Posts Tagged ‘cosmology’
Supercomputer Simulation Shows for the First Time How a Milky Way-Like Galaxy Forms
Check all galactic bulges at the door
That doubt arose from the fact that when previous, lower-resolution models were run based on that cosmological model, a huge central bulge emerged in the galaxy--a bulge that is absent from all but the center of the Milky Way (another way of saying that: there was more bulge and less disc, whereas the Milky way is more disc, less bulge). This had some physicists thinking that perhaps there was a flaw in the cosmological model itself, which seemed incapable of producing via simulation the flat, spiral-armed qualities consistent with observations of our galaxy.
But the problem wasn’t with the model, it turns out, but with the simulation of star formation. In reality, star formation happens in clusters, where dense clouds of gas feed the process of star birth in fairly tightly defined regions. But in low-resolution simulations(resolution in this sense means the ability to track individual particles), gas densities tended to spread out over relatively large