteroids to change the length of their day was only proved in 2007, by a team of astronomers lead by Queen's scientists. It is due to the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect, a force caused by sunlight heating up an irregularly shaped asteroid.
The YORP-effect can cause the asteroid to spin faster or slower and change its spin-axis orientation, explaining many observed phenomena in asteroidal science, such as the creation of binary asteroids. It also affects how the asteroid orbit changes, possibly moving it from a present-day safe path around the Sun to one that might impact the Earth in the far future.
“The precise speed at which YORP spins up and slows down will depend on the size, shape and current orientation.” explained Prof. Fitzsimmons. “It's a very small and difficult to measure effect over a human lifetime, but over tens or hundreds of thousands of years it can have dramatic consequences for the asteroid.”
To investigate this process in detail, the team have been given an astounding 72 nights on the 3.6m New Technology Telescope (NTT) and over 100 hours on the Very Large Telescope (VLT), to measure precisely the spin-rate of the asteroids, detect the tiny changes in period (a few microseconds per year), and measure the physical properties of the asteroids in detail.
In total four asteroids have been seen to exhibit the YORP effect, but uncertainties remain in predicting the magnitude of the effect. This programme, led by Dr. Stephen Lowry (University of Kent), is to monitor the spin rates of a large sample of near-Earth Asteroids with sizes from a few hundred metres to several km. Such a large sample will provide valuable constraints on asteroid surface and shape evolution models as well as models of spin-orbit interactions.
Astronomers in the Astrophysics Research Centre at Queen's will be spearheading the effort to measure the spectra of the asteroids to determine their composition, and also assisting in measuring the precise spin periods.
Prof. Fitzsimmons said “We're starting the observing programme in April, when I'll be spending 3 nights in at the ESO La Silla Observatory in Chile making the first observations. We can't wait to get started.” Team members include: Dr. Stephen Lowry (University of Kent); Professor Alan Fitzsimmons and Dr Samuel Duddy (Queen's University of Belfast); Dr Simon Green, Dr Stephen Wolters and Ben Rozitis (Open University); Dr Colin Snodgrass (Max Planck Institute for Solar System Research, Germany); and Dr Paul Weissman and Dr Michael Hicks (NASA's Jet Propulsion Laboratory, California, USA). | 0.866225 | 3.828331 |
Largest ever galaxy portrait — stunning HD image of Pinwheel Gala
This new Hubble image reveals the gigantic Pinwheel galaxy, one of the best known examples of “grand design spirals”, and its supergiant star-forming regions in unprecedented detail. The image is the largest and most detailed photo of a spiral galaxy ever released.
Giant galaxies weren’t assembled in a day. Neither was this Hubble Space Telescope image of the face-on spiral galaxy Messier 101 (the Pinwheel Galaxy). It is the largest and most detailed photo of a spiral galaxy beyond the Milky Way that has ever been publicly released. The galaxy’s portrait is actually composed from 51 individual Hubble exposures, in addition to elements from images from ground-based photos. The final composite image measures a whopping 16,000 by 12,000 pixels.
The Hubble observations that went into assembling this image composite were retrieved from the Hubble archive and were originally acquired for a range of Hubble projects: determining the expansion rate of the universe; studying the formation of star clusters in giant starbirth regions; finding the stars responsible for intense X-ray emission and discovering blue supergiant stars. As an example of the many treasures hiding in this immense image, a group led by K.D. Kuntz (Johns Hopkins University and NASA) recently catalogued nearly 3000 previously undetected star clusters in it.
The giant spiral disk of stars, dust and gas is 170,000 light-years across or nearly twice the diameter of our Milky Way. The galaxy is estimated to contain at least one trillion stars. Approximately 100 billion of these stars alone might be like our Sun in terms of temperature and lifetime. Hubble’s high resolution reveals millions of the galaxy’s individual stars in this image.
The Pinwheel’s spiral arms are sprinkled with large regions of star-forming nebulae. These nebulae are areas of intense star formation within molecular hydrogen clouds. Brilliant young clusters of sizzling newborn blue stars trace out the spiral arms. The disk of the galaxy is so thin that Hubble easily sees many more distant galaxies lying behind the foreground galaxy.
The Pinwheel Galaxy lies in the northern circumpolar constellation, Ursa Major (The Great Bear) at a distance of 25 million light-years from Earth. We are seeing the galaxy from Earth today as it was at the beginning of Earth’s Miocene Period when mammals flourished and the Mastodon first appeared on Earth. The galaxy fills an area on the sky of one-fifth the area of the full moon.
The newly composed image was assembled from archived Hubble images taken with the Advanced Camera for Surveys and the Wide Field and Planetary Camera 2 over nearly 10 years: in March 1994, September 1994, June 1999, November 2002 and January 2003. The Hubble exposures have been superimposed onto ground-based images, visible at the edge of the image, taken at the Canada-France-Hawaii Telescope in Hawaii, and at the 0.9-meter telescope at Kitt Peak National Observatory, part of the National Optical Astronomy Observatory in Arizona. Exposures taken through a blue filter are shown in blue, through a green filter in green and through a red filter in red.
Lars Christensen | alfa
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Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.
MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...
HZI researchers pave the way for new agents that render hospital pathogens mute
Pathogenic bacteria are becoming resistant to common antibiotics to an ever increasing degree. One of the most difficult germs is Pseudomonas aeruginosa, a...
Scientists from the MPI for Chemical Energy Conversion report in the first issue of the new journal JOULE.
Cell Press has just released the first issue of Joule, a new journal dedicated to sustainable energy research. In this issue James Birrell, Olaf Rüdiger,... | 0.842925 | 3.581696 |
“It has long been an axiom of mine that the little things are infinitely the most important.”
– Sherlock Holmes in “A Case of Identity’; a novel by Sir Arthur Conan Doyle
If you look out toward our galaxy the Milky Way you will see an uneven distribution of stars. In certain parts of the Milky Way, between the stars, things can get a little murky.
Holes in the Heavens
In the constellation of Sagittarius for example there are dark patches that become particularly noticeable towards the point of the Galactic Centre. It was the British astronomer William Herschel who, in the 18th Century, described these regions where starlight from distant stars appears to dim as “holes in the heavens”.
By the late 19th Century Edward Barnard had photographed the regions and reported vast cloud formations with a remarkable structure he described simply as lanes, holes and black gaps. Astronomers in the early 20th Century began to think of these regions in terms of viewing dark bodies of material rather than regions completely devoid of stars – a kind of cosmic fog.
Sir Fred Hoyle and Prof Chandra Wickramasinghe
The world renowned British astronomer Sir Fred Hoyle, who came from my home town of Bingley in West Yorkshire, and Professor Chandra Wickramasinghe, from Colombo in Sri Lanka, began looking at the nature of this cosmic fog.
In 1960, the same year Chandra Wickramasinghe began his postgraduate work under Sir Fred Hoyle at Cambridge University, the cosmic fog was believed to be made up of water‐ice particles.
The collaboration of Hoyle and Wickramasinghe would see them challenge not only the widely held view about the composition of the cosmic fog – which had become known as interstellar grains – but also the orthodox geocentric (Earth centred) theory of biology.
Their initial scepticism about the water‐ice theory was aroused when it became apparent that water‐ice would quickly evaporate away even in the cold depths of interstellar space. The question they asked was a simple question of identity. What were the interstellar grains composed of?
It was known that the grains were of a quantity that was as large as it could be, only if all the carbon, nitrogen and oxygen in interstellar space were actually contained in the dust grains. There was simply too much of it for it to be comprised of the next commonest elements found in interstellar space – magnesium and silicon.
The Road to Organic Carbon
By the mid 1970’s technological advances allowed measurements in both visible and infrared wavelengths to be made with ever increasing resolution. By 1974, after investigating a number of inorganic candidate materials without success, Hoyle and Wickramasinghe found that complex carbon‐based polymers – in particular, polysaccharides – appeared to provide the best match with the data they were seeing. However, it was at this point that the two astronomers inadvertently ran into trouble.
From their perspective, the molecules that comprised the majority of interstellar grains were simply the product of mineral chemical reactions. Radio astronomers had discovered other organic materials in interstellar space as early as 1937. However, on Earth polysaccharides (which include cellulose and starch) are predominantly of biological origin. Hoyle and Wickramasinghe had unwittingly crossed the line of a cultural taboo – mixing observational astronomy with biology.
Shortly after publishing this work Hoyle and Wickramasinghe began to experience hostility from journals referees and grant application assessors, making it increasingly difficult to continue and to promote their work. But continue they did.
A Biological Solution
Over a decade after starting out their investigation into interstellar grains Hoyle and Wickramasinghe had shown the presence of organic compounds formed the major component of the interstellar grains. They had a match for the spectroscopic data in the form of polysaccharides, and a solution to the light refraction properties in the form of hollow particles – all for grains of interstellar dust which just happened to be the size of typical bacteria.
The journal referees and grant application assessors who had been hostile before would soon be having kittens as Hoyle and Wickramasinghe began looking at dead and decaying bacteria as a solution to the nature of the interstellar grains.
Using existing library data for bacteria they calculated what the extinction of starlight for hollow particles would be and found an excellent fit to the astronomical data; one that had previously been unavailable with other theoretical models.
On the strength of this they had one of their colleagues measure the actual infrared properties of a number of different species of bacteria in the laboratory. To everyone’s surprise they found a remarkable consistency of the absorption profiles. The extinction of visible starlight seemed to suggest that bacteria could make up a significant amount of interstellar grains.
If this premise were true then the interstellar grains would need to have the characteristic absorption in the infrared spectrum that had been found for bacteria samples measured in the laboratory.
It wasn’t long before Chandra Wickramasinghe measured the infrared absorption properties of the interstellar grains that lay on a path from the Galactic Centre to the Earth. He found a remarkable correlation between this and the experimentally derived data.
Chemists with experience of Infrared Spectroscopy soon argued against the conclusion stating that the infrared results could be produced by a variety of non‐biological organic materials. Hoyle and Wickramasinghe had examined hundreds of infrared spectra of other materials at this point without success and so they were a little sceptical of the chemist’s certainty.
They asked the chemists to provide them with explicit examples of substances that could account for the observations. None were forthcoming with one possible exception of a claim to have yielded undefined “organic residues” that may possess only some of the desired properties.
The astronomers found that their work was being rejected – not using scientifically acceptable hypothesis testing – but simply as unfounded opposition due to a cultural bias against the nature of the claim.
Carl Sagan famously claimed in his 1980 book Cosmos that “extraordinary claims require extraordinary evidence”.
This quote is often cited by people attempting to justify rejection of ideas that they cannot reject evidentially. Ironically, the statement is itself an extraordinary claim as it is at odds with the accepted paradigm of using the scientific method; involving hypothesis testing with experimentation on falsifiable premises.
The theory of the biological solution to the interstellar dust had simply not been evidentially refuted. It was the strongest theory available for the nature of the interstellar dust.
“The arguments in support of life as a cosmic phenomenon are not readily accepted by a culture in which a geocentric theory of biology is seen as the norm” – Sir Fred Hoyle and Dr N. Chandra Wickramasinghe, Nature Vol. 322, 7 August 1986
A New Domain of Biology
Sir Fred Hoyle and Dr Chandra Wickramasinghe did not assume that the bacteria grew in interstellar space. Their working hypothesis was that the bacteria would likely be dead and in the process of decay.
They proposed that bacterial replication is a product of star formation in environments that are suitable for organisms to grow. After which bacteria are expelled into interstellar space.
They considered that the most likely place where bacteria could flourish would be within comets which, early in a solar systems history, would be heated by radioactive decay – providing a liquid water interior for extended periods of up to millions of years for giant comets. The proposed biomass of the cometary bodies in our own solar system would be more than a billion times the biomass of the Earth.
Only a tiny fraction of viable bacteria would need to survive being expelled into interstellar space in order to seed colonies in other star formations – such as our solar system.
According to NASA a viable strain of Streptococcus mitis was recovered after two years on the surface of the Moon. A little closer to home, bacteria have been found to survive outside of the International Space Station (ISS). Viable bacteria have been recovered from an operating nuclear reactor – where they were actually feeding on the steel in the reactor core.
Bacteria are hardy organisms that have been shown to have the ability to survive extremes of temperature and pressure without loss of viability. The ability of bacteria to survive extremely high doses of radiation and even to repair themselves in environments of continued high radiation are not traits that you would expect for organisms whose genesis and evolution was on the Earth. These are characteristics necessary for survival in space.
The return of comet Halley in 1986 provided an opportunity to test their hypothesis that microbial life exists in the solar system within comets. This premise required that particles ejected from the comets nucleus into the coma would include organic molecules. The existence of organics would refute the widely held premise that comets were simply ice and rock ‐ the “dirty snowball” model.
Using Earth baesed observations and data from the space probes Giotto (ESA) and Vega (Soviet) the dust from Comet Halley was found to be largely organic with about 90% of the comets surface covered by a dark inert material.
Infrared spectra of the comet recorded by the Giotto space probe showed spectra comparable to the bacterial model spectra. A study of comet dust published in the journal Nature rejected the idea that organic components where biological in nature because phosphorus ions (P+) were not detected by the on‐board mass spectrometer. However, Wickramasinghe discovered that the data matched phosphate ions (PO+, PO2+ and PO3+) showing that phosphorus was indeed present.
By the end of 1986 the cosmicrobial model had been shown to be the stronger model than the dirty snowball model. Although it required that astronomers avoid cherry‐picking the data to suit pre‐existing notions and allowed the possibility that life is not limited to the domain of planet Earth.
Carbonaceous chondrite meteorites are fragments of asteroids that have remained relatively unchanged since the formation of the solar system 4.6 billion years ago, and they are commonly found to contain organic compounds. A meteor of this type fell to Earth near the town of Murchison in the Australian outback in 1969.
When examined under a scanning electron microscope a freshly created fracture in fragments revealed complex structures with the appearance of blue‐green algae microfossils.
More recently in January 2013 the mainstream press reported on a study of a rock that fell to Earth in Sri Lanka on December 29th 2012. The specimen reportedly contained evidence of fossilised diatoms (algae) in a carbonaceous chondrite meteor.
This was of course refuted by some respectable scientists and other commentators alike. To date however, no one has refuted the claims by application of hypothesis testing. It would appear that they do not feel that they even need to employ the scientific method to refute something that, in their own world view, is simply not possible.
Incidence upon the Earth
From their initial discovery of bacteria in space, Sir Fred Hoyle and Dr Chandra Wickramasinghe began looking at incidents of diseases. They suggested that problems with the theories regarding person to person transmission of diseases are circumvented when the trigger for the disease originates from space. Diseases ranging from influenza to the bubonic plague, they argue, are examples of predominantly vertical incidence of viruses, viral particles and bacteria from space.
Regardless of what you believe about the moon landings, the outward appearance presented by NASA was that the Apollo astronauts returning to earth needed to be placed in quarantine in case they picked up a disease from space.
The incidence of extra‐terrestrial DNA on the Earth by viruses, according to Hoyle and Wickramasinghe, may solve the problems inherent in neo‐Darwinism when explaining how evolution takes great leaps forward, when the step by step approach doesn’t hold up mathematically.
The problem in essence is that neo‐Darwinian evolution involves a closed system where changes to DNA must occur stepwise and for the betterment of a species. Open that system up to beyond the Earth and new genetic material, originating within comets, can be introduced – not only to lifeless early Earth of 4.6 billion years ago – but periodically throughout the Earth’s history.
Viruses are known to insert their DNA into the DNA of host species – a process called antigenic shift. The suggestion is that contrary to neo‐Darwinian evolution, evolution on Earth may in effect be driven by receipt of new genetic material from space.
By Anthony Beckett B.Sc. (hons) M.Sc.
- First published in UFO Truth Magazine, 2014
- Professor Chandra Wickramasinghe presented a lecture on The Discovery of Extraterrestrial Life at the 5th Annual British Exopolitics Expo being held at The University of Huddersfield on Saturday September 28th, 2013.
- Life on Mars; Hoyle & Wickramasinghe;
- Diseases From Space; Hoyle & Wickramasinghe; 1976
- Lecture: The Discovery of Extraterrestrial Life by Prof Chandra Wickramasinghe; 5th Annual British Exopolitics Expo; 2013
© Anthony Beckett 2013 | 0.857699 | 3.874096 |
The Cassini spacecraft from NASA, which is currently orbiting the ringed planet Saturn, has observed clouds of Methane moving across the far northern areas of its moon Titan. Titan is the largest moon of Saturn. These images were captured in between October 29th and October 30th.
The movie, which is time lapse pictures which were taken every 20 minutes over a period of 11 hours by Cassini cameras. The clouds which occur in between 49 degrees and 55 degrees north latitude were most striking and prominent. The clouds move at a speed of 14 to 22 miles per hour. Most of the cloud streaks appear and then fade slowly.
Some clouds which were less prominent can be seen over the lakes further north and also includes a bright cloud in between Neagh Lacus and Punga Mare moving at a speed of 1 to 2 meters per second. Titan is the only moon in the solar system which has big lakes. However, the lakes are not like the lakes on our home planet and are composed of Methane and ethane which occurs as a gas on Earth.
This kind of time lapse photography helps astronomers understand the dynamics of atmosphere or the surface of distant heavenly bodies. It also contributes to discern between noises in images, which are caused by external radiations like galactic cosmic rays hitting the detector and faint clouds or fog.
Cassini has been observing the clouds for a long time. However, most of the pictures were taken at intervals which were days or even weeks apart. However, this is the first time that photos were taken at frequent and closely timed intervals making it easier for scientists to gauge the dynamics of these clouds. | 0.86164 | 3.293092 |
I honestly wish I knew more about astronomy. I have heard it said it may be the toughest field to be an expert in. Almost everyone has an IQ above 160. Competition is fierce apparently. What if we rethought black holes? Stephan Hawking apparently has. Some of his thoughts are very interesting.
“””””Black holes don’t actually exist in the way we traditionally think of them, renowned physicist Stephen Hawking has proposed in a short but potentially revolutionary paper.
Classical theory holds that no energy or information can ever escape a black hole, but the principles of quantum physics suggest it can. This contradiction has been the subject of debate among physicists for years. In the paper, “Information Preservation and Weather Forecasting for Black Holes,” Dr. Hawking proposes a solution to this paradox: instead of devouring information and energy permanently, black holes release it back into the universe in a garbled, unrecognizable form.
Traditionally, black holes were thought to contain an “event horizon,” a sharp boundary beyond which even light cannot escape the gravitational pull of the black hole’s infinitely dense core. Now Dr. Hawking proposes a shifting boundary, the “apparent” horizon, which fluctuates according to quantum effects.
“THERE ARE NO BLACK HOLES,” THE PAPER CONCLUDES
Among other implications, this new theory would have consequences for any astronaut who happened to fall into a black hole. According to quantum physics, the unlucky astronaut would immediately burn up in a “firewall” of intense radiation. Relativity, however, holds that the astronaut would be gradually pulled and stretched like pasta until being crushed at the black hole’s core. Hawking’s theory dispenses with the paradox because without an event horizon, there would be no firewall.”””””””
verge article on
Here is a link to Hawkins paper. It is fairly short.
Historical Black hole theory
“””””””The story starts in 1784, when a geologist named John Michell was thinking deeply about Isaac Newton’s theory of gravity. In Newtonian physics, a cannonball can be shot into orbit around the Earth if it surpasses a particular speed, known as the planet’s escape velocity. This speed depends on the mass and radius of the object you are trying to escape from. Michell’s insight was to imagine a body whose escape velocity was so great that it exceeded the speed of light – 300,000 kilometers per second – first measured in 1676 by the Danish astronomer Ole Romer.
Michell presented his results to other scientists, who speculated that massive “dark stars” might exist in abundance in the sky but be invisible because light can’t escape their surfaces. The French mathematician Pierre-Simon Laplace later made an independent discovery of these “dark stars” and both luminaries correctly calculated the very small radius – 6 kilometers – such an object would have if it were as massive as our sun.
After the revolutions of 20th century physics, black holes got much weirder. In 1916, a short while after Einstein published the complex equations underpinning General Relativity (which Einstein himself couldn’t entirely solve), a German astronomer named Karl Schwarzschild showed that a massive object squeezed to a single point would warp space around it so much that even light couldn’t escape. Though the cartoon version of black holes has them sucking everything up like a vacuum cleaner, light would only be unable to escape Schwarzschild’s object if it was inside a particular radius, called the Schwarzschild radius. Beyond this “event horizon,” you could safely leave the vicinity of a black hole.
Neither Schwarzschild nor Einstein believed this object was anything other than a mathematical curiosity. It took a much better understanding of the lives of stars before black holes were taken seriously. You see, a star only works because it preserves a delicate balance between gravity, which is constantly trying to pull its mass inward, and the nuclear furnace in its belly, which exerts pressure outward. At some point a star runs out of fuel and the fusion at its core turns off. Gravity is given the upper hand, causing the star to collapse. For stars like our sun, this collapse is halted when the electrons in the star’s atoms get so close that they generate a quantum mechanical force called electron degeneracy pressure. An object held up by this pressure is called a white dwarf.”””””
wired article on black hole theory in History
Afghanistan pullout seen as a peril to US drone mission
” I am not here… This isn’t happening”
Radiohead–How to disappear completely.
Apparently a big concern of pulling out the troops is we will lose use of airbases that we attack militants, women and children with. It seems like a smoke screen to me to be a concern of a pullout might affect something else. Why can we just not build more efficient drones that could take off from further away? Can’t we launch drones from Aircraft carriers or other bases in the Middle East? Hasn’t drone technology improved to the point they can almost fly 24 hours non stop? ( I believe the giant new Navy Drone can do that).
Can I say as matter of my opinion. Karzhi was one of the worst decisions that Bush, Cheney and Rumsfield ever had. In my estimation they had some seriously horrible decision blunders ( Patriot Act, NSA global surveillance, enhanced interrogation, rendition program! black site prisons—I could go on and on) but he is a train wreck that we backed, financed and trained.
“”””””WASHINGTON — The risk that President Obama may be forced to pull all American troops out of Afghanistan by the end of the year has set off concerns inside the American intelligence agencies that they could lose their air bases used for drone strikes against Al Qaeda in Pakistan and for responding to a nuclear crisis in the region.
Until now, the debate here and in Kabul about the size and duration of an American-led allied force in Afghanistan after 2014 had focused on that country’s long-term security. But these new concerns also reflect how troop levels in Afghanistan directly affect long-term American security interests in neighboring Pakistan, according to administration, military and intelligence officials.
The concern has become serious enough that the Obama administration has organized a team of intelligence, military and policy specialists to devise alternatives to mitigate the damage if a final security deal cannot be struck with the Afghan president, Hamid Karzai, who has declined to enact an agreement that American officials thought was completed last year.”””””
Times article discussing drones
NSA– pulling massive data from your apps.
If you follow this blog you know I am fascinated and repulsed to some degree what big brother… I mean the NSA is doing. Nothing would surprise me at this point. I personally use emails that are encrypted and have started using the TOR browser to remain secure on my iMac. I have nothing to hide but it is the point. Why make it easy for them to read you like a book… Somewhere they have a huge database about you, me and almost everyone on the planet.
“””””””””New leaked NSA documents shed a new light on the agency’s assault on the data leaked by smartphone apps. By targeting the app configuration data, the NSA and GCHQ are able to pull date ranging from general characteristics like age and ethnicity to specific location based on GPS. The documents outline multiple tactics for unearthing this data, including a direct tap on app configuration data and information sent to ad networks. Using app data permissions as a jumping off point, the NSA is able to pull any data advertisers have access to, plotting data collected in this manner against the Marina database of web-based metadata. The documents point out Angry Birds as an example of an ad-supported app that sends potentially useful data to ad networks, allowing the NSA to grab the data in transit.
“INTERCEPTING GOOGLE MAPS QUERIES MADE ON SMARTPHONES”
The documents also specifically instruct agency staffers in “intercepting Google Maps queries made on smartphones, and using them to collect large volumes of location information.” A 2010 documents also highlights Android phones as sending GPS information “in the clear” (without encryption), giving the NSA the user’s location every time he or she pulls up Google Maps.””””””””
verge article on apps being used massively by NSA
From the Guardian article
“””””””””The National Security Agency and its UK counterpart GCHQ have been developing capabilities to take advantage of “leaky” smartphone apps, such as the wildly popular Angry Birds game, that transmit users’ private information across the internet, according to top secret documents.
The data pouring onto communication networks from the new generation of iPhone and Android apps ranges from phone model and screen size to personal details such as age, gender and location. Some apps, the documents state, can share users’ most sensitive information such as sexual orientation – and one app recorded in the material even sends specific sexual preferences such as whether or not the user may be a swinger.
Many smartphone owners will be unaware of the full extent this information is being shared across the internet, and even the most sophisticated would be unlikely to realise that all of it is available for the spy agencies to collect.
Dozens of classified documents, provided to the Guardian by whistleblower Edward Snowden and reported in partnership with the New York Times and ProPublica, detail the NSA and GCHQ efforts to piggyback on this commercial data collection for their own purposes.
Scooping up information the apps are sending about their users allows the agencies to collect large quantities of mobile phone data from their existing mass surveillance tools – such as cable taps, or from international mobile networks – rather than solely from hacking into individual mobile handsets.
Exploiting phone information and location is a high-priority effort for the intelligence agencies, as terrorists and other intelligence targets make substantial use of phones in planning and carrying out their activities, for example by using phones as triggering devices in conflict zones. The NSA has cumulatively spent more than $1bn in its phone targeting efforts.
The disclosures also reveal how much the shift towards smartphone browsing could benefit spy agencies’ collection efforts.”””””””””””””
Guardian article outlining program | 0.81012 | 3.48505 |
Zothecula writes "A team of astronomers at The Australian National University working on a five-year project to produce the first comprehensive digital survey of the southern sky has discovered the oldest known star in the Universe. The star dates back 13.7 billion years, only shortly after the Big Bang itself. It's also nearby (at least, from a cosmological perspective) — about 6,000 light-years away. The star is notable for the very small amount of iron it contains (abstract). The lead researcher, Stefan Keller, said, 'To make a star like our Sun, you take the basic ingredients of hydrogen and helium from the Big Bang and add an enormous amount of iron – the equivalent of about 1,000 times the Earth's mass. To make this ancient star, you need no more than an Australia-sized asteroid of iron and lots of carbon. It's a very different recipe that tells us a lot about the nature of the first stars and how they died.'" | 0.825807 | 3.25815 |
A Close Encounter with Asteroid Eros
Listen to this story (requires RealPlayer)
"Although NEAR was very close to Eros -- the closest we've been before was about 35 km in July -- the spacecraft was never in any danger," says Andrew Cheng, the NEAR Shoemaker project scientist at Johns Hopkins University. "We chose to fly over an area of the southern hemisphere where, if we were off-target, the uneven gravity of the irregular asteroid would actually kick us back into a higher orbit." Compared to a commercial airliner flying hundreds of miles per hour above Earth, NEAR traveled slowly through Eros's weak gravitational field. Its maximum speed was only 14 miles per hour (23 kph).
Above: This image was taken in the early hours of October 26, 2000 as NEAR Shoemaker was skimming over the surface of Eros. Most of the 350-meter wide scene is covered in rocks of all sizes and shapes. The large boulder just below the center of the picture is about 15 meters (50 feet) wide. The smallest visible rocks are about 1.4 meters (5 feet) across. [more information]
The Johns Hopkins University Applied Physics Lab, which manages the NEAR mission for NASA, announced on Wednesday that the flyover had gone as planned and that the spacecraft was heading back to a higher orbit.
While the dangers from skimming so close to Eros were slight, the potential rewards were great.
On worlds that are peppered with impact scars (like the Moon or Mercury) there are always many small craters for each large one. That's true on Eros, too, but images of the asteroid collected during the first 8 months of the NEAR mission reveal fewer small craters than researchers expected. On Earth small impact scars wear away because of weather, but there is no weather on airless Eros. Some other process must be at work and scientists would like to know what it is.
"The high-resolution pictures we captured today will show these small scales very clearly," says Cheng. "They may give us some hints about what's going on."
While Eros seems to be running low on diminutive craters, it boasts a surprising surplus of boulders.
"Clark Chapman of the Southwest Research Institute has noticed that the surface of Eros is littered with 10- to 20-meter wide boulders, many more than we would expect [by simply extrapolating the number of large boulders to smaller sizes]," continued Cheng. "This is telling us that there's something funny about Eros's cratering history in the 'recent' geological past.
Above: Another image from NEAR Shoemaker's Oct. 26 low-altitude flyover of Eros. The large boulder near the bottom of the image is about 25 meters (82 feet) across. [more information]
"One possibility is that the cratering rate plummeted a billion or so years ago when Eros exited the main asteroid belt between Mars and Jupiter to become a near-Earth asteroid. After that, there may have been too few impacts to pummel these boulders into smaller pieces. These close-ups of Eros may tell us if the overabundance of 10-meter rocks extends to smaller sizes as well -- that would be an important clue."
Four months from now, NEAR Shoemaker will be poised to record an even closer view of Eros. "We're considering landing on the asteroid at the end of NEAR's one-year mission," says Cheng. "The spacecraft would touch down near the south pole of Eros where the rotational surface velocity is low."
Fans of Arthur C. Clark's science fiction novel "Rendezvous with Rama" might recall that explorers in that story landed near the pole of an asteroid-sized cylindrical spaceship, a spinning behemoth about the same size and shape as Eros. They chose to touch down near Rama's spin axis for the same reason that NEAR would settle near Eros's south pole; it's easier to land where the ground is moving slowly.
"NEAR was designed to orbit Eros, not to land on it," says Cheng. "Most of the science instruments won't even work so close to the asteroid's surface. We want to do this as a proof of concept, to show that a spacecraft can land on an asteroid." Future missions to explore and possibly return samples from the minor planets will depend on maneuvers that NEAR might soon try for the first time.
"Things could go wrong," Cheng stressed, like crashing into one of Eros's many boulders. But if NEAR touches down without mishap and can still communicate with Earth, scientists will enjoy a brief close-up of Eros that will make today's flyby seem remote by comparison.
For more information about asteroid Eros and the NEAR mission, please visit the Near-Earth Asteroid Rendezvous mission home page at http://near.jhuapl.edu. The Johns Hopkins University Applied Physics Laboratory in Laurel, MD, designed and built the NEAR spacecraft and manages the mission for NASA.Web Links
Near Earth Asteroid Rendezvous mission - NEAR home page from Johns Hopkins University Applied Physics Laboratory
Square Craters -- NASA's NEAR Shoemaker spacecraft has spotted square-shaped craters on asteroid Eros, a telltale sign of mysterious goings-on in the asteroid belt long ago.
Asteroids Have Seasons, Too - Later this week, the Sun will rise over the south pole of asteroid Eros, revealing unexplored terrain to the instruments on NASA's NEAR-Shoemaker spacecraft.
collide with Earth.[More]
Guess Who's Coming to Breakfast? - February 13, 2000. SpaceScience.com. Critical science observations of Eros are scheduled to begin 11 hours before NEAR's orbit insertion on Valentines Day, 2000.
First Orbit Around an Asteroid - February 14, 2000. SpaceScience.com. NEAR successfully entered orbit around 433 Eros on Valentines Day, 2000
Highlights from Asteroid Eros - February 19, 2000. SpaceScience.com. Scientists review exciting results from the first few days in orbit.
Wanted: a few good solar flares - March 3, 2000. SpaceScience.com. Solar radiation could reveal new details about Eros
NEAR Shoemaker -- Mar. 14, 2000. SpaceScience.com. NASA has renamed the Near Earth Asteroid Rendezvous (NEAR) spacecraft for planetary science pioneer Gene Shoemaker.
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|For lesson plans and educational activities related to breaking science news, please visit Thursday's Classroom||Author: Dr. Tony Phillips
Production Editor: Dr. Tony Phillips
Curator: Bryan Walls
Media Relations: Steve Roy
Responsible NASA official: Ron Koczor | 0.837471 | 3.602354 |
Sen—You wouldn't think it would be so hard to find water on a comet. There's no question that they're substantially composed of water ice; you can see the stuff clearly in comet tails. But seen up close, comets are not obviously icy. In fact, theirs are among the darkest surfaces in the Solar System.
Churuyumov-Gerasimenko is among these incredibly dark comets. It doesn't look that way in Rosetta's pictures because the comet is the only thing around other than the blackness of empty space. Command your camera to expose the scene for the ambient brightness, and you can see lots of detail on the surface, as well as plumes of comet material spreading into space, as shown on the main image.
Occasionally, a very dark icy world in the Solar System will have some small patches of exposed ice. When your spacecraft camera exposes the scene properly to see the mostly dark surface of the world, the bright patches can saturate the detector, washing out any detail. That's exactly what's going on with the Dawn images of the bright spots on Ceres.
We know there has to be ice close to Churyumov-Gerasimenko's surface, but no Ceres-like bright patches have been visible. So it was news, today, to see these newly published images from OSIRIS, the high-resolution science camera on Rosetta, showing bright patches of material exposed on the comet's surface. As a bonus, they're in color!
Examples of icy bright patches cropped from OSIRIS images of Comet 67P/Churyumov-Gerasimenko during September 2014. The two left hand images were acquired on Sep. 5, 2014; the right hand images were acquired on Sep. 16, 2014. During this time the spacecraft was about 30 to 40 kilometers from the comet. The images are false colour red-green-blue composites assembled from monochrome images acquired at different times with the 882.1nm (red), 649.2nm (green) and 360.0nm (blue) channels. Each channel was stretched and slightly saturated to emphasis the contrasts of colour across the scene such that dark terrains appear redder and bright regions appear significantly bluer compared with what a human eye would normally see. Image credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
The OSIRIS team reports 120 detections of bright material on the comet. These bright patches are not as bright as the ones on Ceres; the text accompanying the images states that they are "up to ten times brighter than the average surface brightness." Previously, Rosetta has reported a six per cent albedo for the comet. A 50 to 60 per cent albedo is darker than pure ice; if these patches are ice, they are still mixed with some dirty material.
Don't just look at the bright patches in these images. Look, too, at the distinctly reddish material around it. That knobbly red dark material is the dominant comet surface. It is what looks so brightly reflective in the NavCam image shown at the top of this post. What a difference a contrast adjustment makes!
The OSIRIS images show that the bright material occurs in boulders, either piles of boulders or isolated chunks. Boulder piles occur at the bases of cliffs; isolated chunks can be anywhere. All of them are in places where they are shadowed for much of the comet's day.
Example of a cluster of bright spots on Comet 67P/Churyumov-Gerasimenko found in the Khepry region (top) and an individual boulder with bright patches on its surface in the Hatmehit region (bottom). The bright patches are thought to be exposures of water-ice. Image credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
These patterns give clues to how the icy material was exposed—and why it's rare on the surface. Piles at cliff bases suggest that recent erosion—the collapse of a cliff wall—has exposed fresh material from the interior of the comet. Isolated boulders are erratics, things that originated elsewhere and were transported to their current locations, likely flung out by cometary activity. Wherever the stuff fell, it was protected by shadow from sublimation. One month's observations by OSIRIS didn't show any obvious changes to any of the patches.
The activity of the comet is keeping the spacecraft at a distance for now, but it's a productive time for the Rosetta instruments that are devoted to studying the icy materials that the comet is jetting into space. MIRO, the Microwave Instrument for the Rosetta Orbiter, has produced a beautiful map of the distribution of water in the comet's coma. Each of the little squiggles represents an average of several individual spectra. Wherever MIRO sees the coma against black space, a characteristic hump in the spectra identifies water molecules emitting radiation; wherever MIRO sees the coma against the comet, a dip in the spectra identifies water molecules absorbing radiation.
Image credit: ESA / N. Biver et al. (2015)
The comet is approaching perihelion now, and is outgassing like crazy. It's likely that the patches that OSIRIS saw will have changed by the time that Rosetta can see them up close again. Rosetta will definitely have the opportunity; ESA has just announced an official extension of the mission for a year, until September 2016. | 0.818522 | 3.787337 |
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The search for Earth-like planets explainedHow close are we to finding alien life? CNET contributor Boonsri Dickinson visits Geoff Marcy's lab at the University of California at Berkeley to hunt for Earth-like planets. Using the Keck telescope in Hawaii and data from the Kepler telescope, Marcy...
-So, as you may notice, it's a little dark outside. It's supposed to be that way 'cause I'm here at the Berkeley campus and I'm gonna go looking for Earth-like planets. Now, I'm just waiting for him to get here. -Kudos, let's go inside. -Okay. -And here's the Remote Observing facility itself. This is Keck I and Keck II. These telescopes are located up high atop a hopefully dormant volcano called Mauna Kea at 14,000 feet. Well, some would say they are the world's best telescopes. You can see pictures of them here. Keck I and Keck II. These telescopes have a mirror that collects the light from the stars and galaxies, and the mirror is 10 meters in diameter. That's 1-tenth the size of a football field, and these mirrors are polished smooth to a parabolic shape to within 1 fraction of a wavelength of light. So, they're enormous mirrors practically the size of football fields. They're polished smooth to collect the light, bring it to a focus. And then what we do is we bring that light not to an eyepiece, but instead, we send the light into a spectrometer, which is a fancy word for prism. And the spectrometer spreads the white light of the star into all of its colors, blue, green, yellow, and red, and we can analyze those wavelengths of light, the colors of the rainbow to measure various properties of the stars. The most important thing is to try to detect planets. We're trying to find small Earth-size planets around nearby stars, stars that are within a few tens of light years of the Earth. And we're also studying stars that have been studied by the Kepler telescope, which is a space-borne telescope and its job is specifically to find Earth-size planets that dim their stars as the Earth cross in front blocking the starlight time and again and again. And so, we're studying the stars that the Kepler telescope has already indicated to us probably have planets. We're trying to verify if they have planets and measure the masses to see if they are truly Earth-size planets, but we found planets. In 1995, a wonderful astronomer in Geneva, Michel Mayor, found the first planet around the star, 51 Pegasi, and then our team found a lot of planets and ever since then, we found hundreds of planets. It's really been just an incredible change for Science, maybe you might even say a change in the way humans view ourselves and our place in the universe because we now know that our Earth and our solar system that goes around the Sun is not unique; there are other planetary systems out there; in fact, billions of them. And so, one of the things we are trying to do is find other Earth-like planets. This is Barnard's Star. This star is the second closest star to us here at the Earth. There's the Sun; there's Alpha Centauri and its system, and then Barnard's Star. So this is an extraordinary star. It's only-- I forgotten now exactly-- It's something like 5 or 6 light years away. You could almost throw a stone. You could pop over to Barnard's Star and borrow a cup of sugar assuming you didn't need the sugar for 700,000 years. The coordinates, the telescopes pointed there now. There's the star right there. The white dot is the star. And see a little black stripe right down the middle of the star? That's the entrance slit of the spectrometer into which the light is passing. And so the light goes into that slit and goes into the spectrometer where the white light gets spread out into all of its colors, blue, green, yellow and red and we analyze them. And that's what shows up over here. This is the actual spectrum and you can kind of see, while you can't really see the colors, but this is sort of a black and blue, white version of the rainbow of colors, and we're monitoring how much light comes from the star at each color, then we analyze that to measure the Doppler effect and the Doppler effect, if it changes with the star, that tells us that it has a planet. -When he was a graduate student, he asked this bold question. Can we find other planets that go around other Suns? He's actually found more than 70 of these extrasolar planets. -And a wonderful privilege and a lucky ride because we thought we wouldn't find any planets. And I thought for many years we would never find any planets and most other people thought we would never find any planets; so, I feel, you know, really lucky that we've been able to find lots of planets, big ones like Jupiter and small ones like nearly the size of the Earth. -I just got down searching for Earth-like planets, and it was super awesome. It puts our place in the universe into perspective. | 0.871966 | 3.114297 |
When observed through a telescope, many stars will actually turn out to be pairs of stars that are situated very close to one another. Such stars are known as physical binary stars. Binary stars rotating around each other are a common phenomenon. It is estimated that for every 100 stars, 30 are a part of a binary system, and 23 are a part of multiple systems. Some of the binary stars went through evolution as a pair and developed simultaneously, others became a pair as a result of one star capturing another during close approach. (This frequently occurs in ball clusters and the central regions of galaxies).
Kepler's third law describes the rotation of binary system components:
| (m1+m2)T 2 ||= || A3 |
|(M+m)P 2 ||a3 |
Where m1 and m2 are masses of two stars rotating with a period T, and A is the major semi-axis of the stars' orbits. Masses Ì and m are masses of the Sun and the Earth, and P = 1 year, while à is the distance from the Earth to the Sun.
If components of a star system are situated close to each other, they may overshadow each other from observer on the Earth. In this case, we will witness an occurrence of fluctuations in the total brightness of a binary star.
This model demonstrates just such a phenomenon. The left-side window shows two stars (blue and yellowish) that revolve around a common center of gravity. You may select one of two systems from the list in the top right corner (AR Lacerta or Algol), or set your own parameters for the system of binary stars. Such parameters primarily comprise the masses of system components m1 and m2, and the distance between them (in astronomical units.) Such values, subject to change through appropriate input windows, fully determine the system's motion, including its period of revolution as indicated below.
Visual Angle parameter determines the angular value of the binary system plane slope in respect to the observer. For example, the angular value of AR Lacerta and Algol is equal to 0? in the "side view" mode. In this case, the stars sometimes overshadow each other from an observer on the Earth, and system brightness varies.
Brightness fluctuations over time are shown on the bottom-left diagram. A vertical line designates the system's current status (it appears once you press "Run" button). When we observe the binary star plane at full circumference (that is, when the angle of observation is equal to 90?), components do not obscure each other and no fluctuations take place (In fact, interference ceases to manifest at a much steeper angle. Try to experiment with the input window and determine the angle of observation at which interference stops.)
Use "Show Orbit" switch to make stellar rotation more visible. Pressing "Stop" button will bring the model to a halt. Press "Reset" to return the model to its initial state. | 0.888254 | 4.026999 |
The Curiosity Rover has taken up a new hobby: astrophotography. Not content to merely photograph cool Martian rocks, the rover has captured the first image of an asteroid as seen from the surface of Mars. Nicely done, Curiosity!
Ceres is a monster of an asteroid at 950 kilometers diameter, large enough to qualify as a dwarf planet. Vesta is just barely smaller, the third-largest asteroid belt object at 563 kilometers wide. The asteroids also share a common NASA mission: the Dawn spacecraft orbited Vesta in 2011 and 2012, and is currently underway to orbit Ceres in 2015.
The photograph was taken on April 20, 2014, or Curiosity sol 606. The night-sky image captures one of the Marian moons, Deimos, in addition to the pair of asteroids Ceres and Vesta. Later that night, Curiosity as photographed the other moon, Phobos, with the planets Jupiter and Saturn. Both images are combined in one massive composite with differing exposure times, insets of images captured by other cameras, and very handy annotations:
From the NASA press release:
In the main portion of the image, Vesta, Ceres and three stars appear as short streaks due to the duration of a 12-second exposure. The background is detector noise, limiting what we can see to magnitude 6 or 7, much like normal human eyesight. The two asteroids and three stars would be visible to someone of normal eyesight standing on Mars. Specks are effects of cosmic rays striking the camera's light detector.
Three square insets at left show Phobos, Jupiter and Saturn at exposures of one-half second each. Deimos was much brighter than the visible stars and asteroids in the same part of the sky, in the main image. The circular inset covers a patch of sky the size that Earth's full moon appears to observers on Earth. At the center of that circular inset, Deimos appears at its correct location in the sky, in a one-quarter-second exposure. In the unannotated version of the 12-second-exposure image, the brightness of Deimos saturates that portion of the image, making the moon appear overly large. | 0.837882 | 3.316399 |
Following its latest close flyby of Jupiter – passing just 4,200 km (2,600 mi) above the gas giant’s cloud tops on February 2nd, 2017, NASA’s Juno mission spacecraft is now heading away from the planet once more and the next of its 53.5 day orbits. As I’ve previously reported in these Space Sunday columns, the original plan had been to use one of these close passes over the planet (October 2016), in conjunction with a sustained burn of the spacecraft’s British-built rocket motor, to move it into a short, 14-day period orbit around Jupiter.
However, a potential fault detected within the engine system meant the October burn was cancelled, and since then, engineers had been trying to assess if the issue – a set of faulty valves – could be overcome, and the consequences of attempting an additional engine burn if not. No definitive answer has been found and so, following the February 2nd flyby, the decision was taken to cancel all plans for the engine burn and leave the spacecraft in its current 53.5 day orbit around Jupiter.
Doing so doesn’t compromise the overall mission objectives, but it does reduce the number of close passes over Jupiter the vehicle can make. If the reduced orbital period had been possible, the spacecraft would have made some 30 close flybys over Jupiter’s cloud tops during the primary mission period, set to end in July 2018. Remaining in the 53.5 day orbit means it will only make around 12 such close flybys in the same period.
A positive point with the spacecraft remaining in its more extended orbit is that it will spend less time within the harsher regions of Jupiter’s radiation belts, and could thus remain active for longer than the primary mission period – and mission planners are already considering applying for further funding to allow the mission to extend beyond July 2018. It also means that the spacecraft will be able to engage in additional science activities.
The close encounters with Jupiter have already allowed the spacecraft to probe deep within the planet’s cloud belts and discover they extend far deeper into the planet’s atmosphere than had been imagined, and that Jupiter’s magnetic field and auroras are more powerful than previously thought.
“Juno is providing spectacular results, and we are rewriting our ideas of how giant planets work,” Juno principal investigator Scott Bolton, of the South-west Research Institute in San Antonio, Texas, said of the decision to leave the spacecraft in its current orbit. “The science will be just as spectacular as with our original plan.”
NASA Considering Crewed Option for Orion / SLS First Launch
NASA is considering making the first launch of its new Space Launch System (SLS) rocket, currently slated for September 2018, a crewed mission.
Under the agency’s existing plans, the first launch of the new rocket, topped by an Orion Multi-Purpose Crew Vehicle and dubbed Exploration Mission 1 (EM-1), would have seen SLS send an uncrewed Orion vehicle to the Moon and back, with around 6 days spent in lunar orbit. A crewed flight of the SLS / Orion combination would not take place until at least 2021, when crew would use Orion to rendezvous to a small asteroid previously captured via robotic means and moved to an extended orbit around the Moon – an idea which has garnered a certain amount of criticism from politicians.
If approved, the new proposal – put forward by NASA’s Acting Administrator, Robert Lightfoot – would see the planned EM-1 mission pushed back to 2019 (allowing the Orion vehicle to be outfitted with the crew lift support and flight systems) and flown with a crew of two. While this would mean a delay in the initial launch of SLS / Orion, it could ultimately accelerate NASA’s plans, allowing the agency to present a wider choice of crewed missions in the 2020s, and respond to criticism that it is not doing enough to demonstrate how it plans to achieve a return to the Moon and / or missions to Mars.
Enceladus: Cradle for Life?
On February 17th, 2005 NASA’s Cassini space probe, part of the Cassini / Huygen mission, made its first flyby of Saturn’s moon Enceladus.
Scientists were naturally curious about the 500 km (360 mi) diameter moon, which is the most reflective object in the solar system, but assumed it was essentially a dead, airless world. However, Cassini immediately found this was not the case.
The first thing that happened was the magnetometer on the spacecraft revealed that Saturn’s magnetic field, which envelops Enceladus, was perturbed above the moon’s south pole in a way that didn’t make sense for an inactive world – it was as if there was some interaction with an atmosphere.
In the second flyby, a month later, Cassini found the interaction seemed to suggest a plume of water vapour was rising from the moon. Then, in the third flyby, in July 2005, the probe imaged geysers of water vapour erupting from the moon’s south polar region, and thus Enceladus became the target of intense study. So much so, that while only those initial 3 flybys of the moon had been a part of the primary Cassini /Huygens mission profile, the mission was updated to allow 20 more flyby of the moon.
Today, we know that beneath the mantle of ice enclosing Enceladus there is an ocean of liquid water – the geysers are the results of that water breaking through this ice and jetting into space, giving rise to Saturn’s E-ring in the process. This ocean is likely to be warmed and kept liquid by hydrothermal vents on the sea floor, and these in turn – just like the vents theorised to be on the ocean floor of Jupiter’s Europa – might provide all the ingredients for basic life to arise.
To celebrate the 12th anniversary of Cassini’s discoveries with Enceladus, NASA has released a video documenting those initial findings from 2005.
SpaceX Inaugurates New Era for KSC Pad 39A
One Sunday, February 19th, and after a 24-hour delay, the SpaceX Cargo ReSupply mission 10 (CRS-10), lifted off from Pad 39A at Kennedy Space Centre (KSC), Florida, marking the first tim that the spaceport’s historic Launch Complex 39 had been used since the retirement on the space shuttle in 2011.
The landmark launch complex, home to every Apollo and space shuttle mission, comprises two major paunch facilities: Pad 39A and Pad 39B. The latter will be home to launches for America’s new Space Launch System, while Pad 39A was leased to SpaceX in 2014, and the company has spent 3 years converting it for use with their Falcon 9 and soon-to-fly Falcon Heavy rockets. Eventually, the company hope to use the pad in conjunction with their facilities at the neighbouring Canaveral Air Force Station to make a Falcon launch every three weeks.
Lifting off for CRS-10, which will rendezvous with the International Space Station some time on February 21st or 22nd, occurred at 14:38:59 UTC. It will deliver just over two tonnes of supplies and science experiments to the station. The weather wasn’t great for viewing the launch, but SpaceX did live stream it, and shortly afterwards they issued a shorter video featuring the rocket’s lift-off, and the entire return from space of the first stage, which culminated in a safe touch-down at the SpaceX Landing Zone 1 at Canaveral Air Force Station (formerly Launch Complex 13). It’s a remarkable piece to watch.
Dawn Discovers Building Blocks of Life on Ceres
The joint NASA / ESA Dawn mission to Ceres, which has featured in previous Space Sunday reports, has revealed startling evidence that the “protoplanet”, which the space vehicle has been observing since March 2015, contains some of the building blocks of Life. The discovery of aliphatic compounds on the surface of Ceres was made by an international team of scientists who have been reviewing data from the Visible and Infra-red Mapping Spectrometer (VIMS) aboard the spacecraft.
Aliphatics are a type of organic compound where carbon atoms form open chains that are commonly bound with oxygen, nitrogen, sulphur and chlorine. They were initially identified in a region roughly 1,000 sq km (386 sq mi) region around Ernutet crater in Ceres’ northern hemisphere. Following the initial discovery, the science team investigated whether the molecules might have been deposited from an external source, such as a comet or carbonaceous chondrite asteroid, but could not find any evidence of this being the case.
Instead, their location on the crater floor, around its rim and in ejecta surrounding the crater suggests they originated within Ceres, a hypothesis supported by smaller traces of the compounds being found around Inamahari Crater, about 400 km (250 mi) from Ernutet.
Their discovery is significant, as they further suggest that organic molecules exist within Ceres, beneath its icy mantle. If so, it might mean that basic life could exist within the protoplanet’s liquid interior in a way that is similar to Jupiter’s Europa and Enceladus, (see above). Further, given that Ceres is believed to have originated 4.5 billion years ago (when the solar system was still in the process of formation), the discovery of the compounds is also significant in that it can shed light on the origin, evolution, and distribution of organic life in the solar system.
Dream Chaser To Fly Hubble Repair Mission?
I’ve previously written about Sierra Nevada Corporation’s (SNC) Dream Chaser mini-shuttle. Originally designed – but not chosen by NASA – to fly crews to / from the International Space Station, it now being developed as a cargo resupply vehicle to help maintain the ISS (see here and here). However, SNC recently put forward a proposal to use the crew variant of the vehicle to fly a servicing mission to the Hubble Space Telescope (HST).
Hubble’s work is largely expected to be overtaken by the James Webb Space Telescope (JWST – (see here and here for an overview of the mission), although Hubble should be able to remain operational through to at least 2030, barring major failures. JWST is due for launch in 2018, but it is an ambitious mission. Not only is the telescope not designed to be serviced / repaired in space, it will also operate in the Sun / Earth L2 position, approximately 1.5 million km (930,000 mi) beyond the Earth, relative to the Sun. Thus, there are fears that if anything goes wrong once it is in operation, or during its launch and 160-day deployment, and if HST is not maintained, Earth could be left without an orbital observatory.
Thus, SNC believe they can offer an insurance policy in offering to fly a potential servicing mission to Hubble, although the idea is not without significant issues of its own. For one thing, Hubble is designed specifically to be serviced within the cargo bay of a space shuttle, where logistics are far easier to manage, and astronauts can use suitable servicing platforms, including the shuttle’s own robotic arm. The much smaller Dream Chaser offers none of these capabilities.
This makes any repair mission an exceptionally complex affair, requiring the astronauts to work without any means to anchor themselves, while also maintaining the Dream Chaser in close proximity to HST to ease the transfer of equipment and tools, but not so close as to risk damage to the telescope. It’s also not clear precisely how far SNC have continued to develop their crewed version of Dream Chaser since the vehicle was dropped from NASA’s Commercial Crew Transportation System programme, or what would be required to bring it up to a status where such a mission could realistically be undertaken.
NASA has yet to provide feedback on the proposal, Although it is understood the idea was also put before the Trump team responsible for handling NASA’s transition to management by the new administration. | 0.867201 | 3.395758 |
United States National Radio Quiet Zone
Date: November 19, 1958
Location: West Virginia, Virginia, and a small part of Maryland.
The National Radio Quiet Zone (NRQZ) is a large area of land in the United States in which radio transmissions are strongly restricted by law, to facilitate scientific research and military intelligence.
The barrage of noise and distractions that are all but inescapable in most American communities is refreshingly absent in this unassuming hamlet, located in the wooded hills of Pocahontas County, 4 hours west of Washington, D.C. Here, no cell phones chirp or jingle, and local kids aren't glued to the glowing screens of their mobile devices. Older residents roll down their car windows to greet each other and leave their front doors unlocked.
But Green Bank, population 143, isn't a technological backwater. On the contrary, it is the proud home of one of the marvels of the space age: the Robert C. Byrd Green Bank Telescope, or GBT for short. Towering nearly 500' above its wide, green valley, with a dish large enough to cradle a football field, the GBT is the world's biggest fully steerable radio telescope, and one of the largest movable objects anywhere on land. Locals jokingly refer to it as the Great Big Thing.
The GBT and other radio telescopes enable astronomers to detect and study objects in space that give off little visible light but emit naturally occurring radio waves objects such as pulsars, gas clouds, and distant galaxies.
Because of its vast size and sophisticated design, the GBT is exquisitely sensitive to even the faintest radio pulses coming from space. For the same reason, it is also extremely susceptible to electronic interference. Any device that generates electromagnetic radiation: a cell phone, a television, a wireless Internet router, can skew its data. And so the people who live in these parts must, by law, forego some of the gadgets that most of us take for granted.
Those restrictions began in the 1950s, when the Federal Communications Commission created the National Radio Quiet Zone, a 13,000 square mile swath of sparsely populated countryside that straddles the borders of West Virginia, Virginia, and Maryland. Use of the airwaves inside the zone is strictly regulated to ensure that the high tech telescopes at Green Bank and nearby Sugar Grove can operate with minimal disturbance.
Astronomers first tilted the GBT's giant ear toward the stars in 2000, and the cosmic whispers they've been hearing ever since have yielded insights into the nature of the universe.
Recently, the GBT contributed to a staggering discovery:
Our Milky Way galaxy is situated in a supercluster of galaxies 500 million light years in diameter, with a mass of 100 million billion suns.
Another project currently under way uses the GBT to search the skies for primordial gas that formed as the universe cooled. Site director says maps of the gas, used in conjunction with computer models, can help determine where theories of the creation and evolution of the universe are correct and where they may need revision.
The GBT also recently detected a hydrogen cloud hurtling toward the Milky Way at 150 miles a second, predicted to crash into our galaxy in about 30 million years. | 0.855839 | 3.213215 |
Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In other words, if the axis of rotation of a body is itself rotating about a second axis, that body is said to be precessing about the second axis. A motion in which the second Euler angle changes is called nutation. In physics, there are two types of precession: torque-free and torque-induced.
In astronomy, precession refers to any of several slow changes in an astronomical body's rotational or orbital parameters. An important example is the steady change in the orientation of the axis of rotation of the Earth, known as the precession of the equinoxes. (See section Astronomy below.)
Torque-free precession implies that no external moment (torque) is applied to the body. In torque-free precession, the angular momentum is a constant, but the angular velocity vector changes orientation with time. What makes this possible is a time-varying moment of inertia, or more precisely, a time-varying inertia matrix. The inertia matrix is composed of the moments of inertia of a body calculated with respect to separate coordinate axes (e.g. x, y, z). If an object is asymmetric about its principal axis of rotation, the moment of inertia with respect to each coordinate direction will change with time, while preserving angular momentum. The result is that the component of the angular velocities of the body about each axis will vary inversely with each axis' moment of inertia.
The torque-free precession rate of an object with an axis of symmetry, such as a disk, spinning about an axis not aligned with that axis of symmetry can be calculated as follows:
where ωp is the precession rate, ωs is the spin rate about the axis of symmetry, Is is the moment of inertia about the axis of symmetry, Ip is moment of inertia about either of the other two equal perpendicular principal axes, and α is the angle between the moment of inertia direction and the symmetry axis.
For a generic solid object without any axis of symmetry, the evolution of the object's orientation, represented (for example) by a rotation matrix R that transforms internal to external coordinates, may be numerically simulated. Given the object's fixed internal moment of inertia tensor I0 and fixed external angular momentum L, the instantaneous angular velocity is
Precession occurs by repeatedly recalculating ω and applying a small rotation vector ω dt for the short time dt; e.g.:
for the skew-symmetric matrix [ω]×. The errors induced by finite time steps tend to increase the rotational kinetic energy:
this unphysical tendency can be counteracted by repeatedly applying a small rotation vector v perpendicular to both ω and L, noting that
Another type of torque-free precession can occur when there are multiple reference frames at work. For example, Earth is subject to local torque induced precession due to the gravity of the sun and moon acting on Earth's axis, but at the same time the solar system is moving around the galactic center. As a consequence, an accurate measurement of Earth's axial reorientation relative to objects outside the frame of the moving galaxy (such as distant quasars commonly used as precession measurement reference points) must account for a minor amount of non-local torque-free precession, due to the solar system’s motion.
Torque-induced precession (gyroscopic precession) is the phenomenon in which the axis of a spinning object (e.g., a gyroscope) describes a cone in space when an external torque is applied to it. The phenomenon is commonly seen in a spinning toy top, but all rotating objects can undergo precession. If the speed of the rotation and the magnitude of the external torque are constant, the spin axis will move at right angles to the direction that would intuitively result from the external torque. In the case of a toy top, its weight is acting downwards from its center of mass and the normal force (reaction) of the ground is pushing up on it at the point of contact with the support. These two opposite forces produce a torque which causes the top to precess.
The device depicted on the right (or above on mobile devices) is gimbal mounted. From inside to outside there are three axes of rotation: the hub of the wheel, the gimbal axis, and the vertical pivot.
To distinguish between the two horizontal axes, rotation around the wheel hub will be called spinning, and rotation around the gimbal axis will be called pitching. Rotation around the vertical pivot axis is called rotation.
First, imagine that the entire device is rotating around the (vertical) pivot axis. Then, spinning of the wheel (around the wheelhub) is added. Imagine the gimbal axis to be locked, so that the wheel cannot pitch. The gimbal axis has sensors, that measure whether there is a torque around the gimbal axis.
In the picture, a section of the wheel has been named dm1. At the depicted moment in time, section dm1 is at the perimeter of the rotating motion around the (vertical) pivot axis. Section dm1, therefore, has a lot of angular rotating velocity with respect to the rotation around the pivot axis, and as dm1 is forced closer to the pivot axis of the rotation (by the wheel spinning further), because of the Coriolis effect, with respect to the vertical pivot axis, dm1 tends to move in the direction of the top-left arrow in the diagram (shown at 45°) in the direction of rotation around the pivot axis. Section dm2 of the wheel is moving away from the pivot axis, and so a force (again, a Coriolis force) acts in the same direction as in the case of dm1. Note that both arrows point in the same direction.
The same reasoning applies for the bottom half of the wheel, but there the arrows point in the opposite direction to that of the top arrows. Combined over the entire wheel, there is a torque around the gimbal axis when some spinning is added to rotation around a vertical axis.
It is important to note that the torque around the gimbal axis arises without any delay; the response is instantaneous.
In the discussion above, the setup was kept unchanging by preventing pitching around the gimbal axis. In the case of a spinning toy top, when the spinning top starts tilting, gravity exerts a torque. However, instead of rolling over, the spinning top just pitches a little. This pitching motion reorients the spinning top with respect to the torque that is being exerted. The result is that the torque exerted by gravity – via the pitching motion – elicits gyroscopic precession (which in turn yields a counter torque against the gravity torque) rather than causing the spinning top to fall to its side.
Precession is the result of the angular velocity of rotation and the angular velocity produced by the torque. It is an angular velocity about a line that makes an angle with the permanent rotation axis, and this angle lies in a plane at right angles to the plane of the couple producing the torque. The permanent axis must turn towards this line, because the body cannot continue to rotate about any line that is not a principal axis of maximum moment of inertia; that is, the permanent axis turns in a direction at right angles to that in which the torque might be expected to turn it. If the rotating body is symmetrical and its motion unconstrained, and, if the torque on the spin axis is at right angles to that axis, the axis of precession will be perpendicular to both the spin axis and torque axis.
Under these circumstances the angular velocity of precession is given by:
where Is is the moment of inertia, ωs is the angular velocity of spin about the spin axis, m is the mass, g is the acceleration due to gravity and r is the perpendicular distance of the spin axis about the axis of precession. The torque vector originates at the center of mass. Using ω = 2π/, we find that the period of precession is given by:
The special and general theories of relativity give three types of corrections to the Newtonian precession, of a gyroscope near a large mass such as Earth, described above. They are:
- Thomas precession a special relativistic correction accounting for the observer's being in a rotating non-inertial frame.
- de Sitter precession a general relativistic correction accounting for the Schwarzschild metric of curved space near a large non-rotating mass.
- Lense–Thirring precession a general relativistic correction accounting for the frame dragging by the Kerr metric of curved space near a large rotating mass.
In astronomy, precession refers to any of several gravity-induced, slow and continuous changes in an astronomical body's rotational axis or orbital path. Precession of the equinoxes, perihelion precession, changes in the tilt of Earth's axis to its orbit, and the eccentricity of its orbit over tens of thousands of years are all important parts of the astronomical theory of ice ages. (See Milankovitch cycles.)
Axial precession (precession of the equinoxes)
Axial precession is the movement of the rotational axis of an astronomical body, whereby the axis slowly traces out a cone. In the case of Earth, this type of precession is also known as the precession of the equinoxes, lunisolar precession, or precession of the equator. Earth goes through one such complete precessional cycle in a period of approximately 26,000 years or 1° every 72 years, during which the positions of stars will slowly change in both equatorial coordinates and ecliptic longitude. Over this cycle, Earth's north axial pole moves from where it is now, within 1° of Polaris, in a circle around the ecliptic pole, with an angular radius of about 23.5°.
Hipparchus is claimed to be the earliest known astronomer to recognize and assess the precession of the equinoxes at about 1° per century (which is not far from the actual value for antiquity, 1.38°). Caltech's Swerdlow disputes Hipparchus's knowledge of precession because Hipparchus apparently did not necessarily indicate anything like a motion of the entire sphere of the fixed stars with respect to the equinoxes. The precession of Earth's axis was later explained by Newtonian physics. Being an oblate spheroid, Earth has a non-spherical shape, bulging outward at the equator. The gravitational tidal forces of the Moon and Sun apply torque to the equator, attempting to pull the equatorial bulge into the plane of the ecliptic, but instead causing it to precess. The torque exerted by the planets, particularly Jupiter, also plays a role.
The orbits of planets around the Sun do not really follow an identical ellipse each time, but actually trace out a flower-petal shape because the major axis of each planet's elliptical orbit also precesses within its orbital plane, partly in response to perturbations in the form of the changing gravitational forces exerted by other planets. This is called perihelion precession or apsidal precession.
In the adjunct image, the Earth apsidal precession is illustrated. As the Earth travels around the Sun, its elliptical orbit rotates gradually over time. The eccentricity of its ellipse and the precession rate of its orbit are exaggerated for visualization. Most orbits in the Solar System have a much smaller eccentricity and precess at a much slower rate, making them nearly circular and stationary.
Discrepancies between the observed perihelion precession rate of the planet Mercury and that predicted by classical mechanics were prominent among the forms of experimental evidence leading to the acceptance of Einstein's Theory of Relativity (in particular, his General Theory of Relativity), which accurately predicted the anomalies. Deviating from Newton's law, Einstein's theory of gravitation predicts an extra term of A/, which accurately gives the observed excess turning rate of 43″ every 100 years.
The gravitational force between the Sun and moon induces the precession in Earth's orbit, which is the major cause of the climate oscillation of Earth that has a period of 19,000 to 23,000 years. It follows that changes in Earth's orbital parameters (e.g., orbital inclination, the angle between Earth's rotation axis and its plane of orbit) is important to the study of Earth's climate, in particular to the study of past ice ages. (See also nodal precession. For precession of the lunar orbit see lunar precession).
|Wikimedia Commons has media related to Precession.|
- Schaub, Hanspeter (2003), Analytical Mechanics of Space Systems, AIAA, pp. 149–150, ISBN 9781600860270, retrieved 1 May 2014
- Boal, David (2001). "Lecture 26 – Torque-free rotation – body-fixed axes" (PDF). Retrieved 2008-09-17.
- Teodorescu, Petre P (2002). Mechanical Systems, Classical Models. Springer. p. 420.
- DIO 9.1 ‡3
- Swerdlow, Noel (1991). On the cosmical mysteries of Mithras. Classical Philology, 86, (1991), 48-63. p. 59.
- Bradt, Hale (2007). Astronomy Methods. Cambridge University Press. p. 66. ISBN 978 0 521 53551 9.
- Max Born (1924), Einstein's Theory of Relativity (The 1962 Dover edition, page 348 lists a table documenting the observed and calculated values for the precession of the perihelion of Mercury, Venus, and Earth.)
- An even larger value for a precession has been found, for a black hole in orbit around a much more massive black hole, amounting to 39 degrees each orbit.
|Wikibooks has a book on the topic of: Rotational Motion| | 0.907851 | 4.013824 |
Gamma-ray bursts were first detected in 1967, but scientists didn’t know what they were. It wasn’t until 1971 that astronomers identified these phenomenon as gamma-ray bursts (GRBs).
What are gamma-ray bursts? Why do they occur? Is there any predictable pattern to their appearance? These questions and many others have been under study by leading scientists and astronomers over the past 30 years.
Scientists know what GRBs are: flashes of gamma-ray light. What they don’t know is what causes them. Scientists are working on two primary theories, with the acknowledgement that a third possibility also exists.
Hypernova (a super-supernova): A star has run out of fuel and this results in the creation of a black hole. In the process, the core of the star collapses and the outer shell explodes outward, releasing energy as a gamma-ray burst.
Binary System: Remains of two exploded neutron stars, which previously exploded as supernovae, orbit each other. They lose energy and spiral inward. When they get close, gravity smashes them into each other, forming a black hole. We detect the energy released as a gamma-ray burst.
Unknown: Scientist acknowledge the possibility that gamma-rays bursts may be caused by another factor that has not yet been considered or might not yet be discovered.
Gamma-ray bursts are violent explosions. They occur throughout the universe, and not just in our Milky Way galaxy as first believed. They occur two to three times a day at random places in our sky. The bursts are thousands of times brighter than a supernova. GRBs are beamed in tight little jets of energy instead of being sprayed in all directions.
GRBs can be in one of two categories: Short – lasting 2 seconds or less, or Long – lasting up to a minute or longer. The two types differ in more ways than just their duration. Spectroscopically, short bursts have more high-energy gamma rays than their counterparts do. According to Scientific American (December 2002), every time a gamma-ray burst occurs, a black hole is born.
Swift is a satellite designed by Penn State researchers and launched by NASA to study gamma-ray bursts. Launched in November of 2005, the satellite was named after the swift, a small, quickly moving bird. Catching a GRB is no easy task. The burst can appear from any direction without warning and can last for only a few milliseconds to just over a minute. So, the satellite has to move quickly and be in position to capture the data. According to NASA, no other satellite turns faster. In addition to GRBs, Swift searches and records other phenomena it observes in the sky.
The Swift satellite is comprised of three telescopes: the Burst Alert Telescope (BAT); the X-ray Telescope (XRT); and the Ultraviolet/Optical Telescope (UVOT). The BAT detects and locates the GRBs. Once one is identified, Swift repositions itself so that the other two telescopes can collect data on the afterglow of the burst. All the data is transmitted to earth and is available publicly within 30 minutes of the GRB detection. | 0.823606 | 4.095486 |
by Staff Writers
San Diego CA (SPX) Aug 31, 2012
Astronomers at the International Astronomical Union meeting announced the discovery of the first transiting circumbinary multi-planet system: two planets orbiting around a pair of stars. The discovery shows that planetary systems can form and survive even in the chaotic environment around a binary star. And such planets can exist in the habitable zone of their stars.
"Each planet transits over the primary star, giving unambiguous evidence that the planets are real," said Jerome Orosz, Associate Professor of Astronomy at San Diego State University and lead author of the study which is published in the journal Science.
The system, known as Kepler-47, contains a pair of stars whirling around each other every 7.5 days. One star is similar to the Sun while the other is a diminutive star only one third the size and 175 times fainter.
The inner planet is only 3x larger in diameter than the Earth, making it the smallest known transiting circumbinary planet. It orbits the stellar pair every 49 days.
The outer planet is slightly larger than Uranus and orbits every 303 days, making it the longest-period transiting planet currently known. More importantly, its orbit puts it in the "habitable zone", the region around a star where a terrestrial planet could have liquid water on its surface.
While the planet is probably a gas-giant planet and thus not suitable for life, its discovery establishes that circumbinary planets can, and do, exist in habitable zones.
Although much more difficult to detect than planets around single stars, the rich dynamics and wild climate changes make these circumbinary planets worth the effort to find. These two planets join the elite group of 4 previously known transiting circumbinary planets, Kepler-16, 34, 35 and 38.
The new planetary system is located roughly 5000 light-years away, in the constellation Cygnus. The planets are much too far away to see, so they were discovered by the drop in brightness they cause when they transit (eclipse) their host stars.
The loss of light caused by the silhouette is tiny, only 0.08% for planet b and 0.2% for planet c. By comparison, Venus blocked about 0.1% of the Sun's surface during its recent transit.
Precise photometric data from NASA's Kepler space telescope allowed the transits and eclipses to be measured, which in turn provided the relative sizes of the objects.
Spectroscopic data from telescopes at McDonald Observatory in Texas enabled the absolute sizes to be determined. "Based on their radii, these probably have masses of approximately 8 and 20 times that of the Earth," Orosz said.
"Kepler-47 shows us that typical planetary architectures, with multiple planets in co-planar orbits, can form around two stars," said co-author Joshua Carter, a Hubble Fellow at the Harvard-Smithsonian Center for Astrophysics.
"We've learned that circumbinary planets can be like the planets in our own Solar System, but with two suns."
The work was presented at the International Astronomical Union meeting by Dr. William Welsh, Professor of Astronomy at San Diego State University, on behalf of the Kepler Science Team.
"The thing I find most exciting," said Welsh, "is the potential for habitability in a circumbinary system. Kepler-47c is not likely to harbor life, but if it had large moons, those would be very interesting worlds."
Funding for this work was provided in part by NASA and the National Science Foundation. "Kepler-47: A Transiting Circumbinary Multi-planet System" by J. A. Orosz, et al. is published on-line in Science Express here.
San Diego State University
Lands Beyond Beyond - extra solar planets - news and science
Life Beyond Earth
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At apogee it has an angular diameter of 29.3 minutes — at perigee, 34.1'
Earth has an aphelion of 152,098,232 km and a perihelion of 147,098,290 km.
At aphelion, the Sun has an angular diameter of 31.6' — at perihelion, 32.7'.
Here's a sort of ASCII-graphics visual aid:
29 30 31 32 33 34 minutes of arc
(I realize that this could go seriously adrift for readers with non-standard browser settings, or who are reading this on their wristwatches.)
For almost half its orbit, toward the apogee end, the Moon is apparently smaller than the Sun. For about a third of its orbit, toward the perigee, it appears larger. For the rest of the time the angular diameters of the two bodies are essentially identical. More competent people than you and me have found that rather amazing.
So what does that mean for solar eclipses? Well, that depends on whether you are A) a trained astronomer or otherwise educated and sane person, or B) Mike Bara.
If you're in Group A, you would say that when the Moon is in the apogee half of its orbit, a solar eclipse cannot ever reach totality because the apparent size of the Moon ain't enough to mask the Sun. Instead you have the rather spectacular effect of an annular eclipse.
If you're in Group B, however, you would disagree. You'd say that an annular eclipse happens when the Moon is near perigee.
Since Mike Bara's automatic response to any criticism of his writings and lectures is "I never said that," the question has to be, "Did Mike Bara write the following on page 214 of The Choice, or didn't he?
"An annular eclipse means that the Moon and Sun are in perfect alignment, but the Sun is not totally blotted out because the Moon is a little too close to the Earth." | 0.804159 | 3.356378 |
ROCKET PROPULSION SYSTEMS
This week I will be discussing space propulsion systems, our way of reaching the stars. I will try not to get too technical as to not lose interest. Today I will discuss the current technology and what we have used in the past. Back around the end of WWII, rockets were being developed by the Germans. Operation Paperclip allowed us to use that technology in developing jet engines, which changed the speed of flight as we know it. All current propulsion systems use biopropellents or solid fuel. Most satellites use simple, reliable chemical thrusts. They consist of a fuel tank, usually made of Titanium or Aluminum. The tank is then pressurized with Helium or Nitrogen. These engines are often small, and require occasional corrections t o compensate being in orbit a long time.
In space, the purpose of a propulsion system is to change velocity. The more massive a craft is, the harder it is to do this. The rate of velocity is called acceleration, and the rate of momentum is called force. The four major components of propulsion are:
This is also referred to a launch pad. The frame is what is used to launch the craft to its required trajectory.
This can be anything that is carried on a spacecraft, such as people, supplies, satellites or probes.
This is what operates the craft, and includes sophisticated sensors, on board computers, radars, and communication systems. The two main roles of the guidance system are stability and control.uel
The function of the propulsion is to provide thrust. I’m sure that we’ve all heard the third rule of Newton’s law: To every action there is a equal and opposite reaction. This simply means, that a spaceship needs enough thrust to negate the force which is putting upon it, which is gravity. The less gravity needed, the less thrust. We saw this on the moon with the LEM. There was not a lot of thrust needed to leave the moon because there is very little gravity, if any.
Rocket engines use fuel and an oxidizer, which are mixed and exploded in a combustion chamber. There are two types of rockets used today-liquid and solid fuel. In liquid rockets, the fuels are stored separately in individual chambers and combined in a combustion chamber, where the chemical reaction occurs and causes an explosion. In solid rockets, propellents are mixed together and packed into a solid cylinder. It is burned when a source of heat lights it, such as an igniter. Liquid fuels are able to be controlled by valves that can control the flow. Solid rockets don’t have this and must all be burned at once.
Rocket systems are slow and cumbersome in the world of space travel, but right now they’re all we have. Using a conventional rocket, it would take 500 days to reach Mars, and 10,000 yrs to reach the nearest star. The amount of fuel it would have to carry would make it virtually impossible to get there. The enormous size of the engines would dwarf anything that we have had in the past, and the astronauts would be subjected to long periods of solitude, inactivity, and exposed to lethal levels of radiation. NASA is currently working on ION propulsion systems,nuclear fusion, and nuclear fission , which will be tomorrow’s topic. Until then, here are today’s links:
NUCLEAR AND ION PROPULSION
Nuclear and ion propulsion systems are not new. Nuclear systems date back to the beginning of the twentieth century. Nuclear fission was first used in warships and submarines during and after WWII. Small nuclear reactors are used in a contained vessel. Several proposed nuclear rocket systems have been in the works since the 1950’s, but due to later nuclear treaties and concern about fallout, they were abandoned. There are several ideas NASA has come up with, but rockets would have to be built in space,, due to radiation concerns. One is using anti-matter catalyzed nuclear pulse propulsion, and another is external pulsed plasma propulsion, where there are small thrusts from plasma waves generated from a series of small super critical fission and fusion pulses behind the object in space. Biomodal nuclear thermal rockets are similar to the power plants in submarines.
Fusion rockets could provide efficient and long term acceleration in space without the need to carry a large fuel supply. The advantages of fusion power would be that the impulse would be very high, allowing less energy to initiate a thrust, and would also produce less radiation. The disadvantages are the large mass of the reactor, and the actual spacecraft would be much larger and more complex than anything currently developed. Although still a concept, if developed, it could propel a spacecraft to Mars is just 90 days, and the nearest star in forty years. Ram jet fusion allows the craft to gather energy from space itself and theoretically would never need refueling.
Ion propulsion is a form of electrical propulsion that creates thrust by accelerating ions by the use of plasma. Ions pass through an electromagnetic grid engine, and converts it to kinetic energy. This does not produce enough energy for escape velocity, however, and is only used in space, where only small thrust is needed. Orbiting satellites and space probes use this technology. As the thrusts are initiated, the spacecraft picks u p speed. This is the slowest form of space propulsion and is inefficient for long journeys. It would take months to even reach the moon using this method.
In my book, Jeff Walker’s race, the Martians use these methods of travel, but have not yet left their own star system. One day we will achieve this travel, and it may be our key to finding out how to colonize Mars and other moons around planets within our own back yards. Tomorrow, we will discuss propulsion straight out of science fiction-Antimatter and Warp drives, which allows travel up to and beyond the speed of light. Until then, here are the links for today:
ANTI-MATTER & WAR DRIVES
When I was a kid, a fantastic and unbelievable show came out called Star Trek. It was based on ideas that were far out and outlandish to say the least, but nonetheless, I was captivated by the show. Even at a young age, its ideas and method of travel fascinated me. It seemed that they could go anywhere in the galaxy in a matter of days, weeks, or months. Although it was science fiction then, Gene Roddenberry based his ideas for the show on real theories developed by Albert Einstein. The ship’s engines used a combined propulsion system based on antimatter and warp drive. But are these ideas even feasible?
The answer theoretically is yes. In an antimatter drive engine, the electrical charges of antimatter particles are reversed, and form a positive charge instead of a negative charge. When the two particles meet, they create an explosion that produces pure energy, electromagnetic radiation that spreads outward at the speed of light. This energy produces 10 million times the energy produced by conventional chemical rockets, 1000 times the energy produced in an atomic bomb, and 300 times the energy than a nuclear fusion engine. The problem of antimatter rocket is that it would take tons of antimatter, which doesn’t exist here. One solution to this problem is to mine it from space, where it does exist in the form of cosmic rays. Another potential problem would be the lethal amount of radiation and gamma rays exposed to the vessel. The crew, payload area and engine would have to be shielded against radiation and extensive heat. Unfortunately, these type of ships would only travel 70% the speed of light, and would still take at least 7 years to reach the nearest star.
Warp drives are similar, but instead of trying to achieve the speed of light, it bends the space time around the vessel, allowing the speed of light or faster. The vessel doesn’t move, only the space in front and behind it. The theoretical solution for warp drive is called the Alcubierre drive, formulated by physicist Miguel Alcubierre in 1994. The model requires massive amounts of negative mass or exotic matter, which we know exists theoretically, but there is currently no proof. The amount of energy needed would be equal to the mass of Jupiter. The gravitational fields produced would rip a ship to shreds, unless we developed a system that could work. The other problem is that if we could create a bubble around the ship to produce the field, how could we turn it on and off without affecting the ship itself?
So far now, Star Trek is just fantasy. It is nice to believe that we could someday visit other worlds and get around in a matter of days, but it won’t be possible for at least 500-1000 yrs. But who knows, years ago, we said we would never fly either. Tomorrow, we will really go in full throttle-into the wormhole with Plank technology. Until then, here are today’s links:
PLANCK TECHNOLOGY & WORMHOLES
Max Planck was a German scientist and the first real physicist to formulate a quantum theory in 1900, and the first explain why black bodies absorb all light that hits it. At the time, it couldn’t be explained with normal physics. He developed an equation to explain this, using (E)energy=(N)integer(h)constant(f)frequency, In determining this equation, Planck came up with the constant, now known as Planck’s constant. His discovery led to the belief that energy, which appears to be emitted in wavelengths, is actually discharged in small packets, or quanta, and led the way to Einstein’s theory of relativity.
I’m sure everyone has heard of these theoretical passages through space and time. They are staples of science fiction, my novel included. In my novel, a wormhole is created, and Jeff Walker is dragged into it by his nemesis, the Tolarions. He ends up in another universe where this type of travel is commonplace. But what are wormholes, and are we able to actually ever travel through them to other places in the universe, or even another universe?
Wormholes, or Einstein-Rosen bridges, are named after two men whose work in the early 20th century led to the first theories involving the warping of space and time. They are four dimensional tunnels through space and time. Although there is conjecture about how they are created, there is a possibly they exist in space, but are extremely small. The major problem that most physicists agree on is their instability. If someone or something enters it, the disruption of energy forces it to collapse, and if it were a spaceship, it would crushed instantly.
There are two types of wormholes, Einstein-Rosen bridges, also known as Schwarzschild wormholes, and traversable wormholes. Bridges are formed with the use of a black hole. Astromoners didn’t have proof of their existence until recently, within the last ten years. It is believed that there is a massive black hole at the center of our own galaxy. Without its existence, we wouldn’t be where we are today. They are givers of life and death in our galaxy. Black holes absorb all light, energy, and matter. The singularity is the point of a black hole where the mass of a star is packed into a tiny point at its center. The super collapsed matter is the remnant of a dead star; many massive stars go through this process, but it takes billions of years. There is a massive black hole at the center of every galaxy in the universe. It is surmised that black holes cannot be used as wormhole passages because they lead to dead ends. The only possible solution to this problem is to use dark energy to spin the wormhole faster than the speed of light to keep it open for passage. It is believed, however, that the mass of a black hole would be too great to pass through it, and it is not known if a spaceship would even find an end to it. Not all black holes would work, only Kerr Newman black holes, where a massive electric charge and a high spin rate are used to achieve the passage.
There is another solution. Traversable wormholes are theoretical in nature, and are small if they do exist. Exotic energy is used to pry open the existing wormhole using the mass equivalent to a star. While the hole is open, the exotic energy keeps the hole open, allowing passage. Although physicists believe this might be possible, they are eons away from making it happen. Stories like mine, and the popular Interstellar are strictly science fiction, and are at least 10,000 yrs away, if possible at all. Maybe some advanced civilization somewhere in the universe has solved this problem. Human beings only use 3% of their brain capacity, so who knows what smarter civilizations can accomplish.
Tomorrow, I will discuss how wormholes, warp drives, and fusion engines can change space travel for mankind. Until then, here are today’s links:
THE FUTURE OF INTERPLANETARY SPACE TRAVEL ON MANKIND
How will space travel affect mankind, and why should we even go there in the first place? First of all, if we want to survive as a species, we will have to go there. Our Earth has limited resources, and unless we learn how to renew them naturally, we will die as a species. It may not be right away, but it will eventually happen. That is the number one reason space is a good idea. There are many others reasons as well; such as finding a world similar to our own to colonize, finding renewable sources of energy not found here, and expansion of the human race.
There are several missions planned in NASA’s agenda. One is the New Horizons mission, in which is currently near Pluto. Within the next few weeks, we will be within 10,000 miles of the dwarf planet, Pluto, closer to any external planet than ever before. This probe will continue to explore the Kuiper belt and the Oort cloud. It will also explore the nature of the Interstellar medium and its influence on the solar system, and nearby solar systems. The Kepler Probe is similar, searching for Earth-like worlds like our own.
In order for us to achieve Interstellar travel, we first we have to tackle the the many and nearly impossible problems we will face in space. The speed of light is 186,000 miles per second, or 670,616,629 miles per hour. One light year is 5,88 trillion miles. Even one of our fastest probes, the Helios II probe, would take 19,000 years to reach Proxima Centauri, our nearest stars. Traveling at the speed of light, we could leave our system within 11 hours. The distances are too great for conventional rockets, and we have learned that other forms of travel have yet to be achieved. Even if we were too achieve FTL travel, or even fusion powered systems, which could get us to the nearest star during a lifetime, there are surmountable obstacles we must overcome first.
First of all, and most important is the effect it would have on humans. The extended exposure to 0 gravity, the cosmic radiation, lack of reference to surroundings, muscular degeneration, sense of solitude, just to name a few. Then there is the fact that there is no rescues billions of miles from home; as from a quote in a familiar movie-In space, no one can hear you scream. Even if we were to solve all of these problems, such as using suspended animation to combat long periods in space, we will still have the major problem of how to get there in a reasonable amount of time. And even with a fusion-based system, there is the problem of protecting against cosmic rays, power sources, and obstacles in space, such as charged particles, asteroids, cosmic dust, and spurious hot gasses. There is no solar energy available in between stars, and no celestial bodies from which to mine and extract fuel, oxygen or water. We no very little about what’s in between stars, even though we have found exoplanets that seem to orbit no stars at all. Dark matter and dark energy are concepts we are only beginning to understand, and currently there is no theory to explain everything in quantum physics.
So for now, Interstellar travel is just a dream of science fiction. It is reality, however, to assume the possibility of other forms of life in our universe, and even our galaxy. We just haven’t found them yet. The universe is too vast, and our solar system is no longer thought to be unique. Kepler is on the verge of discovering these worlds, and within 10-20 years, the verdict will be in. Are we ready? Monday, we will investigate this prospect-what will happen when we finally land on a far away world, in a whole series titled, Distant Worlds. Until then, here are today’s links: | 0.913128 | 3.256273 |
By Matt Williams
To our Solar System, “close-encounters” with other stars happen regularly – the last occurring some 70,000 years ago and the next likely to take place 240,000 to 470,000 years from now. While this might sound like a “few and far between” kind of thing, it is quite regular in cosmological terms. Understanding when these encounters will happen is also important since they are known to cause disturbances in the Oort Cloud, sending comets towards Earth.
Thanks to a new study by Coryne Bailer-Jones, a researcher from the Max Planck Institute for Astronomy, astronomers now have refined estimates on when the next close-encounters will be happening. After consulting data from the ESA’s Gaia spacecraft, he concluded that over the course of the next 5 million years, that the Solar System can expect 16 close encounters, and one particularly close one!
For the sake of the study – which recently appeared in the journal Astronomy & Astrophysics under the title “The Completeness-Corrected Rate of Stellar Encounters with the Sun From the First Gaia Data Release” – Dr. Bailer Jones used Gaia data to track the movements of more than 300,000 stars in our galaxy to see if they would ever pass close enough to the Solar System to cause a disturbance.
As noted, these types of disturbances have happened many times throughout the history of the Solar System. In order to dislodge icy objects from their orbit in the Oort Cloud – which extends out to about 15 trillion km (100,000 AU) from our Sun – and send them hurling into the inner Solar System, it is estimated that a star would need to pass within 60 trillion km (37 trillion mi; 400,000 AU) of our Sun.
One of the goals of the Gaia mission, which launched back in 2013, was to collect precise data on stellar positions and motions over the course of its five-year mission. After 14 months in space, the first catalogue was released, which contained information on more than a billion stars. This catalogue also contained the distances and motions across the sky of over two million stars.
By combining this new data with existing information, Dr. Bailer-Jones was able to calculate the motions of some 300,000 stars relative to the Sun over a five million year period. From this, he determined that 97 of these stars will pass within 150 trillion km (93 trillion mi; 1 million AU), while 16 would come within 60 trillion km. While this would be close enough to disturb the Oort Cloud, only one star would get particularly close.
That star is Gliese 710, a K-type yellow dwarf located about 63 light years from Earth which is about half the size of our Sun. According to Dr. Bailer-Jones’ study, this star will pass by our Solar System in 1.3 million years, and at a distance of just 2.3 trillion km (1.4 trillion mi; 16 ,000AU). This will place it well within the Oort Cloud, and will likely turn many icy planetesimals into long-period comets that could head towards Earth.
What’s more, Gliese 570 has a relatively slow velocity compared to other stars in our galaxy. Basically, it moves at a speed of 50,000 km/h (31,000 mph), compared to the average speed of 100,000 km/h (62,000 mph). As a result, Gliese 570 will have plenty of time to exert its gravitational influence on the Oort Cloud, which could potentially send many, many comets towards Earth and the inner Solar System.
Over the past few decades, this star has been well-documented by astronomers, and they were already pretty certain that it would experience a close encounter with our Solar System in the future. However, previous calculations indicated that it would pass within 3.1 to 13.6 trillion km (1.9 to 8.45 trillion mi; 20,722 to 90,910 AU) from our star system – and with a 90% certainty.
Thanks to Dr. Bailer-Jones study, these estimates have been refined to 1.5–3.2 trillion km, with 2.3 trillion km being the most likely. His study has also allowed for a general estimate of the rate of stellar encounters over the past 5 million years, and for the next 5 million. He determined that the overall rate is about 550 stars per million years coming within 150 trillion km, and about 20 coming closer than 30 trillion km.
This works out to about one potential close encounter every 50,000 years or so. Again, while this might sound like a long time, in terms of the astronomical history, its a regular occurrence. And while not every close encounter is guaranteed to send comets hurling our way, understanding when and how these encounters have happened is intrinsic to understanding the history and evolution of our Solar System.
Understanding when a close encounters might happen next is also vital. Assuming we are still around when anothertakes place, knowing when it is likely to happen could allow us to prepare for the worst – i.e. if a comets is set on a collision course with Earth! Failing that, humanity could use this information to prepare a scientific mission to study the comets that are sent our way.
The second release of Gaia data is scheduled for next April, and will contain information on an estimated 20 billion stars. That’s 20 times as many stars as the first catalogue, and between 5% and 10% the total number of stars within the Milky Way Galaxy. The second catalog will also include information on much more distant stars, will which allow for reconstructions of up to 25 million years into the past and future.
With every new release, estimates on the movements of the galaxy’s stars (and the potential for close encounters) will be refined further. It will also help us to chart when major comet activity took place within the Solar System, and how this might have played a role in the evolution of the planets and life itself.
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Large scale structure of the Universe Hot Big Bang Theory Concepts of General Re
Gerard, Alexis, Founder and President has reference to this Academic Journal, PHwiki organized this Journal Large scale structure of the Universe Hot Big Bang Theory Concepts of General Relativity Geometry of Space/Time The Friedmann Model Dark Matter (Cosmological Constant) Cosmology The large scale structure of the Universe Age of the Universe: 15 billion years. Evidence from dynamics of universe expansion (model) AND age of oldest stars. Size of the Universe: more complicated question. Cosmology is an evolutionary science (at least in principle) which does not allow controlled repetition of the system. (We cannot build a universe in a laboratory). Analogy with archaeology, geology, paleo-biology. Units in astronomy: Astronomical Unit AU = 150 millions km (Earth/Sun distance) Parsec = 3.26 light years (ly) Light Year = 9.46 x 10^15 m Size of Solar System (Plutos orbit) : about 6 light hours. Size of Milky Way: 10^5 ly x 10^3 ly Galaxies: bunches of stars (in evolution), with typically 10^11 stars. Galaxies agglomerate in clusters with size of a few Mpc (e.g. Local Group) Galaxy Clusters agglomerate in Superclusters with size: 200 Mpc Dominant interaction in the Universe: Gravitation
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How distances are measured The Cosmic distance ladder Parallax methods Main-sequence fitting (HR plot) Variable (Cepheid) stars Supernovae, cosmological methods The Universe as seen by us is strongly dishomogeneus in addition to anisotropic. This statement holds true also on the galactic scales (kpc distances) . in addition to remains true also on the scale of galaxy clusters (Mpc distances) However, if seen from distances of 100 Mpc or more, the universe gets homogeneus in addition to isotropic. This is homogeneity in addition to isotropy at large scales! The Hot Big Bang Model Model as long as the large scale structure in addition to evolution of the Universe. Based on important experimental observations. Cosmological Red Shift Radiation is emitted from stars in addition to other celestial bodies This radiation has the same physical origin of the radiation we study in terrestrial laboratories (e.g. atom absorption in addition to emission). Stellar evolution in addition to many other branches of astrophysics are based on such evidence. E.g. chemical composition of star surfaces are well known. The radiation emitted by any source can be affected by the Doppler effect if there is a relative motion between the source in addition to the receiver
Red shift In laboratory From a distant galaxy 1929: Hubble discovered the empirical relation Birth of Modern Cosmology! From the nonrelativistic Doppler as long as mula: A relation between the Galaxy velocity (away from us) in addition to its distance Since our position in the Universe is hardly a privileged one, galaxy superclusters recede from each other with the cosmological Hubble law. Universe is exp in addition to ing! Two immediate consequences: In the far past all matter was lumped in very little space (the Big Bang) The timescale as long as this is roughly 1/H (assuming the expansion law was the same all over, which is not really the case) The Universe is exp in addition to ing into what It is the space itself that is exp in addition to ing Yes. Are rulers exp in addition to ing No, only gravitationally independent systems participate in the expansion! The Hubble law is a linear expansion law which generates an homologous expansion (it is the same as seen from every Galaxy) H = 70 ± 7 km/sec Mpc The expansion looks the same as seen from A or from B
Naïve expansion model (assuming H = const) = Patch of size 100 Mpc What we see in our Patch is consistent with isotropic in addition to homogeneous expansion plus the Cosmological Principle (no privileged place in Universe!) 1 1 2 3 Homogeneous in addition to isotropic expansion: the shape of the triangle must be preserved. There as long as e Seen from patch 1: Seen from patch 2: In any universe undertaking homogeneous in addition to isotropic expansion, the velocity/distance relation must have the as long as m Now we see that: a(t): scale parameter Elements of a naïve thermal history of the Universe Going backward in time means: No structures (No stars, galaxies ) Only Matter in addition to Radiation Higher densities in addition to higher temperatures Matter Radiation e p When E() > 13.6 eV radiation in addition to matter are coupled. This took place at cosmic time 400,000 yrs. Radiations is in equilibrium with atoms. Be as long as e this era, let us imagine: nuclei, electrons in addition to radiation, at some T. Energy ~ kT. Electrons streaming freely at this point. (photodissociation) (radiative recombination)
Nucleosynthesis already taking place at that time (from 1 sec to 300 sec). Electrons cannot free stream. Then by going backward some more in time energy increases to: Then by going backward some more in time energy increases to give a mean energy 10 MeV. There as long as e the reactions became possible. These reactions mix p in addition to n together making nucleosynthesis impossible. This is T around 10^10 K ( in addition to cosmic time 0.1 sec). This took place at about T=10^10 K in addition to cosmic time 100 sec To summarize, a timeline of important events: T>10^10 K, E>10 MeV, t<0.1 sec . Neutrons in addition to protons kept into equilibrium by weak interactions. Neutrinos in addition to photons in equilibrium. t = 1 sec. No more p/n equilibrium. Beginning of nucleosyntesis. Neutrinos decoupling from matter. T=10^9 K ,E =1 MeV, t= 100 sec. Positrons in addition to electrons annihilate into photons t = 300 sec nucleosysnthesis finished because of low energy available in addition to no more free neutrons around Low mass nuclei abundance fixed Protons, photons, electrons, neutrinos (decoupled) T=5000 K, E=10 eV, t=400,000 years. No more radiation,e,p equilibrium. Atoms as long as mation (hydrogen, helium). Photons decouple CMB Primordial Nucleosynthesis Gamow, Alpher in addition to Herman proposed that in the very early Universe, temperature was so hot as to allow fusion of nuclei, the production of light elements (up to Li), through a chain of reactions that took place during the first 3 min after the Big Bang. The elemental abundances of light elements predicted by the theory agree with observations. Y ~ 24% Helium mass abundance in the Universe Cosmic Microwave Background Probably the most striking evidence that something like the Big Bang really happened is the all pervading Cosmic Background predicted by G. Gamow in 1948 in addition to discovered by Penzias in addition to Wilson in 1965. This blackbody gamma radiation originated in the hot early Universe. As the Universe exp in addition to ed in addition to cooled the radiation cooled down. CMB temperature fluctuations (COBE) By way of summary, the 3 experimental evidences as long as Big Bang: Red shift (Cosmic Expansion) Primordial Nucleosynthesis Cosmic Microwave Background Key concepts of the Hot Big Bang Model: General Relativity as a theory of Gravitation (Inflation) Concepts of General Relativity General Relativity: a theory of Gravitation in agreement with the Equivalence Principle Classical Physics concepts Special Relativity concepts Spacetime of Classical Physics in addition to Special Relativity Spacetime must be curved !! Classical Physics Existence of Inertial Reference Frames (IRF) Relativity Principle (Hey man, physics gotta be the same in any IRF!) Invariance of length in addition to time intervals Special Relativity Existence of Inertial Reference Frames (IRF) Relativity Principle (Hey man, physics gotta be the same in any IRF!) Invariance of c Gravitation, a peculiar as long as ce field Gravity field P = m(g) g P = m(i) a m(g)g = m(i)a a = g m(g)/m(i) a = g One as long as all bodies Electric field F = qE F = m(i)a qE = m(i)a a = E q/m(i) Depending on particle charge If gravitation does not depend on the characteristics of a body then it can be ascribed to spacetime. It is a spacetime property. Equivalence between inertial mass in addition to gravitational mass Free fall in gravitational field (apple from a tree) cannot be distinguished from acceleration (the rocket) Free fall the same as long as every body geometric theory of gravitation Gravitation equivalent to non-inertial frames (EP)
Einstein replaced the idea of as long as ce with the idea of geometry. To him the space through which objects move has an inherent shape to it in addition to the objects are just travelling along the straightest lines that are possible given this shape (J. Allday). Underst in addition to ing gravitation requires underst in addition to ing space-time geometry. The concept of elementary interaction Newton Faraday Maxwell Action at a distance Field concept Quantum Fields (field quanta exchange) Gravity (spacetime curvature) Spacetime geometry Geometry: study of the properties of space. Euclidean geometry: based on postulates – example: given an infinitely long line L in addition to a point P, which is not on the line, there is only one infinitely long line that can be drawn through P that is not crossing L at any other point. L P Some consequences: The angles in a triangle when added together sum up to 180° The circumference of a circle divided by its diameter is a fixed number : In a right angled triangle the lengths of the sides are related by (Pythagoras Theorem)
Euclid geometry is a description of our common sense (= classical physics) three-dimensional space However there are spaces that do not obey Euclid axioms. Spaces having a non-Euclidean geometry. We will consider the (2-dimensional) example of the surface of a sphere. What are the straight lines on the sphere surface They are the great cirlces! (the shortest path between two point is an element of a great circle). Now, suppose we choose A as a point in addition to we draw from B the parallel to A. They meet at the North Pole! (Euclid axiom does not hold) Another consequence: the sum of the angles of a triangle is higher than 180° With the example of a bidimensional space (the sphere surface) we have shown the existence of non-Euclidean (Riemannian) spaces. In this case parallel axiom does no hold true! Einsteins theory replaced gravity as a as long as ce with the notion that space can have a different geometry from the Euclidean. It is a curved space. The sphere surface is 2-d in addition to is a curved space when seen from outside (3-d) We live in a 4-d curved (by gravity) spacetime Three kind of geometry are in general possible (depending on energy content of Universe) Newtonian, Minkowski, General Relativity geometries Newtonian physics spacetime. Length of a rules is invariant (as well as time interval dt) Special Relativity spacetime: the 4-interval is invariant g Matrix (spacetime metric) General Relativity Spacetime: similar in structure to Special Relativity spacetime but now the gravity field makes the metric spacetime dependent.
Two suggestions as long as further reading B. F. Schutz, A first course in general relativity, Cambridge University press. B. Ryden, Introduction to cosmology, Addison Wesley
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This Particular Journal got reviewed and rated by Georgia Military College-Augusta Campus and short form of this particular Institution is GA and gave this Journal an Excellent Rating. | 0.84339 | 3.750933 |
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2014 February 14
Explanation: Sprawling across almost 200 light-years, emission nebula IC 1805 is a mix of glowing interstellar gas and dark dust clouds about 7,500 light-years away in the Perseus spiral arm of our galaxy. Stars were born in this region whose nickname, the Heart Nebula, derives from its Valentine's-Day-appropriate shape. The clouds themselves are shaped by stellar winds and radiation from massive hot stars in the nebula's newborn star cluster Melotte 15 about 1.5 million years young. This deep telescopic image maps the pervasive light of narrow emission lines from atoms in the nebula to a color palette made popular in Hubble images of star forming regions. The field of view spans about two degrees on the sky or four times the diameter of a full moon. The cosmic heart is found in the constellation of Cassiopeia, the boastful mythical Queen of Aethiopia .
Authors & editors:
Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
A service of: ASD at NASA / GSFC
& Michigan Tech. U. | 0.883338 | 3.020978 |
How ancient supermassive black holes grew so big so quickly is one of the biggest mysteries hanging over astronomy — but now researchers think they know how these behemoths packed on the pounds.
Supermassive black holes are the most extreme objects in the universe. They can grow to billions of solar masses and live in the centers of the majority of galaxies. Their extreme gravities are legendary and have the overwhelming power to switch galactic star formation on and off.
But as our techniques have become more advanced, allowing us to look farther back in time and deeper into the distant universe, astronomers have found these black hole behemoths lurking, some of which are hundreds of millions to billions of solar masses. This doesn’t make much sense; if these objects slowly grow by swallowing cosmic dust, gas, stars and planets, how did they have time only a few hundred million years after the Big Bang to pack on all those pounds?
Well, when the universe was young, it was a very different place. Closely-packed baby galaxies generated huge quantities of radiation and this radiation had a powerful influence over star formation processes in neighboring galaxies. It is thought that massive starburst galaxies (i.e. a galaxy that is dominated by stellar birth) could produce so much radiation that they would, literally, snuff-out star formation in neighboring galaxies.
Stars form in vast clouds of cooling molecular hydrogen and, when star birth reigns supreme in a galaxy, black holes have a hard time accreting matter to bulk up — these newly-formed stars are able to escape the black hole’s gravitational grasp. But in the ancient universe, should a galaxy that is filled with molecular hydrogen be situated too close to a massive, highly radiating galaxy, these clouds of molecular hydrogen could be broken down, creating clouds of ionized hydrogen plasma — stuff that isn’t so great for star formation. And this material can be rapidly consumed by a black hole.
According to computer simulations of these primordial galaxies of hydrogen plasma, if any black hole is present in the center of that galaxy, it will feed off this plasma “soup” at an astonishingly fast rate. These simulations are described in a study published in the journal Nature Astronomy.
“The collapse of the galaxy and the formation of a million-solar-mass black hole takes 100,000 years — a blip in cosmic time,” said astronomer Zoltan Haiman, of Columbia University, New York. “A few hundred-million years later, it has grown into a billion-solar-mass supermassive black hole. This is much faster than we expected.”
But for these molecular hydrogen clouds to be broken down, the neighboring galaxy needs to be at just the right distance to “cook” its galactic neighbor, according to simulations that were run for several days on a supercomputer.
“The nearby galaxy can’t be too close, or too far away, and like the Goldilocks principle, too hot or too cold,” said astrophysicist John Wise, of the Georgia Institute of Technology.
The researchers now hope to use NASA’s James Webb Space Telescope, which is scheduled for launch next year, to look back to this era of rapid black hole formation, with hopes of actually seeing these black hole feeding processes in action. Should observations agree with these simulations, we may finally have some understanding of how these black hole behemoths grew so big so quickly.
“Understanding how supermassive black holes form tells us how galaxies, including our own, form and evolve, and ultimately, tells us more about the universe in which we live,” added postdoctoral researcher John Regan, of Dublin City University, Ireland. | 0.88311 | 4.145756 |
A strange, pulsing star has revealed a powerful magnetic field around the giant black hole at the heart of Earth’s Milky Way galaxy, scientists say.
The finding may help shed light on how the galaxy's supermassive black hole devours matter around it and spits out powerful jets of superhot matter, the researchers added.
The center of virtually every large galaxy is suspected to host a supermassive black hole with a mass that can range from millions to billions of times the mass of the sun. Astronomers think the Milky Way's core is home to the monster black hole called Sagittarius A* — pronounced "Sagittarius A-star" — that is about 4 million times the mass of Earth's sun. [No Escape: How Black Holes Work (Infographic)]
Scientists want to learn more about how black holes distort the universe around them, hoping to see if the leading theory regarding black holes, Einstein's theory of general relativity, holds up or if new concepts might be necessary. One way to see how black holes warp space and time is by looking at clocks near them. Cosmic versions of clocks are known as pulsars — rapidly spinning neutron stars that regularly give off pulses of radio waves.
Pulsar tells the tale
Astronomers have been searching for pulsars near Sagittarius A* for the past 20 years.
Earlier this year, NASA's NuSTAR telescope helped confirm the existence of such a pulsar apparently less than half a light-year away from the black hole, one that pulsates radio signals every 3.76 seconds. Scientists quickly analyzed the pulsar using the Effelsberg Radio Observatory of the Max Planck Institute for Radio Astronomy in Bonn, Germany.
"On our first attempt, the pulsar was not clearly visible, but some pulsars are stubborn and require a few observations to be detected," said study lead author Ralph Eatough, an astrophysicist at the Max Planck Institute for Radio Astronomy in Bonn, Germany. "The second time we looked, the pulsar had become very active in the radio band and was very bright. I could hardly believe that we had finally detected a pulsar in the galactic center." [See a video of the pulsar and zoom in on the Milky Way's black hole]
Additional observations were performed in parallel and subsequently with other radio telescopes around the world. "We were too excited to sleep in between observations," said study co-author Evan Keane from the Jodrell Bank Observatory in England.
The newfound pulsar, named PSR J1745-2900, belongs to a rare kind of pulsars known as magnetars, which only make up about 1 out of every 500 pulsars found to date. Magnetars possess extremely powerful magnetic fields, ones about 1,000 times stronger than the magnetic fields of ordinary neutron stars, or 100 trillion times the Earth's magnetic field.
The radio pulses from magnetars are highly polarized, meaning these signals oscillate along one plane in space. This fact helped the researchers detect a magnetic field surrounding Sagittarius A*.
Black hole magnetic field revealed
Black holes swallow their surroundings, mainly hot ionized gas, in a process of accretion. Magnetic fields threading within this accretion flow can influence how this infalling gas is structured and behaves.
"The magnetic field we measure around the black hole can regulate the amount of matter the black hole eats and could even cause it to spit matter out in so-called jets," Eatough told SPACE.com. "These measurements are therefore of great importance in understanding how supermassive black holes feed, a process that can affect galaxy formation and evolution."
As radio signals traverse the magnetized gas around black holes, the way they are polarized gets twisted depending on the strength of the magnetic fields. By analyzing radio waves from the magnetar, the researchers discovered a relatively strong, large-scale magnetic field pervades the area surrounding Sagittarius A*.
In the area around the pulsar, the magnetic field is about 100 times weaker than Earth's magnetic field. However, "the field very close to the black hole should be much stronger — a few hundred times the Earth's magnetic field," Eatough said.
If the magnetic field generated by the infalling gas is accreted down to the event horizon of the black hole — its point of no return — that could help explain the radio and X-ray glow long associated with Sagittarius A*, researchers added.
"It is amazing how much information we can extract from this single object," said study co-author Adam Deller at the Netherlands Institute for Radio Astronomy in Dwingeloo.
Astronomers predict there should be thousands of pulsars around the center of the Milky Way. Despite that, PSR J1745-2900 is the first pulsar discovered there. "Astronomers have searched for decades for a pulsar around the central black hole in our galaxy, without success. This discovery is an enormous breakthrough, but it remains a mystery why it has taken so long to find a pulsar there," said study co-author Heino Falcke at Radboud Universiteit Nijmegen in the Netherlands.
"It could be the environment is very dense and patchy, making it difficult to see other pulsars," Eatough added.
The researchers cannot test the leading theory regarding black holes using PSR J1745-2900 — they cannot measure the way it warps space-time accurately enough, since the pulsar is slightly too far away from Sagittarius A* and, being relatively young, its spin is too variable. The researchers suggest pulsars that are closer to the black hole and are older with less variable spins could help test the theory.
"If there is a young pulsar, there should also be many older ones. We just have to find them," said study co-author Michael Kramer, director of the Max Planck Institute for Radio Astronomy.
The scientists detailed their findings online Aug. 14 in the journal Nature.
- Images: Black Holes of the Universe
- Black Hole Quiz: How Well Do You Know Nature's Weirdest Creations?
- The Black Hole That Made You Possible
Copyright 2013 SPACE.com, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. | 0.809223 | 3.98729 |
Three NASA scientists teamed up to develop and demonstrate NASA’s first wide-field-of-view soft X-ray camera for studying “charge exchange,” a poorly understood phenomenon that occurs when the solar wind collides with Earth’s exosphere and neutral gas in interplanetary space.
The unique collaboration involved heliophysics, astrophysics and planetary science divisions at NASA’s Goddard Space Flight Center in Greenbelt, Md., and resulted in the first successful demonstration of the Sheath Transport Observer for the Redistribution of Mass (STORM) instrument and a never-before-flown X-ray focusing technology called lobster-eye optics.
|The Sheath Transport Observer for the Redistribution
of Mass (STORM) is equipped with a never-before-
flown X-ray focusing technology called “lobster-eyeoptics.
The Sheath Transport Observer for the Redistribution of Mass (STORM) is equipped with a never-before-flown X-ray focusing technology called “lobster-eye optics.”
STORM and another NASA-funded experiment, the Diffuse X-ray emission from the Local galaxy (DXL), flew aboard a two-stage Black Brant IX sounding rocket from the White Sands Missile Range, Las Cruces, N.M., in December 2012. DXL, developed by University of Miami professor Massimillano Galeazzi, also studied the same charge-exchange phenomenon but from a different perspective using a refurbished instrument developed by the University of Wisconsin, Madison. This instrument produced the first all-sky map of soft X-rays several years ago. (X-rays are called “soft” when their wavelengths are nearer the ultraviolet portion of the electromagnetic spectrum.)
Though Goddard scientists served as co-principal investigators on DXL, STORM holds a special place in their hearts. Developed and assembled at Goddard, the instrument “is a wonderful example of cooperation across divisions to better understand a process that is of interest to us all, but for different reasons,” said Michael Collier, a planetary scientist who collaborated with astrophysicist Scott Porter and heliophysicist David Sibeck, all of NASA Goddard. “Charge exchange is one of the few phenomena that brings together scientists from three of the science divisions at Goddard,” Porter added.
Mysterious Charge Exchange
Scientists first discovered the charge-exchange effect in the mid-1990s while observing comet Hyakutake. “They got quite a surprise,” Collier said. “They found an intense source of soft X-rays at the comet’s head, which was unusual because comets are cold objects and soft X-rays are associated with hot objects. How could balls of ice emit X-rays? No one could figure it out.”
Scientists soon discovered that the X-ray emission was caused by the solar wind, a constantly flowing stream of charged particles that sweeps across the solar system at about a million miles per hour. When highly charged heavy ions in the solar wind collide with neutral atoms found in space, the heavy ions “steal” an electron from the neutrals — an exchange that puts the heavy ions in a short-lived excited state. As they relax, they emit soft X-rays.
Furthermore, the phenomenon is far from rare. Since its head-scratching discovery nearly 20 years ago, scientists have observed charge exchange and resulting emission of soft X-rays in comets, interplanetary wind, possibly supernova remnants, and galactic halos. Planetary scientists have observed soft X-ray emissions in the atmospheres of Venus and Mars, leading some to question whether the charge-exchange phenomenon that produced the radiation has contributed to atmospheric loss on the Red Planet.
Heliophysicists, likewise, have observed soft X-ray emissions in Earth’s exosphere, the uppermost atmospheric layer that encompasses Earth’s protective magnetosphere, a region particularly sensitive to solar storms that can damage spacecraft electronics, cause spurious readings from global-positioning satellites, and knock out satellite-based communications and terrestrial power grids.
And astrophysicists have observed them, too — as unwanted noise in data collected by all X-ray observatories sensitive to soft X-rays.
“At first blush, STORM seems to have very little to do with astrophysics,” Porter said. But “the emission of soft X-rays provides a very significant temporally, spatially, and spectrally varying foreground to all soft–ray observations from every single X-ray observatory,” he explained. “It’s essential that we, as astrophysicists, understand and are able to model this foreground emission in detail. On all recent X-ray observatories, significant observing time has been lost and errors in scientific interpretation have happened due to our lack of understanding of this phenomenon.”
In other words, planetary scientists and heliophysicist want to measure this emission as treasured data and astrophysicists want to remove it as noise.
STORM Holds Answer
STORM potentially holds the answer for obtaining a more complete understanding of the physical process, giving scientists insights currently impossible with existing instruments, the scientists said. During the sounding-rocket mission, for example, DXL studied the X-ray emission. However, it studied X-rays emitted when the solar wind interacted with gas entering our solar system from the Milky Way.
STORM gave scientists a global view. The wide-field-of-view camera imaged processes near Earth’s magnetosphere, which until now was impossible. “These are extremely important, highly dynamic, and poorly understood regions that channel solar wind energy into the magnetosphere where it drives space weather,” Porter said. If this process is important to determining space weather in and around Earth, it also affects other planetary bodies, to say nothing of its deleterious effect on data collected by multi-million-dollar X-ray observatories.
Making the imagery possible was an emerging technology called lobster-eye optics. As the technology’s name implies, the optics mimic the structure of a lobster’s eyes, which are made up of long, narrow cells that each captures a tiny amount of light, but from many different angles. Only then is the light focused into a single image.
Pioneered by researchers at the United Kingdom’s University of Leicester, a partner in STORM’s development, lobster X-ray optics work the same way. Its eyes are a microchannel plate, a thin curved slab of material dotted with tiny tubes across the surface. X-ray light enters these tubes from multiple angles and is focused through grazing-incident reflection, giving the technology a wide-field-of-view necessary for globally imaging the emission of soft X-rays in Earth’s exosphere. “I’m unaware of any instrument that can do this,” Collier said.
With the successful launch, the team said they are in good position to propose STORM for a possible mission. “We are happy it turned out so well,” Sibeck said. “We all stand to gain from STORM’s development.”
Found here NASA scientists build first-ever wide-field X-ray imager | 0.910169 | 3.872441 |
The mission of the Dawn spacecraft, which spent about a year to examine the giant asteroid Vesta, provided an enormous amount of information that are extremely interesting from a scientific point of view. However, Vesta is grayish and studded with craters of various sizes, not the most spectacular sight. Scientists from the Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany, have changed that reworking the images of Vesta giving them spectacular colors.
Various colors have been assigned to different light wavelengths in the images of the giant asteroid Vesta taken by the framing camera, one of the instruments of the Dawn space probe. The result is really amazing but this work wasn’t done just to get particularly evocative visual effects but with precise scientific purposes.
The colors that result from the processing revealed with details never seen before geological structures invisible to the naked eye as well as the alien beauty of the landscape. They allow you to see layers of molten rock as a result of impact craters hidden by earthquakes and materials brought by space rocks.
That’s how, for example, they obtained the image of the crater Antonia in enormous Rheasilvia basin in the southern hemisphere of Vesta. The light blue colored material is fine-grained, dug from the lower crust. The southern edge of the crater was buried by coarser material shortly after its formation. The dark blue color of the southern rim of the crater is due to the shadow of the blocky material.
In the image of the crater Sextilia you can see the full spectrum of colors of Vesta. The black-colored material was probably brought by the impact of a large asteroid while the red-colored material may have been melted by that impact. Various colors maximize subtle differences in the physical characteristics of the rock units, meaning color, texture and composition. In the color scheme, pyroxene, a iron-rich mineral, is of particular importance.
The Dawn spacecraft left the giant asteroid Vesta in September 2012 but many scientists keep on working on the data it collected. This protoplanet bears traces of the violent history of the solar system, which can now be admired in new extraordinary colors. | 0.858814 | 3.641717 |
Fourth dwarf planet is named Makemake
Makemake orbits at a distance of between 38 and 53 AU from the Sun, and follows a highly inclined (29°) path compared to the main planets in our solar system. As a result, its orbital period is nearly 310 years, which is more than Pluto's 248 years. Its diameter is roughly three-quarters that of Pluto. Makemake has no known satellites and observations suggest an extremely low average temperature of around -243°C (or 30K).
The solar system is currently known to contain three other dwarf planets, Ceres, Pluto and Eris, however, it is expected that many more will be discovered as technology improves. Ceres is the only one of these that is not also a plutoid, because it is located in the asteroid belt between Mars and Jupiter - well inside the orbit of Neptune, which is considered to be the inner boundary of plutoids.
The IAU is an official organization, made up of astronomers from around the world, which decides on all things astronomical, such as the names of stars and of newly discovered objects. This is one of the many tasks it has been performing since the early 1900's. | 0.864125 | 3.15363 |
heic0309 — Science Release
Hubble tracks down a galaxy cluster's dark matter
17 July 2003
Using the powerful trick of gravitational lensing, a European and American team of astronomers have constructed an extensive 'mass map' of one of the most massive structures in our Universe. They believe that it will lead to a better understanding of how such systems assembled and the key role of dark matter.
Clusters of galaxies are the largest stable systems in the Universe. They are like laboratories for studying the relationship between the distributions of dark and visible matter. In 1937, Fritz Zwicky realised that the visible component of a cluster (the thousands of millions of stars in each of the thousands of galaxies) represents only a tiny fraction of the total mass. About 80-85% of the matter is invisible, the so-called 'dark matter'. Although astronomers have known about the presence of dark matter for many decades, finding a technique to view its distribution is a much more recent development.
Led by Drs Jean-Paul Kneib (from the Observatoire Midi-Pyrénées, France/Caltech, United States), Richard Ellis and Tommaso Treu (both Caltech, United States), the team used the NASA/ESA Hubble Space Telescope to reconstruct a unique 'mass map' of the galaxy cluster CL0024+1654. It enabled them to see for the first time on such large scales how mysterious dark matter is distributed with respect to galaxies. This comparison gives new clues on how such large clusters assemble and which role dark matter plays in cosmic evolution.
Tracing dark matter is not an easy task because it does not shine. To make a map, astronomers must focus on much fainter, more distant galaxies behind the cluster. The shapes of these distant systems are distorted by the gravity of the foreground cluster. This distortion provides a measure of the cluster mass, a phenomenon known as "weak gravitational lensing".
To map the dark matter of CL0024+1654, more than 120 hours observing time was dedicated to the team. This is the largest amount of Hubble time ever devoted to studying a galaxy cluster. Despite its distance of 4.5 thousand million light-years (about one third of the look-back time to the Big Bang) from Earth, this massive cluster is wide enough to equal the angular size of the full Moon. To make a mass map that covers the entire cluster required observations that probed 39 regions of the galaxy cluster.
The investigation has resulted in the most comprehensive study of the distribution of dark matter in a galaxy cluster so far and extends more than 20 million light-years from its centre, much further than previous investigations. Many groups of researchers have tried to perform these types of measurements with ground-based telescopes. However, the technique relies heavily on finding the exact shapes of distant galaxies behind the cluster. The sharp vision of a space telescope such as NASA-ESA's Hubble is superior.
The study reveals that the density of dark matter on large scales drops sharply with distance from the cluster centre. This confirms a picture that has emerged from recent detailed computer simulations. As Richard Ellis says: 'Although theorists have predicted the form of dark matter in galaxy clusters from numerical simulations based on the effects of gravity alone, this is the first time we have convincing observations to back them up. Some astronomers had speculated clusters might contain large reservoirs of dark matter in their outermost regions. Assuming our cluster is representative, this is not the case.'
The team noticed that dark matter appears to clump together in their map. For example, they found concentrations of dark matter associated with galaxies known to be slowly falling into the system. Generally, the researchers found that the dark matter traces the cluster galaxies remarkably well and over an unprecedented range of physical scales. 'When a cluster is being assembled, the dark matter will be smeared out between the galaxies where it acts like a glue,' says Jean-Paul Kneib. 'The overall association of dark matter and 'glowing matter' is very convincing evidence that structures like CL0024+1654 grow by merging of smaller groups of galaxies that were already bound by their own dark matter components.'
Future investigations using Hubble's new camera, the Advanced Camera for Surveys (ACS), will extend this work when Hubble is trained on a second galaxy cluster later this year. ACS is 10 times more efficient than the Wide Field and Planetary Camera 2 used for this investigation, making it possible to study finer mass clumps in galaxy clusters and help work out how the clusters are assembled.
The team is composed of Jean-Paul Kneib (Observatoire Midi-Pyrénées, France/Caltech, United States), Patrick Hudelot (Observatoire Midi-Pyrénées, France), Richard S. Ellis (Caltech, United States), Tommaso Treu (Caltech, United States), Graham P. Smith (Caltech, United States), Phil Marshall (MRAO, United Kingdom), Oliver Czoske (Institut für Astrophysik und Extraterrestrische Forschung, Germany), Ian Smail (University of Durham, United Kingdom) & Priya Natarajan (Yale University, United States).
The ground-based observations were done with the Canada-France-Hawaii Telescope (CFHT) using the CFHT12k camera, the Keck telescopes, and the Hale 5-metre telescope at Palomar, United States, using the WIRC camera.
The team will present their study at the General Assembly of the International Astronomical Union. They will also publish their results in a forthcoming issue of Astrophysical Journal.
For broadcasters, animations of the discovery and general Hubble Space Telescope background footage is available from https://www.spacetelescope.org/videos/?search=heic0309
Observatoire Midi-Pyrénées, France/Caltech, United States
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About the Release | 0.866894 | 4.026239 |
NASA's planet-hunting Kepler spacecraft should be able to achieve its primary mission goal regardless of whether or not it can bounce back from a recent malfunction, researchers say.
Kepler launched in March 2009 on a 3.5-year prime mission to determine how common Earth-like planets are throughout the Milky Way galaxy. That goal is likely already attainable, even if the spacecraft is unable to recover from the glitch that halted its exoplanet hunt two months ago, mission team members say.
"We believe we do have enough data to answer the question," said Kepler analysis lead Jon Jenkins of the SETI (Search for Extraterrestrial Intelligence) Institute in Mountain View, Calif. [7 Greatest Kepler Discoveries (So Far)]
"Now, we won't have as tight error bars as we would otherwise have, and we won't have orbital periods out well beyond Earth's in terms of Earth-size planets," Jenkins said during a lecture last month at the SETI Institute. "But we'll still do a credible job and a good enough job delivering the answers that we need."
Kepler spots exoplanets by noting the tiny brightness dips caused when they cross the face of their parent stars. The observatory needs to see three of these "transits" to flag an alien world, so it takes years to detect planets orbiting relatively far from their stars.
This is precision work, and the Kepler space telescope requires three functioning gyroscope-like reaction wheels to stay locked onto its 150,000-plus target stars.
The observatory launched in 2009 with four reaction wheels — three for immediate use, and one spare. One wheel, known as number two, failed in July 2012. Another (number four) stopped working on May 11 of this year, robbing Kepler of its precision pointing ability.
Kepler hasn't searched for exoplanets since the latter wheel failure. Mission engineers have been devising possible fixes for the problem, and they plan to start sending some of these commands to the spacecraft over the next week or two.
(Launching astronauts out to repair Kepler, as was done five separate times with NASA's Hubble Space Telescope, is not an option. Kepler orbits the sun rather than Earth and currently sits millions of miles from our planet.)
If at least one of the failed wheels cannot be brought back, Kepler will almost certainly be given a new mission, researchers say — one that emphasizes scanning instead of its previous point-and-stare operations.
While the Kepler team would love to continue the exoplanet hunt for years to come, researchers can likely determine the Milky Way's frequency of Earth-like worlds with the data the spacecraft has already collected, Jenkins said. But doing so will require a fair bit of work.
For one thing, he said, the team needs to continue pulling planets out of the spacecraft's huge dataset. (To date, Kepler has detected 3,277 candidate planets, 134 of which have been confirmed by follow-up observations. Mission scientists think at least 90 percent of the spacecraft's finds will end up being the real deal.)
Scientists also need to determine the completeness and reliability of Kepler's discovery system, among other things, and understand how the mission's target stars relate to the stellar population of the Milky Way as a whole to enable extrapolation, Jenkins added.
The target stars "were chosen to be really good for discovering transiting planets but undoubtedly have selection biases in them," he said.
All of this work should keep mission scientists busy for some time to come.
"We have about two years of data that we have yet to fully search; we're still in the process of searching through the third year of data," Jenkins said. "I think that this could occupy us for another two to three years, easily."
The Kepler mission's total pricetag is about $600 million thus far, and it costs about $20 million per year to operate the spacecraft and analyze the data, NASA officials have said.
- 7 Ways to Discover Alien Planets
- Gallery: A World of Kepler Planets
- The Search For Another Earth | Video
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Using NASA’s Spitzer Space Telescope, researchers are taking a closer look at exoplanets known as Hot Jupiters, revealing a wide range of climates, raging winds and other aspects of their turbulent nature.
Our galaxy is teeming with a wild variety of planets. In addition to our solar system’s eight near-and-dear planets, there are more than 800 so-called exoplanets known to circle stars beyond our sun. One of the first “species” of exoplanets to be discovered is the hot Jupiters, also known as roasters. These are gas giants like Jupiters, but they orbit closely to their stars, blistering under the heat.
Thanks to NASA’s Spitzer Space Telescope, researchers are beginning to dissect this exotic class of planets, revealing raging winds and other aspects of their turbulent nature. A twist to come out of the recent research is the planets’ wide range of climates. Some are covered with a haze, while others are clear. Their temperature profiles, chemistries and densities differ as well.
“The hot Jupiters are beasts to handle. They are not fitting neatly into our models and are more diverse than we thought,” said Nikole Lewis of the Massachusetts Institute of Technology, Cambridge, lead author of a new Spitzer paper in the Astrophysical Journal examining one such hot Jupiter called HAT-P-2b. “We are just starting to put together the puzzle pieces of what’s happening with these planets, and we still don’t know what the final picture will be.”
The very first exoplanet discovered around a sun-like star was, in fact, a hot Jupiter, called 51 Pegasi b. It was detected in 1995 by Swiss astronomers using the radial velocity technique, which measures the wobble of a star caused by the tug of a planet. Because hot Jupiters are heavy and whip around their stars quickly, they are the easiest to find using this strategy. Dozens of hot Jupiter discoveries soon followed. At first, researchers thought they might represent a more common configuration for other planetary systems in our galaxy beyond our own solar system. But new research, including that from NASA’s Kepler space telescope, has shown that they are relatively rare.
In 2005, scientists were thrilled when Spitzer became the first telescope to detect light emitted by an exoplanet. Spitzer monitored the infrared light coming from a star and its planet — a hot Jupiter — as the planet disappeared behind the star in an event known as a secondary eclipse. Once again, this technique works best for hot Jupiters, because they are the biggest and hottest planets.
In addition to watching hot Jupiters slip behind their stars, researchers also use Spitzer to monitor the planets as they orbit all the way around a star. This allows them to create global climate maps, revealing how the planets’ atmospheres vary from their hot, sun-facing sides to their cooler, night sides, due in part to fierce winds. (Hot Jupiters are frequently tidally locked, with one side always facing the star, just as our moon is locked to Earth.)
Since that first observation, Spitzer has probed the atmospheres of dozens of hot Jupiters, and some even smaller planets, uncovering clues about their composition and climate.
“When Spitzer launched in 2003, we had no idea it would prove to be a giant in the field of exoplanet science,” said Michael Werner, the Spitzer project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, California. “Now, we’re moving farther into the field of comparative planetary science, where we can look at these objects as a class, and not just as individuals.”
In the new study, Lewis and colleagues made the longest Spitzer observation yet of a hot Jupiter. The infrared telescope stared at the HAT-P-2 system continuously for six days, watching it cross in front of its star, slip behind, and then reappear on the other side, making a full orbit. What makes the observation even more exciting to scientists is that the planet has a comet-like eccentric orbit, carrying it as close as 2.8 million miles (4.5 million kilometers) to the star and out to as far as 9.3 million miles (15 million kilometers). For reference, Mercury is about 28.5 million miles from our sun.
“It’s as if nature has given us a perfect lab experiment with this system,” said Heather Knutson, a co-author of the new paper at the California Institute of Technology, Pasadena, California. “Because the planet’s distance to the sun changes, we can watch how fast it takes to heat up and cool down. It’s as though we’re turning the heat knob up on our planet and watching what happens.” Knutson led the first team to create a global “weather” map of a hot Jupiter, called HD 189733 b, in 2007.
The new HAT-P-2b study is also one of the first to use multiple wavelengths of infrared light, instead of just one, while watching a full orbit of a hot Jupiter. This enables the scientists to peer down into different layers of the planet.
The results reveal that HAT-P-2b takes about a day to heat up as it approaches the hottest part of its orbit, and four to five days to cool down as it swings away. It also exhibits a temperature inversion — a hotter, upper layer of gas — when it is closest to its star. What’s more, the carbon chemistry of the planet seems to be behaving in unexpected ways, which the astronomers are still trying to understand.
“These planets are much hotter and more dynamic than our own Jupiter, which is sluggish by comparison. Strong winds are churning material up from below, and the chemistry is always changing,” said Lewis.
Another challenge in understanding hot Jupiters lies in parsing through the data. Lewis said her team’s six-day Spitzer observation left them with 2 million data points to map out while carefully removing instrument noise.
“Theories are being shot down right and left,” said Nick Cowan of Northwestern University, Evanston, Illinois, a co-author of the HAT-P-2b study. “Right now, it’s like the wild, wild west.”
NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA. For more information about Spitzer, visit http://spitzer.caltech.edu and http://www.nasa.gov/spitzer.
Publication: Nikole K. Lewis, et al., “ORBITAL PHASE VARIATIONS OF THE ECCENTRIC GIANT PLANET HAT-P-2b,” 2013, ApJ, 766, 95: doi:10.1088/0004-637X/766/2/95
PDF Copy of the Study: Orbital Phase Variations of the Eccentric Giant Planet HAT-P-2b
Source: Whitney Clavin, Jet Propulsion Laboratory; NASA | 0.923642 | 3.990506 |
Asteroid 624, the largest known Trojan asteroid, discovered in 1907 by the German astronomer August Kopff (1882–1960). It is a member of the group of Trojans at the L4 Lagrangian point 60° ahead of Jupiter. Hektor's brightness varies by a factor of three as it rotates with a period of 6.92 hours. The light curve indicates that Hektor is highly elongated, 150 × 300 km; alternatively, it might be dumbbell-shaped, two asteroids in contact, or a close binary. Hektor is a D-class asteroid. Its orbit has a semimajor axis of 5.238 AU, period 11.99 years, perihelion 5.12 AU, aphelion 5.36 AU, and inclination 18°.2.
Subjects: Astronomy and Astrophysics. | 0.840462 | 3.04288 |
Presentation on theme: "The Solar System Topic 11. SUNSPOTS Sunspots are temporary phenomena on the photoshere of the Sun that appear visibly as dark spots compared to surrounding."— Presentation transcript:
SUNSPOTS Sunspots are temporary phenomena on the photoshere of the Sun that appear visibly as dark spots compared to surrounding regions. Manifesting intense magnetic activity, sunspots host secondary phenomena such as cornonal loops (prominences) and reconnection events. We study the sunspots because they are a very good indicator of how active the Sun is. A large group of sunspot means that there may be other things and events going on as well, like flares and prominences. If two spots come together (it happened today! 17.December.2009) then they simply make one bigger spot. The main reason for observing sunspot activity, nowadays, is that it can interfere with power grids and sensitive equipment on board satellites. Sunspots appear in regions, and they can merge quite easily WITHIN their respective regions. However, there are only a few cases of regions merging. In most cases (>95%), regions do avoid each other. This is because they are magnetic. If two regions are north and south of each other, and in the same hemisphere, then there would be a rather distinct clear area between them. It is only when regions are end-on when the trailing spots of one can 'intermingle' with the leading spots of the other region, but this rarely happens. I can only think of two cases in the last 30 years.
SOLAR FLARE A solar flare is a sudden flash of brightness observed over the Sun’s surface or the solar limb, which is interpreted as a large energy release of up to 6 × 10 25 joules of energy. They are often, but not always, followed by a colossal coronal mass ejection. The flare ejects clouds of electrons, ions, and atoms through the corona of the sun into space. These clouds typically reach Earth a day or two after the event. hey produce radiation across the electromagnetic spectrum at all wavelengths, from radio waves to gamma rays, although most of the energy is spread over frequencies outside the visual range and for this reason the majority of the flares are not visible to the naked eye and must be observed with special instruments. Flares occur in active regions around sunspots, where intense magnetic fields penetrate the photosphere to link the corona to the solar interior. Flares are powered by the sudden (timescales of minutes to tens of minutes) release of magnetic energy stored in the corona.
PROMINENCES A prominence is a large, bright, gaseous feature extending outward from the Sun's surface, often in a loop shape. Prominences are anchored to the Sun's surface in the photosphere, and extend outwards into the Sun's corona.
SOLAR STORMS Also known as a geomagnetic storm. A geomagnetic storm is a temporary disturbance of the Earth’s magnetosphere caused by a solar wind shock wave and/or cloud of magnetic field which interacts with the Earth’s magnetic field.
Eight PlanetsDwarf planetsMoons Asteroids and asteroid belt Meteoroids, meteors & meteorites Comets Kuiper Belt & Oort Cloud
Eight planets Needs to travel in an orbit. Almost spherical shaped Keep orbital path clear of other objects Inner rocky planets: Mercury, Venus, Earth and Mars. Other gas giants: Jupiter, Saturn, Uranus, Neptune. Dwarf planets Does not keep a clear path of other objects. Pluto is now classified as a dwarf planet. Other examples are: Eris, Ceres & Makemake
Moons This is a body that revolves around a planet. They do not have their own source of light, they reflect the sun’s light. Always move around the same planet. Asteroids & asteroid belt An asteroid is a rock found between the orbits of Mars and Jupiter. This area is called an asteroid belt. They have iron cores just like Earth.
Meteoroids, meteors & meteorites A meteoroid is a solid object that is smaller than an asteroid. When a meteoroid enters the Earth’s atmosphere it starts to burn up and is called a meteor – we call this a shooting star. Sometimes meteors crash into the ground before completely burning up. The remains are called meteorites.
Comets Made up of frozen gas and bits of rock. Come from the beyond the furthest planets. Three distinct parts: HEAD, COMA (outer circle of light) and TAIL (points away from the sun) Head of rock and frozen gas, melts and releases gas and dust. Kuiper belt & Oort Cloud Kuiper belt is beyond Neptune & is a ring of icy and rocky objects. Oort Cloud is even further away and is spherical.
Shape of the solar system It is disk shaped The Sun is at the centre of the solar system All the planets move in the same direction Planets and other objects are kept in their orbits by gravity. – The larger the mass of the objects the larger the gravity experienced.
Practical task Page 202 – On a separate piece of paper answer questions 1 – 8 of Part A. Make a spider summary of the eight planets including the following information: – Name, temperature, number of moons, rings, time taken for one day, time taken for one year, composition, size (diameter)& distance from the Sun.
Supporting life As far as we know, Earth is the only planet in our Solar System that can support life. At NASA the hunt for exoplanets (planets outside of our solar system), astronomers have been desperately searching for is another planet like Earth that’s capable of supporting life. Astronomers have found Earth-sized planets in other solar systems. They have found planets in the “habitable zone” (an orbit where temperatures would be potentially conducive to life) of other solar systems. But they haven’t found an Earth-sized planet in the habitable zone of another star…yet! – http://www.forbes.com/sites/alexknapp/2014/04/17/nasa-has-discovered-the-first-potentially-habitable-earth- sized-planet/ http://www.forbes.com/sites/alexknapp/2014/04/17/nasa-has-discovered-the-first-potentially-habitable-earth- sized-planet/ – http://www.telegraph.co.uk/science/space/11011861/We-will-see-signs-of-life-on-other-planets-within-20-years- scientists-hope.html http://www.telegraph.co.uk/science/space/11011861/We-will-see-signs-of-life-on-other-planets-within-20-years- scientists-hope.html
Temperature on Earth Distance from the Sun is the most important factor affecting temperature range. Atmosphere also plays a role. Earth is just the right distance from the Sun. – Average temp range is -40°C to 40°C.
Sunlight & the Food Chain Energy is produced in the Sun by the nuclear reactions. This energy is sent out (radiates) into space. This energy (heat and light) enables life on Earth in the following ways: – Sunlight is used by plants to produce food (photosynthesis). – Animals depend on this food and oxygen produced by plants. – Sunlight heats up parts of the Earth and creates winds and rain which is needed for life.
Water on Earth In Earth’s temperature range water can exist in all three states: – Liquid – ocean, lakes, rivers, swamps and underground. – Gas – water vapour in the air. – Solid – frozen ice caps for the Arctic and Antarctic. Water is constantly changing between these states in the water cycle. – Water cycle ensures that amount of water stays constant and that there is fresh water available.
Oxygen About 21% of Earth’s atmosphere consists of oxygen. Oxygen is essential for respiration. It is believed that the amount of oxygen has increased as life has become more complex. – Early simple life forms (types of bacteria – green blue algae) were the first to start producing oxygen.
Why Mars? After the Earth, Mars is the most habitable planet in our solar system due to several reasons: – Its soil contains water to extract – It isn’t too cold or too hot – There is enough sunlight to use solar panels – Gravity on Mars is 38% that of our Earth's, which is believed by many to be sufficient for the human body to adapt to – It has an atmosphere (albeit a thin one) that offers protection from cosmic and the Sun's radiation – The day/night rhythm is very similar to ours here on Earth: a Mars day is 24 hours, 39 minutes and 35 seconds The only other two celestial bodies in orbits near the Earth are our Moon and Venus. There are far fewer vital resources on the Moon, and a Moon day takes a month. It also does not have an atmosphere to form a barrier against radiation. Venus is a veritable purgatory. The average temperature is over 400 degrees, the barometric pressure is that of 900 meters underwater on Earth, and the cherry on top comes in the form of occasional bouts of acid rain. It also has nights that last for 120 days. Humans cannot live on Mars without the help of technology, but compared to Venus it's paradise! – See more at: Mars one See more at: Mars one | 0.857484 | 3.96406 |
By Nola Taylor Redd for Astrobiology Magazine
Moffet Field CA (NASA) Jun 05, 2015
Beneath the rocks scarring California's Mojave Desert are colonies of cyanobacteria, tiny creatures thought to be some of the first on Earth to convert light from the Sun into energy in the process known as photosynthesis. By studying how these creatures adapt to life in the hot, dry desert, biologists hope to glean insight into how microbial life of some sort might fare on Mars.
A recent study published last year in the International Journal of Astrobiology examined how these organisms survived when different types of rock stood between them and the Sun. It found that the dominant type, Chroococcidiopsis, thrived beneath a variety of geologic types, from quartz to talc.
"The versatility of Chroococcidiopsis in inhabiting dry niches with different light availability to support photosynthesis extends our appreciation of the limit of photosynthesis," biologist Daniela Billi of the University of Rome, told Astrobiology Magazine by email.
Billi worked with lead author and biologist Heather Smith of Utah State University to categorize the bacteria hiding beneath various rocks in the Mojave Desert in order to better understand the environments bacteria on Earth endure. The results forge a link between Chroococcidiopsis and potential life forms on past or present Mars.
Lights on, power up
"On Mars, in the past 3.8 billion years, water existed in the liquid phase on the surface," planetary scientist Jean-Pierre Paul de Vera of the German Aerospace Center Institute of Planetary Research told Astrobiology Magazine by email. "At the time life on Earth started it is also possible that the first bacteria also originated in the lakes or oceans of Mars."
De Vera studies bacteria and lichens that thrive in challenging environments, and is working with Billi to study Chroococcidiopsis on the International Space Station as part of the Biology and Mars Experiment.
If life on Earth and Mars evolved in similar ways at about the same time, cyanobacteria could help scientists better understand what to look for on the Red Planet, should there be remains to be found.
"Cyanobacteria might be a good reference system for searching for life on Mars, and we could expect similar remnants of membrane structures like these bacteria, although it is not clear if photosynthesis could have been invented also on Mars," de Vera said.
Billi worked with a team of scientists to study the effects of different rocks in the Mojave Desert on the photosynthesis process. Examining cyanobacteria beneath talc, marble, quartz, and red- and white-coated carbonate, they determined that the genus Chroococcidiopsis dominated the environment beneath each sample.
Chroococcidiopsis is one of the most primitive cyanobacteria, thriving in a wide range of extreme environments across Earth. In the past, it has been suggested as an organism that could help to change the Martian dirt into a more arable soil that humans could farm during long-term colonization.
"In dry areas, cyanobacteria of the genus Chroococcidiopsis are often dominant," Billi said.
One reason they thrive might have to do with how they respond to the different waves of light that pass through the edges of each rock. Rather than remaining stagnant, the cyanobacteria were able to change the types of light they required for photosynthesis based on what was available.
"Chroococcidiopsis displayed the capability to adapt to the different light availability by changing the spectroscopic features of the photosynthetic pigments," said Billi.
If similar cyanobacteria developed on Mars, it is possible that they, too, could have boasted the potential to thrive under the different types of rocks on the Red Planet.
The research was funded by the Italian Ministry of Foreign Affairs, Direzione Generale per la Promozione del Sistema Paese, NASA's Astrobiology Science and Technology for Exploring Planets (ASTEP), and the NASA Graduate Student Research Program. The BIOMEX research is supported by the European Space Agency and the German Aerospace Center/Federal Ministry of Economics and Energy.
The last survivors?
For scientists, cyanobacteria come in handy in determining how life persists in extreme conditions and might even endure on a place as seemingly inhospitable as Mars.
Although the harsh landscape photographed by Curiosity may appear similar to Earth's deserts, the two types of regions can also be very different. Mars is dry-drier than any of Earth's desert. The temperatures are colder, the atmospheric pressures lower, and the atmosphere so thin that intense radiation from the Sun pierces the surface.
"We can use cyanobacteria in Mars simulation experiments and test them under Mars-like conditions in specific simulation chambers," de Vera said.
"If they are able to grow, to be metabolically active, and also to photosynthesize during Mars simulation experiments, this could give very good indications that Mars was recently a habitable planet."
The huge temperature difference between the Martian night and day affects the humidity levels on Mars, because warm air can hold more water vapor than cold air. At night, the air is saturated with water vapor-reaching humidity levels of 100 percent-while during daylight hours, the humidity level is far lower.De Vera cited the work of Dirk Mohlmann, a physics professor at the Collegium Budapest who studies water on Mars and asks whether or not the planet could be habitable today.
These conditions would depend on the ability of cyanobacteria to use the high humidity of Martian soil at night, as well as in the very early morning or evening when light might be available for photosynthesis. Cyanobacteria found in salt deposits in former lakes in the Chilean Atacama Desert, the driest non-polar desert on Earth, have the potential to use salty liquids similar to those found flowing down Martian slopes seasonally.
At some point, Mars lost its protective atmosphere and its water. Hardy cyanobacteria, or something similarly robust, could be the last survivors of a devolving ecosystem on Mars.
"The first such refuges were likely in ice-free areas, similar to those found in the Antarctic Dry Valleys," Billi said, referring to one of the most extreme cold deserts on Earth.
As Mars' water retreated from its surface, any potential lifeforms would have hunkered down beneath the regolith to escape the harsher environment.
According to Billi, studying the cyanobacteria in conditions on Earth that simulate those on Mars can help researchers to define and spot biosignatures on Mars that could indicate life. Such investigations could prove useful for future missions to Mars that will scout for signs of life.
For now, however, it's a step in the right direction to know that our earthly cyanobacteria can thrive and adapt to living beneath Martian rocks of various types, be they quartz or shale.
Life Beyond Earth
Lands Beyond Beyond - extra solar planets - news and science
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Sir Isaac Newton (January 4, 1643 - March 31, 1727) was an English mathematician, physicist, astronomer, alchemist, and natural philosopher who is generally regarded as one of the greatest scientists and mathematicians in history. Newton wrote the Philosophiae Naturalis Principia Mathematica, in which he described universal gravitation and the three laws of motion, laying the groundwork for classical mechanics. By deriving Kepler's laws of planetary motion from this system, he was the first to show that the motion of objects on Earth and of celestial bodies are governed by the same set of natural laws. The unifying and deterministic power of his laws was integral to the scientific revolution and the advancement of heliocentrism.
Among other scientific discoveries, Newton realized that the spectrum of colors observed when white light passes through a prism is inherent in the white light and not added by the prism (as Roger Bacon had claimed in the thirteenth century), and notably argued that light is composed of particles.
He also developed a law of cooling, describing the rate of cooling of objects when exposed to air.
He enunciated the principles of conservation of momentum and angular momentum.
Finally, he studied the speed of sound in air, and voiced a theory of the origin of stars.
Despite this renown in mainstream science, Newton actually spent more time working on alchemy than physics, writing considerably more papers on the former than the latter.
Newton played a major role in the development of calculus, sharing credit with Gottfried Leibniz. He also made contributions to other areas of mathematics, for example the generalized binomial theorem. The mathematician and mathematical physicist Joseph Louis Lagrange (1736-1813), said that "Newton was the greatest genius that ever existed and the most fortunate, for we cannot find more than once a system of the world to establish."
Born in the hamlet of Woolsthorpe, Newton was the only son of a local yeoman, also Isaac Newton, who had died three months before, and of Hannah Ayscough. That same year, at Arcetri near Florence, Galileo Galilei had died; Newton would eventually pick up his idea of a mathematical science of motion and bring his work to full fruition. A tiny and weak baby, Newton was not expected to survive his first day of life, much less 84 years.
From the age of about twelve until he was seventeen, Newton was educated at The King's School in Grantham (where his signature can still be seen upon a library window sill). He was removed from school and by Oct 1659 he was to be found at Woolsthorpe, where his mother attempted to make a farmer of him. He was, by later reports of his contemporaries, thoroughly unhappy with the work. It appears to be Henry Stokes, master at the King's School, who persuaded his mother to send him back to school so that he might complete his education.
In June 1661 he matriculated to Trinity College, Cambridge. At that time, the college's teachings were based on those of Aristotle, but Newton preferred to read the more advanced ideas of modern philosophers such as Descartes and astronomers such as Galileo, Copernicus and Kepler.
When Newton arrived in Cambridge in 1661, the movement now known as the scientific revolution was well advanced, and many of the works basic to modern science had appeared. Astronomers from Copernicus to Kepler had elaborated the heliocentric system of the universe. Galileo had proposed the foundations of a new mechanics built on the principle of inertia. Led by Descartes, philosophers had begun to formulate a new conception of nature as an intricate, impersonal, and inert machine. Yet as far as the universities of Europe, including Cambridge, were concerned, all this might well have never happened. They continued to be the strongholds of outmoded Aristotelianism, which rested on a geocentric view of the universe and dealt with nature in qualitative rather than quantitative terms.
Like thousands of other undergraduates, Newton began his higher education by immersing himself in Aristotle's work. Even though the new philosophy was not in the curriculum, it was in the air. Some time during his undergraduate career, Newton discovered the works of the French natural philosopher Rene Descartes and the other mechanical philosophers, who, in contrast to Aristotle, viewed physical reality as composed entirely of particles of matter in motion and who held that all the phenomena of nature result from their mechanical interaction.
A new set of notes, which he entitled Quaestiones Quaedam Philosophicae (Certain Philosophical Questions), begun sometime in 1664, usurped the unused pages of a notebook intended for traditional scholastic exercises; under the title he entered the slogan "Amicus Plato amicus Aristoteles magis amica veritas" ("Plato is my friend, Aristotle is my friend, but my best friend is truth").
Newton's scientific career had begun.
The "Quaestiones" reveal that Newton had discovered the new conception of nature that provided the framework of the scientific revolution. He had thoroughly mastered the works of Descartes and had also discovered that the French philosopher Pierre Gassendi had revived atomism, an alternative mechanical system to explain nature. The "Quaestiones" also reveal that Newton already was inclined to find the latter a more attractive philosophy than Cartesian natural philosophy, which rejected the existence of ultimate indivisible particles.
The works of the 17th-century chemist Robert Boyle provided the foundation for Newton's considerable work in chemistry. Significantly, he had read Henry More, the Cambridge Platonist, and was thereby introduced to another intellectual world, the magical Hermetic tradition, which sought to explain natural phenomena in terms of alchemical and magical concepts. The two traditions of natural philosophy, the mechanical and the Hermetic, antithetical though they appear, continued to influence his thought and in their tension supplied the fundamental theme of his scientific career.
Although he did not record it in the "Quaestiones," Newton had also begun his mathematical studies. He again started with Descartes, from whose La Geometrie he branched out into the other literature of modern analysis with its application of algebraic techniques to problems of geometry. He then reached back for the support of classical geometry. Within little more than a year, he had mastered the literature; and, pursuing his own line of analysis, he began to move into new territory. He discovered the binomial theorem, and he developed the calculus, a more powerful form of analysis that employs infinitesimal considerations in finding the slopes of curves and areas under curves.
When Newton received the bachelor's degree in April 1665, the most remarkable undergraduate career in the history of university education had passed unrecognized. On his own, without formal guidance, he had sought out the new philosophy and the new mathematics and made them his own, but he had confined the progress of his studies to his notebooks.
Then, in 1665, the plague closed the university, and for most of the following two years he was forced to stay at his home, contemplating at leisure what he had learned. During the plague years Newton laid the foundations of the Calculus and extended an earlier insight into an essay, "Of Colors," which contains most of the ideas elaborated in his Opticks.
It was during this time that he examined the elements of circular motion and, applying his analysis to the Moon and the planets, derived the inverse square relation that the radially directed force acting on a planet decreases with the square of its distance from the Sun--which was later crucial to the law of universal gravitation. The world heard nothing of these discoveries. He chose not to share concepts he had discovered unless he was asked.
Newton became a fellow of Trinity College in 1669. In the same year he circulated his findings in De Analysi per Aequationes Numeri Terminorum Infinitas (On Analysis by Infinite Series), and later in De methodis serierum et fluxionum (On the Methods of Series and Fluxions), whose title gave rise to the "method of fluxions". Despite the fact that only a handful of savants were even aware of Newton's existence, he had arrived at the point where he had become the leading mathematician in Europe.
Newton and Gottfried Leibniz developed the calculus independently, using different notations. Although Newton had worked out his method years before Leibniz, he published almost nothing about it until 1693, and did not give a full account until 1704. Meanwhile, Leibniz began publishing a full account of his methods in 1684. Moreover, Leibniz's notation and "differential Method" were universally adopted on the Continent, and after 1820 or so, in the British Empire.
Newton claimed that he had been reluctant to publish his calculus because he feared being mocked for it. Starting in 1699, other members of the Royal Society accused Leibniz of plagiarism, and the dispute broke out in full force in 1711. Thus began the bitter calculus priority dispute with Leibniz, which marred the lives of both Newton and Leibniz until the latter's death in 1716. This dispute created a divide between British and Continental mathematicians that may have retarded the progress of British mathematics by at least a century.
Newton is generally credited with the generalized binomial theorem, valid for any exponent. He discovered Newton's identities, Newton's method, classified cubic plane curves (polynomials of degree three in two variables), made substantial contributions to the theory of finite differences, and was the first to use fractional indices and to employ coordinate geometry to derive solutions to Diophantine equations.
He approximated partial sums of the harmonic series by logarithms (a precursor to Euler's summation formula), and was the first to use power series with confidence and to revert power series. He also discovered a new formula for pi.He was elected Lucasian professor of mathematics in 1669.
In that day, any fellow of Cambridge or Oxford had to be an ordained Anglican priest. However, the terms of the Lucasian professorship required that the holder not be active in the church (presumably so as to have more time for science). Newton argued that this should exempt him from the ordination requirement, and Charles II, whose permission was needed, accepted this argument. Thus a conflict between Newton's religious views and Anglican orthodoxy was averted.
Replica of Newton's 6-inch reflecting telescope of 1672 for the Royal Society
From 1670 to 1672 he lectured on optics. During this period he investigated the refraction of light, demonstrating that a prism could decompose white light into a spectrum of colours, and that a lens and a second prism could recompose the multicoloured spectrum into white light. He also showed that the coloured light does not change its properties, by separating out a coloured beam and shining it on various objects.
Newton noted that regardless of whether it was reflected or scattered or transmitted, it stayed the same color. Thus the colors we observe are the result of how objects interact with the incident already-colored light, not the result of objects generating the color. Many of his findings in this field were criticized by later theorists, the most well-known being Johann Wolfgang von Goethe, who postulated his own color theories.
From this work he concluded that any refracting telescope would suffer from the dispersion of light into colours, and invented a reflecting telescope (today known as a Newtonian telescope) to bypass that problem.
By grinding his own mirrors, using Newton's rings to judge the quality of the optics for his telescopes, he was able to produce a superior instrument to the refracting telescope, due primarily to the wider diameter of the mirror. (Only later, as glasses with a variety of refractive properties became available, did achromatic lenses for refractors become feasible.)
In 1671 the Royal Society asked for a demonstration of his reflecting telescope. Their interest encouraged him to publish his notes On Color, which he later expanded into his Opticks.
When Robert Hooke criticized some of Newton's ideas, Newton was so offended that he withdrew from public debate. The two men remained enemies until Hooke's death.
In one experiment, to prove that color perception is caused by pressure on the eye, Newton slid a darning needle around the side of his eye until he could poke at its rear side, dispassionately noting "white, darke & colored circles" so long as he kept stirring with "ye bodkin."
Newton argued that light is composed of particles, but he had to associate them with waves to explain the diffraction of light (Opticks Bk. II, Props. XII-XX).
Later physicists instead favored a purely wavelike explanation of light to account for diffraction.
Today's quantum mechanics restores the idea of "wave-particle duality", although photons bear very little resemblance to Newton's corpuscles (e.g., corpuscles refracted by accelerating toward the denser medium).
Newton is believed to have been the first to explain precisely the formation of the rainbow from water droplets dispersed in the atmosphere in a rain shower.
In his Hypothesis of Light of 1675, Newton posited the existence of the ether to transmit forces between particles. Newton was in contact with Henry More, the Cambridge Platonist who was born in Grantham, on alchemy, and now his interest in the subject revived.
During a period of isolation, Newton was greatly influenced by the Hermetic tradition with which he had been familiar since his undergraduate days.
Newton, always somewhat interested in alchemy, now immersed himself in it, copying by hand treatise after treatise and collating them to interpret their arcane imagery. Under the influence of the Hermetic tradition, his conception of nature underwent a decisive change.
Until that time, Newton had been a mechanical philosopher in the standard 17th-century style, explaining natural phenomena by the motions of particles of matter. Thus, he held that the physical reality of light is a stream of tiny corpuscles diverted from its course by the presence of denser or rarer media. He felt that the apparent attraction of tiny bits of paper to a piece of glass that has been rubbed with cloth results from an ethereal effluvium that streams out of the glass and carries the bits of paper back with it.
This mechanical philosophy denied the possibility of action at a distance; as with static electricity, it explained apparent attractions away by means of invisible ethereal mechanisms.
Newton's Hypothesis of Light of 1675, with its universal ether, was a standard mechanical system of nature. Some phenomena, such as the capacity of chemicals to react only with certain others, puzzled him, however, and he spoke of a "secret principle" by which substances are "sociable" or "unsociable" with others.
About 1679, Newton abandoned the ether and its invisible mechanisms and began to ascribe the puzzling phenomena - chemical affinities, the generation of heat in chemical reactions, surface tension in fluids, capillary action, the cohesion of bodies, and the like, to attractions and repulsions between particles of matter.
More than 35 years later, in the second English edition of the Opticks, Newton accepted an ether again, although it was an ether that embodied the concept of action at a distance by positing a repulsion between its particles. The attractions and repulsions of Newton's speculations were direct transpositions of the occult sympathies and antipathies of Hermetic philosophy--as mechanical philosophers never ceased to protest.
Newton, however, regarded them as a modification of the mechanical philosophy that rendered it subject to exact mathematical treatment. As he conceived of them, attractions were quantitatively defined, and they offered a bridge to unite the two basic themes of 17th-century science--the mechanical tradition, which had dealt primarily with verbal mechanical imagery, and the Pythagorean tradition, which insisted on the mathematical nature of reality. Newton's reconciliation through the concept of force was his ultimate contribution to science.
John Maynard Keynes, who acquired many of Newton's writings on alchemy, stated that "Newton was not the first of the age of reason: he was the last of the magicians."
Newton's interest in alchemy cannot be isolated from his contributions to science. He lived at a time when there was no clear distinction between alchemy and science. Had he not relied on the occult idea of action at a distance, across a vacuum, he might not have developed his 'theory of gravity.'
In 1704 Newton wrote Opticks, in which he expounded his corpuscular theory of light. He considered light to be made up of extremely subtle corpuscles, that ordinary matter was made of grosser corpuscles and speculated that through a kind of alchemical transmutation "Are not gross Bodies and Light convertible into one another,...and may not Bodies receive much of their Activity from the Particles of Light which enter their Composition?" Newton also constructed a primitive form of a frictional electrostatic generator, using a glass globe (Optics, 8th Query). Controversy
Among the most important dissenters to Newton's paper was Robert Hooke, one of the leaders of the Royal Society who considered himself the master in optics and hence he wrote a condescending critique of the unknown parvenu. One can understand how the critique would have annoyed a normal man. The flaming rage it provoked, with the desire publicly to humiliate Hooke, however, bespoke the abnormal. Newton was unable rationally to confront criticism. Less than a year after submitting the paper, he was so unsettled by the give and take of honest discussion that he began to cut his ties, and he withdrew into virtual isolation.
In 1675, during a visit to London, Newton thought he heard Hooke accept his theory of colors. He was emboldened to bring forth a second paper, an examination of the colour phenomena in thin films, which was identical to most of Book Two as it later appeared in the Opticks.
The purpose of the paper was to explain the colors of solid bodies by showing how light can be analyzed into its components by reflection as well as refraction. His explanation of the colors of bodies has not survived, but the paper was significant in demonstrating for the first time the existence of periodic optical phenomena.
He discovered the concentric coloured rings in the thin film of air between a lens and a flat sheet of glass; the distance between these concentric rings (Newton's rings) depends on the increasing thickness of the film of air. In 1704 Newton combined a revision of his optical lectures with the paper of 1675 and a small amount of additional material in his Opticks.
A second piece which Newton had sent with the paper of 1675 provoked new controversy. Entitled "An Hypothesis Explaining the Properties of Light," it was in fact a general system of nature. Hooke apparently claimed that Newton had stolen its content from him, and Newton boiled over again. The issue was quickly controlled, however, by an exchange of formal, excessively polite letters that fail to conceal the complete lack of warmth between the men.
Newton was also engaged in another exchange on his theory of colors with a circle of English Jesuits in Lige, perhaps the most revealing exchange of all. Although their objections were shallow, their contention that his experiments were mistaken lashed him into a fury. The correspondence dragged on until 1678, when a final shriek of rage from Newton, apparently accompanied by a complete nervous breakdown, was followed by silence. The death of his mother the following year completed his isolation. For six years he withdrew from intellectual commerce except when others initiated a correspondence, which he always broke off as quickly as possible.
In 1679, Newton returned to his work on mechanics, i.e., gravitation and its effect on the orbits of planets, with reference to Kepler's laws of motion, and consulting with Hooke and Flamsteed on the subject. He published his results in De Motu Corporum (1684). This contained the beginnings of the laws of motion that would inform the Principia.
The Philosophiae Naturalis Principia Mathematica (now known as the Principia) was published on 5 July 16871 with encouragement and financial help from Edmond Halley.
In this work Newton stated the three universal laws of motion that were not to be improved upon for more than two hundred years. He used the Latin word gravitas (weight) for the force that would become known as gravity, and defined the law of universal gravitation. In the same work he presented the first analytical determination, based on Boyle's law, of the speed of sound in air.
With the Principia, Newton became internationally recognised. He acquired a circle of admirers, including the Swiss-born mathematician Nicolas Fatio de Duillier, with whom he formed an intense relationship that lasted until 1693. The end of this friendship led Newton to a nervous breakdown.
In the 1690s Newton wrote a number of religious tracts dealing with the literal interpretation of the Bible. Henry More's belief in the infinity of the universe and rejection of Cartesian dualism may have influenced Newton's religious ideas. A manuscript he sent to John Locke in which he disputed the existence of the Trinity was never published.
Later works - The Chronology of Ancient Kingdoms Amended (1728) and Observations Upon the Prophecies of Daniel and the Apocalypse of St. John (1733) - were published after his death.
He also devoted a great deal of time to alchemy.
Newton was also a member of the Parliament of England from 1689 to 1690 and in 1701, but his only recorded comments were to complain about a cold draft in the chamber and request that the window be closed.
Newton moved to London to take up the post of warden of the Royal Mint in 1696, a position that he had obtained through the patronage of Charles Montagu, 1st Earl of Halifax, then Chancellor of the Exchequer. He took charge of England's great recoining, somewhat treading on the toes of Master Lucas (and finagling Edmond Halley into the job of deputy comptroller of the temporary Chester branch). Newton became perhaps the best-known Master of the Mint upon Lucas' death in 1699, a position Newton held until his death. These appointments were intended as sinecures, but Newton took them seriously, retiring from his Cambridge duties in 1701, and exercising his power to reform the currency and punish clippers and counterfeiters.
As Master of the Mint Newton unofficially moved the Pound Sterling to the gold standard from silver in 1717; great reforms at the time and adding considerably to the wealth and stability of England. It was his work at the Mint, rather than his earlier contributions to science, that earned him a knighthood from Queen Anne in 1705.
Newton was made President of the Royal Society in 1703 and an associate of the French Academie des Sciences. In his position at the Royal Society, Newton made an enemy of John Flamsteed, the Astronomer Royal, by prematurely publishing Flamsteed's star catalogue.
Newton died in London on March 20th, 1727, and was buried in Westminster Abbey. His half-niece, Catherine Barton Conduitt, served as his hostess in social affairs at his house on Jermyn Street in London; he was her "very loving Uncle", according to his letter to her when she was recovering from smallpox. Newton died intestate and his considerable estate was divided between his half-nieces and half-nephews.
After his death, Newton's body was discovered to have had massive amounts of mercury in it, probably resulting from his alchemical pursuits. Mercury poisoning could explain Newton's eccentricity in late life.
The law of gravity became Newton's best-known discovery. He warned against using it to view the universe as a mere machine, like a great clock. He said, "Gravity explains the motions of the planets, but it cannot explain who set the planets in motion. God governs all things and knows all that is or can be done."
His scientific fame notwithstanding, Newton's study of the Bible and of the early Church Fathers were among his greatest passions. He devoted more time to the study of the Scriptures, the Fathers, and to Alchemy than to science, and said, "I have a fundamental belief in the Bible as the Word of God, written by those who were inspired. I study the Bible daily."
Newton himself wrote works on textual criticism, most notably An Historical Account of Two Notable Corruptions of Scripture.
Newton also placed the crucifixion of Jesus Christ at 3 April, AD 33, which is now the accepted traditional date. He also attempted, unsuccessfully, to find hidden messages within the Bible.
Despite his focus on theology and alchemy, Newton tested and investigated these ideas with the scientific method, observing, hypothesizing, and testing his theories. To Newton, his scientific and religious experiments were one and the same, observing and understanding how the world functioned.
Newton rejected the church's doctrine of the trinity, and was probably a follower of arianism. In a minority view, T.C. Pfizenmaier argues that he more likely held the Eastern Orthodox view of the Trinity rather than the Western one held by Roman Catholics, Anglicans, and most Protestants.
In his own day, he was also accused of being a Rosicrucian (as were many in the Royal Society and in the court of Charles II).
In his own lifetime, Newton wrote more on religion than he did on natural science. He believed in a rationally immanent world, but he rejected the hylozoism implicit in Leibniz and Baruch Spinoza. Thus, the ordered and dynamically informed universe could be understood, and must be understood, by an active reason, but this universe, to be perfect and ordained, had to be regular.
Newton and Robert Boyle's mechanical philosophy was promoted by rationalist pamphleteers as a viable alternative to the pantheists and enthusiasts, and was accepted hesitantly by orthodox preachers as well as dissident preachers like the latitudinarians.
Thus, the clarity and simplicity of science was seen as a way to combat the emotional and metaphysical superlatives of both superstitious enthusiasm and the threat of atheism, and, at the same time, the second wave of English deists used Newton's discoveries to demonstrate the possibility of a "Natural Religion."
The attacks made against pre-Enlightenment "magical thinking," and the mystical elements of Christianity, were given their foundation with Boyle's mechanical conception of the universe. Newton gave Boyle's ideas their completion through mathematical proofs, and more importantly was very successful in popularizing them.
The perceived ability of Newtonians to explain the world, both physical and social, through logical calculations alone is the crucial idea in the disenchantment of Christianity.
Newton saw God as the master creator whose existence could not be denied in the face of the grandeur of all creation.
But the unforeseen theological consequence of his conception of God, as Leibniz pointed out, was that God was now entirely removed from the world's affairs, since the need for intervention would only evidence some imperfection in God's creation, something impossible for a perfect and omnipotent creator.
Leibniz's theodicy cleared God from the responsibility for "l'origine du mal" by making God removed from participation in his creation. The understanding of the world was now brought down to the level of simple human reason, and humans, as Odo Marquard argued, became responsible for the correction and elimination of evil.
On the other hand, latitudinarian and Newtonian ideas taken too far resulted in the millenarians, a religious faction dedicated to the concept of a mechanical universe, but finding in it the same enthusiasm and mysticism that the Enlightenment had fought so hard to extinguish.
As warden of the royal mint, Newton estimated that 20% of the coins taken in during The Great Recoinage were counterfeit. Counterfeiting was treason, punishable by death by drawing and quartering. Despite this, convictions of the most flagrant criminals could be extremely difficult to achieve; however, Newton proved to be equal to the task.
He gathered much of that evidence himself, disguised, while he hung out at bars and taverns. For all the barriers placed to prosecution, and separating the branches of government, English law still had ancient and formidable customs of authority.
Newton was made a justice of the peace and between June 1698 and Christmas 1699 conducted some 200 cross-examinations of witnesses, informers and suspects. Newton later ordered all records of his interrogations to be destroyed. Newton won his convictions and in February 1699, he had ten prisoners waiting to be executed.
Newton's greatest triumph as the king's attorney was against William Chaloner. One of Chaloner's schemes was to set up phony conspiracies of Catholics and then turn in the hapless conspirators whom he entrapped. Chaloner made himself rich enough to posture as a gentleman.
Petitioning Parliament, Chaloner accused the Mint of providing tools to counterfeiters (a charge also made by others). He proposed that he be allowed to inspect the Mint's processes in order to improve them. He petitioned Parliament to adopt his plans for a coinage that could not be counterfeited, while at the same time striking false coins. After being exposed by Newton, Chaloner was hanged, drawn and quartered on March 23, 1699.
Enlightenment philosophers chose a short history of scientific predecessors - Galileo, Boyle, and Newton principally - as the guides and guarantors of their applications of the singular concept of Nature and Natural Law to every physical and social field of the day. In this respect, the lessons of history and the social structures built upon it could be discarded.
It was Newton's conception of the universe based upon Natural and rationally understandable laws that became the seed for Enlightenment ideology. Locke and Voltaire applied concepts of Natural Law to political systems advocating intrinsic rights; the physiocrats and Adam Smith applied Natural conceptions of psychology and self-interest to economic systems and the sociologists criticized the current social order for trying to fit history into Natural models of progress. Monboddo and Samuel Clarke resisted elements of Newton's work, but eventually rationalized it to conform with their strong religious views of nature.
Newton's laws of motion and gravity provided a basis for predicting a wide variety of different scientific or engineering situations, especially the motion of celestial bodies. His calculus proved vitally important to the development of further scientific theories.
Finally, he unified many of the isolated physics facts that had been discovered earlier into a satisfying system of laws. Newton's conceptions of gravity and mechanics, though not as accurate as Einstein's Theory of Relativity or quantum mechanics, still represent an enormous step in the evolution of human understanding of the universe. For this reason, he is generally considered one of history's greatest scientists.
In 1717, the Kingdom of Great Britain went on to an unofficial gold standard when Newton, then Master of the Mint, established a fixed price of 44 guineas per standard (22 carat) troy pound. Under the gold standard the value of the pound (measured in gold weight) remained largely constant until the beginning of the 20th century.
Newton is reputed to have invented the cat flap. This was said to be done so that he would not have to disrupt his optical experiments, conducted in a darkened room, to let his cat in or out.
Newtonmas is a holiday celebrated by some scientists as an alternative to Christmas, taking advantage of the fact that Newton's birthday fell on 25 December in the Julian calendar in use at the time of his birth.
To this day, Newton's achievements have been immortalized in popular culture. Almost all schoolchildren are familiar with the apocryphal story of Newton's apple and his subsequent discovery of gravity; even the likeness of Newton holding an apple under a tree is a well-known image of science. English poet Alexander Pope was sufficiently moved by Newton's accomplishments to write the famous epitaph:
Newton has also featured in conspiracy theories and fiction.
Newton has been identified as a "Grand Master of the Priory of Sion" from 1691-1727 in documents that have been dismissed as a hoax concocted by Pierre Plantard.
This information was incorporated into the 1982 book The Holy Blood and the Holy Grail, which was later one of the primary source books for the bestselling 2003 Dan Brown novel The Da Vinci Code.
The famous three laws of Newton are:
The question was not whether gravity existed, but whether it extended so far from Earth that it could also be the force holding the moon to its orbit. Newton showed that if the force decreased as the inverse square of the distance, one could indeed calculate the Moon's orbital period, and get good agreement. He guessed the same force was responsible for other orbital motions, and hence named it "universal gravitation".
A contemporary writer, William Stukeley, recorded in his Memoirs of Sir Isaac Newton's Life a conversation with Newton in Kensington on April 15, 1726, in which Newton recalled "when formerly, the notion of gravitation came into his mind. It was occasioned by the fall of an apple, as he sat in contemplative mood. Why should that apple always descend perpendicularly to the ground, thought he to himself. Why should it not go sideways or upwards, but constantly to the earth's centre." In similar terms, Voltaire wrote in his Essay on Epic Poetry (1727), "Sir Isaac Newton walking in his gardens, had the first thought of his system of gravitation, upon seeing an apple falling from a tree." These accounts are probably exaggerations of Newton's own tale about sitting by a window in his home (Woolsthorpe Manor) and watching an apple fall from a tree.
Various trees are claimed to be "the" apple tree which Newton describes, the King's School, Grantham, claims that the tree was purchased by the school, uprooted and transported to the headmaster's garden some years later, the staff of the [now] National Trust-owned Woolsthrope Manor dispute this, and claim that a tree present in their gardens is the one described by Newton. It is also claimed that the tree was replanted in front of the council buildings in Grantham, which is unlikely, considering that they were built over 300 years after Newton's death. A clone of the original tree can be seen growing outside the main gate of Trinity College, Cambridge, below the room Newton lived in when he studied there.
Isaac Newton: Who He Was, Why Google Apples Are Falling
National Geographic - January 4, 2010
Unpublished Papers Reveal Lesser-known, but Significant Research of Sir Issac Newton PhysOrg - September 11, 2006
Known primarily for his foundational work in math and physics, Sir Issac Newton actually spent more time on research in alchemy, as well as its interrelationships with science, history and religion, and its implications for economics.
Alchemy, as Newton practiced it in the 17th and 18th centuries, was research into the nature of chemical substances and processes - primarily the transmutation of materials from one type of matter to another. Newton and others conducted experiments, but also incorporated philosophical thought in their attempts to uncover the mysteries of the physical universe.
"NewtonŐs extensive work on universal history (which presents human history as a coherent unit governed by certain immutable principles) provides an essential setting for linking his work on alchemy and his work heading EnglandŐs mint in the 1690s," said Georgia Institute of Technology Professor Kenneth Knoespel, who chairs the School of Literature, Communication and Culture. "It is not at all farfetched to think of history as a kind of alchemical process that looks to the creation of value and wealth."
Knoespel presented a talk titled NewtonŐs Alchemical work and the creation of economic value at the American Chemical SocietyŐs 232nd national meeting in San Francisco. The talk was part of a session dedicated to scholarship based on the unpublished manuscripts of Newton, most of which are housed at the University of Cambridge and in the Edelstein Center at Hebrew University in Jerusalem. For the past 15 years, Knoespel has studied both collections -- some portions of which weren't available to scholars until the 1970s.
By integrating the study of these manuscripts, Knoespel determined that NewtonŐs alchemical practice functions as a translation code for a new language of economics in which an investigation of material-spiritual value becomes transformed into a systematic structure of social value understood through economics.
Newton began to translate his notions of value in alchemy to an economic setting when he was appointed to head EnglandŐs mint Đ several years after the 1687 publication of "The Principia," in which Newton described universal gravitation and the three laws of motion, laying the groundwork for classical mechanics.
"Newton moves from an academic research position to a position of considerable visibility within the state," Knoespel noted. "He became the symbol of the stability of the British economy at this time. It is hardly an exaggeration to think of such a move as involving a shift from private research to the broad application of policy formed by decades of private research."
Newton took the new job very seriously, undertaking new research on the history of money and combining it with his work in mathematics, alchemy and metallurgy. He improved the edging of coins, much like U.S. coins are formed today, to prevent people from clipping the edges. Newton also assayed the coins of Europe to determine the amount of gold and silver they contained to help establish EnglandŐs economic basis.
As the economic system of capitalism began to be institutionalized in Europe in the decades following Newton, many thought that capital, or value, within capitalism was being mystified in the same way that gold is within its alchemical transformation. Newton thought by improving the English economic system, he was going to contribute to the ongoing transformation of England into GodŐs kingdom on Earth. A Newtonian approach to matter carries with it a Messianic force that finally grounds itself in natural philosophy that includes an interpretation of human and natural history.
Newton never makes economic value the sole force that determines history. Instead, the practice of economics is at least twofold, involving both the practice of a monetary system and a conceptual framework that sees within an economic system, the workings of God in time.
Connecting the published work of Newton the mathematician and the physicist with the unpublished work of Newton the alchemist, historian and religious philosopher provides broader insight into his legacy. The history of science has often separated Newton the complex mathematician from the Newton of the Newtonians. The purists say: 'Newton is a mathematician and a physicist. DonŐt mix him up with religion or alchemy because youŐll turn him into Harry Potter.' But it is this purist belief that for 200 years suppressed NewtonŐs unpublished work in alchemy until the mid-20th century. Newton was profoundly interested in the relationship between physics and religion, but that doesnŐt turn him into a magician."
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Access to the past would open all sorts of new possibilities of more than travel.
By Charles Q. Choi, ISNS Contributor via Inside Science
(ISNS) — Time travel is often a way to change history in science fiction such as “Back to the Future” and “Looper.” Now researchers suggest a certain kind of time machine could also possess another powerful capability — cloning perfect copies of anything.
However, scientists noted the way these findings violate what is currently known about quantum physics might instead mean such time machines are not possible.
We are all time travelers in that we all move forward in time. However, scientists have suggested it might be possible to move back in time by manipulating the fabric of space and time in our cosmos. All mass distorts space-time, causing the experience of gravity, a bit like how a ball sitting on a rubber sheet would make nearby balls on the sheet roll toward it. Physicists have proposed time machines that could bend the fabric of space and time so much that timelines actually turn back on themselves, forming loops technically known as “closed timelike curves.”
These space-time warps can develop because of wormholes — tunnels that can in theory allow travel anywhere in space and time, or even into another universe. Wormholes are allowed by Einstein’s general theory of relativity, although whether they are practically possible is another matter.
A key limitation of this kind of time machine would be that any traveler using it cannot go back to a time before the device was built. It only permits travel from the future back to any point in time after the machine was constructed.
Scientists have for decades explored what closed timelike curves are capable of if they are possible.
One complication they would encounter is the no-cloning theorem in quantum physics, which basically forbids the creation of identical copies of any particle one does not know everything about to begin with.
In classical physics, one can generate a perfect copy of anything by finding out every detail about it and arranging the same components in the same order. However, in the bizarre world of quantum physics — the best description so far of how reality behaves on its most fundamental levels — one cannot perfectly measure every detail of an object at once. This is related to Heisenberg’s uncertainty principle, which notes that one can perfectly measure either the position or the momentum of a particle, but not both with unlimited accuracy.
Nearly 25 years ago, theoretical physicist David Deutsch at the University of Oxford in England suggested closed timelike curves might actually violate the no-cloning theorem, allowing perfect copies to be constructed of anything. Now scientists reveal this might be true in findings detailed in the Nov. 8 issue of the journal Physical Review Letters.
To understand this research, imagine one builds a time machine in the year 2000. One could place a letter into the device in the year 3000 and pick it up within this box in 2000 or any year between then and 3000. From the perspective of the letter, it goes inside this time machine into one mouth of a wormhole in the future and comes out the other mouth of the wormhole in the past.
However, theoretical physicist Mark Wilde at Louisiana State University, in Baton Rouge, and his colleagues found this scenario may be more complex than previously thought. Instead of the time machine containing just one wormhole, it could possess many wormholes, each at some point in time between the future and the moment of its creation. A letter entering the box in 3000 might exit from a wormhole in 2999, instantaneously go back into that wormhole and emerge in 2998, and so on.
“It’s like there are 1,000 different particles emerging from all the wormholes, but in fact they’re all the same particle you sent in the beginning,” Wilde said. “You just have all these temporary copies emerging from and going back into these wormholes.”
Members of the Flat Earth Society claim to believe the Earth is flat. Walking around on the planet’s surface, it looks andfeelsflat, so they deem all evidence to the contrary, such as satellite photos of Earth as a sphere, to be fabrications of a “round Earth conspiracy” orchestrated by NASA and other government agencies.
The belief that the Earth is flat has been described as the ultimate conspiracy theory. According to the Flat Earth Society’s leadership, its ranks have grown by 200 people (mostly Americans and Britons) per year since 2009. Judging by the exhaustive effort flat-earthers have invested in fleshing out the theory on their website, as well as the staunch defenses of their views they offer in media interviews and on Twitter, it would seem that these people genuinely believe the Earth is flat.
But in the 21st century, can they be serious? And if so, how is this psychologically possible?
Through a flat-earther’s eyes
First, a brief tour of the worldview of a flat-earther: While writing off buckets of concrete evidence that Earth is spherical, they readily accept a laundry list of propositions that some would call ludicrous. The leading flat-earther theory holds that Earth is a disc with the Arctic Circle in the center and Antarctica, a 150-foot-tall wall of ice, around the rim. NASA employees, they say, guard this ice wall to prevent people from climbing over and falling off the disc. Earth’s day and night cycle is explained by positing that the sun and moon are spheres measuring 32 miles (51 kilometers) that move in circles 3,000 miles (4,828 km) above the plane of the Earth. (Stars, they say, move in a plane 3,100 miles up.) Like spotlights, these celestial spheres illuminate different portions of the planet in a 24-hour cycle. Flat-earthers believe there must also be an invisible “antimoon” that obscures the moon during lunar eclipses.
Furthermore, Earth’s gravity is an illusion, they say. Objects do not accelerate downward; instead, the disc of Earth accelerates upward at 32 feet per second squared (9.8 meters per second squared), driven up by a mysterious force called dark energy. Currently, there is disagreement among flat-earthers about whether or not Einstein’s theory of relativity permits Earth to accelerate upward indefinitely without the planet eventually surpassing the speed of light. (Einstein’s laws apparently still hold in this alternate version of reality.)
As for what lies underneath the disc of Earth, this is unknown, but most flat-earthers believe it is composed of “rocks.” [Religion and Science: 6 Visions of Earth’s Core]
Then, there’s the conspiracy theory: Flat-earthers believe photos of the globe are photoshopped; GPS devices are rigged to make airplane pilots think they are flying in straight lines around a sphere when they are actually flying in circles above a disc. The motive for world governments’ concealment of the true shape of the Earth has not been ascertained, but flat-earthers believe it is probably financial. “In a nutshell, it would logically cost much less to fake a space program than to actually have one, so those in on the Conspiracy profit from the funding NASA and other space agencies receive from the government,” the flat-earther website’s FAQ page explains.
It’s no joke | 0.81744 | 3.701239 |
(PhysOrg.com) -- Exploring distant parts of the galaxy, astrophysicist Denis Sullivan has collaborated on the discovery of about six extrasolar planets--not bad for an accidental astronomer.
Next Tuesday Professor Sullivan will discuss his most recent research into some of the universe's deepest mysteries in his inaugural professorial lecture at Victoria University of Wellington, New Zealand.
"The world of modern astronomy presents a vast laboratory for investigating physical phenomena," says Professor Sullivan, who will draw on his astronomy research and teaching to give a physicist’s view on life and the universe.
The lecture will focus on different aspects of his research, including extrasolar planets, and the curiously named pulsating "White Dwarfs".
White Dwarfs are the dying remnants of stars like our sun. They are slowly cooling because the energy they radiate into space in the form of photons and neutrinos from the star’s surface and core is no longer replenished by internal nuclear reactions.
Using a one metre telescope at the Mt John Observatory in Lake Tekapo, Professor Sullivan has been observing White Dwarfs to study how stars evolve and die.
"Imagine something the mass of the sun (333,000 times the mass of the earth) eventually collapsing into something the size of earth. White Dwarfs are incredibly dense, with high surface gravities, and internal matter at extremely high pressures and temperatures," he says.
As part of the NZ-Japan Microlensing Observations in Astrophysics (MOA) group, Professor Sullivan has also contributed to the discovery of six planets using a technique called gravitational microlensing.
Professor Sullivan says the title of his lecture—'The Accidental Astronomer: A Personal Tour of the World of Astrophysics'—reflects the way he has drifted into astronomy after initially pursuing electrical engineering.
Born in Sydney, he completed his PhD in nuclear physics from the Australian National University (ANU) in Canberra. In 1968 he joined the Physics Department at Victoria University and his interest in instrumentation has led to his gradual move into astronomy.
Victoria University Vice-Chancellor Professor Pat Walsh says Professor Sullivan is an outstanding researcher and teacher in the area of astrophysics.
"Professor Sullivan has been at the forefront of astronomical research in this part of the world. His work at Mt John Observatory and at Victoria University is helping to make sense of the some of the universe’s deepest mysteries."
Professor Walsh says Victoria's Inaugural Lecture series is an opportunity for new professors to provide family, friends, colleagues and the wider community with an insight to their specialist area of study.
"It is also an opportunity for the University to celebrate and acknowledge our valued professors."
Provided by Victoria University of Wellington
Explore further: Newly discovered extrasolar planet is the smallest known and has smallest host star | 0.823259 | 3.320906 |
Astronomers from the United States modeled the processes of ejecting young earth-like planets from their systems and came to the conclusion that this is a very frequent event. For one star, there may be an average of two or three “lost” by her planet, wandering in the interstellar space.
They are practically invisible due to the absence of a noticeable radiation of their own. If this is so, the vagabond planets are the most numerous class of large objects in our Galaxy, and their total number may exceed one and a half trillion.
Scientists have simulated the process of formation of the planetary system of stars of the Solar type. The simulated systems had the same parameters as ours – including giant planets and the same mass of earth-like planets. During the simulated formation due to the interaction of protoplanets and large planets, the middle system emits about a third of the mass of the protoplanetary disk. Out of it, 0.79 of the Earth’s mass flies out of the system in the form of planets with an average size of about Mars, and as many as the same – in the form of bodies the size of a large asteroid or dwarf planet.
The average number of such planets was 7.9 for one star of the Sun type, and their average mass was 0.1 terrestrial. These are relatively small bodies, with gravity corresponding to approximately 0.4 g. True, stars that do not have giant planets have been thrown out only by asteroids. Without large planets, there were no small ones to “shove” out of the system.
The researchers proceeded from the assumption that only a minority of the stars of the Galaxy have large planets, since it is believed that red dwarfs (the most massive type of stars) are deprived of them. Based on this, the average number of planets-tramps the size of Mars is 2.5 per one star. In total, the galaxy has about 200 billion stars, which can account for half a trillion “free planets.”
The authors of the work tried to find out how realistic it was to find them with telescopes, and they came to disappointing conclusions. In the general case, they will be invisible. In interstellar space, there is almost no light that they could reflect, and their own thermal radiation is negligible. Frozen atmosphere and oceans will form an ice crust, playing the role of a heat-insulating material.
Even the ninth planet of the solar system, which is tens of times more massive and, possibly, with an incompletely frozen atmosphere, is still not found in telescopes, although it is only 100 billion kilometers from the Sun. The planet-tramps are on the average removed from the nearest stars by trillions of kilometers, besides they are much smaller.
This means that in telescopes they can be seen only if they accidentally pass between the Earth and the distant star. But it will be difficult to confirm such a transit. In most cases, it will be one-time, since the planet-tramp does not rotate around such a “highlighting” star, but simply flies by. | 0.897866 | 3.974003 |
Phases reveal glowing exoplanet
Four centuries after Galileo first observed the changing phases of Venus, astronomers have captured the phases of a planet outside our solar system.
The observations, made using the Convection Rotation and Planetary Transit satellite (CoRot), appear today in the journal Nature.
The planet, named CoRot-1b, was the first so-called 'hot Jupiter' to be found by the French satellite about two and a half years ago.
Hot Jupiters are a class of extrasolar planets that orbit their parent star at very close distances.
Dutch astronomer Dr Ignas Snellen, of Leiden University, and colleagues observed 36 orbits of CoRot-1b over a period of 55 days and found that the planet is 'tidally locked' - one side always facing its parent star.
Australian astronomer Daniel Bayliss, of the Research School of Astronomy and Astrophysics, at the Australian National University in Canberra, says optical observations of extrasolar planets have been a holy grail.
He says the results show that much of the light reflected by CoRot-1b is actually radiated heat, with the dayside of the planet having a temperature about 2000°C.
Bayliss, who recently completed his PhD on hot Jupiters, says the study shows that although the dayside gets extremely hot, the heat is not distributed to the night side of the planet whose year is just 1.5 days long.
He says infrared observations have been made of hot Jupiters, but optical observations are important because they provide extra information about the planet's atmosphere, such as the presence and composition of clouds.
Dr Michael Ireland, of the University of Sydney's School of Physics, says it was possible for the authors to detect this planet for two reasons.
First, the data is of extremely good quality because they are taken with a dedicated satellite, far from the reach of annoying effects of the earth's atmosphere, he says.
"Secondly, this planet is a known freak. It is the seventh closest hot Jupiter to its host star, and its host star is hotter than most," says Ireland.
"With both the temperature of the host star and the small star-planet distance taken together, this is one of the hottest hot Jupiters known."
He says the findings show the planet is "literally glowing red hot". "At 2000°C it is as hot as the coolest stars."
Bayliss hopes similar observations of planets further from their host star will occur soon.
"If you can start to see the atmosphere you can get a good guess as to whether they are habitable," he says.
Bayliss says this may be possible with the Kepler telescope, which was launched last month.
The telescope will soon begin scanning 100,000 stars, less than 3000 light away, for earth-sized planets as they move across the face of their host stars. | 0.878596 | 3.942609 |
An international team of scientists has found the brightest gamma-ray binary ever seen, and it's the first to be seen outside the Milky Way galaxy.
The team combined data from NASA's Fermi Gamma-ray Space Telescope with those from other facilities and confirmed that what was once thought to be a high-mass X-ray binary (HMXB) was in fact, a gamma-ray binary system.
Their findings have been published in The Astrophysical Journal.
The newly found gamma-ray binary, named LMC P3, was discovered in a small nearby galaxy called the Large Magellanic Cloud (LMC), located 163,000 light-years away.
Gamma-ray binaries are systems wherein there are two stars, one orbiting the other.
One is usually a massive star and the other is either a black hole or a neutron star (an extremely magnetic star), and are very rare, with only five found in our galaxy to date.
And so far, LMC P3 is the most luminous gamma-ray binary system ever found in terms of gamma rays, X-rays, radio waves, and visible light.
"Fermi has detected only five of these systems in our own galaxy, so finding one so luminous and distant is quite exciting," NASA Goddard Space Flight Centre lead researcher Robin Corbet says.
"Gamma-ray binaries are prized because the gamma-ray output changes significantly during each orbit and sometimes over longer time scales. This variation lets us study many of the emission processes common to other gamma-ray sources in unique detail."
Cosmic death rays
Having two extremely high-energy bodies within a system undoubtedly causes immense energy to be unleashed.
On a regular day, the ozone layer protects us from gamma rays beaming around from outer space.
However, gamma-ray bursts can wipe out life in an entire planet, if that planet happens to be in its beam direction. And some postulate that such an event did just that to Earth 450 million years ago.
It is estimated that gamma-ray binaries emit between 0.1 to over 100 gigaelectron-volts (GeV) of energy.
According to the American Geophysical Union:
"Alpha and Beta rays are easily stopped by paper, clothes and skin. Gamma Rays are the bad ones. It takes a few inches of lead or a few feet of concrete and dirt to slow or stop them.
A detonating nuclear device will produce a LOT of gamma rays. Even if the blast doesn't get you, the dose of radiation could be very high, and perhaps fatal."
Such discoveries are incredibly humbling experiences.
Even with all of our knowledge and technological achievements, we are still discovering new and exciting phenomena. This exemplifies the importance of scientific curiosity and exploration. | 0.859476 | 4.06509 |
Stars. They are such stuff as dreams are made on. They shine in the night sky, reminders of our insignificance and the vastness of the universe. They may sit millions of light years away, but they are closer than you think.
Simply put, stars are massive balls of plasma held together by their own gravity. Once a critical mass of interstellar dust and debris and accumulates, its gravity pulls it together, heating its core enough to fuse hydrogen into helium. The heat from these reactions balances the gravitational force of the outer shells, preventing the star from collapsing under its own mass. Stars spend most of their lives on what is called the main sequence, fusing hydrogen into helium as they orbit galactic centers at incredible speed.
So where do we fit into this? Current theories suggest that following the Big Bang, the universe was composed mostly of hydrogen. This raises an important question: where did all the other stuff come from? Our planet contains elements spanning the periodic table, and without many of them life on Earth could not exist. The answer lies in the end of the stellar life cycle.
When a sufficiently massive star runs low on hydrogen, its gravity compresses the core, heating it enough to fuse helium into carbon. As the star ages this process repeats itself, each time creating enough heat to create a new element. This continues along the periodic table until it reaches iron. At this point the star can no longer support itself and collapses in a spectacular supernova, creating even heavier elements and giving off as much energy as entire galaxies. These massive stars leave behind either neutron stars or black holes.
A supernova blasts the star’s outer layers into space, zooming through the cosmos at nearly the speed of light. The dust and debris create stellar nurseries, where materials come together to form stars and solar systems. As new stars take shape, the heavier elements coalesce into asteroids, comets, and new planets. At least one of these planets has fostered life.
So all the carbon, oxygen, iron, nitrogen, and most other elements in your body formed in the core of a star. These atoms have travelled millions of light years, drifting across the galaxy until they ended up in our solar system. Next time you gaze up at the night sky, remember that you are made of those glamorous stars.
For me, this is one of the most fascinating and beautiful secrets of outer space. Just looking at the stars amazes me, let alone thinking of how the elements of my body were born in a supernova. What do you think? Is this as incredible as I make it out to be? Share your thoughts in the comments section below. As always, please like, share, or reblog this post if you enjoy it. That small click really helps me out! Be sure to check me out on Twitter and Facebook as well. Thanks for reading! Don’t forget to subscribe for new content every Wednesday! IT’S FREE!
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What’s the most amazing secret of outer space? | 0.903615 | 3.770301 |
The fireball was at least partly recorded by automatic digital all-sky fireball cameras at Czech stations Churáňov, Kocelovice, Kunžak, Ondřejov, Růžová and Svratouch. These stations are part of the European Fireball Network, which covers central Europe and has the headquarters at the Astronomical Institute of the Czech Academy of Sciences in Ondřejov. Figure 1 shows the fireball recorded low over the SSW horizon by the camera located at the station of the Czech Hydrometeorological Institute in Kocelovice. The interruptions of the luminous path of the fireball are caused by an electronic shutter. They enable us to determine the velocity and atmospheric deceleration of the fireball. Although the fireball was outside Czech territory and relatively distant from the cameras (125 – 320 km), the photographic records and the precise light curve from photometers, which are also parts of the cameras, made possible to determine all parameters of the atmospheric passage with very good precision. In addition, a digital photographic spectrum of the fireball containing 60 spectral lines was obtained at the Kunžak station in southern Bohemia. Only one recorded meteorite fall has a more detailed spectrum – the Benešov meteorite fall of May 7, 1991. The fireball was photographed also at several places in Austria and Germany but these records were not suitable for the determination of trajectory and velocity.
At 21:36:51 universal time (22:36:51 local time), relatively large meteoroid of mass of about 600 kg and size about 70 cm entered the terrestrial atmosphere and started to weakly radiate at a height of 86 km near the city of Mattighofen in Upper Austria. Thanks to the steep trajectory with the slope of 70 degrees to the surface, the brightness increased rapidly and reached magnitude –15.5 in maximum (recomputed to the distance of 100 km), i.e. many times more than that of the full Moon. The body entered the atmosphere with a speed of 14 km/s and continued the flight almost exactly in the northern direction, subject to deceleration and also fragmentation. The luminous trajectory was 72 km long and lasted for 5.5 seconds. The projection of the atmospheric trajectory to the surface is plotted in Fig. 2 and is relatively short because of the steep trajectory. Thanks to the low speed, steep trajectory, large initial mass, and sufficient strength of the material, the fireball ceased to radiate at a relatively low height of 17.6 km to the east from the town Braunau am Inn, exactly on the Austrian-German border, formed here by the river of Inn. Such a deep penetration is rare, which is demonstrated by the fact that such a low terminal height was observed only exceptionally during several decades of our systematic observations. It also means that meteorite fall certainly occurred. Since there were several conspicuous flares along the fireball trajectory, representing fragmentation events, it is obvious that large number of fragments of masses from grams to kilograms reached the surface. The fall area lies mostly on German territory, to the north of Inn river, between towns Stubenberg on the west and Ering on the east (see Fig. 3). Small fragments are expected in the eastern part of the fall area and fragment mass will increase toward west and northwest. The largest fragments are expected to be located in the forest east of Stubenberg.
Before the collision with the Earth, the meteoroid followed a heliocentric orbit with low eccentricity and low inclination to the plane of ecliptic (i.e. Earth’s orbit). In perihelion, the meteoroid was only slightly closer to the Sun than the Earth. In aphelion, it reached the inner asteroid belt (see Fig. 4). The meteoroid therefore originated in an inner belt of asteroids.
The searches for meteorites started shortly after we announced the fall area to our German colleagues the next day after the fireball passage. The effort on German side is mostly coordinated by Dieter Heinlein, who is a long-term collaborator of the European Fireball Network. A more detailed description of the fall area and the proposed optimal search strategy (related to the expected meteorite masses) was submitted to him on March 10. The first search in large group was performed on March 12. The search was successful shortly after the noon, when several fragments of total mass of about 45 grams (see Fig. 5) were found. They were evidently part of a single meteorite, which broke up at the impact. The total mass well corresponded to the expected meteorite masses at given location. The finders R. Sporn and M. Neuhofer were so kind to lend one 1.6 g piece to us for classification. The classification was performed by Dr. Jakub Haloda in the laboratories of the Czech Geological Survey. The meteorite was classified as an ordinary chondrite of type LL6, containing also a clast with achondritic composition. It is a breccia, i.e. meteorite composed from more types of material. The inner structure of the meteorite is shown in Fig. 6. Another fragment was classified by Prof. Addi Bischoff from the Münster University and it was also the LL6 breccia (link to the press release). The composition of meteorite confirmed its asteroidal origin. The unofficial name of the meteorite is Stubenberg.
At the present time, about 25 meteorites with instrumentally determined trajectory and orbit are known. In 15 cases, including the very first one, the Příbram meteorite of April 7, 1959, the trajectory computation was performed by the scientists of the Astronomical Institute of the Czech Academy of Sciences. Recently, meteorites Ždár nad Sázavou, which fell on December 9, 2014, were recovered on the basis of their computation.
Finally, we would like to thank for
all reports of the fireball observation sent to us by casual witnesses
Press release in pdf | 0.803631 | 3.797899 |
The existence of neutrinos was first postulated in 1930 by Wolfgang Pauli to ensure conservation of energy and angular momentum in beta decay; effectively, it carries away excess energy in nuclear reactions. Three different types of neutrinos exist, known as electron-, mu-, and tau-neutrinos, corresponding to the three massive leptons: electrons, muons, and tau leptons.
The Sun produces neutrinos from thermonuclear fusion reactions in its core and, since these neutrinos pass clean through the Sun and then all the way to Earth, they provide a way of glimpsing into the heart of a star. A large flux of neutrinos carries away most of the energy of a supernova and neutrinos are one of the candidates for dark matter. So, neutrino astronomy offers an important new window on the universe beyond the electromagnetic spectrum. Because neutrinos pass so easily through matter, they're very hard to detect: large masses of stopping material and indirect detection of the effects of neutrino absorption are needed. Among the most powerful neutrino "telescopes" are the Sudbury Neutrino Observatory in Canada and the Super-Kamiokande in Japan.
One of the great puzzles of astrophysics in recent decades, has been the discrepancy between the number of neutrinos detected coming from the Sun and the number expected from theory. The so-called solar neutrino problem, which emerged from measurements by Ray Davis and his pioneering neutrino detector in a South Dakotan gold mine, suggesting that only one-third the expected number of solar neutrinos were arriving at Earth, has now been effectively cleared up by recent data from the Canadian and Japanese instruments. These data show that some of the electron-neutrinos produced in the Sun's core change into the other types of neutrino while en route to Earth. Earlier experiments, including that of Davis, only registered the electron-neutrinos and therefore suggested a shortfall. The newer experiments, such as that at Sudbury, pick up all the varieties of neutrino and have shown that the total count of solar neutrinos is in line with the rate of electron-neutrino predicted by orthodox theory of nuclear reactions inside the Sun.
Related category PARTICLE PHYSICS
Home • About • Copyright © The Worlds of David Darling • Encyclopedia of Alternative Energy • Contact | 0.859433 | 4.110978 |
Black holes are areas in the universe where gravity pulls in everything, even light. Nothing can get out and all objects are squeezed into a tiny space. Because there is no light in black holes we cannot see them. But scientists can detect the immense gravity and radiation around them. They are the most mysterious objects in astronomy. Scientists think that the first black holes were formed when the universe began about 13 billion of years ago.
Albert Einstein was the first scientist to predict that black holes existed. But it was in 1971 that the first black hole was actually discovered.
Black holes can have various sizes, some may be even as small as an atom. But they all have one thing in common – a very large mass.
There are three kinds of black holes :
- A stellar occurs when very large stars burn away the rest of the fuel that they have and collapse. It is so massive that several of our suns could fit in it. Our sun, however, could never become a stellar because it is too small.
- Supermassives are the largest and most dominating black holes in our universe. They have masses of a million or more suns put together. Every galaxy has a supermassive in its centre. As they become larger and larger they pull in more material. The black hole at the centre of our Milky Way is four million times as massive as our sun and surrounded by very hot gas.
- Intermediate mass black holes have not been found yet, but scientists think they probably exist. They have the mass of between a hundred and a thousand suns.
A black hole consists of three parts:
- The outer event horizon is the farthest away from the centre. Gravity here is not so strong and you would be able to escape from it.
- The inner event horizon is the middle part of a black hole. In this area an object would be slowly pulled to the centre.
- The singularity is the centre of a black hole, where gravity is strongest.
What a black hole in the universe might look like
- The Milky Way
- Albert Einstein
- Light and Optics
- The Sun
- Stars - Great Balls of Gas in the Universe
- IRIS - NASA's New Solar Telescope
- Scientists Discover Gravitational Waves
- collapse = break apart
- consist of = to be formed by two or more parts
- detect = discover something that is not easy to see
- discover = to find something for the first time
- dominate = stand out
- escape = get away from
- farthest = far away
- fuel = here: the material that makes a star burn
- galaxy = one of the large groups of stars that make up the universe
- gravity = the power that makes something fall to the ground or pulled by another planet or star
- however = but
- immense = very large
- in common = the same as something else
- intermediate = middle sized
- mass = the amount of a material
- massive = large
- mysterious = strange, unexplained
- occur = happen
- predict =to say that you think something exists or will happen
- probably = maybe, most likely
- radiation = energy in the form of heat or light that is sent out in waves
- scientist = a person who is trained in science and works in a lab
- size = how big something is
- squeeze = to press something together
- surrounded = to be all around something
- tiny = very small
- various = different | 0.848557 | 3.850168 |
The nearby Magellanic Cloud galaxies are tidally interacting with each other, displacing over 2 billion times the mass of the Sun in gas. A tidal feature called the Leading Arm is spearheading these galaxies on their trajectory to the Milky Way. Its fragmented morphology suggests that it is already interacting with our galaxy and supplying it with star-forming material in the form of gas. We present new optical observations of the Leading Arm with which we derive a heliocentric distance to the structure.
Located inside the Large Magellanic Cloud, fierce explosions called supernovae have thrown out massive amounts of gas in every direction. A portion of this gas is aimed toward the Milky Way and is on a crash course with our galaxy. We are observing this gas with the Wisconsin H-Alpha Mapper, which provides a window into how the gas is distributed. These observations show two periods of supernovae explosions that created two distinct gas winds. One of these winds is currently active while the other was produced roughly 300 Million years old. Studying these gas clouds will provide information on how massive these winds are and the rate at which they are produced. The ejected gas is headed toward the Milky Way could supply our galaxy with additional gas to form stars in the future.
Studying something as large as the Milky Way can be a daunting task, and studying the galaxy in its entirety is impossible, so astronomers use small pieces, such as star clusters, to “trace" the behavior and make-up of the galaxy. With the advent of large-scale surveys covering 70%-100% of the sky, more of these tracer components are available than ever before. But they aren’t trivial to pick out of the massive datasets. We have developed a program that integrates data from multiple large scale surveys to identify star clusters and determine fundamental parameters that trace the galaxy in that location (3D velocity and location, chemical make-up, age). We also present initial work using these clusters to study the distribution of chemicals in the Milky Way.
Author(s): Md Tanvir Hasan Physics & Astronomy Roberto Gonzalez-Rodriguez Chemistry & Biochemistry Anton Naumov Physics & Astronomy Conor Ryan Physics & Astronomy Brian Senger Physics & Astronomy
Advisor(s): Anton Naumov Physics & Astronomy
Location: Session: 2; 3rd Floor; Table Number: 1
(Poster is private)
Graphene oxide (GO) inherits high transparency, substantial conductivity, high tensile strength from its parent materials graphene. Apart from these properties, it emits fluorescence which makes it a potential material to use in optoelectronics and bio-sensing applications. In this work, we have utilized systematic ozone treatment to alter the optical band gap of single-layered graphene oxide in aqueous suspensions. Due to controlled ozonation, additional functionalization takes place in GO graphitic sheet which changes GO electronic structure. This is confirmed by the increase in vibrational transitions of a number of oxygen-containing functional groups with treatment and the appearance of the prominent carboxylic group feature at c.a. 1700 1/cm. Albeit, timed ozone induction introduces only slight change in color and absorption spectra of GO samples, the emission spectra show a gradual increase in intensity with a significant blue shift up to 100 nm from deep red to green. This large blue shift suggests an increase in optical band gap with additional functionalization introduced by ozone treatment. We utilize a semi-empirical theoretical approach to describe the effects of functionalization-induced changes. This model attributes the origins of fluorescence emission to the quantum confined sp² carbon islands in GO encircled by the functional groups. As we decrease the graphitic carbon cluster size on the GO sheet, the optical bandgap calculated via HyperChem molecular modeling increases, which supports the experimentally observed blue shifts in emission. This theoretical result is further supported by the TEM measurement of ozone-treated samples, which shows a decreasing trend of average ordered graphitic carbon cluster size on GO sheets with treatment time. Theoretical modeling, as well as the experimental results, indicate that the optical bandgap and emission intensity of GO are alterable with controlled ozone treatment, which allows tailoring the optical properties of GO for specific applications in optoelectronics and bio-sensing.
Two small galaxies outside the Milky Way, called the Magellanic Clouds, are violently interacting with each other. As they interact, gas is stripped out of them, which leaves a huge gaseous tail as they orbit the Milky Way. This tidal debris covers a quarter the sky from earths perspective. The goal of this to project determine the properties of the gas that is trailing behind the Magellanic Clouds by creating maps of the neutral and ionized gas. We trace the neutral hydrogen with radio observations taken with the Arecibo Observatory and the ionized hydrogen using optical observations taken with the Wisconsin H-alpha Mapper telescope. This gaseous stream will one day fall onto the Milky Way and provide our galaxy with material to create new stars.
A massive gas cloud, known as Complex A, is headed towards our Galaxy. This high-velocity cloud is made up of 2 million times the mass of the Sun of neutral and ionized hydrogen. This cloud is traveling towards the Milky Way's disk, through the Galactic halo. This halo is made up of low density gas at a million degrees Kelvin that acts as a headwind that damages the cloud. Light escaping the Milky Way’s disk also hits the cloud and ionizes it. Using 21-cm radio observations from the Green Bank Telescope, we studied the motions of the gas. We found that diffuse gas is lagging behind the denser parts of the cloud. These motions suggest that gas is being stripped off the cloud and that it is dissolving into the Galactic halo. This disruptive process means that less gas will safely reach the disk of Milky Way and therefore the cloud will provide less gas for making future stars.
Resonances occurring in quantum mechanical cross-sections can be attributed to the existence of complex eigenvalues of the associated Schrödinger equation. For sufficiently narrow resonances the real part of such eigenvalues corresponds to the energy of the resonance and the imaginary part is directly related to its width.
Recently, mathematicians settled a more than 30-year-old controversy regarding the distribution of such resonance eigenvalues for a specific model scattering potential. The controversy arose due to the fact that two different numerical approaches applied to solving the non-relativistic Schrödinger equation gave rise to two different results. In addition to providing a mathematical proof as to which of the two methods was correct, the recent study predicted the approximate location of additional resonance eigenvalues in the complex energy plane.
The present study seeks to revisit this problem in an attempt to provide more accurate eigenvalues for these additional resonances. The complex rotation method was applied to the Riccati equation corresponding to the one-dimensional Schrödinger equation and a Python code was written to numerically integrate the logarithmic derivative of the wave function and search for energy eigenvalues in the complex plane.
We use 3D plots and short videos to illustrate our technique, the original controversy, as well as the reason for the difficulty in locating the new resonances. Much improved numerical values for these resonances are also presented.
Author(s): Hana Jaafari Physics & Astronomy Hung Doan Physics & Astronomy Sangram Raut Physics & Astronomy
Advisor(s): Zygmunt Gryczynski Physics & Astronomy
Location: Session: 1; 2nd Floor; Table Number: 3
Medical therapeutics is an ever-growing field seeking to improve patients’ livelihoods through means including efficient drug delivery, which ensures that the medication reaches its maximum efficacy. The micro-viscosities within a cell may affect the diffusion of medication, and can be measured through molecular viscometers in order to potentially increase the quality of future therapeutic research. The BODIPY dye is utilized as a molecular viscometer and past spectroscopic and lifetime studies have characterized BODIPY monomers, as well as rotor and non-rotor BODIPY dimers. Triazine-based rotor and non-rotor BODIPY trimers were synthesized for this study, and then the dyes’ photophysical properties and behavior within cells were measured. The results of this study indicated that the BODIPY trimer is a fluorophore with a high molar extinction coefficient, and may successfully be employed as a molecular viscometer within cells.
Author(s): Matthew Melendez Physics & Astronomy John Donor Physics & Astronomy Peter Frinchaboy Physics & Astronomy Julia O'Connell Physics & Astronomy
Advisor(s): Peter Frinchaboy Physics & Astronomy
Location: Session: 1; B0; Table Number: 6
The Open Cluster Chemical Abundances and Mapping (OCCAM) survey is a systematic survey of Galactic open clusters using data primarily from the SDSS-III/APOGEE-1 survey. However, neutron capture elements are limited in the IR region covered by APOGEE. In an effort to fully study detailed Galactic chemical evolution, we are conducting a high resolution (R~60,000) spectroscopic abundance analysis of neutron capture elements for OCCAM clusters in the optical regime to complement the APOGEE results. As part of this effort, we present Ba II, La II, Ce II and Eu II results for a few open clusters without previous abundance measurements using data obtained at McDonald Observatory with the 2.1 m Otto Struve telescope and Sandiford Echelle Spectrograph.
Author(s): Hope Murphy Physics & Astronomy Elizabeth Sizemore Physics & Astronomy
Advisor(s): Hana Dobrovolny Physics & Astronomy Anton Naumov Physics & Astronomy
Location: Session: 2; B0; Table Number: 8
Three million women have breast cancer in US, causing breast cancer to be the second most common cause of death from cancer for women. Doxorubicin is a commonly used drug for cancer treatment. The focus of my research is characterizing the drug efficacy for doxorubicin in the human breast cancer cell line MCF-7. There are two quantities that characterize the effect of a drug: E_max is the maximum possible effect from a drug and IC_50 is the drug concentration where the effect diminishes by half. We are using mathematical modeling to extract E_max and IC_50 for Doxorubicin in MCF-7 cells. This work is intended to characterize the efficacy of anticancer drug treatments and determine the correct doses before trying those in patients to get the most effective therapeutic treatment for patients.
Graphene is thought to be revolutionary material due to its vast inherent properties. It can give us thinner, faster, and cheaper electronics. Graphene oxide (GO) inherits its properties from graphene and as opposed to graphene, can be conveniently mass- produced using chemical synthesis. We seek to classify new derivatives of graphene with specific optical properties for applications in optoelectronics. The properties of graphene can be tailored through chemical modifications, such as hydrogenation and halogenation.
In this work we present various methods for the synthesis of graphene derivatives by utilizing different functional groups and study their optical properties. The successfully functionalized graphitic derivatives include diazonium functionalized graphene; lightly oxidized graphene; nitro-graphene; and bromo-graphene. The presence of functional groups is confirmed by FTIR spectra showing characteristic vibrational frequencies. All of functionalized graphitic derivatives exhibit fluorescence regarding their functionalization. This leads us to understand that the fluorescence in GO appears not to be dependent on specific functional groups but rather on the confinement of the graphitic regions produced by those.
Such functional derivatives of graphene may expand its applications in optoelectronics and make it a more versatile material for a variety of applications.
Thus we also look into the behavior of graphene oxide in applications related to microelectronics studying the fluorescence of GO in the electric fields.
Emission quenching was observed using GO films under electric fields of the order of 10^6 V/m. A dried GO/PVP film was subject up to 1500V in between transparent conductive ITO electrodes. As high voltage was applied to the slides, a fluorescence signal decreased by 35.9%.
A capability of such electric-field controlled emission is highly applicable in optoelectronic transistors and can advance modern microelectronics.
Respiratory viral infections are a leading cause of mortality worldwide. As many as 40% of patients hospitalized with influenza-like illness are reported to be infected with more than one type of viruses. Mathematical models can be used to help us understand the dynamics of respiratory viral coinfections and their impact on the severity of the illness. We develop a mathematical model which allows for respiratory cells to be infected simultaneously with two types of viruses. A mathematical analysis is performed to assess the full behavioral dynamics of the model. We find that chronic coinfection does not occur in this model; infection grows due to only one viral species. Some other mechanism must be responsible for the long-lasting coinfections in humans.
The goal of this study was to conduct a survey of 913 M-dwarf stars from the Lepine and Shara Proper Motion(LSPM) catalog within 33 parsecs. This research was conducted to improve upon the statistics of nearby multiple M-dwarf star systems. Identifying and confirming multiple systems at both wide and small separations will expand understanding of M-dwarf formation by comparing these results to existing star formation models. Data for these targets was collected with the Robo-AO camera on the Palomar 60in telescope. Separation and position angles were determined and compared for two epochs of the images containing multiple stars, one taken in 2012 and the other taken in 2014, to look for changes in these values. Stars with little change in position with respect to one another suggest they are common proper motion pairs. The Washington Double Star(WDS) catalog and other resources were used to further determine binarity. There were 50 multiple star system candidates found with a multiplicity fraction of 28.6±3.0 and a companion star fraction of 34.7±2.1.
Author(s): Hannah Richstein Physics & Astronomy Kat Barger Physics & Astronomy Jing Sun Physics & Astronomy
Advisor(s): Kat Barger Physics & Astronomy
Location: Session: 1; 3rd Floor; Table Number: 3
Our universe contains billions of galaxies, made up of stars, gas, and interstellar dust. We can examine the light emitted from these galaxies to learn about the different energetic events occurring within them. These include supernova explosions in the disk and active black holes at the center, which are both enhanced by galaxy interactions. Before the light from the stellar activity and the warm gas reaches us, it scatters off dust along its path. This causes the light to appear redder than it originally was. If we do not correct for this reddening effect, we could misinterpret the processes occurring within the galaxies. This project examines the properties of two galaxies interacting over a large distance and illustrates the importance of reddening correction for better understanding galaxy evolution.
Many influenza experiments are done in vitro, however, not all cell lines used in these experiments possess the proteins necessary to cleave hemagglutinin, an important step in cell infection. Trypsin is a protein used to facilitate in vitro influenza infections. Trypsin cleaves the viral surface protein hemagglutinin, allowing it to fuse with the cell membrane and enter the cell. We use data from in vitro influenza infections in the presence and absence of trypsin to parameterize a within-host mathematical model of influenza infection. This allows us to quantify the dynamical changes caused by the presence of trypsin.
Author(s): Elizabeth Sizemore Physics & Astronomy Marais Culp Physics & Astronomy Md. Tanvir Hasan Physics & Astronomy
Advisor(s): Anton Naumov Physics & Astronomy
Location: Session: 2; 1st Floor; Table Number: 4
Graphene and its derivatives are novel materials with a number of unique properties that can be applied in electronics, sensing and biotechnology. Particularly, graphene oxide (GO) is an exceptional system that, unlike graphene, can be chemically mass-produced at low cost and possesses physical properties that are critical for biomedical applications. GO exhibits pH-dependent fluorescence emission in the visible/near-infrared, providing a possibility of molecular imaging and pH-sensing. It is also water soluble and has a substantial platform for functionalization, which allows for the delivery of multiple therapeutics, or the attachment of different sensing moieties. Some of these properties can be adjusted by the means of chemical/physical processing to fit the desired therapeutic delivery or sensing approaches. We utilize and modify these properties to yield a multifunctional delivery/imaging/sensing platform geared toward the analysis of cancer therapeutics delivery in vitro. In our work GO serves as a drug transport agent when paired with cancer therapeutic drugs and as a molecular marker for imaging the delivery pathways. The optimal emission and excitation of the graphene oxide flakes are selected to maximize the imaging modality in the spectrally-confined region and reduce the effects of biological autofluorescence. We also modify GO physical properties via controlled oxidation to maximize the emission and reduce the cytotoxicity to low/negligible levels: we report over 90% cell viability with GO concentration levels of 15 ug/mL based on the MTT assay in HEK-293 cells. GO emission in healthy (HEK-293) and cancer (HeLa) cells is quantified for a variety of pH environments, as well as flake sizes, to identify the ideal conditions for cellular internalization and pH-sensing of acidic cancerous environments. In addition, in-vitro fluorescence microscopy analysis provide quantitative assessment of the drug delivery and preferential targeting for cancer versus healthy cells. The results of this work suggest GO as an innovative and effective multifunctional platform for cancer therapeutics.
A galaxy environment influences its internal properties. All galaxies start out small and grow bigger after merging with other galaxies. We are conducting a statistical study on isolated and interacting galaxies to determine how their environment impacts on their star-formation ability. We are using observations from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, which has already observed more than 3000 galaxies. We are examining the differences and similarities of the gas and stars in isolated and interacting galaxies to explore their past and current star formation activity. From these comparisons, we will identify which conditions promote and hinder star formation to learn how different types of galaxies evolved. An example of an isolated galaxy is shown here.
Restitution describes a functional relationship between the action potential duration (APD) and the preceding diastolic interval (DI). It plays an important role in the function of the heart and is believed to determine the stability of heart rhythms. We investigate the effects of various antiarrhythmic drugs on dynamic and S1-S2 restitution properties of action potential duration of ventricular cells by using a human ventricular cell model. The restitution hypothesis suggests that the slope of the restitution curve governs the transition to alternans. Our study examines the slope of these curves for three classes of drug to determine whether they are proarrhythmic or antiarrhythmic. | 0.831717 | 4.062167 |
The Cosmic Microwave Background Radiation is the afterglow of the Big Bang; one of the strongest lines of evidence we have that this event happened. UCLA’s Dr. Ned Wright explains.
“Ok, I’m Ned Wright, and I’m a professor of physics and astronomy at UCLA, and I work on infrared astronomy and cosmology.”
How useful is the cosmic microwave background radiation?
“Well, the most important information we get is from the cosmic microwave background radiation come from, at the lowest level, is it’s existence. When I started in astronomy, it wasn’t 100 percent certain that the Big Bang model was correct. And so with the prediction of a cosmic microwave background from the Big Bang and the prediction of no cosmic microwave background from the competing theory, the steady state, that was a very important step in our knowledge.”
“And then the second aspect of the cosmic microwave background that is very important, is that it’s spectrum is extremely similar to a black body. And so, by being a black body means that universe relatively smoothly transitioned from being opaque to being transparent, and then we actually see effectively an isothermal cavity when we look out, so it looks very close to a black body.”
“And the fact that we are moving through the universe can be measured very precisely by looking at what is called the dipole anisotropy of the microwave background. So one side of the sky is slightly hotter (about 3 millikelvin hotter) and one side of the sky – the opposite side of the sky – is slightly colder (about 3 millikelvin colder), so that means that we are moving at approximately a tenth of a percent of the speed of light. And in fact we now know very precisely what that value is – it’s about 370 kilometers per second. So that’s our motion, the solar system’s motion, through the universe.”
“An then the final piece of information we’re getting from the microwave background now, in fact the Planck satellite just gave us more information along these lines is measurement of the statistical pattern of the very small what I call anisotropies or little bumps and valleys in the temperature. So in addition to the 3 millikelvin difference, we actually have plus or minus 100 microkelvin difference in the temperature from different spots. And so, when you look at these spots, and look at their detailed pattern, you can actually see a very prominent feature, which is there’s about a one and a half degree preferred scale, and that’s what’s caused by the acoustic
waves that are set up by the density perturbations early in the history of the universe, and how far they could travel before the universe became transparent. And that’s a very strong indicator about the universe.”
What does it tell us about dark energy?
“The cosmic microwave background actually has this pattern on a half degree scale, and that gives you effectively a line of position, as you have with celestial navigation where you get a measurement of one star with a sextant, then you get a line on the map where you are. But you can look at the same pattern – the acoustic wave setup in the universe, and you see that in the galaxy’s distribution a lot more locally. We’re talking about galaxies, so it might be a billion light years away, but to cosmologists, that’s local. And these galaxies also show the same wave-like pattern, and you can measure that angle at scale locally and compare it to what you see in history and that gives you the crossing line of position. And that really tells us where we are in the universe, and how much stuff there is and it tells us that we have this dark energy which nobody really understands what it is, but we know what it’s doing. It’s making the universe accelerate in it’s expansion.” | 0.834046 | 4.106385 |
Research from a team at the University of Southampton have spotted red flashes coming from a black hole 7,800 light-years from Earth.
The flashes from the black hole (named V404 Cygni) took place in June 2015 over a two week span where the black hole went through a burst of activity. A study detailing the issues was published in the Monthly Notices of the Royal Astronomical Society.
The red coloration in the bursts is caused by the speed at which they were captured by ULTRACAM, a super fast imaging camera on the William Herschel Telescope (located in La Palma on the Canary Islands). The flashes lasted just 1/40th of a second, but packed a power equivalent of roughly 1,000 Suns per burst.
“The very high speed tells us that the region where this red light is being emitted must be very compact,” says the author of the study, Poshak Gandhi. “Piecing together clues about the color, speed, and the power of these flashes, we conclude that this light is being emitted from the base of the black hole jet.”
The activity was caused by the black hole devouring a nearby star that occurred in 1989. The black hole wasn’t able to devour the entire mass of the object, and was fired back into space in the form of jets, which produce the bright red flashes visible to our telescopes.
It’s not exactly understood how these jets form, but it’s though magnetic fields have a significant effect. Nonetheless, observing these events provides evidence as to how black holes interact with material in their orbit.
“We speculate that when the black hole was being rapidly force-fed by its companion orbiting star, it reacted violently by spewing out some of the material as a fast-moving jet,” says Dr. Gandhi. “The duration of these flashing episodes could be related to the switching on and off of the jet, seen for the first time in detail.
“The 2015 event has greatly motivated astronomers to coordinate worldwide efforts to observe future outbursts.”. | 0.827884 | 3.794853 |
Our Own Planet
Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Terra.
Home to millions of species, including humans, Earth is the only place in the universe where life is known to exist. The planet formed 4.54 billion years ago, and life appeared on its surface within a billion years. Since then, Earth's biosphere has significantly altered the atmosphere and other abiotic conditions on the planet, enabling the proliferation of aerobic organisms as well as the formation of the ozone layer which, together with Earth's magnetic field, blocks harmful radiation, permitting life on land. The physical properties of the Earth, as well as its geological history and orbit, allowed life to persist during this period. The world is expected to continue supporting life for another 1.5 billion years, after which the rising luminosity of the Sun will eliminate the biosphere.Earth's outer surface is divided into several rigid segments, or tectonic plates, that gradually migrate across the surface over periods of many millions of years. About 71% of the surface is covered with salt-water oceans, the remainder consisting of continents and islands; liquid water, necessary for all known life, is not known to exist on any other planet's surface. Earth's interior remains active, with a thick layer of relatively solid mantle, a liquid outer core that generates a magnetic field, and a solid iron inner core.
Earth interacts with other objects in outer space, including the Sun and the Moon. At present, Earth orbits the Sun once for every roughly 366.26 times it rotates about its axis. This length of time is a sidereal year, which is equal to 365.26 solar days. The Earth's axis of rotation is tilted 23.4° away from the perpendicular to its orbital plane, producing seasonal variations on the planet's surface with a period of one tropical year (365.24 solar days). Earth's only known natural satellite, the Moon, which began orbiting it about 4.53 billion years ago, provides ocean tides, stabilizes the axial tilt and gradually slows the planet's rotation. Between approximately 4.1 and 3.8 billion years ago, asteroid impacts during the Late Heavy Bombardment caused significant changes to the surface environment.Both the mineral resources of the planet, as well as the products of the biosphere, contribute resources that are used to support a global human population. The inhabitants are grouped into about 200 independent sovereign states, which interact through diplomacy, travel, trade and military action. Human cultures have developed many views of the planet, including personification as a deity, a belief in a flat Earth, and a modern perspective of the world as an integrated environment that requires stewardship.
The famous "Blue Marble" photograph of Earth, taken from Apollo 17
Scientists have been able to reconstruct detailed information about the planet's past. The earliest dated solar system material is dated to 4.5672 ± 0.0006 billion years ago, and by 4.54 billion years ago (within an uncertainty of 1%) the Earth and the other planets in the Solar System formed out of the solar nebulaa disk-shaped mass of dust and gas left over from the formation of the Sun. This assembly of the Earth through accretion was largely completed within 1020 million years. Initially molten, the outer layer of the planet Earth cooled to form a solid crust when water began accumulating in the atmosphere. The Moon formed soon afterward, most likely as the result of a Mars-sized object (sometimes called Theia) with about 10% of the Earth's mass impacting the Earth in a glancing blow. Some of this object's mass would have merged with the Earth and a portion would have been ejected into space, but enough material would have been sent into orbit to form the Moon.
and volcanic activity produced the primordial atmosphere. Condensing water vapor,
augmented by ice and liquid water delivered by asteroids and the larger proto-planets,
comets, and trans-Neptunian objects produced the oceans. Two major models have
been proposed for the rate of continental growth: steady growth to the present-day
and rapid growth early in Earth history. Current research shows that the second
option is most likely, with rapid initial growth of continental crust followed
by a long-term steady continental area. On time scales lasting hundreds of millions
of years, the surface continually reshaped itself as continents formed and broke
up. The continents migrated across the surface, occasionally combining to form
a supercontinent. Roughly 750 million years ago (mya), one of the earliest known
supercontinents, Rodinia, began to break apart. The continents later recombined
to form Pannotia, 600540 mya, then finally Pangaea, which broke apart 180
Since the 1960s, it has been hypothesized that severe glacial action between 750 and 580 mya, during the Neoproterozoic, covered much of the planet in a sheet of ice. This hypothesis has been termed "Snowball Earth", and is of particular interest because it preceded the Cambrian explosion, when multicellular life forms began to proliferate.
Following the Cambrian explosion, about 535 mya, there have been five mass extinctions. The last extinction event was 65 mya, when a meteorite collision probably triggered the extinction of the (non-avian) dinosaurs and other large reptiles, but spared small animals such as mammals, which then resembled shrews. Over the past 65 million years, mammalian life has diversified, and several mya, an African ape-like animal gained the ability to stand upright. This enabled tool use and encouraged communication that provided the nutrition and stimulation needed for a larger brain. The development of agriculture, and then civilization, allowed humans to influence the Earth in a short time span as no other life form had, affecting both the nature and quantity of other life forms.
The present pattern of ice ages began about 40 mya and then intensified during the Pleistocene about 3 mya. The polar regions have since undergone repeated cycles of glaciation and thaw, repeating every 40100,000 years. The last ice age ended 10,000 years ago.
planet size comparisons
A terrestrial planet is a planet that is primarily composed of silicate rocks. The term is derived from the Latin word for Earth, "Terra", so an alternate definition would be that these are planets which are, in some notable fashion, "Earth-like". Terrestrial planets are substantially different from gas giants, which might not have solid surfaces and are composed mostly of some combination of hydrogen, helium, and water existing in various physical states. Terrestrial planets all have roughly the same structure: a central metallic core, mostly iron, with a surrounding silicate mantle. Terrestrial planets have canyons, craters, mountains, volcanoes and secondary atmospheres. | 0.847037 | 3.174513 |
October 18, 2011
Researchers Explain How The Milky Way Killed Off Its Satellites
Two researchers from Observatoire Astronomique de Strasbourg have revealed for the first time the existence of a new signature of the birth of the first stars in our galaxy, the Milky Way. More than 12 billion years ago, the intense ultraviolet light from these stars dispersed the gas of our Galaxy's nearest companions, virtually putting a halt to their ability to form stars and consigning them to a dim future. Now Pierre Ocvirk and Dominique Aubert, members of the Light in the Dark Ages of the Universe (LIDAU) collaboration, have explained why some galaxies were killed off, while stars continued to form in more distant objects. The two scientists publish their results in the October issue of the letters of the journal Monthly Notices of the Royal Astronomical Society.
The first stars of the Universe appeared about 150 million years after the Big Bang. Back then, the hydrogen and helium gas filling the universe was cold enough for its atoms to be electrically neutral. As the ultraviolet (UV) light of the first stars propagated through this gas, it broke apart the proton-electron pairs that make up hydrogen atoms, returning them to the so-called plasma state they experienced in the first moments of the Universe. This process, known as reionization, also resulted in significant heating, which had dramatic consequences: the gas became so hot that it escaped the weak gravity of the lowest mass galaxies, thereby depriving them of the material needed to form stars.It is now widely accepted that this process can explain the small number and large ages of the stars seen in the faintest dwarf galaxy satellites of the Milky Way. It also helps scientists understand why galaxies like the Milky Way have so few satellites around them — the 'missing satellites' problem. The stripping out of gas from these galaxies makes them sensitive probes of the UV radiation in the reionization epoch.
The satellite galaxies are also relatively close, from 30000 to 900000 light-years away, which allows us to study them in great detail, something that will be enhanced by the coming generation of larger telescopes. Comparing the population of their stars in each galaxy with its position could give us a unique insight into the structure of the UV radiation emitted from the earliest stars in the Milky Way.
Until now, models for this process assumed that the radiation leading to the removal of gas from galaxy satellites was produced collectively by all the large galaxies nearby, resulting in a uniform background of UV light. The new model put together by the two French researchers proves this assumption wrong.
Ocvirk and Aubert looked at the way the invisible 'dark matter' that makes up about 23% of the Universe structured itself with the stars in our Galaxy and its environs from shortly after the Big Bang to the present day. They used the high resolution numerical simulation Via Lactea II to model the formation of stars in gas trapped in the dark matter haloes that envelop galaxies, and then to describe how this gas reacted to UV radiation.
Pierre Ocvirk comments, "This is the first time that a model accounts for the effect of the radiation emitted by the first stars formed at the center of the Milky Way on its satellite galaxies.
'In contrast to previous models, the radiation field produced is not uniform, but decreases in intensity as one moves away from the center of the Milky Way.
'The satellite galaxies close to the galactic center see their gas evaporate very quickly. They form so few stars that they can be undetectable with current telescopes. At the same time, the more remote satellite galaxies experience on average a weaker irradiation. Therefore they manage to keep their gas longer, and form more stars. As a consequence they are easier to detect and appear more numerous."
The new model appears to be a close match to observations of our Galaxy and its neighborhood and suggests that the first stars of our galaxy played a major role in the photo-evaporation of the satellite galaxies' gas, adds Dr Ocvirk. "It is not large nearby galaxies but our own that caused the demise of its tiny neighbors, asphyxiating them through its intense radiation."
The results appear in the paper "A signature of the internal reionization of the Milky Way?", Pierre Ocvirk and Dominique Aubert, Monthly Notices of the Royal Astronomical Society, in press.
Image Caption: An image of the dwarf galaxy Bootes II, one of 21 known companions to the Milky Way. Credit: V. Belokurov / SDSS collaboration
On the Net:
- Observatoire Astronomique de Strasbourg
- Royal Astronomical Society
- Monthly Notices of the Royal Astronomical Society | 0.812801 | 4.048689 |
Saturday, March 13, 2010
William Herschel announces discovery of Uranus
It was on this day in 1781 that the astronomer William Herschel announced he had discovered the planet Uranus — only at first he was cautious and did not call it a "planet."
European astronomers went to work trying to confirm the planethood of Uranus, making calculations about things like its Earth-Sun distance and the shape of its orbit. Soon, everyone agreed that what Herschel reported was a planet, and in 1783 — two years after he first spotted the celestial object from his garden in Bath, England — William Herschel announced humbly but formally that he'd discovered a planet.
A German astronomer, Bode, proposed the planet be named "Uranus," after the Greek god of the sky. Astronomers generally prefer to pronounce the planet's name with the emphasis on the first syllable, as in "YUR uh nuhs," which is the way it's said in Latin. But English speakers have adopted the pronunciation with emphasis on the second syllable.
Uranus is the seventh planet from the Sun. Its equator is four times longer than Earth's equator, and its mass is about 14½ times greater than Earth's. It takes 84 Earth years to make one complete orbit around the Sun. Its day — the amount of time it takes to make a full spin on its axis — is just 17 hours and 14 minutes, compared with Earth's 24 hours.
It is known as one of the "ice giants," and its atmosphere is the coldest in the solar system, with a temperature of about negative 215 degrees Celsius, and is made up mostly of hydrogen and helium gases. Most of what we know about Uranus comes from an unmanned NASA expedition, Voyager 2, in the mid-1980s. The spacecraft flew within about 50,000 miles of the planet's top layer of clouds, taking pictures and collecting data.
Uranus, (YUR uh nuhs or yu RAY nuhs), is the seventh planet from the sun. Only Neptune and Pluto are farther away. Uranus is the farthest planet that can be seen without a telescope. Its average distance from the sun is about 1,784,860,000 miles (2,872,460,000 kilometers), a distance that takes light about 2 hours 40 minutes to travel.
Uranus is a giant ball of gas and liquid. Its diameter at the equator is 31,763 miles (51,118 kilometers), over four times that of Earth. The surface of Uranus consists of blue-green clouds made up of tiny crystals of methane. The crystals have frozen out of the planet's atmosphere. Far below the visible clouds are probably thicker cloud layers made up of liquid water and crystals of ammonia ice. Deeper still -- about 4,700 miles (7,500 kilometers) below the visible cloud tops -- may be an ocean of liquid water containing dissolved ammonia. At the very center of the planet may be a rocky core about the size of Earth. Scientists doubt Uranus has any form of life.
Uranus was the first planet discovered since ancient times. British astronomer William Herschel discovered it in 1781. Johann E. Bode, a German astronomer, named it Uranus after a sky god in Greek mythology. Most of our information about Uranus comes from the flight of the United States spacecraft Voyager 2. In 1986, that craft flew within about 50,000 miles (80,000 kilometers) of the planet's cloud tops.
Orbit and rotation
Uranus travels around the sun in an elliptical (oval-shaped) orbit, which it completes in 30,685 Earth days, or just over 84 Earth years. As it orbits the sun, Uranus also rotates on its axis, an imaginary line through its center. The planet's interior (ocean and core) takes 17 hours 14 minutes to spin around once on its axis. However, much of the atmosphere rotates faster than that. The fastest winds on Uranus, measured about two-thirds of the way from the equator to the south pole, blow at about 450 miles per hour (720 kilometers per hour). Thus, this area toward the south pole makes one complete rotation every 14 hours.
Uranus is tilted so far on its side that its axis lies nearly level with its path around the sun. Scientists measure the tilt of a planet relative to a line at a right angle to the orbital plane, an imaginary surface touching all points of the orbit. Most planets' axes tilt less than 30¡. For example, the tilt of Earth's axis is about 23 1/2. But Uranus's axis tilts 98 degrees, so that the axis lies almost in the orbital plane. Many astronomers think that a collision with an Earth-sized planet may have knocked Uranus on its side soon after it was formed.
Uranus has a mass (quantity of matter) 14 1/2 times larger than that of Earth. However, the mass of Uranus is only about 1/20 as large as that of the largest planet, Jupiter.
Uranus has an average density of 1.27 grams per cubic centimeter, or about 1 1/4 times the density of water. Density is the amount of mass in a substance divided by the volume of the substance. The density of Uranus is 1/4 that of Earth, and is similar to that of Jupiter.
The force of gravity at the surface of Uranus is about 90 percent of that at the surface of Earth. Thus, an object that weighs 100 pounds on Earth would weigh about 90 pounds on Uranus.
The atmosphere of Uranus is composed of about 83 percent hydrogen, 15 percent helium, 2 percent methane, and tiny amounts of ethane and other gases. The atmospheric pressure beneath the methane cloud layer is about 19 pounds per square inch (130 kilopascals), or about 1.3 times the atmospheric pressure at the surface of Earth. Atmospheric pressure is the pressure exerted by the gases of a planet's atmosphere due to their weight.
The visible clouds of Uranus are the same pale blue-green all over the surface of the planet. Images of Uranus taken by Voyager 2 and processed for high contrast by computers show very faint bands within the clouds parallel to the equator. These bands are made up of different concentrations of smog produced as sunlight breaks down methane gas. In addition, there are a few small spots on the planet's surface. These spots probably are violently swirling masses of gas resembling a hurricane.
The temperature of the atmosphere is about -355 degrees F (-215 degrees C). In the interior, the temperature rises rapidly, reaching perhaps 4200 degrees F (2300 degrees C) in the ocean and 12,600 degrees F (7000 degrees C) in the rocky core. Uranus seems to radiate as much heat into space as it gets from the sun. Because Uranus is tilted 98¡ on its axis, its poles receive more sunlight during a Uranian year than does its equator. However, the weather system seems to distribute the extra heat fairly evenly over the planet.
Uranus has 21 known satellites. Astronomers discovered the 5 largest satellites between 1787 and 1948. Photographs by Voyager 2 in 1985 and 1986 revealed 10 additional satellites. Astronomers later discovered more satellites by using Earth-based telescopes.
Miranda, the smallest of the five large satellites, has certain surface features that are unlike any other formation in the solar system. These are three oddly shaped regions called ovoids. Each ovoid is 120 to 190 miles (200 to 300 kilometers) across. The outer areas of each ovoid resemble a race track, with parallel ridges and canyons wrapped about the center. But in the center, ridges and canyons crisscross one another randomly.
Uranus has a strong magnetic field. The axis of the field (an imaginary line connecting its north and south poles) is tilted 59 degrees from the planet's axis of rotation.
The magnetic field has trapped high-energy, electrically charged particles -- mostly electrons and protons -- in radiation belts around the planet. As these particles travel back and forth between the magnetic poles, they send out radio waves. Voyager 2 detected the waves, but they are so weak that they cannot be detected on Earth.
Uranus in science fiction [the arts] is sparse. This is the only film devoted to a trip to Uranus and other than showing up now and then in pulp scifi magazines doesn't appear to be a favorite place for adventure.
Journey to the Seventh Planet was a 1962 science fiction film. It was shot in Denmark with a budget of only US $75,000. The seventh planet is, of course, Uranus, and a crew is being dispatched there by the United Nations on a mission of space exploration. The film's ideas of astronauts exploring outer space only to confront their inner mindscapes and memories precede the similar-themed Solaris by a full decade (Although the novel Solaris precedes this film by a year). It is also reminiscent of Ray Bradbury's 1948 short story Mars is Heaven! that appeared in the 1950 book The Martian Chronicles.
During their journey to the planet an alien presence briefly assumes control of the crew's minds. They awaken safely but notice that an unexplained long period of time has passed by.
Upon landing on Uranus, they find a forested land oddly like our own (rather than the cold, bleak world they were expecting.) This forest is surrounded by a mysterious barrier. One of the crew pushes his arm through the barrier, only to have it frozen.
New features and forms begin to appear each time they are imagined by the crew. Soon, however, the crew discover that they have been the victim of mind-control by a one-eyed brain living in a cave. Naturally the alien brain plans to possess the astronaut's bodies and have them take it back to Earth where it will, of course, implement a plan for global domination. The crew finally outwits the supposedly mind-reading creature.
Japanese anime developed Sailor Uranus.
Sailor Uranus...is one of the central characters in the Sailor Moon metaseries. Her real name is Haruka Tenoh,or Amara Tenoh in the English anime, a masculine schoolgirl who can transform into one of the series' specialized heroines, the Sailor Senshi.
Haruka is one of the most famous out lesbians in the anime fandom. Her masculine persona (by shōjo standards) is one of the standard archetypes in yuri.
Haruka is a stubborn, protective individual, but is also strong-willed, capable, charming, and occasionally even doting. She is formally introduced in the third story arc, although she appears in silhouette alongside Sailor Neptune in the final episode of Sailor Moon R.
Haruka is a racecar driver, even though she is barely sixteen years old when she appears. However, the timing of her birthday to the Japanese school year means she is one grade ahead of the Guardian Senshi.
Among fans in North America, Haruka and Michiru are among the most famous out lesbian characters in anime. Haruka is also extremely flirtatious and loves to tease pretty girls who sometimes mistake her gender due to Haruka's tomboyish behavior. In the manga, she even kisses Usagi. Throughout the manga, she is lightly flirting with Usagi, either out of habit from the first arc she appeared in or just for fun, and eventually Usagi would occasionally flirt back out of pure playfulness.
Although her relationship with Michiru is not implicitly sexual until later in the series, their romantic situation is referred to early on and generally understood by most of the metaseries' characters fairly quickly. It is sometimes a source of good natured humor, particularly because few of the other Senshi have serious romantic prospects in comparison and because the otherwise flirtatious Haruka finds it impolite to discuss romantic matters in public. All fan rumors about Haruka being a man, the reincarnation of one, or a hermaphrodite, are untrue. Naoko Takeuchi has explicitly stated that "Haruka has always been a girl. Always will be."
She further complicates the perception of her gender by appearing as a "Tuxedo Mask" instead of a Sailor Senshi in the first appearance. This form is never mentioned again.
Besides her relationship with Michiru, Haruka is also close friends with Setsuna, because the three of them work closely together as Outer Senshi. Following the destruction of the Death Busters and the rebirth of Sailor Saturn as an infant, they vow to be her family and care for her. Later story arcs show that the four live together happily for some time. Nothing about Haruka's family life is ever discussed, although she and Michiru Kaioh appear noticeably wealthy by unknown means. In the manga, Haruka says that she and Michiru have "wealthy patrons." Haruka is the target of sexism in episode 98 of the anime, but never of homophobia.
The anime and manga versions of the character are reasonably interchangeable, although her standoffishness is more pronounced in the anime. Like the other Outer Senshi, Haruka is sometimes considered colder and almost unfeeling. Aside from a brief vignette in a special, Haruka and the others do not return after the third season until the final fifth season, generally retaining the same personalities.
In the Sailor Moon musicals (Seramyu), Haruka and Michiru's relationship remains largely unchanged; they are always shown together, which is consistent with both manga and anime, and while their romance in the musicals is usually kept low-key, the actresses for the two do kiss on stage in the omake of Kaguya Shima Densetsu Kaiteiban. They are also the only two Senshi to engage in physical combat with Galaxia. The other Senshi only use their powers to combat her. As in the anime, however, neither Uranus or Neptune are capable of harming Galaxia in combat. It is seen that Uranus could sense Neptune's death when Galaxia gravely injures Neptune, who had been weakened while protecting Sailor Mars. Otherwise, the two are shown to be more willing to work as a team with the Guardian Senshi in the musicals than in the anime, except where plot-lines are directly drawn from the anime, such as their pretended betrayal of the other Senshi in Stars.
Haruka's greatest dream, prior to becoming a Sailor Senshi, was to be a professional racer. Thereafter it is still a well-loved hobby, and driving is listed in the manga as her best skill. She is also a skilled runner, belonging to the track-and-field club at school. On occasion, Haruka can be seen playing piano in accompaniment during Michiru's violin performances. While Physical Education is her best class, Modern Japanese is her worst. Haruka is highly private, able to tease others while becoming flustered if teased herself, and has difficulty with confessions. Her favorite food is salad, and her least favorite is natto (fermented soybeans); she also likes the color gold. According to Michiru, Haruka has had trouble with popular men on more than one occasion. Haruka denies this, but it clearly annoys her.
Haruka and the other Outer Senshi appear in the SuperS movie, although this conflicts with the general timeline of the series in several ways. Notably, they are more overtly friendly and helpful than they had been when they last met and Sailor Pluto is present (in contradiction of certain events in the third series).
Wikipedia [edited] offers a list of venues where Uranus has appeared.
An anonymous author writing as a Mr. Vivenair published A Journey Lately Performed Through the Air in an Aerostatic Globe, Commonly Called an Air Balloon, From This Terraquaeous Globe to the Newly Discovered Planet, Georgium Sidus in 1784.
In the Buck Rogers series (1928), Uranus is portrayed as having biodomes and robots.
In Stanley G. Weinbaum's 1935 story "The Planet of Doubt", Uranus' North pole is shrouded in a perpetual fog.
R. R. Winterbotham's "Clouds over Uranus" was published by Astounding in March 1937.
Fritz Leiber's 1962 short story "Snowbank Orbit" has three Earth-ships, fleeing from interstellar invaders, attempt a desperate aero-braking maneuver in the atmosphere of Uranus at 100 miles per second.
In Ramsey Campbell's The Insects from Shaggai (1964), a Cthulhu Mythos story, Uranus is known as L'gy'hx and is inhabited by cubical metallic many-legged creatures who worship Lrogg. They entered in religious conflict with the Shan.
Uranus is the source of radio signals investigated by Chris Godfrey and his team in First Contact, written by Hugh Walters and published in 1971.
The novels #5 ("Push towards Uranus") and #22 ("Position Oberon") in the Mark Brandis SF book series take place on and around Uranus.
In Larry Niven's novel A World Out of Time (1976), Uranus is outfitted with a massive fusion motor and used to gently move the Earth outward from an artificially brightening sun caused by a civil war between Earth and its colonies.
Geoffrey A. Landis's short story "Into the Blue Abyss," part of his short-story collection Impact Parameter and other Quantum Fictions (2001) discussed an expedition to Uranus in search of life.
Film and television
In the 1962 film Journey to the Seventh Planet, astronauts on Uranus encounter a strange intelligence.
In Space Patrol (1962) episode: "The Dark Planet" - Professor Heggerty and his daughter Cassiopeia are baffled by a plant sample from Uranus with a mind of its own. Following the disappearance of a 20 strong survey team on Uranus, Colonel Raeburn dispatch the Space Patrol crew to locate larger versions of the plant, where they discover the adult specimens of the plant are far from friendly.
In Space Patrol (1962) episode: "The Invisible Invasion"- On Uranus, the Duo's are planning to seize power on Earth by taking over the minds of everyone at Space Headquarters, including Colonel Raeburn. The one person seemingly unaffected by the Duo's power is Professor Heggerty, who is installed beneath his electronic hair-restorer!
In the Doctor Who (1963) serial "The Daleks' Master Plan", Uranus is described as being the only location in the universe where the mineral Taranium can be acquired. | 0.888636 | 3.612153 |
Euro space 'scopes go for 14 May launch
Herschel and Planck set to probe universe
The 'scopes are destined for "L2", the second Lagrangian point of the Sun-Earth system lying around 1.5m km from Earth. ESA explains that this is one of five locations discovered by Joseph Louis Lagrange "where all the gravitational forces acting between two objects cancel each other out and therefore can be used by spacecraft to 'hover'".
Described as a "great place from which to observe the larger universe", L2 provides a "stable viewpoint" free from the need to orbit the Earth, and therefore pass through its shadow, as well as lying beyond the reach of our planet's radiated heat.
The latter will prove important in the case of Herschel (see pic), the largest infrared telescope ever put into space and boasting a 3.5 m diameter primary mirror.
Herschel will for the first time probe the "entire range from far-infrared to sub-millimetre wavelengths and bridge the two", enabling scientists to study "otherwise invisible dusty and cold regions of the cosmos, both near and far".
To do this, the 3.4 tonne Herschel is carrying a high-resolution spectrometer dubbed the Heterodyne Instrument for the Far Infrared (HIFI) plus a pair of cameras/imaging spectrometers: the Photoconductor Array Camera and Spectrometer (PACS) and the Spectral and Photometric Imaging REceiver (SPIRE). The instruments (further details here) are cooled to near ablsolute zero by a helium cryogenic system, and powered by around 12m2 of solar arrays.
The spacecraft's main objective during its slated three-and-a-half year mission is to discover "how the first galaxies formed and how they evolved to give rise to present day galaxies like our own". Scientists also hope it will give insights into "clouds of gas and dust where new stars are being born, disks out of which planets may form and cometary atmospheres packed with complex organic molecules".
The 1.9 tonne vessel's instrument payload consists of telescope and twin radio detector arrays. The 'scope uses an "off-axis tilted Gregorian system" with a primary 1.9 × 1.5 m, mirror (effective aperture 1.5m) to feed the Low Frequency Instrument (LFI) detector tuned to the 27 to 77 GHz frequency range and the High Frequency Instrument operating in the 84 GHz to 1 THz range (more details here).
ESA summarises: "These receivers will determine the black body equivalent temperature of the background radiation and will be capable of distinguishing temperature variations of about one microkelvin. These measurements will be used to produce the best ever maps of anisotropies [small fluctuations in the temperature across the sky] in the CMB radiation field."
Planck has a nominal life of 15 months following its "Calibration and Performance Verification Phase". It will arrive at L2 around six weeks after launch, while Herschel - travelling independently - is expected to reach its destination after roughly 100 days. ® | 0.897355 | 3.875947 |
December 20, 2011
Slowpoke Pulsar Found Nestled In Young Supernova Remnant
Astronomers have discovered a very slowly rotating X-ray pulsar still embedded in the remnant of the supernova that created it. This unusual object was detected on the outskirts of the Small Magellanic Cloud, a satellite galaxy of the Milky Way, using data from a number of telescopes, including ESA's XMM-Newton. A puzzling mismatch between the fairly young age of the supernova remnant and the slow rotation of the pulsar, which would normally indicate a much older object, raises interesting questions about the origin and evolution of pulsars.
The spectacular supernova explosion that marks the end of a massive star's life also has an intriguing aftermath. On the one hand, the explosion sweeps up the surrounding interstellar material creating a supernova remnant that is often characterized by a distinctive bubble-like shape, on the other hand, the explosion also leaves behind a compact object — a neutron star or a black hole. Since supernova remnants shine only for a few tens of thousands of years before dispersing into the interstellar medium, not many compact objects have been detected while still enclosed in their expanding shell.An international team of astronomers has now discovered one of these rarely observed pairs, consisting of a strongly magnetized, rotating neutron star — a pulsar — surrounded by the remains of the explosion that generated it.
The newly found pulsar, named SXP 1062, is located at the outskirts of the Small Magellanic Cloud (SMC), one of the satellite galaxies of the Milky Way. SXP 1062 is an X-ray pulsar, part of a binary system in which the compact object is accreting mass from a companion star, resulting in the emission of copious amounts of X-rays. The astronomers first detected the pulsar's X-ray emission using data from ESA's XMM-Newton as well as NASA's Chandra space-based observatories. A later study of optical images of the source and its surroundings revealed the bubble-shaped signature of the supernova remnant around the binary system.
"The most interesting aspect of this pulsar is possibly its extremely long period — 1062 seconds — which makes it one of the slowest pulsars on record," comments Lidia Oskinova from the Institute for Physics and Astronomy in Potsdam, Germany, coordinator of the team that analyzed the X-ray data. Pulsars rotate quite rapidly in their early stages, with periods of only a fraction of a second, and then slow down gradually with age. "Slowly spinning pulsars are particularly difficult to detect. Only a few with periods longer than a thousand seconds have been observed to date," she adds.
To further investigate the binary system hosting this unusually slow pulsar, the team looked at the source at optical wavelengths, conducting follow-up observations with the European Southern Observatory's Very Large Telescope (VLT) and inspecting archival and newly acquired images from the Cerro Tololo Inter-American Observatory (CTIO).
"The VLT spectra confirm that the pulsar is accreting mass from a massive, hot, blue 'Be' star. The two bodies form a Be/X-ray binary, a class of X-ray binary that's very common in the SMC," explains Vincent Hénault-Brunet, PhD student at the Institute of Astronomy, University of Edinburgh, UK. Hénault-Brunet is the first author of a paper in which these results are reported. It will appear as a letter in the January 2012 issue of the Monthly Notices of the Royal Astronomical Society.
The result relies on the combined power of a number of complementary observatories. "XMM-Newton's large effective area was instrumental in achieving high-sensitivity observations of the pulsar and the supernova remnant around it over a broad range of X-ray wavelengths," says Norbert Schartel, ESA's XMM-Newton Project Scientist. These data were combined with Chandra's, which probe the source at a higher angular resolution, albeit with lower sensitivity, to arrive at a comprehensive picture of the pulsar's X-ray emission.
The optical images, on the other hand, revealed the bubble-shaped nebula that harbors the binary system. This nebula appears to be the remnant of the supernova from which the pulsar itself originated. "Not many pulsars have been observed within their supernova remnant, and this is the first clear example of such a pair in the SMC," comments Hénault-Brunet.
Opportunities like this enable astronomers to study the complex relationship between the expanding remains of stellar explosions and the compact objects they leave behind. The case of SXP 1062 is particularly puzzling because of an apparent mismatch between the ages of the supernova remnant and that of the pulsar.
"Extremely slow rotation in pulsars normally points to old objects — something that doesn't quite agree in this case with the fairly young age of the supernova remnant, which ranges between 20,000 and 40,000 years," notes Oskinova.
The reason for the slow rotation of this pulsar remains a mystery: if it was born with a normal spin rate, how could it slow down to this extent in such a short time? Alternatively, was the pulsar born with a much slower rotation period than typically expected? Since the pulsar is located in the Wing of the SMC, an interesting peripheral region of this galaxy that is characterized by low density of stars, gas and dust, as well as by low metallicity, the environment may have played a role by affecting the properties of the pulsar's progenitor star before its demise in a supernova explosion.
The rich data set that this team of astronomers have gathered may yet contain an explanation for this peculiar case. "Our plan is to fully mine the X-ray data to study the system's variability in greater detail, and further study the optical spectra to investigate the properties of the companion star," says Oskinova. "We can't wait to see what the data tell us."
The findings presented here report the discovery of a Be/X-ray binary system consisting of a pulsar, SXP 1062, and a companion 'Be' star, 2dFS 3831, located in the Wing of the Small Magellanic Cloud (SMC).
The study is based on complementary data from ESA's XMM-Newton and NASA's Chandra X-ray observatories. XMM-Newton's large effective area was key to high-sensitivity observations of the pulsar and supernova remnant over a broad range of X-ray wavelengths, while the Chandra data provide higher angular resolution, albeit at a lower sensitivity.
The Fibre Large Array Multi Element Spectrograph (FLAMES) on ESO's Very Large Telescope was used for follow-up optical spectroscopy. Archival images from the Magellanic Cloud Emission-Line Survey (MCELS) conducted at NOAO's Cerro Tololo Inter-American Observatory, as well as newly acquired images, were also used to study this portion of the sky in a number of emission lines: the H-alpha line of neutral hydrogen and two forbidden lines of oxygen [OIII] and sulphur [SII]. These lines trace emission from some of the elements produced during supernova explosions, making them excellent diagnostic tools for the study of supernova remnants.
An X-ray pulsar is one component of a binary system where the X-ray emission is produced by accretion of matter from the stellar companion onto the pulsar. Such pulsars generally have longer periods — typically between 1 and several hundred seconds — than the more common radio pulsars.
Neutron star X-ray binaries are classified into high-mass X-ray binaries (HMXB) and low-mass X-ray binaries (LMXB) depending on the mass of the companion star. HMXB are further divided into supergiant X-ray binaries (SGXB) and Be/X-ray binaries (BeXB). Be/X-ray binaries consist of a neutron star and a 'Be' companion star — a B-type star characterized by prominent hydrogen emission lines in its spectrum. Virtually all known Be/X-ray binaries harbor X-ray pulsars.
The SMC, a satellite galaxy of the Milky Way, is known to host about 50 HMXB — a surprisingly large population considering that its mass is only a few per cent of that of the Milky Way, in which about 70 HMXB are known to exist to date. All but one of the HMXB detected in the SMC are BeXB.
Image 1: The X-ray pulsar SXP 1062 embedded in the remnant of the supernova that created it. Credit: ESA/XMM-Newton/ L.Oskinova/ M.Guerrero; CTIO/R.Gruendl/Y.H.Chu
Image 2: A star-forming region in the Wing of the Small Magellanic Cloud, with the X-ray pulsar SXP 1062 embedded in its supernova remnant (right) and the nebula N90, home to the star cluster NGC 602 (left). Credit: NASA/Chandra/ESA/XMM-Newton/CTIO
On the Net:.
- Institute for Physics and Astronomy, Potsdam
- Very Large Telescope (VLT)
- Cerro Tololo Inter-American Observatory (CTIO)
- University of Edinburgh
- Monthly Notices of the Royal Astronomical Society | 0.814795 | 4.025438 |
A space experiment may have identified a new particle that is the building block of dark matter, the mysterious stuff said to pervade a quarter of the universe that neither emits nor absorbs light.
The results are based on a small amount of data and are far from definitive, scientists said Wednesday. Yet, they provide a provocative hint that the puzzle of dark matter—a cosmic prize as eagerly sought as the now-discovered Higgs boson—may also be on its way to being solved.
The results are the first obtained by a $2 billion particle detector, known as Alpha Magnetic Spectrometer, or AMS, that is mounted on the exterior of the international space station. It collects and identifies charged cosmic rays arriving from the far reaches of space.
The experiment is sponsored by the U.S. Department of Energy. It is led by Nobel laureate Samuel Ting of the Massachusetts Institute of Technology and involves hundreds of scientists from all over the world. The latest data will be published in the journal Physical Review Letters.
The AMS findings are consistent with particles that could be formed "from the annihilation of dark matter particles in space, but not yet sufficiently conclusive to rule out other explanations," according to a statement by the European particle-physics laboratory, CERN, in Geneva, which assembled the particle detector.
Figuring out what makes up dark matter is a big prize because it is the key to understanding the shape, size and even the fate of the universe.
Knowing how much dark matter there is will tell us whether the universe will keep expanding; expand to a point and then collapse; or get bigger and bigger and then stop. It also can help predict how Earth's neighborhood, the Milky Way galaxy, formed and how it might evolve.
Dark matter is invisible, yet its presence is felt by the immense gravitational tug it exerts on stars, galaxies and other cosmic bodies. What could this mysterious substance be made of? One of the leading candidates is a WIMP, or weakly interacting massive particle.
WIMPs are elusive. They rarely interact with normal matter such as atoms; indeed, billions of WIMPs may be darting right through the Earth every second without hitting anything.
About 25% of the universe is believed to be dark matter, about 70% is the little-understood dark energy, and about 5% is ordinary matter made of atoms. Scientists have been looking for WIMPs in deep mines; in particle smash-ups in colliders; and, now, with detectors in space.
"This is the decade of the WIMP," said Michael Turner, a cosmologist at the University of Chicago. "All of these experiments are zeroing in on the outrageous idea that most of the matter in the universe is" made up of WIMPs, a new form of matter.
In 1990, Dr. Turner and a colleague suggested a way in which WIMPs might be discovered in galaxies, which provided the theoretical underpinning for the AMS experiment. The idea is that when WIMPs crash into each other, they annihilate and produce two particles—electrons and positrons—which are much easier to detect than the WIMPs themselves.
The theory predicts two outcomes: that the annihilations should produce a large number of positrons; and that after the excess, there should be a sudden decline in positron production.
In its first 18 months, AMS analyzed 25 billion primary cosmic ray events. It identified more than 400,000 positrons. The positron numbers then start to flatten out—a possible sign that the hoped-for plunge in positron numbers could come next.
So far, though, there isn't enough data to confirm that expected plunge. Physicists also need to ensure that the positrons they are seeing don't emanate from a pulsar, a type of star; that wouldn't be a finding about dark matter.
"What's tantalizing is that the positrons are leveling-off," said Dr. Turner, who wasn't involved in the AMS experiment. "But we're not there yet" because not enough data have been crunched. | 0.803658 | 3.994159 |
The New Horizons spacecraft has currently traveled half the distance between the dwarf planet, Pluto, and its next flyby target, which is an extremely smaller object circling in the Solar System's twilight zone, called the Kuiper Belt, the US National Aeronautics and Space Administration (NASA) says.
The New Horizons, dashing out of our solar system at about 32,000 miles per hour, was on Tuesday 486.19 million miles beyond Pluto and the same distance from 2014 MU69, a tiny Kuiper Belt object (KBO), which is barely one percent of the dwarf planet’s size, NASA announced in a statement.
The Kuiper Belt, which contains numerous icy comets, asteroids, and other small bodies, is a circumstellar region located beyond the planets extending from the orbit of Neptune, the farthest planet from the Sun, to approximately 50 AU from it. An AU, which stands for astronomical unit, is by definition a unit of length roughly the average distance from Earth to the Sun, which is equal to some 93 million miles.
The spacecraft is scheduled to make a flyby of the MU69 on New Year’s Day 2019, added the US space organization.
“It’s fantastic to have completed half the journey to our next flyby; that flyby will set the record for the most distant world ever explored in the history of civilization,” said Alan Stern, the New Horizons principal investigator from the Southwest Research Institute in Boulder, Colorado.
The nuclear-powered New Horizons made history after it managed to make its flyby of Pluto at 1149 GMT on July 14, 2015, following a decade-long journey.
Time to sleep
NASA also announced that its spacecraft would go into a 157-day period of hibernation later this week after being “awake” for the past two and a half years.
“The January 2019 MU69 flyby is the next big event for us…,” but “in addition to MU69, we plan to study more than two-dozen other KBOs in the distance and measure the charged particle and dust environment all the way across the Kuiper Belt,” said Hal Weaver, the New Horizons project scientist in Laurel, Maryland.
The spacecraft, the farthest man-made object from the Earth after Voyager 1 and Voyager 2, is currently 3.5 billion miles from our cosmic home. At that distance, it takes about five hours and 20 minutes for radio signals sent from the operations team to reach the New Horizons. | 0.864304 | 3.147339 |
There may be some frantic activity going on in the narrow, dusty disk surrounding a nearby star named Fomalhaut. Scientists have been trying to understand the makeup of the disk, and new observations by the Herschel Space Observatory reveals the disk may come from cometary collisions. But in order to create the amount of dust and debris seen around Fomalhaut, there would have to be collisions destroying thousands of icy comets every day.
“I was really surprised,” said Bram Acke, who led a team on the Herschel observations. “To me this was an extremely large number.”
Fomalhaut is a young star, just a few hundred million years old, about 25.1 light years away and twice as massive as the Sun. It is the brightest star in the constellation Piscis Austrinus and one of the brightest stars in our sky, visible in the southern sky in the northern hemisphere in fall and early winter evenings.
Fomalhaut’s toroidal dust belt was discovered in the 1980s by the IRAS satellite. It’s been viewed several times by the Hubble Space Telescope, but Herschel’s new images of the belt show it in much more detail at far-infrared wavelengths than ever before.
The narrow and asymmetrical properties of the disk are thought to be due to the gravity of a possible planet in orbit around the star, but the existence of the planet is still under study.
Acke, from the University of Leuven in Belgium, and his team colleagues analyzed the Herschel observations and found the dust temperatures in the belt to be between –230 and –170 degrees C, and because Fomalhaut is slightly off-center and closer to the southern side of the belt, the southern side is warmer and brighter than the northern side.
Those observations collected starlight scattering off the grains in the belt and showed it to be very faint at Hubble’s visible wavelengths, suggesting that the dust particles are relatively large. But that appears to be incompatible with the temperature of the belt as measured by Herschel in the far-infrared.
While observations with Hubble suggested the grains in the dust disk would be relatively large, the Herschel data show that the dust in the belt has the thermal properties of small solid particles, with sizes of only a few millionths of a meter across. HST observations suggested solid grains more than ten times larger.
To resolve the paradox, Acke and colleagues suggest that the dust grains must be large fluffy aggregates, similar to dust particles released from comets in our own Solar System. These would have both the correct thermal and scattering properties.
However, this leads to another problem.
The bright starlight from Fomalhaut should blow small dust particles out of the belt very rapidly, yet such grains appear to remain abundant there.
So, the only way to explain the contradiction is to resupply the belt through continuous collisions between larger objects in orbit around Fomalhaut, creating new dust.
This isn’t the first time that evidence of cometary collisions have been seen around another star. Last year, astronomers using the Spitzer Space Telescope detected activity resembling a ‘heavy bombardment’ type of event where icy bodies from the outer solar system are possibly pummeling rocky worlds closer to the star.
At Fomalhaut, however, to sustain the belt, the rate of collisions must be remarkable: each day, the equivalent of either two 10 km-sized comets or 2,000 1 km-sized comets must be completely crushed into small, fluffy dust particles.
In order to keep the collision rate so high, scientists say there must be between 260 billion and 83 trillion comets in the belt, depending on their size. This is not unfathomable, the team says, as our own Solar System has a similar number of comets in its Oort Cloud, which formed from objects scattered from a disc surrounding the Sun when it was as young as Fomalhaut.
“These beautiful Herschel images have provided the crucial information needed to model the nature of the dust belt around Fomalhaut,” said Göran Pilbratt, ESA Herschel Project Scientist. | 0.868025 | 4.041286 |
The Kepler Space Telescope has been staring constantly at the same part of the Galaxy for over three years, looking for the tell-tale dimming and wobbling of stars that reveals the presence of planets around them. During this time it has discovered a number of remarkable planetary systems that have revolutionized our thinking on how such systems form and evolve.
In a paper published on the online arXiv database at Cornell University Library on 20 June 2012, and in the journal Science on 21 June 2012, a team of scientists led by Joshua Carter of the Harvard-Smithsonian Center for Astrophysics announce the discovery of a new, and rather remarkable, planetary system named as Kepler-36.
The system's star, Kepler-36A, is an essentially sun-like star that has reached the subgiant stage of its life; it is coming to the end of its hydrogen supply and starting to fuse helium. This generates more heat than hydrogen, causing the star to expand. Kepler-36A has 1.071 times the mass of the Sun, and an effective surface temperature of 5911 K (compared to 5778 K for our Sun).
This is orbited at a distance of 0.115 AU (i.e 11.5% of the distance between the Earth and the Sun) every 13.8 days, by Kepler-36b, a super-Earth type planet with a mass 4.45 times that of the Earth, thought to be most likely composed largely of rock and water, and at 0.128 AU every 16.2 days by Kepler-36c, a mini-Neptune type planet with a mass 8.08 times that of the Earth, thought to be composed largely of gaseous hydrogen and helium.
The orbits of these two planets are remarkably close together, closer than any pair of planets previously discovered, separated by just 0.013 AU (1.945 milion km), so that at their closest the two planets are only five times as far apart as the Earth and the Moon, at which distance Kepler-36c would be 2.5 times as large in the sky of Kepler-36b as the full moon is in the sky of Earth.
An artist's impression of how Kepler-36c would appear from Kepler-36c at the closest point in the two planets' orbits. Harvard-Smithsonian Center for Astrophysics/David Aguilar.
As well as being remarkably close, the two planets are remarkably different in composition. In our Solar System there is a clear differentiation between rocky and gaseous planets, with the former confined to the inner part of the system and the later to the outer parts. This is thought to be a result of the way in which the Solar System formed, with volatile gasses largely driven out of the inner system by the heat of the early Sun. Since we have begun studying other planetary systems, we have come to understand that this is not always the case, with many systems having large gaseous planets close to their stars. Scientists believe such planets are likely to have formed further out in their systems, then migrated inwards as friction with material in the protoplanetary disks slowed them down in their orbits. However this is the first time we have seen a rocky and a gaseous planet in such close proximity, and modeling the formation of the Kepler-36 system is difficult based upon our current understanding of the formation of planetary systems.
See also HATSouth network discovers its first planet, A new study of the Kepler 11 planetary system, The formation of a Keplerian Disk in the L1551 NE Protostellar System, Thermal imaging 55 Cancri e and Exoplanets on Sciency Thoughts YouTube.
Follow Sciency Thoughts on Facebook. | 0.824125 | 3.968536 |
We've discovered many rocky planets around distant stars, but they're mostly super-Earths, much larger and more massive than our planet. Plus, most of these "super Earths" orbit stars vastly different from our Sun. Now we've discovered two planets that really could be Earth's twins.
Kepler-20e and Kepler-20f are part of the five-planet solar system called Kepler-20, named for the exoplanet-hunting NASA probe that discovered it. They are located about a thousand light-years away in the constellation Lyra. Unfortunately, these two planets are much too close to their parent star to be in their solar system's habitable zone, which means in that rather crucial way they're not exact duplicates of Earth. But otherwise, they're astonishingly close.
In particular, Kepler-20f is nearly identical to Earth in terms of size, with a radius that's just 1.03 times larger than that of our planet. Kepler-20e is smaller, at just 0.87 times Earth's radius, which means it's slightly smaller than Venus. They represent the very first Earth-sized exoplanets ever found. Until now, Kepler-10b, the first rocky exoplanet ever found, was the smallest known exoplanet, at 1.4 times Earth's radius.
What really clinches the physical similarity between these two planets and Earth is their star. Kepler-20 is a class G star, just like the Sun, and it's only slightly smaller and cooler than ours. However, while the dimensions of the planets and stars may be similar, their positioning is vastly different. Kepler-20e orbits the star every 6.1 days and has an average temperature of 1,400 degrees Fahrenheit, while Kepler-20f clocks in at 19.6 days and 800 degrees.
While these Earth-sized exoplanets naturally attract the most attention, the entire Kepler-20 system is fascinating. The other planets - Kepler-20b, Kepler-20c, and Kepler-20d - are all between the size of Earth and Neptune, making them super-Earths. They orbit every 3.7, 10.9, and 77.6 days, respectively, which means the smaller rocky planets slot in between those orbits. We've never seen such alternation between bigger and smaller planets before. In our solar system, for instance, there's clear segregation between the small rocky planets and the big gas giants.
This announcement comes hot on the heels of the discovery of Kepler-22b, a planet in another solar system that is in the habitable zone but likely too large to have a rocky surface. As Kepler deputy science team lead Natalie Batalha observes, we keep finding exoplanets with some, but not all, of the qualities needed to support life. With this latest find, it seems the discovery of a true Earth-2 really is just a matter of time. | 0.803901 | 3.883576 |
The Hubble Space Telescope has captured beautiful auroras active around Jupiter’s north pole. The auroras cover areas larger than Earth, and are fueled not only by solar winds but also by charged particles from the area surrounding Jupiter.
Not only are the auroras huge in size, they are also hundreds of times more energetic than auroras on Earth. And, unlike those on Earth, they never cease. While on Earth the most intense auroras are caused by solar storms — when charged particles rain down on the upper atmosphere, excite gases and cause them to glow red, green and purple — Jupiter has an additional source for its auroras.
The strong magnetic field of the gas giant grabs charged particles from its surroundings. This includes not only the charged particles within the solar wind but also the particles thrown into space by its orbiting moon Io, known for its numerous and large volcanoes. | 0.807202 | 3.436896 |
WHAT IS A BOSE EINSTEIN CONDENSATE (BEC)?
Some Background First
Just like a solid, liquid, gas or plasma, a BEC is a state of matter. We come across three states of matter - solids, liquids and gases - every day. Life on Earth relies on the fact that one substance in particular, water, exists in these three states within a relatively narrow temperature range. What determines the state of matter is the average kinetic energy of the atoms that make it up. Generally speaking, atoms are most tightly packed within solids, less so in liquids and farther apart still in gases, but when collections of atoms are subjected to pressure this trend can reverse. As you might know, increasing the pressure of a gas, liquid or solid will also increase its temperature. Solids, depending on the kinds of atoms making them up, are not very compressible but they will eventually compress under sufficient pressure into a dense liquid state when the internal energy increases enough to break apart the inter-molecular bonds that make the solid stiff. The resulting very dense liquid will compress into a very dense gas and the gas, a much more compressible state, will compress further into an extremely dense example of a fourth state called plasma. Not all plasmas are hot and dense like this, but the Sun's hydrogen/helium plasma is a good example. Plasmas can also be diffuse cold ionized gases such the those that populate interstellar nebulae. Excited atoms in plasmas emit electromagnetic radiation. You can witness the light emitted by plasmas when you see sunlight or a lit neon sign. In the case of sunlight, pressure and heat are both at work. In the case of the neon sign, atoms in the plasma are excited by an electrical current. Atoms in a plasma state have so much energy they can no longer hold onto their outermost electrons. They are in an excited state, creating a separation of electrical charge.
Under even more extreme pressure and heat, additional exotic physical states are possible, such as electron degenerate matter inside white dwarf star remnants (our Sun is destined to become one eventually). Atoms in this exotic state are crushed by pressure. Nuclei have lost all of their electrons and a high-energy dense sea of negative charge surrounds them. As pressure is increased further, neutron degenerate matter forms. In this case atoms are crushed into an ultra-dense neutron sea, the strange stuff of neutron stars, pulsars and magnetars. Electrons are so energetic that they combine with free protons to create additional neutrons. Increasing pressure further theoretically produces the densest state of matter possible - quark matter. In this state, neutrons are crushed into their normally confined component particles - quarks. Above this pressure, matter is completely crushed in the infinite gravity well of a black hole - a state, in which matter at the atomic scale can no longer be described using our current theory of quantum mechanics.
Just as there is a maximum threshold of energy above which atomic matter as we know it can't exist, there is a minimum threshold of energy below which atoms no longer behave in the ways we expect. Atoms become excited when their energy increases. In an analogous way, atoms become "de-excited" when their energy decreases. As atoms approach absolute zero, they become sluggish and ultimately condense into an additional physical state called a Bose Einstein Condensate (BEC). Consider a balloon filled with steam, the gaseous state of water. Cool it down to room temperature and it will contain a small puddle of water inside it. Put it in a freezer and that water will solidify into ice. It's easy to visualize the atoms in steam moving around fast and bumping into each other, or atoms sliding around one another in liquid water, but there is no visible motion within a block of ice. Yet, undetectable to our eyes, there is. As the water freezes into ice, the atoms get close enough and slow down enough to form attractive chemical bonds with each other. In the case of water ice, they create a three-dimensional lattice. The type of bond arrangement depends on the kinds of atoms involved. No matter what the solid material is, the bonds hold the atoms more or less in place but they don't stop the atoms from jiggling about, like a runner jogging in place. This jiggling or oscillating motion, averaged over the material, is what we perceive as its heat or temperature. Lets say we cool our balloon down much further inside a special box that removes energy. The oscillations, on average, will slow down. Eventually, the ice will theoretically get so cold that the atoms no longer oscillate at all. At this point it has reached absolute zero, a temperature measured as - 273.15°C or - 459°F or 0K. I say theoretically because it is not possible in practice to remove all the energy from a system (we are treating our balloon as a physical system). Scientists are finding ways to get very close to absolute zero, and as they do, matter begins to act very strangely. In theory, the ice in our balloon could transform from a solid into a BEC, and when it does it will exhibit some very interesting properties.
Now To the BEC Itself
Exotic states such as degenerate matter, which is thought to exist inside stellar remnants, represent the highest energy extreme of atomic matter, while BEC's represent matter's lowest energy extreme. Degenerate matter cannot be directly studied in the lab. Its creation would require an enormous input of energy that would be impossible to achieve and maintain. The gravitational pressure of an entire star is required. Unlike degenerate matter, which cannot be lab-created, no BEC should exist naturally at all. This state of matter is made in-lab only. Even the coldest atomic gas clouds in deep space are a million times too warm, at about 3K, to harbour any BEC matter. A temperature above even just a few microkelvins will disrupt the quantum mechanical quiescence of a BEC and transform it back into its original gas state. But why would such a cold state be a gas and not a solid? More on this to come.
Each particle in matter is described mathematically as a quantum wave function. Click on this HyperPhysics link to get an idea of what these kinds of equations looks like. Any matter particle exhibits wave/particle duality. It can act like a particle and like a wave. In a BEC, particles act completely like waves. These matter waves, as they are called, stretch out as the atoms slow down. They start to overlap one another, and eventually they completely overlap into one large matter wave. At this point the gas is condensed into a BEC state.
Though predicted decades earlier by Albert Einstein and Satyendra Nath Bose, the first BEC wasn't created until Eric Cornell and Carl Wieman succeeded in doing so in 1995. Hydrogen atoms were the logical first choice but providing the right conditions for BEC formation proved too difficult. Helium atoms were turned to next but they presented too many challenges as well. Instead, rubidium was the first successful BEC. Two techniques, lasers and evaporative cooling, which will be described in detail later on, were used to cool a diffuse cloud of rubidium atoms into a BEC state. The two men received the 2001 Nobel Prize in physics for their success in creating this new state of matter.
I mentioned that the universe is far too warm for natural BEC formation. It is possible, however, that all of the matter in the universe could very slowly transform into a BEC state as the universe continues to expand, and therefore, cool. Right now the universe is still "warmed" by radiation from the Big Bang. What were once the highest energy gamma rays possible are now stretched across the expanding universe into low energy microwaves, and they will continue to stretch into extremely long and imperceptibly weak radio waves. At this point, interstellar atomic gas clouds in the universe might be so cold that those atoms will begin to condense into BEC's.
We live within a very narrow range of temperatures, from about -50°C (for a few minutes) to about +50°C (for a few hours) with about 20°C being most comfortable. In this range, hydrogen is always a gas; iron is always a solid and so on, but every element can exist as a solid, liquid, gas and plasma, with each state having its own unique physical and chemical properties. As atoms are energized further, they lose their chemical and physical identities altogether when the nuclei themselves are torn apart. Although practical research is still at a young stage, BEC's also lose some of their original classical chemical and physical properties. In this case, a group of atoms takes on the properties of one single atom, and their normally hidden quantum nature reveals itself.
So, what does this look like? We can visualize what's going on by looking at how the atoms fall into a single lowest-possible energy state. The graphs below plot the energy distribution of a gas of rubidium atoms. At room temperature, the energy levels of the atoms (measured as their velocities) would be spread across a wide range. They would be evenly distributed across a grid like the ones shown below and it would be entirely red. Energy density increases from red, yellow, green, blue to white, the highest density. The three graphs below illustrate, left to right, an already very cold gas cooling into a BEC state. The change in energy distribution below is calculated using Bose Einstein statistics, which we will investigate further later on. The middle graph shows the energy distribution just before the appearance of a BEC and the graph on the right is of a nearly pure concentrate (notice the reduction in yellow around the peak). At this point, nearly all the atoms have condensed into identical lowest accessible (ground) quantum energy states, contributing to the peak density at the centre. Some researchers call this state a super atom, not to be confused with "superatom" which not a BEC but a cluster of distinct atoms.
|Image created by NIST/JILA/CU-Boulder|
The BEC state has been observed in very cold gases, in very cold liquids such as helium, and even within solid materials, in a special form. In addition to rubidium, lithium and other elements have been used, as well as a variety of molecules. Non-matter particles that have unique properties (these are boson particles such as quasiparticles) can also condense into BEC's. These particles do not form atoms. They can be thought of as localized excitations in an energy field. They include polaritons. A type of quasiparticle, polaritions are half matter/half light particles that will condense into a BEC state inside a solid semiconductor under the right conditions. Quasiparticle BEC's, like this example, can form at a much higher temperature than other BEC's do, at about 19 degrees above absolute zero. This makes them an interesting research focus because their unique BEC properties might have practical applications at temperatures that aren't too hard to achieve. Polaritons can also be created in gas BEC's, and as we will see later on, they play a key role in how light interacts with atoms in the BEC state. In 2010, researchers reported in Nature that they were even able to confine and condense photons (particles of light) into a BEC. Trapped in a "white box," blackbody radiation photons begin to act like a two-dimensional gas of massive bosons in a BEC state (photons are massless force-carrier bosons). As we will see, atoms also act like massive bosons in a BEC (in a three dimensional gas). It is fascinating that massless force-carrying bosons (photons) and matter particles (atoms) can be nudged into an identical quantum state. It is yet another hint at how closely light and matter interact with one another.
BEC's ARE RULE-BREAKERS
Normally, atomic matter doesn't act like boson particles of force. The particles follow very different rules. Atoms won't overlap in one spot. That's why even matter crushed down to a neutron star still takes up space. But photons, for example, can and do (think of constructive and destructive interference of light). Only when atomic matter is very cold will it fall into a single ground energy state (into a single matter wave), and when it does, it breaks a fundamental rule of matter called the Pauli Exclusion Principle (PEP). Matter particles are called fermions. Two or more identical fermions (electrons, protons, neutrons or composite particles such as atoms) cannot share the same quantum state at the same time. This energy distribution rule of atoms is laid out by Fermi-Dirac statistics from which the PEP is derived. It means that at most just one particle can occupy one quantum state in a system. Notice that this is NOT what you see happening in the graphs above. The atoms as matter waves are falling into the same energy state at the same place at the same time. The PEP is being broken.
This rule holds until the atoms approach BEC critical temperature. At this point, the atoms are quiet enough to fall into a single lowest possible energy state, breaking the PEP and now obeying Bose-Einstein statistics instead of Fermi-Dirac statistics. Bose-Einstein statistics describe the energy distribution of bosons (particles of force such as photons, and W and Z bosons of the weak force). Under these statistical rules, particles are described mathematically as symmetric wave functions (rather than fermionic asymmetric wave functions) and that means they can overlap. In a BEC, matter particles act like bosons.
They become one big single wave function. It is still atomic matter, but it is overlapped in one location. A BEC trapped in a magnetic bowl looks like a tiny spherical cloud with a dark dot in its centre. A gas cloud of atoms surrounds the actual BEC (the dark dot, which corresponds to the white peak in the graphs above). BEC's created from normally bosonic particles like photons and polaritons don't break the PEP because they don't fall under Fermi-Dirac statistics.
As an interesting aside, the Pauli Exclusion Principle (PEP) plays an essential role in atomic matter at the highest energy scales too. In these cases, rather than the principle being broken, it takes on a hero-like role that proves just how strong quantum forces within matter are. It explains degeneracy pressure. Ordinary atoms take up space because electron degeneracy pressure keeps electrons with the same quantum spin apart. Electrons also repel one another through electrostatic (same-charge) repulsion. That's a different force that's also at play here. Because of charge repulsion, electrons in atoms tend to spread out and partially occupy several orbitals, like passengers on a jet tend to do when it's half full. When outward nuclear fusion pressure no longer counteracts inward gravitational pressure, atoms are squeezed together and the electrons are forced to fill up the lower energy quantum states. (There's a bunch of cargo in the back of the jet so everyone has to fill up the first few rows). Electrons are forced to get close despite electrostatic repulsion, a classically described force. They refuse, however, to overlap into identical quantum states (two people can't sit in the same spot).
This much more powerful quantum, rather than classical, resistance is called quantum degeneracy pressure. Atomic matter in this state, with electrons forced into all the lowest but not identical orbitals, is found in the extremely dense electron degenerate matter of white dwarfs. In a more massive and even denser stellar remnant such as a neutron star, where gravitational pressure is much higher, the electrons, forced against the electrostatically repulsive (positively charged) nucleus are so energized they approach the speed of light. At this point it is more energetically favourable for them to undergo electron capture through inverse beta decay than to remain traveling near light speed because, at this velocity, their relative masses are approaching infinity, a prediction made by special relativity. Electrons combine with protons in the nucleus and transform them into neutrons (therefore the name "neutron" star). Unlike the white dwarf, just one kind of pressure prevents the neutron star from collapsing. This is the quantum degeneracy pressure of neutrons. These particles don't repel one another electrostatically because they are electrically neutral. In fact, they bind strongly to one another through the strong force, which operates at very short (intra-atomic) distances. As outlined by the PEP, neutrons, like electrons and protons, are matter particles whose wave functions cannot overlap. If the stellar remnant is more massive than a neutron star, matter collapses altogether into a black hole (of which a quantum mechanical description is not yet available). Are the neutron wave functions forced to overlap inside a black hole? Is it a BEC? There is currently no way to know. Isn't it fascinating? Even under the pressure of a massive collapsing star matter waves refuse to overlap one another. Yet, when energy approaches zero, matter waves expand and smear across one another of their own accord.
HOW A BEC IS MADE
The first rubidium BEC was made by trapping a tiny ball of a few rubidium atoms using lasers and magnetic fields. This process is tricky. If the atoms get too close to each other they will form Rb2 molecules. A gas at an ultra-cold temperature will condense into a liquid and then into a solid if the atoms are allowed to interact with each other. To cool the gas, infrared lasers bombard the atoms from every direction. One would think this should have the opposite effect of cooling. The intense photon energy should excite the atoms and add momentum to them, heating them up.
One trick to laser cooling is to understand temperature as the average random kinetic energy of a group of atoms. By making the atomic motions less random, lasers narrow the energy distribution of the group of atoms (and create the single sharp peak in the series of graphs above.). When a photon strikes an outer electron in an atom, it can be absorbed, exciting the atom, and then be re-emitted or it can be reflected. An electron will only absorb a photon that matches its orbital energy (called transition energy). This is where the word quantum derives its meaning; energy can only transition in discrete packets. In this case, a laser with a frequency just below that of the transition energy is used. A stationary atom in the cloud won't even "see" the photons. It won't absorb them because they aren't the right energy. An atom moving away from the laser also won't absorb a photon. It will "see" it as red-shifted, having even lower energy in other words. An atom moving toward the laser, however, will "see" the photon as blue-shifted, and therefore at just the right energy to absorb. The atom is excited and then re-emits the photon, in a random direction. Now statistics comes into play: the photon hits the atom coming toward it. The photon slows it. That's a pure loss of momentum. But the atom then re-emits a photon (with the same energy) in a random direction. This time the direction is random so the change in momentum is not a pure gain. When absorption and emission are repeated many times over a group of atoms, the average random kinetic energy of the group decreases (pure losses and not-pure gains) and that means the temperature decreases. In other words, the lasers eventually align all the velocity vectors of the atoms, and when that happens they are close to transforming into a BEC. Just like the laser light (which is made of aligned in-phase photons) used to make a BEC, the BEC itself is made of aligned particles. They act like waves in phase with one another rather than as discrete particles of matter.
Atoms are also tiny magnets because their spinning electrons create magnetic fields. By applying a carefully aligned magnetic field to the group of atoms, they can be held in one place once they are cooled. The lasers can be turned off at that point. The lasers aren't perfect; some atoms will still have higher kinetic energy than others. They are still "hot." These atoms simply jump out of the magnetic trap, and are eliminated, leaving only the coldest atoms, the ones that can't jump out, inside. This is evaporative cooling. Heisenberg's uncertainty principle ensures that even in a quiet state such as this, there are tiny random movements in the system that eventually destroy the perfectly aligned quantum state. The original group of about 2000 rubidium atoms, that formed a BEC in 1995, lasted for about 20 seconds before it lost its coherence and dissipated back into ordinary gas.
This 6-minute video describes how a Bose Einstein Condensate is made:
As mentioned earlier, the technology has steadily improved since 1995, creating new kinds of BEC's that last longer, as well as solid-state quasiparticle BECs that can exist at higher temperatures.
Any element's physical and chemical properties change as they transform from one physical state to another. For example, rubidium, the first element made into a BEC, is a very soft silvery white metal at room temperature. Rubidium gets its name from the dark purplish red colour of its flame. With a melting point of just 39.3°C, it is partly melted in the vacuum sample tube shown below.
The most important reason why rubidium works as a BEC is that these atoms are bosonic atoms. They are not actually bosons as we've previously learned, but under the right conditions they can display a bosonic nature. The general rule for bosonic atoms is simple (but the actual calculations are usually very complex). If an atom contains an even number of subatomic particles, it's a "boson." All neutral atoms have an equal number of electrons and protons so it's the neutron number that matters. Rubidium-87 is an isotope of rubidium with 50 neutrons, an even number, so it is a boson. From a quantum mechanical point of view it means that all the subatomic particles in rubidium can be spin-matched or polarized. This doesn't mean that all bosonic atoms make good BEC's (again, it's complicated). It also doesn't mean that a fermionic atom can't make a BEC. Helium-3, for example, is a fermionic atom - it has an uneven number of neutrons (one). It will, however, under extreme cooling, form a pair with another helium-3 atom (a Cooper pair like those in superconductors), which in effect creates a bosonic composite particle, which will condense into a BEC. Because it is fermionic, helium-3 must be much colder than helium-4, a bosonic atom, to condense.
In addition to being plentiful, fairly easy to vapourize, and bosonic, rubidium-87 atoms have one lone electron outside a completely filled electron shell and this lone (interactive) electron makes it ideal for magnetic trapping.
HOW DOES A BEC BEHAVE?
BEC's act a lot like superfluids. Superfluid helium, for example, is created when liquid helium is cooled to almost absolute zero. Helium happens to be the only element that will remain liquid under normal pressure right down to absolute zero. Interactions between helium atoms are so weak that its ground state energy stays too high to allow it to condense into a solid, unless additional pressure forces the atoms closer together. Helium will, however, transition into a superfluid state. In this state, these atoms, like those in a gaseous BEC, no longer vibrate much at all with heat energy. Instead, they enter a calm state where many atoms begin to vibrate in unison like a single particle. This sounds like a BEC but there are key differences. Still, the two states are strongly linked and it is easy to see why many of the strange behaviours of superfluids also apply to BEC's.
Comparison to a Superfluid
A condensed gaseous atomic BEC is not a liquid. Nor does it follow the laws of ordinary gas behaviour. But is it an example of a superfluid? The little bead of rubidium BEC in the magnetic trap is a very rare case of a macroscopic fully coherent quantum object. Loss of phase coherence is the hallmark of the transition from quantum BEC into classical gas. The group of rubidium atoms will grow out of phase with each other in a matter of seconds and return to a classical object, an ordinary gas. Superfluids such as ultra-cold helium exhibit many of the same strange behaviours we explore here with BEC's and they are of quantum origin as well, but these behaviours are hidden in the dense liquid - you can't directly track the gradual loss of interference and other behaviours, as you can with a gaseous BEC. Furthermore, with a BEC, you can fine-tune experimental parameters such as the kinetic energy of the atoms, or its density (more about this in a bit), things you cannot readily do with a superfluid.
Even though the interactions between helium atoms are weak compared to other elements in a liquid state, helium atoms in a superfliud state interact quite strongly with each other compared to those in a diffuse gas BEC. These atom-atom interactions complicate the behaviour of a superfluid, complications generally not encountered in BEC's.
Both superfluids and BEC's rely on bosonic atoms. Cold liquid helium-4 transitions into a superfluid at about 2.17K. Below 1K (well below superfluid transition temperature), it exhibits zero viscosity even though only about 7% of the atoms are at ground state. Compare this to a BEC, where all the atoms are at ground state. Helium-3 will not transition into a superfluid until temperatures dip to 2.5 mK (milli-Kelvins). At this point, helium-3 atoms pair up into bosonic Cooper pairs. A BEC must be much colder than a superfluid. A gas will not transition into a BEC until the temperature dips to just a few uK (micro-Kelvins). There is some disagreement among researchers whether a BEC is type of superfluid but most researchers agree that a superfluid is an example of partial Bose Einstein condensation.
Macroscopic Quantum Behaviour
You might be wondering at this point how you can observe a physical wave when what you seem to have is a coherent singular quantum wave, or mathematically put, a wave function. At this point quantum mechanics students get riled because they know a quantum wave function is a purely mathematical construct made up of a real part and an imaginary (not physically possible) part. You can't see one: it doesn't exist in the real world. However, there is a way around this conundrum. The probability density of the wave, which is the absolute value of the wave function squared, always gives you a real and positive value, a value, which amounts to the real standing wave that you can observe. In other words the probability density is the mathematical description of the physical phenomenon. Can we ever "see" the quantum wave function in action? Yes, we can. We can generate and observe a BEC interference pattern. Rather than mixing together like two gases would, two BEC's in different phases will interfere when they combine, setting up positive and negative lines of quantum interference, a quantum effect, which can be observed. In the negative lines there is only vacuum. Here, the matter waves of atoms interfere resulting in a space with no atoms. Although the total number of atoms in the mixture is conserved, the atoms simply disappear along lines of negative interference, a purely quantum effect that you can observe.
Perhaps the most intriguing behaviour of BEC's is the quantum vortex, a behaviour that is already well studied in superfluids such as superfluid helium. The classical analogue is stirring a cup of coffee. A little liquid tornado forms with a depression or hole in its centre. Internal friction eventually slows down the rotational motion and this classical vortex dissipates. Both superfluids and BEC's are frictionless. They exhibit zero viscosity and this means the fluid flows without any loss of kinetic energy. If you could stir a superfluid it would just flow around the spoon with no resistance. You can't stir a BEC with a spoon because all current BEC's are too small. The "dot" mentioned earlier tends to be a spherical or pancake shape that is around a millimetre across. But you can whirl it around by rotating the magnetic trap that contains it and, when you do, you create multiple tiny string-like whirlpools in it. Unlike any classical system, all the rotational motion of the BEC is sustained only by these quantized vortices because all the atoms in a BEC are in one quantum wave function. Because these vortices are quantum, their angular momenta must be quantized. The angular momentum can only be expressed in whole integer packets. When a wave rotates (any wave, even a quantum wave), it forms a closed curve. In this case, those closed curves are confined to de Broglie wavelengths. Like any standing wave, the wavelengths must be whole (an integer value). In a classical fluid like coffee the velocity of rotation increases smoothly from the spoon in the centre toward the walls of the cup. In a quantum fluid (superfluid or BEC), the velocity can only increase in packets like 0, 1, 2, . . . It takes less energy for the system to form lines rather than sheets, so you get a series of string-like vortices. In the BEC, the vortices tend to be multiple and they have very tiny holes, the width of which can vary depending on the atoms used. These holes, called filaments in a quantum system, don't decay by diffusion as they would in a classical system.
Put mathematically, a BEC quantum vortex is a direct result of the macroscopic wave function of the system. A BEC rotates by puncturing the condensate with filaments along which the quantum wave function vanishes to zero. These filaments are singularities in the wave function. A number in the wave equation, called the winding number, must be a whole integer (0,1,2, . . .). Mathematically this ensures that the wave function doesn't change value after each rotation. In physical terms this means that the velocity of the circulation has to be quantized. A quantum vortex can only spin at a discrete set of speeds and it can never die down smoothly like a classical vortex does. However, the motion around each vortex, called superflow velocity, acts classically like it does in the cup of coffee, and it can be described using ideal fluid dynamics.
The study of quantum turbulence (in which vortices are an example) began in the 1950's using superfluid helium. The availability of cold gas BEC's now offers a great advantage in this study because the turbulence can now be directly visualized in a BEC, rather than being hidden inside a dense liquid, which, depending on the temperature, can contain a complicating mixture of superfluid and classical viscous fluid. Even with this advantage, a lot of questions remain. It is not yet possible to predict where and how many vortices form and what their shapes will be. This problem isn't limited to the quantum vortex. Turbulence itself is a very complicated phenomenon. It is strongly nonlinear and this means you can't input data into an equation and get a predictably straightforward answer. This is why weather forecasts are notoriously unpredictable.
The study of quantum vortices might make the study of turbulence easier. A classical vortex tends to be messy: it's unstable, it appears and disappears randomly and its circulation is not conserved. Quantum turbulence is a simpler system. It is composed of a tangle of vortices that all have the same conserved circulation in the BEC. Even so, quantum turbulence is complicated; it is still a system with many (albeit fewer) degrees of freedom.
In a perfectly condensed BEC, well below its critical temperature, you might expect vortices to be indefinitely stable because there is no friction to diffuse them, but they do decay over time. Quantum vortices spontaneously and randomly reconnect, much like water spouts over an ocean do. This behaviour is analogous to eddies that form in a turbulent classical fluid. A quantum vortex can lose energy, dissipate over time in other words, by emitting sound. Sound appears to come from two processes. First, during the process of reconnection (depending on the angle of reconnection), vortex line length is destroyed. When this happens a rarefaction pulse is emitted, a sound in other words. A second source of sound emission may come from a cascade of Kelvin waves, which are excitations in the BEC that result from vortex reconnections. These particular waves, which usually have very long wavelengths in nature, may be short enough to cause sound radiation in this case. By these mechanisms of energy dissipation (loses through sound energy), all quantum vortices eventually decay.
Under the right conditions, a BEC made of rubidium-85 will explode in a manner that resembles a tiny supernova, a bosenova (also less cutely called a BEC loss). Rubidium-85 is one of two naturally occurring isotopes of rubidium, the other being rubidium-87, the isotope which created the first BEC. Like rubidium-87, rubidium-85 is a bosonic atom, this time with 48 neutrons. One of the key differences between the two isotopes is that rubidium-87 has a positive s-wave scattering length. This means that the atoms naturally repel each other at low temperatures so it is easy to evaporatively cool the gas. Rubidium-85, in contrast, has a negative scattering length. This means that a condensate made of this isotope will tend to collapse in on itself, especially in a zero magnetic field. Because the atoms attract each other, it's also more difficult to cool it into a stable (non-interacting) BEC. It has to be just 3 billionths of a degree K above zero. Even with these challenges, rubidium-85 offers a unique bonus. In 2001, physicist Carl Wieman (half of the team that created the first BEC in 1995) adjusted the fine-tuning of a BEC droplet of rubidium-85 by changing the magnetic field in which the atoms are trapped. Doing this amounted to adjusting the self-interactions of the wave function (remember a BEC is a superimposed macroscopic wave function). In effect, he could dial between repulsion and attraction.
Dialed to repulsion, all the parts of the wave function push each other apart. The BEC droplet swells accordingly. Dialed to attraction, they pull together, and this is when unexpected dramatics begin. It starts to shrink gradually as expected, but then it shrinks suddenly, triggering an outward explosion that is tiny by everyday standards but with significant energy (about 100 nano Kelvins, nK) considering only a few thousand very low energy atoms are involved. After a few microseconds a much smaller remnant of BEC is left behind, surrounded by an expanding gas cloud of rubidium-85 atoms. This sudden collapse followed by an explosion that leaves behind a remnant and a gas cloud reminds one of a supernova, although the actual mechanisms involved are very different.
About half the original atoms vanish during the explosion. Researchers first thought that they might have either formed Rb2 molecules in the explosion or that some atoms flew out of detector range before they were measured. Or (sharp breath in), they really disappeared. Perhaps an even deeper mystery presented here is how very cold BEC atoms with minimal energy available to them could explode in the first place. The thermal energy released is greater than the free energy of the original BEC. And, just to season the broth, why does some of the BEC survive?
In 2003, Masahito Ueda and Hiroki Saito explained theoretically how a BEC collapses and explodes, thus resolving some of the mystery. The idea is that even though the BEC state is a single matter wave, it still consists of a diffuse gas of atoms and they will interact when they are nudged closer together. When the magnetic field is tuned to just barely favour attractive atomic interactions, the number of inelastic (interactive) collisions between atoms remains negligible at first. But as the atomic density gradually increases, the density of the concentrate increases toward it centre. After a short period of time, the collision rate suddenly jumps and becomes significant, but just within a tiny localized central portion of the BEC (about a millionth of the volume). This triggers instability in the BEC. Not one but several intermittent explosions/implosions occur in rapid-fire, and each time several tens of atoms are lost from the condensate. These researchers determined that atoms are removed due to three-body loss. Three-body loss, or three-body decay, occurs when three rubidium atoms get very close to each other, as they do in a shrinking condensate. Two of the atoms form a molecule (Rb2) in an excited state while the third atom carries away the energy released by the formation of the chemical bond. Each of these energies is much higher than the depth (energy confinement) of the magnetic trap, so three atoms (and their energies) fly off out of the system.
Although atoms are not lost irretrievably, the implosion viewed in terms of a closed system acts like a tiny atom drain, a tiny black hole. After the atoms are lost, outward kinetic pressure from the atoms minus the combined mass of the lost three atoms just surpasses the attractive force. This slight surplus in kinetic energy is enough to trigger a subsequent burst or explosion. Afterward, attractive energy then dominates and the BEC shrinks again. The cycle repeats until the number of atoms remaining is too small for attraction to overcome outward kinetic pressure. Because the collision-heavy region is confined to such a small portion of the BEC, some it survives the ensuing explosion.
BEC's Can Slow Down and Stop Light
The bosenova is a very interesting phenomenon but it seems to have few practical applications. The interaction between light and a BEC, on the other hand, is not only fascinating, it hints at new possibilities for storing and communicating information in the future.
The speed of light in a vacuum is an exact value, approximately 300,000,000 m/s (denoted c). In practice, however, a pulse of light contains many particles of light, or photons. Their average velocity is c. A pulse of light slows down (it refracts) when it travels from one medium such as air into another medium of different density such as water. If it strikes the new medium at an angle, the pulse of light appears to bend as its speed differs on different points along its wave front. The individual photons in that pulse do not slow down, however. They remain at vacuum light speed. What slows down is the pulse, because multiple interactions between the photons and the atoms in the medium take tiny amounts of time. As density increases, so does the number of photon-electron interactions, because there are more atoms for the photons to interact with. Photons may reflect off atoms and resume travel or they may be absorbed by an atom's outermost electron and then be re-emitted. These interactions mean it takes longer for the group of photons as a whole to get from point A to point B through the medium. The light pulse slows.
How about the photons themselves? Can anything slow a photon down? It turns out that a BEC can. In fact, it can even stop a photon (in effect) for a few seconds, then reconstitute it (with all the quantum information it contains still intact) and allow it to resume its course.
In 1999, Lene Hau and her associates slowed a light pulse down to just 17 m/s (that's 20 million times slower than light traveling in a vacuum, c) in a BEC. A BEC, as we know now, is a condensate of atoms. The atoms are still a diffuse gas. As matter waves, however, they spread or smear out as their atomic vibrations slow down. Compared to an ordinary gas at room temperature, the matter waves (the de Broglie wavelengths) are about 10,000 times shorter than the average distance between the atoms. These waves are longer than the distances between the atoms, so the matter waves overlap. It might be tempting to imagine a BEC as a clump of super-dense matter where the atoms themselves have all collapsed into one spot, but it is not. Only the matter waves superimpose.
Refraction, even at its extreme, slows light only by a small fraction (about a third). For example, gallium phosphide has one of the highest known refractive indexes of any material, and even through this, light slows only to about 86,000,000 m/s. A diffuse gas generally has a refractive index of just one, which means it does not slow light at all. To achieve slowing on the extreme scale here, something other than refraction must be involved. There are currently three theories used to explain how extreme slowing occurs. They are briefly described on the Wikipedia entry here. I will focus on the polariton (more precisely called microcavity exciton-polariton) approach. It's the theory that best explains stopped light (which we will talk about next). A polariton is a not a physical particle in the same sense that a particle of matter is a physical particle. It is a quantum-only entity that is a hybrid light/matter quasiparticle. It is an emergent phenomenon called a collective electromagnetic excitation. It can take on particle characteristics, which, as a result, can have physical (measurable) effects on a system. These particular particles act like a gas, they can be trapped, and they can move just like real particles do.
Normally you can't shine light through a BEC gas condensate. As the gas cools, it changes from transparent to opaque. However, Lene Hau and her associates were able to electromagnetically induce transparency in a BEC within a very narrow spectral range. In this case, a cloud of sodium atoms is treated the same way as the rubidium BEC explored earlier. It is cooled by lasers and by evaporative cooling into a BEC state that is confined within a magnetic trap. The BEC is then made transparent by exposing it to a specific arrangement of laser beams. The lasers also allow photons traveling through the BEC to combine with atoms to create polariton quasiparticles. More technically put, the laser treatment induces strong light-matter coupling into a structure that combines quantum wells (think of an atom stuck in one spot as a standing wave) and photon cavities (imagine a photon trapped between two very close tiny mirrors). This coupling is equivalent to a boson particle that is composed of a quantum well exciton and an optical cavity photon. Polaritons get mass from the atoms, so they travel slower than c. Remember that a BEC is, in effect, one big super-atom. It has the mass of all the atoms condensed into a single quantum state. It's mass is therefore the sum of the masses of all the atoms, so polaritons formed with incoming photons are likewise very massive and this means they must travel much slower than light speed. It is a quantum effect that significantly slows the photons traveling through the BEC because they enter a different particle state. This slowing effect is an entirely different mechanism from refraction, described earlier.
This 3-minute video describes how a BEC is used to slow down light.
In 2001, Ron Walsworth and his associates went one big step further. They stopped the propagation of light through a BEC altogether (and then restarted it). This time, using rubidium atoms once again, they gradually turned down the lasers once they had made the BEC transparent. The behaviour of the polaritons in the BEC shifted accordingly from photon toward atom. Eventually the polariton nature turned entirely into atom nature, and at this point the photons were effectively stopped in their tracks inside the BEC. Light stored in the polaritons as quantum information was now hidden in their atom-nature. Perhaps a better way of looking at it is to consider all the quantum information encoded in the light now trapped within the BEC gas, not in the atoms themselves but as quantum excitations within the gas. An exciton-polariton is a localized quantum excitation. Light in this way can be stored for up to seconds inside a BEC (and perhaps longer as the technique improves).
When the lasers were turned back up, the photon component of the polaritons increased and the light resumed its travel.
The ability to stop and restart photons could be very useful in a number of technologies. Imagine that instead of solid-state electronic qubits delivering information in a computer, photons could be used instead. They carry information faster, they don't heat up sensitive components and as we just saw their information storage can now be precisely controlled. One problem with using photons in communications has been how to stop them and decode their information. After flying down an optical cable they have to be stopped at your computer somehow. Nowadays, the information is transferred into an electronic system. The only way to stop a photon is to interact with it. A photon is absorbed by an ordinary atom. As it is absorbed it loses its quantum information, for example its polarization state, and an entirely new photon of equivalent energy is re-emitted in a random direction. In a laser-irradiated BEC, the laser is tuned in a way to prevent photons from being absorbed by the electrons in the gas atoms. The atoms instead form a cluster around each photon, creating a polariton quasiparticle. A BEC can stop and capture each photon, store its information intact (again, polarization could be used instead of 0's and 1's) for a specific period of tine and then send it on its way as a signal.
MANY POTENTIAL USES FOR BEC's
There is a potential goldmine of possibilities for BEC's both as research tools and in practical applications. This research is still in its early stages; it is less than two decades old, but as BEC-making technology improves and the list of BEC's with various properties grows, there is no doubt that some of their exciting quantum features will be exploited in new technologies. Because BEC's greatly magnify phenomena confined to the formerly inaccessible quantum world, BEC's might be manipulated as tools to directly observe and verify currently theoretical quantum behaviours such as the mass acquisition of a normally massless particle called a quasi-Nambu-Goldstone boson, which is thought to be the result of tiny quantum fluctuations. Until now, almost all investigations into the quantum world must be carried out in incredibly large and expensive particle accelerators. As well as expense, this limits the kinds of questions that can be asked. BEC's could be used as customizable quantum laboratories. They might also provide a direct window into the mysterious phenomenon of quantum entanglement. BEC's don't normally contain entangled atoms but researchers have very recently discovered it might be possible to fine-tune the magnetic field around the condensate in such a way to entangle all the atoms in it.
BEC's are already being exploited to learn more about solid-state physics. You can create an optical lattice in a BEC by using several lasers to make an interference pattern that looks (and acts) much like the crystal lattice patterns of atoms found in many solid materials. The big advantage here is that the same optical lattice can be repeatedly tuned and manipulated in different ways to see what happens. When using a solid, you have to regrow your sample every single time (and I assume you've got to be very consistent). The fine-tune-ability of a BEC also means it could be potentially used as a variety of high-precision measuring instruments. There is no obscuring noise to tune out in a purely quantum system. In quick succession science and technology have evolved through the golden age, the industrial age and the information age, Now, it seems that BEC's will help us usher in a quantum age. | 0.849194 | 3.894699 |
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Cassini continues its exploration of the Saturn system with the 12-day Rev 241, which begins on August 25 at its farthest distance from the planet. This is also called the orbit’s apoapse. At this point, Cassini is 1.50 million kilometers (0.93 million miles) from Saturn’s cloud tops. Rev 241 occurs during the second inclined phase of the Cassini Solstice Mission. Over the next several orbits, Cassini will use encounters with Titan to gradually increase the inclination of its orbit. Nine ISS observations are planned for Rev 241 with the majority focused on Saturn’s rings.
On August 27 and 28, the Composite Infrared Spectrometer (CIRS) will acquire a nearly 36-hour, distant observation of Titan from a distance of 1.11 million kilometers (0.69 million miles). This will allow for thermal measurements of Titan’s north polar region. For its first observation for Rev 241, on August 29, ISS will acquire a 17-hour movie of the F ring, a narrow ring just outside the main ring system. The movie will be used to monitor the creation of clumps and channels, formed by the gravitational interaction between F ring material and nearby moons and moonlets. On August 30, ISS will ride along with the Visual and Infrared Mapping Spectrometer (VIMS) to observe a stellar occultation of the red supergiant star Antares by the rings. Stellar occultations can be used to probe the fine-scale structure of Saturn’s rings. Another stellar occultation, this time of the Mira-variable X Ophiuchi, will be observed on August 31 as Cassini is crossing below the ring plane.
On August 31 at 13:16 UTC, Cassini will reach periapse for Rev 241 at an altitude of 400,480 kilometers (248,850 miles) above Saturn's cloud tops, between the orbits of Dione and Rhea. During periapse, ISS will be conducting a 15-hour-long survey of the propellers in the outer A ring. Propellers are voids in the ring created by the gravity of large, 100 – 1000 meter (328 – 3280 foot) ring particles. Due to the influence of the rings on their motion, these observations are used to keep track of previously discovered propellers, like Earhart and Bleriot. On September 1, ISS will acquire a color scan using the Narrow-Angle Camera (NAC) of the unlit face of the A and B rings. Afterwards, VIMS will observe a solar occultation by the rings. Like the stellar occultations, but using the Sun, this will be used to look at the fine-scale structure of the rings, particularly in the C ring.
On September 2, VIMS will acquire another stellar occultation by the ring system, this time of the red supergiant Betelgeuse. Afterwards, ISS will observe the unlit side of the F ring for 11 hours. On September 4, ISS will ride along with the Ultraviolet Imaging Spectrometer (UVIS) as it acquires scans across Saturn. ISS will perform similar observations on September 5, this time while riding along with CIRS.
On September 6, Cassini will reach apoapse, bringing Rev 241 to a close and starting up the next orbit, Rev 242.
Image products created in Celestia. All dates in Coordinated Universal Time (UTC). | 0.85353 | 3.725642 |
[grav-i-tee] /ˈgræv ɪ ti/
noun, plural gravities.
the force of attraction by which terrestrial bodies tend to fall toward the center of the earth.
heaviness or weight.
gravitation in general.
a unit of acceleration equal to the acceleration of gravity. Symbol: g.
serious or critical nature:
He seemed to ignore the gravity of his illness.
serious or dignified behavior; dignity; solemnity:
to preserve one’s gravity in the midst of chaos.
lowness in pitch, as of sounds.
noun (pl) -ties
the force of attraction that moves or tends to move bodies towards the centre of a celestial body, such as the earth or moon
the property of being heavy or having weight See also specific gravity, centre of gravity
another name for gravitation
seriousness or importance, esp as a consequence of an action or opinion
manner or conduct that is solemn or dignified
lowness in pitch
(modifier) of or relating to gravity or gravitation or their effects: gravity wave, gravity feed
c.1500, “weight, dignity, seriousness,” from Middle French gravité “seriousness, thoughtfulness,” and directly from Latin gravitatem (nominative gravitas) “weight, heaviness, pressure,” from gravis “heavy” (see grave (adj.)). The scientific sense of “force that gives weight to objects” first recorded 1640s.
The fundamental force of attraction that all objects with mass have for each other. Like the electromagnetic force, gravity has effectively infinite range and obeys the inverse-square law. At the atomic level, where masses are very small, the force of gravity is negligible, but for objects that have very large masses such as planets, stars, and galaxies, gravity is a predominant force, and it plays an important role in theories of the structure of the universe. Gravity is believed to be mediated by the graviton, although the graviton has yet to be isolated by experiment. Gravity is weaker than the strong force, the electromagnetic force, and the weak force. Also called gravitation. See more at acceleration, relativity.
Our Living Language : With his law of universal gravitation, Sir Isaac Newton described gravity as the mutual attraction between any two bodies in the universe. He developed an equation describing an instantaneous gravitational effect that any two objects, no matter how far apart or how small, exert on each other. These effects diminish as the distance between the objects gets larger and as the masses of the objects get smaller. His theory explained both the trajectory of a falling apple and the motion of the planets—hitherto completely unconnected phenomena—using the same equations. Albert Einstein developed the first revision of these ideas. Einstein needed to extend his theory of Special Relativity to be able to understand cases in which bodies were subject to forces and acceleration, as in the case of gravity. According to Special Relativity, however, the instantaneous gravitational effects in Newton’s theory would not be possible, for to act instantaneously, gravity would have to travel at infinite velocities, faster than the speed of light, the upper limit of velocity in Special Relativity. To overcome these inconsistencies, Einstein developed the theory of General Relativity, which connected gravity, mass, and acceleration in a new manner. Imagine, he said, an astronaut standing in a stationary rocket on the Earth. Because of the Earth’s gravity, his feet are pressed against the rocket’s floor with a force equal to his weight. Now imagine him in the same rocket, this time accelerating in outer space, far from any significant gravity. The accelerating rocket pushing against his feet creates a force indistinguishable from that of a gravitational field. Developing this principle of equivalence, Einstein showed that mass itself forms curves in space and time and that the effects of gravity are related to the trajectories taken by objects—even objects without mass, such as light. Whether gravity can be united with the other fundamental forces understood in quantum mechanics remains unclear.
Another term for gravitation, especially as it affects objects near the surface of the Earth.
[gree-see, ‐zee] /ˈgri si, ‐zi/ adjective, greasier, greasiest. 1. smeared, covered, or soiled with . 2. composed of or containing ; oily: greasy food. 3. greaselike in appearance or to the touch; slippery. 4. insinuatingly unctuous in manner; repulsively slick; oily. 5. Veterinary Pathology. affected with . /ˈɡriːzɪ; -sɪ/ adjective greasier, greasiest 1. coated or […]
[gri-gair-ee-uh s] /grɪˈgɛər i əs/ adjective 1. fond of the company of others; sociable. 2. living in flocks or herds, as animals. 3. Botany. growing in open clusters or colonies; not matted together. 4. pertaining to a flock or crowd. /ɡrɪˈɡɛərɪəs/ adjective 1. enjoying the company of others 2. (of animals) living together in herds […]
[han-dee-kapt] /ˈhæn diˌkæpt/ adjective 1. Sometimes Offensive. physically or mentally disabled. 2. of or designed for handicapped people: handicapped parking. 3. Sports. (of a competitor) marked by, being under, or having a : a handicapped player. noun 4. (used with a plural verb) Sometimes Offensive. handicapped persons collectively (usually preceded by the): increased job opportunities […]
[hahr-mon-ik] /hɑrˈmɒn ɪk/ adjective 1. pertaining to , as distinguished from melody and rhythm. 2. marked by harmony; in harmony; concordant; consonant. 3. Physics. of, relating to, or noting a series of oscillations in which each oscillation has a frequency that is an integral multiple of the same basic frequency. 4. Mathematics. noun 5. Music. […] | 0.80157 | 3.566722 |
A team of scientists have discovered a hypervelocity star that defies current astronomical theories by breaking the galactic speed record. The hypervelocity star they found blasts through space at around 1,200 kilometers per second – about 2.7 million miles per hour. This speed allows the star to reach escape velocity to exit the Milky Way Galaxy, something that has never been seen before. To put this into a better perspective, the team said at this speed a spacecraft could reach the moon in just five minutes.
The astronomers said that contrary to a few other known stars escaping the galaxy, this new star, identified has US 708, was expelled from an intensely tight binary system by an immense thermonuclear explosion, or supernova. Their results were published in the current issue of the journal Science.
A hypervelocity star is one that surpasses a velocity of 200 kilometers per second. According to scientists, the speed of hypervelocity stars could be around 1,000 kilometers per second. Current theories state that there are around 1,000 hypervelocity stars in the Milky Way Galaxy. Although this sound like a lot, there are over 100 billion stars in the Milky Way. Even if all potential hypervelocity stars were found, this equates to only 0.000001 percent. Most astronomers believe hypervelocity stars achieve either speeds by coming close to a black hole.
Medium-size stars like the Sun are gravitationally bound to the Milky Way by its orbiting around the center of the Galaxy, at a relatively normal velocity on the galactic scale of 120 miles per second. Until now, only a few stars have been observed to reach speeds that do not hold them in orbit with their galactic hosts. These hypervelocity stars travel at speeds hitherto unknown to astronomy. Though, astronomers believe that the most plausible mechanism for these stars to escape the grasp of the Milky Way is to come close enough to the supermassive black hole at the center. This would jettison the star at hypervelocity by its mass interacting with extreme forces in gravity around an orbital point.
Stephan Geier, an astronomer at the European Southern Observatory, led the research that discovered US 708, the aforementioned hypervelocity star. By using the Echllette Spectrograph and Imager, two distinct systems on the Keck II telescope, they were able to measure the radial velocity of US 708, the speed at which it travels either away or towards a point of view. By consolidating the coordinates measured and the speeds at which the star was traveling in between them, they measured the tangential component of acceleration of the star, or the speed at which it moves perpendicular to a point of view.
The team calculated the total velocity of US 708 at 1,200 kilometers per second – about 742 miles per second. This is much higher than all other stars that have been observed in the Milky Way Galaxy. Beforehand, they theorized that the hypervelocity star was powered by a potential close encounter with the supermassive black hole in the center of the galaxy. However, by using the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1) to measure its trajectory, they were able to determine that US 708 did not achieve such an extreme velocity by coming close to the black hole.
Eugene Magnier, one of the led astronomers on the study, explained they used Pan-STARRS1 to deduce the location and speeds of US 708. This system observes stars on a continuous basis and maps their movements through space. He said this system allows scientists to make a “movie” of the motions of stars. Therefore, they are able to study and analyze unbelievably rare and extraordinary hypervelocity stars like US 708.
US 708 has additional unusual characteristics that put it in a different category in regards to other hypervelocity stars: it is a rapidly rotating, extremely compact helium star. Maginer said helium stars like this are a result of a stellar interactions from nearby companion stars, remnants from a previous super giant that lost its hydrogen chromosphere.
The team stated US 708 could have possibly been linked to a compact binary star system, which transferred helium to a white dwarf companion, inevitably causing a massive thermonuclear reaction, known as a type Ia supernova. As a result, US 708 was violently blasted from the former binary system, and is now speeding through the galaxy at hypervelocity.
These findings provide actual evidence to the theories of hypervelocity stars and the origin of their unusual speed. Moreover, it provides a link between helium stars and the thermonuclear reactions that destroy them. Magnier stated this is a crucial step towards understanding the theoretical properties of hypervelocity stars and supernovae.
By Alex Lemieux
Photo by Kevin Gill – Flickr License | 0.883653 | 3.818714 |
NASA released a new batch of photos from the Curiosity rover following the Mars Science Laboratory's landing in Gale Crater yesterday. The above photo was taken as the robotic lab was rushing toward the Martian surface and had jettisoned its heat shield.
Meanwhile, Dan Stolte of UA News brings us more details about the astonishing work that the UA Lunar and Planetary Lab's HiRISE team did in capturing a picture of Curiosity's descent:
Dangling from its parachute, Mars rover Curiosity was photographed by the UA-led HiRISE camera aboard NASA's Mars Reconnaissance Orbiter. HiRISE images will serve as road maps once the rover sets out to explore Gale Crater.
In a carefully choreographed maneuver high in the sky above Mars, two man-made spacecraft zipped past each other as NASA scientists and engineers stared at screens inside Mission Control at NASA's Jet Propulsion Laboratory, anxiously enduring the "7 minutes of terror"—the time it would take the Curiosity rover to plunge into Mars' atmosphere and touch down on the bottom of Gale Crater near the Martian equator.
While Curiosity—the centerpiece of the Mars Science Laboratory Mission, or MSL—hurtled toward the ground at twice the speed of sound, another spacecraft, NASA's Mars Reconnaissance Orbiter, or MRO, pointed its HiRISE camera at Curiosity and snapped a photo of the spacecraft with the rover tucked inside, suspended from its 50-foot-diameter parachute. HiRISE stands for High-Resolution Imaging Science Experiment.
"We have been planning this for some time," said Alfred McEwen, a professor in the University of Arizona Lunar and Planetary Laboratory and principal investigator of the HiRISE mission. "We gradually adjusted MRO's orbit to make sure it would be right over Curiosity as it landed, and that put us in a great position for this image. It came back exactly as we expected in terms of brightness and contrast. The parachute looked beautiful, nice and sharp, fully inflated and working perfectly."
The snap shot required months of preparations to make sure the two spacecraft, traveling in directions perpendicular to each other and at several miles per second in the case of MRO, wouldn't miss each other. McEwen said it would have been great to have the descent image in color, but because HiRISE's color channel has a narrower field of view than the black and white channels, that wasn't possible under the circumstances. "It's a good thing our field of view wasn¹t very much narrower or we could have missed it entirety," McEwen said.
"Touch-down confirmed. We're safe on Mars!" The announcement, shortly after 10:30 p.m. on Aug. 5, sent Mission Control into cheering and high-fiving.
No other planet has claimed as many spacecraft in its 50 years of exploration, said Shane Byrne, an assistant professor in the UA department of planetary sciences. More than half of the 40 attempts to land a probe on the Red Planet failed, either never making it out of Earth¹s orbit or crashing and burning upon arrival.
“The successful landing of rover Curiosity gets us one closer to tying the score,” said Byrne, adding that landing on Mars is no easy feat. “Previous attempts have shown that you can go hundreds of millions of miles only to trip on your shoe laces.”
The latest and greatest in a series of Mars exploration vehicles owes its safe touchdown on the floor of Gale Crater near the Martian equator in no small way to the data gathered by the UA-led HiRISE camera, which has been photographing Mars aboard NASA¹s Mars Reconnaissance Orbiter for the past six years.
Selecting a landing site for Curiosity that is both safe to touch down and promising to yield as much scientific insight as possible would not have been possible without the high-resolution images taken by HiRISE.
“HiRISE imaged all potential landing sites that were being discussed,” said Byrne, who is a co-investigator on the HiRISE team. “By the time it came down to four candidate sites, we had wall-to-wall covering of all the areas in question.”
Powerful enough to reveal details on the surface the size of a coffee table, HiRISE has returned about 26,000 images so far, less than 2 percent of the Martian surface. But Byrne said that what has been imaged so far has been chosen carefully.
He explained that although Mars is smaller than the Earth, its surface area is comparable to Earth¹s when combining the landmass of all continents and leaving out the oceans.
“Mars is a big place with lots to see. Some areas are uniform and boring, but there are others like the Grand Canyon. HiRISE has focused on the most interesting and most informative sites.”
HiRISE has flown over and photographed some sites over and over again to document seasonal changes and help scientists better understand how the climate on Mars varies from year to year. By repeatedly imaging a site from different viewing angles, the HiRISE team can assemble three-dimensional images of the Martian terrain.
The resulting images, called digital terrain models, will serve as roadmaps for the Curiosity rover as it slowly rolls across the Martian soil.
“HiRISE data helps the Curiosity team plan the traverses the rover will take,” Byrne said. “These data help the engineers choose how to best get from A to B.”
He added that with the two high-resolution cameras mounted atop its mast just shy of 7 feet, Curiosity can see quite a long distance, and make out features HiRISE can¹t.
“As the mission develops, I expect Curiosity¹s routes to be constantly revised. HiRISE is going to give the team the first cut, but when it comes to day-to-day details like avoiding rocks, they will rely on the rover¹s onboard cameras.”
Scouting out safe passages is crucial. Opportunity, one of an identical pair of NASA¹s Mars Exploration Rovers, once got stuck in what the mission team called the “purgatory” a dune field with waist-high ripples of sand. It took weeks of maneuvering to guide the vehicle back onto firm ground.
“HiRISE has been able to help NASA avoid similar situations and allows them to plan out safe yet interesting routes,” Byrne said. “It¹s the only instrument that can resolve boulders as small as 3 feet.”
When the stationary lander Phoenix was sent to Mars several years ago, it was already approaching the planet when engineers changed the landing site when HiRISE reconnaissance revealed the landing spot it was approaching was littered with rocks not seen in previous images.
“With HiRISE, we were able to avert a potential crash,” Byrne said.
“Phoenix set the stage for the Mars Science Laboratory mission,” said Peter Smith of the UA¹s Lunar and Planetary Laboratory who is the principal investigator of the Phoenix Mars Mission, the first and only NASA mission ever to be led by a public university.
He remembers his time as team leader of the Mars Pathfinder Mission in 1997, when NASA landed rover Sojourner on Mars, which looks like a toy next to Curiosity.
A stationary camera on the lander guided the roughly breadbox-sized Sojourner rover. This camera, called Imager for Mars Pathfinder, was designed and built at the UA.
“Sojourner managed to drive about 50 meters around the lander in three months,” Smith said. “All it could do is roll up to nearby rocks and determine their composition.”
“It¹s been a tremendous thrill to be part of this keeping in mind that it was only eight years ago that we sent autonomous rovers to Mars that carried everything they needed with them,” Smith said, pointing out that Opportunity has explored a lot of terrain, able to drive down into craters, explore the side walls up close and then move on to the next crater.
“And now we sent a car-sized, nuclear powered rover, and we landed it in a really interesting area.”
Smith said the Phoenix and MSL missions complement each other, with Phoenix digging into the permafrost soil to explore the chemistry and mineral composition in Mars¹ North Polar Region and MSL probing the chemistry and minerals in the equatorial region.
“With Phoenix, we are looking for current habitability,” Smith said. “In other words, are the polar regions on Mars like deep freezers of the planet where life could have been preserved, similarly to Antarctica? Curiosity, on the other hand, is looking for habitability of ancient Mars, something we couldn¹t do with Phoenix. Curiosity will look at exposed layers that may reveal clues to if and how life could have existed on Mars in the past.”
McEwen said that with the rover safely on the ground, HiRISE will look for the rover and the other parts of the spacecraft.
"We¹re going to take another image tonight or early tomorrow of Curiosity on the ground," he said, adding that there is more to look for.
"In past missions, there was a rover, a heat shield and the shell attached to the parachute. With Curiosity, we have additional components like the sky crane that lowered the rover onto the ground, and ballast that dropped off some distance to the east. Those should have come in at high enough impact to make craters."
McEwen said he just received notice that the heat shield may have been located in one of the images HiRISE transmitted back to Earth, as it was still falling.
And with reference to the HiRISE image capturing the Phoenix Mars Lander parachuting to the surface in May 2008, he added: “We¹re two for two. Every time we image, it¹s a successful landing." | 0.856609 | 3.150234 |
Stephen Potter and Encarni Romero-Colmenero from the South African Astronomical Observatory (SAAO), along with other collaborators, have found evidence for the existence of an extraordinary planetary system where two giant planets are orbiting a close pair of “suns”.
If confirmed, this would be an example of a very strange planetary system, given the nature of the stellar pair.
The discovery was made possible by new SAAO and Southern African Large Telescope (SALT) observations combined with archival data spanning 27 years, gathered from multiple observatories and satellites.
White and red dwarf
The two stars, referred to as a “white dwarf” and a “red dwarf”, are each smaller than our Sun and are so close that they take only a couple of hours to orbit each other – the pair of them would actually fit comfortably within our Sun.
By chance, the system is oriented in such a way that the stars appear to eclipse each other once every orbit as viewed from Earth.
“Potter and his collaborators noticed that the eclipses were not occurring on time, but were sometimes too early or too late,” the SAAO said in a statement last week. “This led them to hypothesise the presence of two giant planets whose gravitational effect would cause the stars’ orbit to wobble and consequently slightly alter the measured time between eclipses.”
Constantly ‘stealing’ material
The astronomers were also able to infer that the masses of the two planets must be at least 6 and 8 times that of Jupiter and take 16 and 5 years respectively to orbit the two stars, the SAAO said. The system is too far away from us to be imaged directly.
This binary star system (known as UZ For) would be an extremely inhospitable environment. Due to their close proximity, the gravity of the white dwarf is constantly “stealing” material from the surface of the red dwarf in a continuous stream.
This stream crashes onto the white dwarf, where it gets super-heated to millions of degrees and subsequently floods the entire planetary system with enormous amounts of deadly X-rays. | 0.91323 | 3.64203 |
Toyoaki Suzuki at the University of Tokyo conducted observations of M101 with AKARI at four infrared wavelengths (65, 90, 140, and 160 micrometres) using the Far-Infrared Surveyor (FIS) instrument.
This is a composite image of the spiral galaxy M101. The image shows the distribution of cold (blue) and warm (red) dust overlaid on the visible (green, showing distribution of stars) and far-ultraviolet (cyan, indicating the location of young stars) images of M101. Credits: Composite: JAXA, visible (green): the National Geographic Society, far-ultraviolet (cyan): GALEX/NASA
Many young high-temperature stars populate the spiral arms, revealing the areas of star formation and warming the interstellar dust. This causes the galaxy to shine at shorter infrared wavelengths. In contrast, the longer wavelengths show where the ‘cold’ dust is located. Normal stars, typically like our own Sun, warm this dust.
FIS data was compared to an image of M101 in the visible and far-ultraviolet. It shows that warm dust is distributed along the spiral arms, with many hot spots located along the outer edge of the galaxy. These spots correspond to giant star-forming regions. This is unusual because star formation is generally more active in the central parts of spiral galaxies.
The evidence points to M101 having experienced a close encounter with a companion galaxy in the past, dragging out gas from the hapless companion. The gas is now falling onto the outer edge of M101 at approximately 150 km/s, triggering the active star formation.
Alberto Salama | alfa
Hope to discover sure signs of life on Mars? New research says look for the element vanadium
22.09.2017 | University of Kansas
22.09.2017 | Forschungszentrum MATHEON ECMath
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
22.09.2017 | Life Sciences
22.09.2017 | Medical Engineering
22.09.2017 | Physics and Astronomy | 0.811216 | 4.011227 |
As the article explains, Earth is constantly hit by cosmic rays, or radiation from space, but our atmosphere absorbs it and converts it into Carbon-14. This isn’t radiation like the threat from the Fukushima reactors, but it is more like miscellaneous particles flying through space from all kinds of sources. Earth usually gets hit by a steady amount of it every day, and so we have a steady amount of Carbon-14 daily, yearly, etc. More or less.
Carbon-14, or “radiocarbon”, is not the same as the standard Carbon-12 (tanso 炭素 in Japanese by the way), so it only exists in very small amounts on earth, and apparently trapped in trees. It also exists in your body by the way, and thus people are “naturally” radioactive. ;p
Anyhow, in the years 774 and 775, scientists in Japan have noticed that there was a 1% increase in Carbon-14 in tress from that time, and it’s not clear why. The 1% increase represents a big change, but it’s not clear what the source is.
Since Carbon-14 is produced in the atmosphere from cosmic rays, something hit the Earth with a lot of energy from 774-775, but what?
Researchers don’t believe it’s the Sun because solar-flares usually aren’t strong enough, and the timing doesn’t seem right.
So, they thought it might come from an exploding star. In space, most stars die in a typical way: when they start to run out of fuel, they swell into a red-giant star, then eventually collapse into a tiny white dwarf. Our sun will do this in 5 billion years.
But if a star is really heavy, at least 8 times more massive than our sun, it will have a different death called a supernova. The star’s own gravity is so strong, it will collapse, then cause an extremely powerful explosion of energy. Supernovae are among the brightest things in space. So, the energy from a supernova would definitely hit our atmosphere and create more carbon-14.
But supernova are rare and easy to track, because they leave behind colorful clouds called nebula, and scientists can estimate when nebula were created:
There are no nearby supernova that happened around 774-775 that could explain the mystery.
So, maybe there are other possibilities. Maybe Earth was hit by a distant gamma-ray burst. But some believe that if a gamma-ray burst hit Earth, all life would immediately die. Also, the evidence points to a long-sustained increase across 2 years, not a quick burst.
Maybe it’s a supernova that’s untracked? It’s possible, but supernova are rare and really obvious.
Maybe it was energy from a much more distant object that finally hit Earth? It’s possible, but hard to prove.
Maybe something unusual happened to the Sun? That’s also possible, but hard to prove.
Anyhow, until there’s more evidence, it’s a scientific mystery of what happened to the Earth in 774 and 775. | 0.833282 | 3.857432 |
Two of the host galaxies of long-duration gamma-ray bursts observed by NASA's Hubble Space Telescope. The green crosshairs pinpoint the location where the gamma-ray bursts occurred. Most of the long gamma-ray bursts in the study occurred in the brightest regions of irregular galaxies where the most massive stars are forming.
Photo: NASA, ESA, Andrew Fruchter (STScI), and the GRB Optical Studies with HST (GOSH) collaboration
May 15, 2006
Hubble surveys find gamma-ray bursts and supernovae in different environments
By Tim Stephens
Long gamma-ray bursts (GRBs) are associated with the deaths of only the most massive stars and occur relatively rarely in spiral galaxies such as our own Milky Way, according to research published online in Nature on May 10.
That's good news, because a nearby gamma-ray burst could wreak havoc on Earth by destroying the ozone layer in the upper atmosphere. But researchers already knew that a gamma-ray burst near enough to threaten our planet was highly unlikely. They are more interested in the implications of the new study for understanding how gamma-ray bursts and supernovae are triggered by the collapse of massive stars.
"The fundamentally interesting observation is that the stars that explode as gamma-ray bursts have a different distribution from stars that explode as supernovae. Gamma-ray bursts tend to take place in galaxies not like ours," said Stephen Thorsett, professor of astronomy and astrophysics at UCSC and a coauthor of the Nature paper.
Thorsett first described the terrestrial implications of a nearby gamma-ray burst in a 1995 paper, but he said the likelihood of such an event now appears to be very small.
The new paper is a comprehensive analysis of observations of gamma-ray bursts and supernovae made by NASA's Hubble Space Telescope over the past 10 years. The Hubble observations show that long-duration GRBs--those lasting more than one to two seconds--tend to occur in small irregular galaxies where stars are deficient in the heavier elements. Spiral galaxies like the Milky Way tend to be rich in heavier elements.
The study involved a large team of researchers led by Andrew Fruchter of the Space Telescope Science Institute in Baltimore, Md. Stan Woosley, professor of astronomy and astrophysics at UCSC and a leading expert on gamma-ray bursts and supernovae, is also a coauthor of the paper.
The paper looks at long-duration gamma-ray bursts and type II or core-collapse supernovae, both of which result from the violent deaths of massive stars. When such a star exhausts its fuel, the core collapses and explodes. The new findings shed light on the conditions that determine whether the collapse will generate a brilliant supernova or an even more powerful gamma-ray burst (GRB).
Fruchter's team used Hubble to examine the environments of 42 long-duration GRBs and 16 core-collapse supernovae. The researchers found that most of the long GRBs in the sample were detected in small, faint, misshapen galaxies. Such "irregular" galaxies are usually deficient in heavier elements. Only one of the GRBs was spotted in a spiral galaxy. By contrast, the hosts of supernovae were divided equally between spiral and irregular galaxies.
The researchers also found that long GRBs are far more concentrated on the brightest regions of their host galaxies where the most massive stars reside. Supernovae, on the other hand, occur throughout their host galaxies.
"The discovery that long-duration GRBs lie on the brightest regions of their host galaxies suggests that they come from the most massive stars--20 or more times as massive as our Sun," Fruchter said. "Their occurrence in small irregulars implies that only stars that lack heavy chemical elements [elements heavier than hydrogen and helium] tend to produce long-duration GRBs."
Galaxies build up a stockpile of heavier chemical elements through the ongoing evolution of successive generations of stars. Massive stars abundant in heavy elements are unlikely to trigger GRBs because they may lose too much material through stellar "winds" off their surfaces before they collapse and explode. When this happens, the stars don't have enough mass left to produce the proper conditions that would trigger GRBs.
These findings fit with the predictions of Woosley's "collapsar model," which describes how a long GRB is produced when a massive star collapses to form a black hole. The more massive a star is when it dies, the more likely it is to form a black hole. And stars with low metallicity lose less mass as they burn and are more massive and rotate more rapidly when they die, Woosley said.
"The core of the star has to be rotating rapidly to make a gamma-ray burst, and as stars lose mass by blowing away material in stellar winds, they rotate more slowly," Woosley said.
When the core of a massive star collapses to form a black hole, the energy from the collapse escapes along a narrow jet, which burns its way through the remnants of the star. The formation of directed jets that concentrate energy along a narrow beam explains why GRBs are so powerful.
GRBs can be divided into two classes: short bursts, which last between milliseconds and about two seconds and produce very high-energy radiation, and long bursts, which last between two and tens of seconds and create less energetic gamma rays. Short bursts are believed to arise from collisions between two compact objects, such as neutron stars. | 0.859062 | 3.979817 |
The discovery by an undergraduate student of tubes of plasma drifting above Earth has made headlines in the past few days. Many people have asked how the discovery was made and, in particular, how an undergraduate student was able to do it.
The answer is a combination of an amazing new telescope, a very smart student and an unexpected fusion of two areas of science.
Here is how it all happened, from my perspective as the academic who supervised the project at the Sydney Institute for Astronomy.
My research involves studying the variability of stars and galaxies using a new radio telescope, the Murchison Widefield Array (MWA). My colleagues and I were worried about the ionosphere being a problem for this research, because at low frequencies it can distort the radio signals that we receive from outer space.
This makes celestial objects appear to jiggle around, be stretched and squeezed, and change in brightness. I knew this would be a problem for my plan to study how the brightness of stars and galaxies varied, so I wanted to find out how severe the distortion was.
The ionosphere is the part of the Earth’s atmosphere that has been ionised by radiation from the sun. It is made up of a plasma in which the gas molecules have lost one or more electrons. It stretches between 50 to 1,000 kilometres above the Earth’s surface (commercial aeroplanes typically fly at 10 kilometres above the Earth). Importantly, it refracts radio waves, affecting radio communication around the world.
At the beginning of last year I had a final-year undergraduate student, Cleo Loi – who also contributed to this article – looking for a research project, so I gave her the task of investigating how much the ionosphere was affecting astronomical observations with the MWA.
Around that time, a postdoctoral researcher from Curtin University, Natasha Hurley-Walker, was examining MWA data and came across a night that looked rather unusual.
Celestial objects were dancing around wildly, distorting strongly in shape and flickering in brightness. She flagged this night as one that the ionosphere had rendered unusable for our astronomy research.
Cleo then developed a way of visualising the distortions caused by the ionosphere on the images of distant background galaxies. She took the data Natasha had identified and applied her analysis to it.
When she showed me and other researchers the distortion maps she was generating, we were surprised to see huge waves of correlated motion rippling through the image. They looked like spokes radiating from a point outside the image.
Looking for answers
To try to work out what they were, Cleo transformed the coordinates from a celestial reference frame (that astronomers usually use) to an Earth-based reference frame, which is fixed with respect to the atmosphere. This crucial transformation revealed that the bands were hanging almost stationary in the Earth’s sky.
In the process of writing up our research, we emailed Cleo’s preliminary results to collaborators. The MWA collaboration consists of hundreds of radio astronomers and engineers from Australia, New Zealand, the United States, India and Canada. They were quick to respond with a list of suggestions as to what the bands might be.
It is a critical part of science that good scientists respond to unexpected results with scepticism, particularly if they come from an inexperienced student. But the sheer volume of emails was initially quite overwhelming for Cleo. However, she stayed focused on solving the problem.
The suggestions ranged from possible problems with the telescope, the observing set-up, the imaging process and Cleo’s analysis techniques. Hundreds of emails were exchanged over a few months as Cleo tested and ruled out each suggestion.
Once we had run out of things to test we were left with an interesting dataset, an unexplained phenomenon and an increasing suspicion that the strange distortion pattern was a real effect caused by the ionosphere.
As she was preparing her honours thesis, Cleo had a geometrical insight into explaining the radial spoke-like pattern. She realised that a set of parallel lines viewed at an angle would appear to converge due to perspective distortion, like train tracks going into the distance.
However, without much knowledge of geophysics, it was several weeks until she made a second critical link: the layout of the spokes matched the Earth’s magnetic field. These strange tubular structures were tracing the magnetic field lines, which are parallel to one another but at an angle to the ground. The agreement was perfect.
Armed with solid evidence, Cleo and I got in touch with geospace physicists to help us interpret what we were seeing. Suggestions to explain the phenomena included plasma bubbles, travelling ionospheric disturbances and ultra-low-frequency waves.
Finally, Fred Menk from the University of Newcastle suggested they might be “whistler ducts”. These are cylindrical structures aligned to a magnetic field, where the electron content is higher inside than outside. They are thought to guide the propagation of electromagnetic waves called “whistlers” in the same way that optic fibres guide light.
Whistler ducts had never been seen before, but all their properties deduced by scientists over the years matched what we were seeing with the MWA. Except for one thing: we didn’t know how high they were.
Until now, we had only used the MWA to take two-dimensional pictures of the sky. Whistler ducts exist at very high altitudes, and an altitude measurement was necessary if we were to confirm them as a known phenomenon.
Cleo was reluctant to publish the result without an altitude estimate. However, we couldn’t derive that from our data, so we encouraged her to publish the results as they were.
At that point Cleo had a brainwave. She realised that the MWA could be used stereoscopically to achieve 3D vision, like a giant pair of eyes. By splitting the data from the eastern and western receivers of the MWA, she revealed a slight parallax shift in the distortion pattern that let us triangulate the altitude: around 600km above the ground.
We were all astounded that this idea had worked, confirming that these were likely to be whistler ducts.
It has been an exciting year of research. We started out with an astronomy question and found a surprising answer in geospace physics. To the layperson, these might seem like the same field, but to scientists focused deeply within their narrow field of expertise, the gap is wide.
Cleo has shown how a talented but novice researcher can have an advantage over experienced researchers. By approaching the problem without preconceptions she was able to bridge these two disciplines and use a novel technique on a new radio telescope to discover plasma tubes in the sky. | 0.858126 | 3.793379 |
There’s a rule of thumb that can come in handy when you hear about new planet discoveries from the Kepler space mission. If they’re talking about a handful of new worlds orbiting distant stars, it’s an actual discovery. If they’re talking about hundreds, it’s not actual planets but “planet candidates,” which haven’t yet been independently verified — a key step before scientists can claim they’ve genuinely found something.
But the latest announcement from the Kepler science team has just turned that reliable rule on its head. As of yesterday, astronomers knew of about a thousand verified planets beyond our solar system, the majority of them found with telescopes other than Kepler. Today, Kepler added an unprecedented 715 new ones to the list, nearly doubling the count of bona fide exoplanets known to science. “For years, I’ve trained myself to say ‘planet candidate’ rather than ‘planet’ most of the time,” said SETI Institute and Kepler scientist Jason Rowe in a press conference. “I have to change that.”
Of these new worlds, none is what NASA scientist Jack Lissauer calls “Earth 2.0,” meaning an Earth-size planet in an Earth-like orbit around a sun-like star. Just four of the planets, in fact, sit in their stars’ so-called habitable zones, where water could plausibly exist in liquid form on the surface. And in these cases, the stars are smaller and dimmer than the sun, while the planets are bulkier than Earth. But most of the new planets are between Neptune and Earth in size, confirming a trend of moderate-size planets that astronomers have been seeing for several years now — and giving them good reason to think that true twins of Earth aren’t at all uncommon.
(MORE: Waterworld Found)
The reason for such a huge leap in planet verifications is based on another trend astronomers have noticed: most of the planets they’re finding come not singly but in solar systems containing two, three, four or more planets. That’s not a huge surprise, given our solar system's eight (formerly nine).
Lissauer and other theorists realized, however, that that fact gave them a way to vet planet candidates in wholesale fashion. The reason you need a double check at all is that Kepler finds new worlds by looking for a slight dimming as a planet passes in front of its star, blocking a tiny bit of the star’s light. Other astronomical phenomena can mimic that effect, though — most notably a pair of stars that orbit each other, with one passing in front of the other. S o astronomers confirm candidates using other techniques — looking for the gravitational wobble the planet imposes on the star, for example — which have to be done one candidate at a time.
It would be much less likely, however, for something to mimic a swarm of planets passing in front of a star and dimming it, each with its own rhythm based on orbital distance. The risk of a false positive, in other words, is exceedingly low. All of the planets just announced are indeed multiples, with 715 worlds distributed among just 305 stars.
Verifying a huge number of new planets all in one shot is a big enough deal, but what makes it especially interesting is that so many of them are clustered very tightly near their stars — multiple worlds bigger than Earth but huddled in packs with orbits smaller than Venus’ or even Mercury’s. “So why isn’t Earth crammed close to the sun?” asked MIT astronomer Sara Seager, who joined the press conference as an independent commenter. One possible answer: these planets formed from a primordial disk of gas and dust much denser than the one from which we emerged. But that’s just speculation at this point. What’s clear, she said, “This just reminds us that planetary systems can be very different from ours."
The fact that so many exoplanets are like mini-Neptunes in size is also a surprise that astronomers have been coming to grips with over the past few years. “We have none of these in our solar system,” said Seager, “so we don’t really know for sure what they’re made of.”
Much of that could become clearer with a new generation of space telescopes scheduled to go into orbit later in the decade. One is the Transiting Exoplanet Survey Satellite, or TESS, which will look for planet-induced dimming in bright stars, mostly close to Earth; another is the James Webb Space Telescope, whose huge mirror and powerful infrared-sensitive cameras will look for chemical signatures of life in the atmospheres of nearby exoplanets.
Kepler, meanwhile, will keep finding planets — not so much through new observations, since a malfunction last spring has left it crippled, but via the backlog of observations that still haven’t been analyzed. The new planets, said Lissauer, come from the first two years’ worth of Kepler data. That means a lot of planets are yet to come, including some with longer, more Earth-like orbits.
“Kepler,” said Seager, “is the gift that keeps on giving.” | 0.88507 | 3.733943 |
Free Search (21116 images)
Saturn’s B-ring close-up
- Title Saturn’s B-ring close-up
- Released 20/03/2017 10:00 am
- Copyright NASA/JPL-Caltech/Space Science Institute
This image shows the incredible detail at which the international Cassini spacecraft is observing Saturn’s rings of icy debris as part of its dedicated close ‘ring grazing’ orbits.
This image focuses on a region in Saturn’s B ring, which is seen in twice as much detail as ever before, revealing a wealth of rich structure.
Saturn’s rings are composed mainly of water ice and range from tiny dust-size specks to boulders tens of metres across. Some of the patterns seen in Cassini’s close images of the rings are generated by gravitational interactions with Saturn’s many moons, but many details remain unexplained.
Cassini is expected to return a library of new detailed images of the rings in the coming months, which will help planetary scientists learn more about the mysterious patterns.
The spacecraft’s ring-grazing orbits began last November, and will continue until late April, when the mission enters its ‘grand finale’ phase. During 22 finale orbits Cassini will repeatedly dive through the gap between the rings and Saturn before plunging into the planet’s atmosphere in mid-September to conclude its incredible 13-year odyssey in the Saturn system.
The image was taken in visible light with Cassini’s wide-angle camera on 18 December 2016, at a distance of about 51 000 km from the rings, and looks towards the unilluminated side of the rings. Image scale is about 360 m per pixel.
In order to preserve the finest details, this image has not been processed to remove the many small bright blemishes, which are created by cosmic rays and charged particle radiation near the planet.
The Cassini–Huygens mission is a cooperative project of NASA, ESA and ASI, the Italian space agency
The image was first featured in a release published on 30 January 2017.
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Lava tubes large enough to house cities could be structurally stable on the moon, according to a theoretical study presented at the Lunar and Planetary Science Conference on March 17.
The volcanic features are an important target for future human space exploration because they could provide shelter from cosmic radiation, meteorite impacts and temperature extremes.
Lava tubes are tunnels formed from the lava flow of volcanic eruptions. The edges of the lava cool as it flows to form a pipe-like crust around the flowing river of lava. When the eruption ends and the lava flow stops, the pipe drains leave behind a hollow tunnel, said Jay Melosh, a Purdue University distinguished professor of earth, atmospheric and planetary sciences who is involved in the research.
“There has been some discussion of whether lava tubes might exist on the moon,” he said. “Some evidence, like the sinuous rilles observed on the surface, suggest that if lunar lava tubes exist they might be really big.”
Sinuous rilles are large channels visible on the lunar surface thought to be formed by lava flows. The sinuous rilles range in size up to 10 kilometers wide, and the Purdue team explored whether lava tubes of the same scale could exist.
David Blair, a graduate student in Purdue’s Department of Earth, Atmospheric and Planetary Sciences, led the study that examined whether empty lava tubes more than 1 kilometer wide could remain structurally stable on the moon.
“We found that if lunar lava tubes existed with a strong arched shape like those on Earth, they would be stable at sizes up to 5,000 meters, or several miles wide, on the moon,” Blair said. “This wouldn’t be possible on Earth, but gravity is much lower on the moon and lunar rock doesn’t have to withstand the same weathering and erosion. In theory, huge lava tubes — big enough to easily house a city — could be structurally sound on the moon.”
Blair worked with Antonio Bobet, a Purdue professor of civil engineering, and applied known information about lunar rock and the moon’s environment to civil engineering technology used to design tunnels on Earth.
The team found that a lava tube’s stability depended on the width, roof thickness and the stress state of the cooled lava, and the team modeled a range of these variables. The researchers also modeled lava tubes with walls created by lava placed in one thick layer and with lava placed in many thin layers, Blair said.
Only one other study, published in 1969, has attempted to model lunar lava tubes, he said.
In addition to Melosh, Blair and Bobet, team members include Loic Chappaz and Rohan Sood, graduate students in the School of Aeronautics and Astronautics; Kathleen Howell, Purdue’s Hsu Lo Professor of Aeronautical and Astronautical Engineering; Andy M. Freed, an associate professor of earth, atmospheric and planetary sciences; and Colleen Milbury, a postdoctoral research associate in the Department of Earth, Atmospheric and Planetary Sciences. | 0.836955 | 3.847679 |
With the use of NASA’s Chandra X-Ray Observatory, Swift Gamma Ray Burst Explorer, and ESA’s XMM-Newton, scientists were given a bird’s eye view when a star ventures too close to a black hole. The star gets ripped apart in the extreme environment and it looks truly amazing.
Because of the intense gravity of a black hole, when a star gets too close, the tidal forces will rip the star apart. These events are called “tidal disruptions,” and with this tidal disruption, called ASASSN-14li, astronomers observed some of the stellar debris sent outward at high speeds, while the rest continued toward the black hole.
Watch as this artist’s rendering illustrates new findings about a star shredded by a black hole from NASA Goddard:
The event happened in the center of galaxy PGC 043234, which is about 290 million light years away, making it the closest tidal disruption discovered in 10 years. The supermassive black hole is estimated to weigh a few million times the mass of the sun. The event was discovered during an optical search by the All-Sky Automated Survey for Supernovae (ASAS-SN) in November 2014.
Jon Miller, of the University of Michigan in Ann Arbor, who led the study said in a statement: “We have seen evidence for a handful of tidal disruptions over the years and have developed a lot of ideas of what goes on,” adding:
This one is the best chance we have had so far to really understand what happens when a black hole shreds a star
According to NASA, after the star is destroyed, the black hole’s strong gravitational force pulls most of the remains of the star toward it. This infalling debris is heated to millions of degrees and generates a huge amount of X-ray light. Soon after this surge of X-rays, the amount of light decreases as the material falls beyond the black hole’s event horizon, the point beyond which no light can escape.
Scientists know that gas will often move toward a black hole by spiraling inward in a disk, but what remains unknown is how the whole process starts. By using X-ray light at different wavelengths (known as the “X-ray spectrum“), astronomers were able to watch the formation of the ASASSN-14li disk by tracking how that changed over time.
NASA’s Swift satellite spots black hole devouring a star, by Universe Odyssey:
“All previous observations of tidal disruption events revealed an already formed disc around the black hole. But this is the first time that we catch such a disc in its infancy, so we can study the details of how matter starts flowing from the shattered star towards the black hole and settles in circular orbits around it,” said Miller.
The researchers determined that the X-rays being produced come from material that is either very close to or is actually in the smallest possible stable orbit around the black hole, NASA wrote.
Jelle Kaastra of the Institute for Space Research in the Netherlands and co-author said: “The black hole tears the star apart and starts swallowing material really quickly, but that’s not the end of the story.
The black hole can’t keep up that pace so it expels some of the material outwards.
The data from the X-rays suggests that there was wind that was moving away from the black hole. Because the wind was not moving fast enough to be able to escape the black hole’s gravitational pull, NASA has an alternative explanation, writing:
“The relatively low speed is that gas from the disrupted star is following an elliptical orbit around the black hole and is at the greatest distance from the black hole where it is traveling the slowest.”
NASA accidentally discovers giant black holes, by DNews:
Cole Miller, from the University of Maryland in College Park and a co-author, said: “These results support some of our newest ideas for the structure and evolution of tidal disruption events. In the future, tidal disruptions can provide us with laboratories to study the effects of extreme gravity.”
By finding more events like ASASSN-14li, astronomers are hoping they can test theoretical models on how black holes affect their environments, and how they affect anything that wanders too close. | 0.899888 | 4.066856 |
International Research Team Confirms Very Distant Rare Galaxy Cluster
Today, after years of intensive observation, an international team of researchers associated with such universities as Caltech, Observatorie di Paris, and Osservatorio Astronomico di Brera has confirmed the existence of a rare distant galaxy cluster. Team leader Andrew Newman claimed that their research made this galaxy cluster "one of the best-studied structures from the early universe."
An image of the newly confirmed galaxy cluster can be seen below:
Many of the oldest galaxies can be found in clusters, enormous structures in which up to thousands of galaxies are bound together by gravity. Galaxy clusters are the largest gravitationally bound structures in the universe, but to date only a few have been observed in the distant universe. These clusters are considered in the scientific community to be crucial to the understanding of the life cycles of galaxies in the early stages of our Universe, particularly the as yet unknown reason why these galaxies stop forming new stars and become quiescent, or dormant.
The Astrophysical Journal published Newman's research paper, which detailed the team's use of the Hubble Space Telescope to perform spectroscopy, a process in which the telescope splits the starlight from the galaxies into its component colors and captures images of the distant cluster. The team observed nineteen galaxies at precisely the same distance, 9.9 billion light years. This is the most distant cluster of its size that has ever been discovered.
When galaxies become dormant, they continue to expand in size. Scientists hypothesize that this phenomenon occurs when galaxies collide with each other and combine to form larger galaxies, and that early clusters are optimal locations for these collisions. Newman and his team found that, contrary to this belief, non-cluster galaxies grow at the same rate as the galaxies in the observed cluster. | 0.828307 | 3.65621 |
The Hubble Space Telescope spied an asteroid breaking up into as many as 10 smaller pieces — a phenomenon that scientists have never seen before.
While we've seen more fragile comet nuclei disintegrate as they approached our Sun — the massive comet ISON famously broke apart near the Sun last year and was seen again in pieces shortly after — scientists haven't ever observed a breakup like this in an asteroid.
See also: The Hunt for Killer Asteroids
"This is a really bizarre thing to observe — we've never seen anything like it before,” says Jessica Agarwal of the Max Planck Institute for Solar System Research, Germany. "The break-up could have many different causes, but the Hubble observations are detailed enough that we can actually pinpoint the process responsible.”
This illustration, below, shows one possible explanation for the disintegration of the asteroid, which has been dubbed P/2013 R3.
We know that P/2013 R3 didn't collide with another asteroid because it didn't explode, but rather gradually broke apart. This means that it had a weak, fractured interior, likely the result of it surviving near-death collisions with other asteroids over the past 4.5 billion years. Now it's disintegrating because the sunlight is speeding up its rotation.
The photos below, which the Hubble telescope captured on Oct. 29, 2013, show the asteroid as it broke apart.
The grainy spots that form the comet-like tails are actually dust coming from rotating rock.
This week, two asteroids flew by Earth, coming closer to our planet than our own moon. The space rocks are just two of about 20 rocks per year that fly by Earth at a similar distance, NASA says. | 0.873105 | 3.523441 |
Editor's Note: This story was updated at 11:30 a.m. ET on September 30.
At 7:19 a.m. ET (11:19 a.m. GMT) on September 30, a robotic pioneer went from dust to dust: The European Space Agency intentionally crash-landed its Rosetta spacecraft, the first probe to orbit a comet.
Launched in March 2004, Rosetta arrived at Comet 67P/Churyumov-Gerasimenko on August 6, 2014, after a decade of zipping through the solar system. And for more than two years, the Rosetta orbiter and its Philae lander made good on the mission’s name, helping scientists decipher the makeup of comets—primeval balls of ice and dust that have preserved pristine material from the early solar system.
But like all good things, the Rosetta mission had to come to an end. Comet 67P made its closest approach to the sun on August 13, 2015, coming within 116 million miles—with Rosetta there to watch it all. Now the comet is swinging back out toward the orbit of Jupiter, and at ever farther distances, Rosetta’s solar panels would have struggled to produce the power necessary to keep the probe warm enough to survive.
The spacecraft was also feeling its age: In all, it weathered 12 years in the harsh conditions of space, and two of those years were spent snuggled up against a dusty, icy comet. But Rosetta didn't go gently into that good night. By intentionally crashing the probe into the surface, mission scientists hoped to get as many close-up images and chemical samples of Comet 67P as they can during its descent.
In its final moments, Rosetta beamed back as much data as it could as it careened toward the Ma’at region on the two-lobed comet’s “head.” The site contains active pits that spew out some of the comet’s dust jets, as well as lumpy structures called goosebumps, thought to be remains of the mini-comets that aggregated to form the larger body.
To honor Rosetta’s historic mission, take a look back at some of the probe’s most exciting achievements:
Other spacecraft have flown by comets—the European Space Agency’s first deep-space mission sent a probe hurtling by Halley’s Comet in 1986. But in August 2014, Rosetta became the first to orbit a comet proper, settling into a gravitational embrace some 12.5 miles above Comet 67P’s surface by the end of September.
On November 12, 2014, Rosetta let loose its Philae lander, which became the first spacecraft to perform a soft landing on a comet. But it didn’t exactly go to plan: Philae’s harpoon system didn’t work the first time it touched down, causing it to tumble for two hours before ultimately settling in a shadowy crack.
Philae was working at first, sending back data on the comet’s surface, but scientists struggled to pinpoint its exact position. Three days later, its batteries ran out of juice, and Philae went into hibernation, a sleep that mission scientists declared eternal in February 2016. Earlier this month, mission scientists at last found Philae using images from Rosetta.
When Philae landed on Comet 67P, scientists learned that the surface contained ammonia, hydrogen cyanide, and hydrogen sulfide, which together smell like pungent urine, almonds, and rotten eggs. That noxious but scientifically intriguing odor inspired a U.K. company to develop a limited-run perfume that approximated the aroma.
In 2014 and 2015, Rosetta spotted phosphorus and organic compounds such as glycine, the simplest amino acid, in the haze around Comet 67P. This discovery suggests that comets could have helped bring about life on Earth by seeding our planet with the necessary raw materials.
As Comet 67P neared the sun, Rosetta witnessed its color and brightness change. Between August and November 2014, the sun’s heat stripped away older surface material to expose fresh ices underneath. The comet’s brightness went up by a third, and it became gradually bluer. And on August 13, 2015, Rosetta got a front-row seat to Comet 67P’s closest approach, when the sun’s heat helped to trigger jets and outbursts of dust that streamed from the comet’s core.
Scientists have been debating for years whether early Earth was too hot to hold on to water from its formation, with one popular theory arguing that our oceans and aquifers were delivered by comets after the planet cooled. But Rosetta’s measurements of Comet 67P’s water ice show that it has much more deuterium—a heavy isotope of hydrogen—than the water in Earth’s oceans. This finding seems to rule out comets from beyond Neptune’s orbit as potential sources for Earth’s water, although there’s still a case for asteroids being Earth’s early water-bearers.
Comet 67P has two distinct, bulbous lobes, making it look surprisingly like a rubber duck. Data from Rosetta show that each lobe began life as an independent body, but billions of years ago, the two objects collided with each other and fused together to form the comet we see today.
Rosetta’s mapping of Comet 67P’s surface reveals steep-sided pits, some of which are 600 feet wide and 600 feet deep. It’s thought that the pits formed as gases accumulated inside the comet, weakening its internal structure enough to collapse its crust inward. | 0.833069 | 3.703763 |
How is it that some stars look so much younger than their years? They’ve discovered a fountain of youth that requires some violent tactics: vampirism and high-speed collisions.
Picturing Hollywood beauties like Michelle Pfieffer and Susan Sarandon engaging in bizarre sacrificial rituals so they can stay preternaturally youthful-looking? Think bigger … as in stars of cosmic proportions.
Scientists say that some stars within the ancient Messier 30 group located 28,000 light-years away from Earth that look much younger than they should manage to do so by sucking the life out of their companion stars.
Scientists have been trying to discover the secrets of these deceptively young-looking stars for decades. The youthful stars stay bright and blue while others around them are bloated and red, a sign that they’re nearing the end of their lives — but all of the stars in Messier 30 are thought to be about 13 billion years old.
"It's like seeing a few kids in the group picture of a rest-home for retired people," said Francesco Ferraro of the University of Bologna in Italy. "It is natural to wonder why they are there."
When two stars orbit each other, the smaller one siphons fresh hydrogen from the larger one, causing the smaller one to heat up and grow bluer.
But this strange form of vampirism isn’t the only way these stars defy signs of aging. Some stars retain their youth by colliding head-on with others. Scientists believe that about 2 billion years ago, the core of Messier 30 collapsed, causing stars to crash against each other, generating more of the hot young things.
"Our observations demonstrate that blue stragglers formed by collisions have slightly different properties from those formed by vampirism," said study team member Giacomo Beccari from the European Space Agency. | 0.859768 | 3.037408 |
A new portrait released by NASA combines an unlikely group of space bodies each located in entirely separate regions of the universe.
Captured by the Wide-Field Infrared Survey Explorer (WISE), the image depicts the Helix nebula, found far outside our solar system, with tracks of asteroids located within the solar system.
The image was discovered by accident during a hunt for asteroids. It comes at a time when the mission's team is celebrating its four year anniversary of the launch of the probe that was renamed NEOWISE in August after being switched back on to look for more asteroids.
"I was recently looking for asteroids in images collected in 2010, and this picture jumped out at me," said Amy Mainzer, the NEOWISE principal investigator at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "I recognized the Helix nebula right away."
In the picture, sets of yellow dots represents a pictures of single asteroids taken as they moved across WISE's view. Using this data, scientists are able to both discover and characterize asteroids - including those whose paths bring them relatively near Earth.
The Helix nebula is depicted in a range of colors depending on the infrared wavelengths emitted. Longer wavelengths are depicted as red and shorter wavelengths blue.
WISE blasted off the launch pad at Vandenberg Air Force Base in California Dec. 14, 2009. Within just two years, it had completed scanning the entire sky in infrared light not once, but twice. In all, the mission amassed pictures of nearly 1 billion objects, ranging from far away galaxies to stars and asteroids.
Having completed what it set out to do, WISE went to sleep, but now engineers are bringing it back to life in the search for even more asteroids.
"WISE is the spacecraft that keeps on giving," said Ned Wright of UCLA, the principal investigator of WISE before it transitioned into NEOWISE. | 0.837129 | 3.325441 |
Oct 20, 2014
Saturn’s moon Mimas exhibits a significant libration.
In past Picture of the Day articles, several moons in the Solar System were analyzed in terms of their electrical connection with their parent bodies. In particular, the discovery that Jupiter’s moon Io and Saturn’s moon Enceladus are exchanging powerful flows of electric charge with their gas giant hosts suggests that electricity plays a larger role in planetary dynamics than conventional astrophysics acknowledges. Instead, the scientific community prefers gravity in the form of “tidal force” as their sine qua non.
Mimas is only 397 kilometers in diameter, one of the smaller moons in the Solar System. It compares in size to both Enceladus and to one of Neptune’s moons, Proteus. It possesses a giant crater that dominates one of its hemispheres: about one-eighth the diameter of the entire moon. A similar scale crater on Earth would cover almost half of the Pacific basin.
Herschel crater, named for Sir William Herschel who discovered Mimas in 1789, is 130 kilometers wide with a towering central peak. Such craters are theorized to form from asteroid impacts. However, there is little debris within the crater and not many boulders or other fragments surround it. Researchers think that one reason for the lack of debris is that Mimas has little gravitational attraction, so the blast remnants did not remain nearby. It sounds like a plausible explanation, except that the craters on large planets like Earth and Mars—some many hundreds of kilometers wide—also demonstrate little eruptive fallback; their floors and sidewalls are swept clean, though some glassified breccia is often incorporated into them.
The strangest aspect to the crater is its hexagonal shape. How can an asteroid explosion cause a hexagonal crater? No high velocity gun experiments have demonstrated a polygonal crater after an explosive event. Impact events do not result in such formations. Instead, they are chaotic and leave behind circular depressions with conical bottoms.
Mimas is also extremely cold. Infrared measurements by the Cassini spacecraft reveal it to range from -146 Celsius to -160 Celsius. The strange pattern of cold is confusing to NASA mission team members. They expected that Mimas would be warmer where the Sun’s energy shines straight down. However, the infrared map generated by Cassini indicates that the warmest temperature is along the western limb.
Other false-color images seem to suggest that the temperature differences correspond to surface composition, but no one is sure why. It is thought that the ice grains on Mimas vary in size, causing them to change the way they reflect light.
Recently, the moon Mimas made the news again because of its unusual orbital oscillation. Could the temperature and oscillation anomalies be related?
Electric Universe advocates suggest that plasma discharges on Saturn’s moons, including lightning bolts, diffuse glow-mode clouds of energetic particles, and rotating Birkeland currents could be the agents for the bizarre conditions found there. For instance, Mimas has collected a coating of some compounds that were eroded from the other moons in the Saturnian system, especially Phoebe. Perhaps the splotches of dark red and sooty black coloring the faces of Rhea, Tethys, Iapetus, and Mimas are made of ultra fine dust electrically etched from Phoebe.
Mimas might have once been caught in the grip of an interplanetary particle beam that excavated Herschel crater and the other geological features incised on its face. Due to the plasma instabilities in the discharge, a hexagon was cut deeply into its crust. When the electrical energy was withdrawn, Herschel crater remained, a “fossilized” geometric shape permanently burned in.
The electric currents that cut the craters and rilles on Mimas most likely left evidence of their passages in other ways. The anomalous temperature measurement that cannot be attributed to the Sun’s influence is probably one sign of those past catastrophes. It may be that the unusual V-shaped pattern in the false color images from Cassini is a warmer layer of dust and ice that was excavated from Herschel crater and ionically deposited “downwind” by a high-energy plasma discharge in the recent past.
Along with those phenomena, the orbital libration could be caused by the forces that gave birth to Mimas in the first place. It is a well-known fact of electrical theory that transient responses to charge flow can cause oscillations. Such oscillations result from a sudden rise in voltage and another oscillation from a sudden drop in voltage. Since Mimas is most likely connected to Saturn by so-called “electromagnetic flux ropes”, as it revolves, that connection could create the moon’s “wobble” due to changes in the electricity flowing between the two bodies. | 0.930519 | 3.918841 |
Beyond Our Planet
Since NASA studies both Earth and other planets, what we learn from Earth's oceans can help us make sense of clues to the watery pasts of other planets. Water is essential at the molecular level to moving life beyond its basic building blocks; thus, searches for extraterrestrial life usually involve a search for liquid water.
This map centered on the north pole of Mars is based on gamma rays from the element hydrogen - mainly in the form of water ice. Regions of high ice content are shown in violet and blue and those low in ice content are shown in red. The very ice-rich region at the north pole is due to a permanent polar cap of water ice on the surface. Credit: University of Arizona.
Mars is a cold desert planet that currently has no liquid water on its surface. Yet the terrain of Mars suggests that the red planet once had much more water on its surface than it does today. Some scientists wonder whether Mars may have had an ocean in its northern hemisphere long ago. While the word is still out on that, recent spacecraft findings have shown rocks that only could have formed in the presence of water, as well as evidence of lakebeds and other interesting features associated with water.
Discoveries made by the Mars Odyssey orbiter in 2002 show large amounts of subsurface water ice in the northern arctic plain. In 2008, the Phoenix Mars Lander will investigate this circumpolar region using a robotic arm to dig through the protective top soil layer to the water ice below and ultimately, to bring both soil and water ice to the lander platform for sophisticated scientific analysis.
During the Galileo mission to Jupiter, its magnetometer observed the moon Europa. Strangely, it got a magnetic signal. Planetary scientists have deduced that Europa does not have enough mass to contain a metallic core, which would ordinarily be necessary for a body to produce its own magnetic field. So how could Europa have a magnetic field? The relatively weak field Galileo observed is consistent with what could be conducted by liquid salty water. Like an ocean.
False-color composite of Europa. Bright plains in the polar areas (top and bottom) are shown in tones of blue. Long, dark lines are fractures in the crust, some of which are more than 3,000 kilometers (1,850 miles) long. The bright feature containing a central dark spot in the lower third of the image is a young impact crater some 50 kilometers (31 miles) in diameter. Credit: NASA/JPL
But the surface of Europa is far too cold for liquid water to exist. Water may reside under the crust - the constant heaving of the moon as it's subjected to Jupiter's brutal gravity may produce enough heat to keep salt water in liquid state.
Europa is thought to be one of the most promising places to search for microscopic life in our solar system. The ice-covered world may have liquid water, energy, and organic compounds - all three of the ingredients necessary for life to survive.
Sometimes the search for extraterrestrial life takes place right here on Earth. Parts of the ocean are nearly as extreme as the environments we could find elsewhere in the solar system - and they contain life! Not puppies or kittens or even goldfish of course - they contain creatures called "extremophiles". These creatures live in harsh environmental conditions: hot, with a lot of extremely active volcanoes, and with little to no oxygen in the atmosphere. Today varieties of extremophiles are found thriving in circumstances once thought inhospitable to life, such as hot springs and deep ocean thermal vents. Studying extremophiles on Earth helps scientists design experiments to search for life on other planets. | 0.852008 | 3.943592 |
Whether speculating on the havoc it wreaks when it’s full or waxing poetic on the beauty of its glow, people love talking about the moon. This age-old fascination with our celestial satellite has resulted in a lexicon loaded with lunar-themed words, phrases, and meanings. Consider the array of senses we have for the word moon itself: in addition to referencing our silvery orb, the term can mean “to act or wander abstractly or listlessly,” “to sentimentalize or remember nostalgically,” “to gaze dreamily,” or even “to expose one’s buttocks.” Here’s a look at the meanings and histories of 9 moony terms and phrases.
Nowadays, most of us would describe a lunatic as a person of unsound mind. But in the Middle Ages, one might describe a lunatic as a person who is acting under the influence of luna, the Latin word for “moon.” The notion that the moon causes certain kinds of madness or evokes dangerous aspects of our personalities has been around for millennia; Aristotle suggested that the moon could cause insanity by manipulating fluids in the brain, much in the same way it commands the tides.
In sailing, a moonraker is a light sail set at the top of the mast. But this term is also a demonym for people from Wiltshire, England. As the story goes, a few men from Wiltshire were discovered trying to rake the moon’s reflection out of a pond. However, if you ask a Wiltshire native, he or she might tell you another version of the story: the men were raking a pond for kegs of smuggled brandy, and when authorities appeared, the rakers feigned madness.
Many of us use this term to mean “dreamily romantic,” a sense that was famously evoked in the 1987 movie titled Moonstruck starring Cher and Nicolas Cage, but drawing on the theme of moon-induced madness, moonstruck can also mean “mentally deranged, supposedly by the influence of the moon.”
Not all moon words conjure insanity or dreamy contemplation—moonlight, for example, can evoke industriousness. In addition to the noun meaning of “light of the moon,” moonlight can also mean “to work at an additional job, especially at night.” Approximately 70 years before that dutiful verb sense arose, moonlight meant to commit a crime at night. Starting at the turn of the 20th century, moonlighting also described fleeing one’s residence under the cover of darkness to skip out on paying rent.
First appearing in the 1400s as another term for moonlight, moonshine is now most commonly used to refer to smuggled or illicitly distilled liquor, a popular term during Prohibition. This black-market booze likely earned this moony moniker because it was smuggled by the light (or shine) of the moon. Moonshine can also mean “nonsense.”
Many old languages had one word for both month and moon, since it takes approximately one month for the moon to orbit around Earth. The moon in honeymoon draws on this temporal sense, reminding newlyweds that their period of blissful harmony has an expiration date.
This phrase is commonly means “very rarely,” as in “once in a blue moon,” and is sometimes used to suggest that something nearly never happens. Although the phrase is also commonly used to refer to the second full moon in a calendar month, it seems more likely that the “very rarely” sense came from the occasional appearance of a moon as blue in color due to extreme atmospheric conditions.
Over the moon
One of the earliest uses of this idiom, which means “extremely delighted” or “very pleased,” comes courtesy of the following nursery-rhyme line from the 1700s: “High diddle, diddle, The Cat and the Fiddle, The Cow jump’d over the Moon.” Centuries later, J.R.R. Tolkien explained the fantastical abilities of the high-vaulting cow in his book of poetry, The Adventures of Tom Bombadil.
Reach for the moon
A few centuries before cows began jumping over the moon to express their glee, people talking about the moon as a place or thing that is difficult or impossible to reach or obtain. The idiom “reach for the moon,” which means “to desire or attempt something unattainable or difficult to obtain,” incorporates this this wistful theme.
What are some of your favorite moon-related words or terms?
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A group of researchers discovered a very distant galaxy, which is about a thousand times brighter than the Milky Way.
As per the researchers, it is the brightest of the submillimetre galaxies, a class of ultraluminous infrared galaxies.
The discovery was published recently in the Astrophysical Journal Letters.
How it is the brightest ever galaxy?
• To measure this galaxy, the researchers used the Gran Telescopio Canarias (GTC) at the Roque de los Muchachos Observatory (Garafía, La Palma) in Spain.
• In order to identify the brightest submillimetre galaxies, researchers carried out a search of the whole sky, combining the data bases of NASA's WISE satellite and European Space Agency's Planck satellite.
• The galaxy's light, amplified by a much nearer galaxy cluster acting as a lens, forms an image which appears much bigger than it should, and it is due to this effect that the researchers could characterise its nature and properties spectroscopically using the GTC.
• This phenomenon, known as gravitational lensing, is comparable to that produced by lenses on light rays, and acts as a sort of magnifier, changing the size and intensity of the apparent image of the original object.
• Due to the gravitational lens produced by a cluster of galaxies between ourselves and the source, which acts as if it was a telescope, the galaxy appears 11 times bigger and brighter than it really is.
• The galaxy is notable for having a high rate of star formation. It is forming stars at a rate of 1000 solar masses per year, compared to the Milky Way, which is forming stars at a rate of some twice a solar mass per year. | 0.847165 | 3.604359 |
Friday, January 31 - With plenty of dark sky tonight, let's head around a fingerwidth northeast of Zeta Orionis and right on the celestial equator for a delightful bright nebula known as M78 (Right Ascension: 5:46.7 - Declination: +00:03). This is both a binocular and small telescope Messier challenge object.
Often overlooked in favor of the Great Orion Nebula, this 8th magnitude diffuse area is easily captured under dark skies. Discovered by Pierre Mechain in 1789, M78 is part of the vast complex of nebulae and star birth that comprise the Orion region. Fueled by twin 10th magnitude stars, the nebula almost appears to resemble a "double comet" in binoculars. Upon close scrutiny with a telescope, observers will note two lobes separated by a dark band of dust. Each lobe bears its own designation - NGC 2067 to the north and NGC 2064 to the south.
While studying, you will notice the entire area is surrounded by a region of absorption, making the borders appear almost starless. Filled with T Tauri-type stars and residing 1,600 light-years away, this reflection nebula is a cloud of interstellar dust which reflects the light of these young stars, the brightest of which is HD 38563A. In 1919, Vesto Slipher was the first to discover its reflective nature. As of 1999, seventeen Herbig-Haro objects are also associated with M78, and are believed to be jets of matter being expelled from newly forming stars.
Saturday, February 1 - Are you ready for a challenge? Then take advantage of dark sky time to head to the eastern-most star in the belt - Zeta Orionis.
Alnitak resides at a distance of some 1600 light-years, but this 1.7 magnitude beauty contains many surprises - like being a triple system. Fine optics, high power and steady skies will be needed to reveal its members. About 15' east and you will see that Alnitak also resides in a fantastic field of nebulosity which is illuminated by our tripartite star. NGC 2024 (Right Ascension: 5:41.9 - Declination: -01:51) is an outstanding area of emission that holds a rough magnitude of 8 - viewable in small scopes but requiring a dark sky. So what's so exciting about a fuzzy patch? Look again, for this beauty is known as the Flame Nebula.
Larger telescopes will deeply appreciate this nebula's many dark lanes, bright filaments and unique shape. For the large scope, place Zeta out of the field of view to the north at high power and allow your eyes to re-adjust. When you look again, you will see a long, faded ribbon of nebulosity called IC 434 to the south of Zeta that stretches for over a degree. The eastern edge of the "ribbon" is very bright and mists away to the west, but look almost directly in the center for a small dark notch with two faint stars positioned to the south. You have now located one of the most famous of the Barnard dark nebulae - B33.
B33 is also known as the Horsehead Nebula. It's a very tough visual object - the classic chess piece shape is only seen in photographs - but those of you who have large aperture can see a dark "node" that is improved with a filter. B33 itself is nothing more than a small area cosmically (about 1 light-year in expanse) of obscuring dark dust, non-luminous gas, and dark matter - but what an incredible shape. If you do not succeed at first attempt? Do not give up. The "Horsehead" is one of the most challenging objects in the sky and has been observed with apertures as small as 150mm.
Sunday, February 2 - Tonight we're going in search of another Herschel 400 object. Wait until Orion has well risen and our lunar companion has ducked west. Our mark will triangulate with Xi and Nu Orionis and point back in the direction of Betelgeuse. It's name? Collinder 83...
It is believed that it may have been observed by Hodierna before 1654, but its discovery is credited to William Herschel in 1784 and cataloged by him as H VIII.24. It hangs out in space some 3600 light-years away and most catalogs refer to it as NGC 2169 (Right Ascension: 6:08.4 - Declination: +13:57). At a rough magnitude of 6, it is very well suited to even smaller binoculars. Although diffuse nebulosity accompanies this 50 million year old cluster, even a small telescope should be able to resolve out its 30 or so stellar members. But no matter which optics you chose to look at this cluster with, one bright asterism will stand out - the number '37' written in stars. Enjoy and write down your observations!
Until next week? Wishing you clear skies!
About Tammy Plotner - Tammy is a professional astronomy author, President Emeritus of Warren Rupp Observatory and retired Astronomical League Executive Secretary. She's received a vast number of astronomy achievement and observing awards, including the Great Lakes Astronomy Achievement Award, RG Wright Service Award and the first woman astronomer to achieve Comet Hunter's Gold Status. | 0.883239 | 3.75681 |
A new study provides the first conclusive proof of the existence of a space wind first proposed theoretically over 20 years ago.
By analysing data from the European Space Agency’s Cluster spacecraft, researcher Iannis Dandouras detected this plasmaspheric wind, so-called because it contributes to the loss of material from the plasmasphere, a donut-shaped region extending above the Earth’s atmosphere. The results are published today in Annales Geophysicae, a journal of the European Geosciences Union (EGU).
“After long scrutiny of the data, there it was, a slow but steady wind, releasing about 1 kg of plasma every second into the outer magnetosphere: this corresponds to almost 90 tonnes every day. It was definitely one of the nicest surprises I’ve ever had!” said Dandouras of the Research Institute in Astrophysics and Planetology in Toulouse, France.
The plasmasphere is a region filled with charged particles that takes up the inner part of the Earth’s magnetosphere, which is dominated by the planet’s magnetic field.
To detect the wind, Dandouras analysed the properties of these charged particles, using information collected in the plasmasphere by ESA’s Cluster spacecraft. Further, he developed a filtering technique to eliminate noise sources and to look for plasma motion along the radial direction, either directed at the Earth or outer space.
As detailed in the new Annales Geophysicae study, the data showed a steady and persistent wind carrying about a kilo of the plasmasphere’s material outwards each second at a speed of over 5,000 km/h. This plasma motion was present at all times, even when the Earth’s magnetic field was not being disturbed by energetic particles coming from the Sun.
Researchers predicted a space wind with these properties over 20 years ago: it is the result of an imbalance between the various forces that govern plasma motion. But direct detection eluded observation until now.
“The plasmaspheric wind is a weak phenomenon, requiring for its detection sensitive instrumentation and detailed measurements of the particles in the plasmasphere and the way they move,” explains Dandouras, who is also the vice-president of the EGU Planetary and Solar System Sciences Division.
The wind contributes to the loss of material from the Earth’s top atmospheric layer and, at the same time, is a source of plasma for the outer magnetosphere above it. Dandouras explains: “The plasmaspheric wind is an important element in the mass budget of the plasmasphere, and has implications on how long it takes to refill this region after it is eroded following a disturbance of the planet’s magnetic field. Due to the plasmaspheric wind, supplying plasma – from the upper atmosphere below it – to refill the plasmasphere is like pouring matter into a leaky container.”
The plasmasphere, the most important plasma reservoir inside the magnetosphere, plays a crucial role in governing the dynamics of the Earth’s radiation belts. These present a radiation hazard to satellites and to astronauts travelling through them. The plasmasphere’s material is also responsible for introducing a delay in the propagation of GPS signals passing through it.
“Understanding the various source and loss mechanisms of plasmaspheric material, and their dependence on the geomagnetic activity conditions, is thus essential for understanding the dynamics of the magnetosphere, and also for understanding the underlying physical mechanisms of some space weather phenomena,” says Dandouras.
Michael Pinnock, Editor-in-Chief of Annales Geophysicae recognises the importance of the new result. “It is a very nice proof of the existence of the plasmaspheric wind. It’s a significant step forward in validating the theory. Models of the plasmasphere, whether for research purposes or space weather applications (e.g. GPS signal propagation) should now take this phenomenon into account,” he wrote in an email.
Similar winds could exist around other planets, providing a way for them to lose atmospheric material into space. Atmospheric escape plays a role in shaping a planet’s atmosphere and, hence, its habitability.
This research is presented in the paper ‘Detection of a plasmaspheric wind in the Earth’s magnetosphere by the Cluster spacecraft’ to appear in the EGU open access journal Annales Geophysicae on 2 July 2013. Please mention the publication if reporting on this story and, if reporting online, include a link to the paper or to the journal website.
The scientific article is available online, free of charge at: http://www.ann-geophys.net/31/1143/2013/angeo-31-1143-2013.html
The paper is authored by Iannis Dandouras of the Research Institute in Astrophysics and Planetology (IRAP), a joint institute of the French National Centre for Scientific Research (CNRS) and the Paul Sabatier University in Toulouse, France. The data was acquired by the CIS, Cluster Ion Spectrometry, experiment onboard ESA’s Cluster, a constellation of four spacecraft flying in formation around Earth.
The European Geosciences Union (EGU) is Europe’s premier geosciences union, dedicated to the pursuit of excellence in the Earth, planetary and space sciences for the benefit of humanity, worldwide. It is a non-profit interdisciplinary learned association of scientists founded in 2002. The EGU has a current portfolio of 15 diverse scientific journals, which use an innovative open access format, and organises a number of topical meetings, and education and outreach activities. Its annual General Assembly is the largest and most prominent European geosciences event, attracting over 11,000 scientists from all over the world. The meeting’s sessions cover a wide range of topics, including volcanology, planetary exploration, the Earth’s internal structure and atmosphere, climate, energy, and resources. The 2014 EGU General Assembly is taking place is Vienna, Austria from 27 April to 2 May 2014. For information regarding the press centre at the meeting and media registration, please check http://media.egu.eu closer to the time of the conference.
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Photons from far-off light sources, like blazars, are capable of going up against a constant exchange of identity in their journey through the Universe just like a nail-biting thriller packed with escapes and subterfuge.
This is an operation that permits these extremely small particles of light to escape an enemy which, if stumbled upon, would crush them. This phenomenon has been studied by a team of Researchers from the University of Salento, Bari, the National Institute for Nuclear Physics (INFN), the National Institute for Astrophysics (INAF) and SISSA thanks to brand new simulation models capable of reproducing the complexity of the cosmos as never before.
Extremely high energy photons (gamma rays) should normally "collide" with the background light emitted by galaxies converted into pairs of matter and antimatter particles, as envisioned by the Theory of Relativity. It is for this reason that it is essential for the sources of very high energy gamma rays to appear considerably less bright than what is observed in a number of cases.
One possible explanation for this surprising anomaly refers to the fact that light photons are changed into hypothetical weakly-interacting particles, "axions" which, in turn, would transform into photons, because of the interaction with magnetic fields. With these metamorphoses, it is possible for a part of the photons to escape interaction with the intergalactic background light that is capable of making them disappear.
The study published In Physical Review Letters emphasizes the importance of this process, which re-created an extremely sophisticated model of the Cosmic Web, a network of filaments made up of gas and dark matter existing throughout the Universe and of its magnetic fields. The above-mentioned effects are now expecting comparison with those obtained experimentally via Cherenkov Telescope Array new generation telescopes.
In this research, through unprecedented and complex computer simulations made at the CSCS Supercomputing Centre in Lugano, Scholars have succeeded in reproducing the so-called Cosmic Web and the magnetic fields linked with this. This is in order to analyze the possibility, advanced from earlier theories, that photons from a light source are converted into axions, hypothetical elementary particles, when they interact with an extragalactic magnetic field.
It is now possible to retransform axions into photons by working together with other magnetic fields. Researchers Daniele Montanino, Franco Vazza, Alessandro Mirizzi and Matteo Viel explain, "Photons from luminous bodies disappear when they encounter extragalactic background light (EBL). But if on their journey they head into these transformations as envisaged by these theories, it would explain why, in addition to giving very important information on processes that occur in the universe, distant celestial bodies are brighter than expected from an observation on Earth. These changes would, in fact, enable a greater number of photons to reach the Earth."
In the simulations developed by Scientists, thanks to the wealth of magnetic fields existing in the Cosmic Web’s filaments reconstructed with the simulations, the conversion phenomenon would now seem to be much more applicable than predicted by earlier models, "Our simulations reproduce a very realistic picture of the cosmos’ structure. From what we have observed, the distribution of the Cosmic Web envisaged by us would markedly increase the probability of these transformations."
As a next step, the research will focus on comparing simulation results with the experimental data attained by employing the Cherenkov Telescope Array Observatories detectors, the new-generation astronomical observatories, one of which is situated in Chile and the other in the Canary Islands, that will analyze the Universe through extremely high energy gamma rays. | 0.847661 | 4.093791 |
Time is not completely separate from and independent of space as you would ordinarily assume. In his Special Relativity theory, Einstein assumed that the fundamental laws of physics do not depend on your location or motion. Two people, one in a stationary laboratory and another in a laboratory aboard a train or rocket moving in a straight line at uniform speed, should get the same results in any experiment they conduct. In fact, if the laboratory in the train or rocket is soundproof and has no windows, there is no experiment a person could conduct that would show he/she is moving.
The laws of physics include the laws of electromagnetism developed by James Maxwell and Maxwell found that electromagnetic waves should travel at a speed given by the combination of two universal constants of nature. Since the laws of physics do not depend on your location or motion, Einstein reasoned that the speed of light will be measured to be the same by any two observers regardless of their velocity relative to each other. For example, if one observer is in a rocket moving toward another person at half the speed of light and both observers measure the speed of a beam of light emitted by the rocket, the person at rest will get the same value the person in the rocket ship measures (about 300,000 kilometers/second) instead of 1.5 times the speed of light (=rocket speed + speed of beam of light). This assumption has now been shown to be correct in many experiments. To get the same value of the speed (= distance/time) of light, the two observers moving with respect to each other would not only disagree on the distance the light travelled as Newton said, they would also disagree on the time it took.
Einstein found that what you measure for length, time, and mass depends on your motion relative to a chosen frame of reference. Everything is in motion. As you sit in your seat, you are actually in motion around the center of the Earth because of the rapid rotation of the Earth on its axis. The Earth is in motion around the Sun, the Sun is in orbit around the center of our Galaxy, the Galaxy is moving toward a large group of galaxies, etc. When you say something has a velocity, you are measuring its change of position relative to some reference point which may itself be in motion. All motion is relative to a chosen frame of reference. That is what the word ``relativity'' means in Einstein's Relativity theories. The only way observers in motion relative to each other can measure a single light ray to travel the same distance in the same amount of time relative to their own reference frames is if their ``meters'' are different and their ``seconds'' are different! Seconds and meters are relative quantities.
Two consequences of Special Relativity are a stationary observer will find (1) the length of a fast-moving object is less than if the object was at rest, and (2) the passage of time on the fast-moving object is slower than if the object was at rest. However, an observer inside the fast-moving object sees everything inside as their normal length and time passes normally, but all of the lengths in the world outside are shrunk and the outside world's clocks are running slow.
One example of the slowing of time at high speeds that is observed all of the time is what happens when cosmic rays (extremely high-energy particles, mostly protons) strike the Earth's atmosphere. A shower of very fast-moving muon particles are created very high up in the atmosphere. Muons have very short lifetimes---only a couple of millionths of a second. Their short lifetime should allow them to travel at most 600 meters. However they reach the surface after travelling more than 100 kilometers! Because they are moving close to the speed of light, the muons' internal clocks are running much slower than stationary muons. But in their own reference frame, the fast-moving muons's clocks run forward ``normally'' and the muons live only a couple of millionths of a second.
Time and space are relative to the motion of an observer and they are not independent of each other. Time and space are connected to make four-dimensional spacetime (three dimensions for space and one dimension for time). This is not that strange---we often define distances by the time it takes light to travel between two points. For example, one light year is the distance light will travel in a year. To talk about an event, you will usually tell where (in space) and when (in time) it happened. The event happened in spacetime.
Another consequence of Special Relativity is that nothing can travel faster than the speed of light. Any object with mass moving near the speed of light would experience an increase in its mass. That mass would approach infinity as it reached light speed and would, therefore, require an infinite amount of energy to accelerate it to light speed. The fastest possible speed any form of information or force (including gravity) can operate is at the speed of light. Newton's law of gravity seemed to imply that the force of gravity would instantly change between two objects if one was moved---Newton's gravity had infinite speed (a violation of Special Relativity). The three strange effects of Special Relativity (shrinking lengths, slowing time, increasing mass) are only noticeable at speeds that are greater than about ten percent of the speed of light. Numerous experiments using very high-speed objects have shown that Special Relativity is correct.
Special Relativity also predicts that matter can be converted into energy and energy in to matter. By applying Newton's second law of motion to the energy of motion for something moving at high speed (its ``kinetic energy''), you will find that energy = mass × (speed of light)2. More concisely, this is Einstein's famous equation, E = mc2. This result also applies to an object at rest in which case, you will refer to its ``rest mass'' and its ``rest energy'', the energy equivalent of mass. The amount of rest energy in something as small as your astronomy textbook, for example, is tremendous. If all of the matter in your textbook was converted to energy, it would be enough energy to send a million tons to the Moon!
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last updated: 17 May 2001 | 0.855597 | 3.939259 |
The four coolest NASA robots
NASA may be known for sending men to the moon, establishing the International Space Station, and planning for a base on Mars—but apart from astronauts, its best-known spokesmen aren’t men at all—they’re robots.
Rovers like Spirit, Opportunity, and Curiosity, and landers like Viking and Philae, make the perfect ambassadors into hostile, freezing, and nearly airless environments. Not only do these explorers bring back valuable scientific data from Earth’s planetary neighbors, they also make perfect showcases for practical robotics.
Venus is no one’s idea of a vacation home. Its atmosphere is a mixture of sulfuric acid and carbon dioxide, and with a surface temperature of 863 degrees Fahrenheit, only the toughest machine could possibly survive on its surface.
This is why it was surprising when a probe launched as part of the Pioneer 13 exploration satellite in 1978 managed to survive and transmit data. This probe wasn’t designed as a lander—it was supposed to fall through the atmosphere, collect chemical data, and then destruct on impact with the surface. Instead, it survived and managed to transmit data automatically for 67 minutes after landing. By comparison, a purpose-built Russian probe called Venera 7 only lasted 20 minutes at Venusian ground level.
The Philae lander was not quite a success, and not quite a failure either. Anyway you care to put it, the explorer embodies the ancient philosophy of Ad Astra, Per Aspera—to the stars, through difficulties. Philae’s landing system was always considered to be quite experimental. As the first space vehicle ever to attempt a landing on a comet, Philae needed to contend with low-gravity conditions, as well as the comet’s surface, which was fragile, uneven, and icy.
Gravity on 67P was so low that Philae couldn’t “land” in the traditional sense. Instead, the plan was for Philae to fire harpoons into the crust, and then a landing rocket to essentially glue itself down onto the comet’s surface. This didn’t happen—neither the harpoons nor the retro rocket fired as intended, and thus Philae didn’t so much land as bounce. Philae survived the unplanned bounces, however, and was able to send valuable exploration data in spite of its unconventional landing.
Let’s face it—we probably could have written this entire entry just on the topic of NASA’s Mars rovers. For the sake of restraint, however, we’ve just picked two.
Opportunity is special. The rover landed on Mars in 2004, and was designed for a mission lasting just 92 days. This proved to be a pessimistic assessment, as the vehicle didn’t just outlast its original mission plan—it’s still operating today, over 4,500 days after it was expected to fail. NASA chalks this viability up to two factors: sturdy construction, and good operational choices. Importantly, both the Spirit and Opportunity rovers would stay parked for months at a time, allowing them to conserve power during months of weak sunlight.
The Opportunity rover also possesses limited autonomy. Depending on the position of the planets, radio signals can lag between 4 and 24 minutes between Mars and Earth. This makes it impractical to drive a rover like an RC car. Unless the rovers are in the midst of particularly difficult terrain, NASA controllers will simply pick a point a short distance away and tell the rovers to go there. Using 3D terrain maps generated by a stereo camera, Opportunity picks the best available path, drives down it, re-calculates, and drives again.
In many ways, Curiosity is an iteration of the Spirit and Opportunity rovers. Everything about it is bigger, its systems are more robust, and it possesses even more autonomy. This level of engineering and processing power allowed it to perform incredible feats starting on Day One of its mission. You may remember Curiosity’s landing—gently spooled to the ground on a crane held aloft by rockets. Not only was this process controlled entirely by the mission’s onboard computers, those computers were less powerful than a 2012 iPhone.
While NASA has sent most of its wheeled rovers to Mars, there are plans in works for the space exploration agency to send its robotic explorers to several other locations. NASA is currently formulating plans for a potentially aquatic rover to drill and explore beneath the icy oceans of Europa, and the agency recently launched a sample return mission—Osiris Rex—which will recover a portion of a near-Earth asteroid.
NASA’s designs are everything we want to see out of robotics. Maximum autonomy using minimal computer power. Robust designs that last years beyond their intended lifespan. These results aren’t just perfect for space exploration—they also result in innovations that drive the adoption of low-cost practical robotics here on our home planet of Earth. | 0.865463 | 3.505613 |
Lead scientist Dr Jason Dittmann, from the Harvard-Smithsonian Centre for Astrophysics in Cambridge, US, said: "This is the most exciting exoplanet I've seen in the past decade".
The rocky planet, named LHS 1140b, orbits a red dwarf star 40 light years away.
In a paper detailing the discovery, the researchers also say they believe the planet has an atmosphere, adding that both star LHS 1140 and planet LHS 1140b are so close to Earth that "telescopes now under construction might be able to search for specific atmospheric gases in the future".
There's been compelling evidence lately that some of these planets around red dwarfs could, in fact, retain an atmosphere.That's the case of GJ 1132b, a hellish world with Venus-like temperatures around an M-dwarf star that, despite all odds, seems to hold on to an atmosphere. Meaning, one side of the planet always faces the star while the other faces away. That means in the next several years, new telescopes can spy its atmosphere in a targeted search for signs of life. It is over six-times as massive as Earth and about 1.5-times larger - fitting the description of a so-called "super Earth": It's bigger and more massive than Earth but smaller and less massive than the next biggest planet, Neptune.
The newfound planet is described in a paper appearing in the April 20thissue of the journal Nature.
The super-Earth and its parent star are located in the constellation Cetus, the Whale, 39 light years from the Sun, thus - relatively speaking - putting it in our galactic "neighbourhood", according to Felipe Murgas, the coauthor of the study and a researcher with Spain's Canary Islands Institute of Astrophysics.
Currently, the MEarth project is studying small stars that are less than a third the size of the Sun. "LHS 1140 is brighter at optical wavelengths because it's slightly bigger than the TRAPPIST-1 star".
The MEarth-South instruments enabled scientists to measure the planet's diameter and, using the HARPS spectrograph at the LaSilla ESO Observatory in Chile, they also were able to measure its mass, density and orbital period.
With Earth Day fast approaching, it's once again time for us to take stock of how we are treating our planet.
There are also lessons to glean from, and apply to, the TRAPPIST-1 system whose discovery was announced in February this year. This planet, designated LHS 1140 b, orbits its star every 25 days. They have called it LHS 1140b and said that it probably formed in its current location in a similar way to our planet.
Researchers believe it may be one of the best candidates for a closer look in the future by the James Webb Space Telescope, which NASA will launch in 2018. Three of the planets are in the Goldilocks zone, though all of the TRAPPIST-1 planets are believed to be rocky.
Just because LHS 1140b shares a few key traits with Earth doesn't mean this planet is exactly like ours, though.
"We originally thought it was just something amusing going on in the atmosphere", Harvard astronomer Jason Dittmann, the study's lead author, told Gizmodo.
In the case of LHS 1140b, the starlight is bright, the orbit is only 25 days and the planet is seen nearly edge-on from Earth. If the planet gets bombarded by too much high-energy radiation, at least we know to look elsewhere for alien life.
The planet is 10 times closer to the star than Earth is to the sun, but red dwarfs are much smaller and much cooler than the giant inferno that keeps us warm.
"For now, we do not have the technology to travel at a velocity close to the speed of light", Astudillo-Defru said. "Because LHS 1140 is nearby, telescopes now under construction might be able to search for specific atmospheric gases in the future". "We plan to search for water, and ultimately molecular oxygen". | 0.906113 | 3.827307 |
Researchers have created a new map of the Milky Way which shows that nearly a third of the stars have dramatically changed their orbits.
The discovery, by a team of scientists with the Sloan Digital Sky Survey (SDSS), brings a new understanding of how stars are formed, and how they travel throughout our galaxy.
“In our modern world, many people move far away from their birthplaces, sometimes halfway around the world,” said Michael Hayden, New Mexico State University (NMSU) astronomy graduate student and lead author of the new study.
“Now we’re finding the same is true of stars in our galaxy – about 30 per cent of the stars in our galaxy have travelled a long way from where they were born,” Hayden said.
To build a new map of the Milky Way, scientists used SDSS Apache Point Observatory Galactic Evolution Explorer (APOGEE) spectrograph to observe 100,000 stars during a 4-year period.
For the last six years, NMSU astronomers in the College of Arts and Sciences, and collaborators, have been using the 2.5-metre SDSS telescope at the Apache Point, located in the Sacramento Mountains to complete experiments that includes studies of Milky Way stars.
The key to creating and interpreting map of the galaxy is measuring the elements in the atmosphere of each star. The chemical information comes from spectra, which are detailed measurements of how much light the star gives off at different wavelengths.
Spectra show prominent lines that correspond to elements and compounds. Astronomers can tell what a star is made of by reading these spectral lines.
“Stellar spectra show us that the chemical makeup of our galaxy is constantly changing,” said Jon Holtzman, NMSU astronomy professor who was involved in the study.
“Stars create heavier elements in their cores, and when the stars die, those heavier elements go back into the gas from which the next stars form,” Holtzman said.
As a result of this process of “chemical enrichment,” each generation of stars has a higher percentage of heavier elements than the previous generation did.
In some regions of the galaxy, star formation has proceeded more vigorously – and in these more vigorous regions, more generations of new stars have formed.
Astronomers can determine what part of the galaxy a star was born in by tracing amount of heavy elements in that star.
Hayden and his colleagues used APOGEE data to map the relative amounts of 15 separate elements, including carbon, silicon, and iron for stars all over the galaxy.
They found that up to 30 per cent of stars had compositions indicating that they were formed in parts of the galaxy far from their current positions.
When the team looked at the pattern of element abundances in detail, they found that much of the data could be explained by a model in which stars migrate radially, moving closer or farther from the galactic centre with time.
These random in-and-out motions are referred to as “migration,” and are likely caused by irregularities in the galactic disk, such as the Milky Way’s famous spiral arms, researchers said. | 0.806617 | 4.029089 |
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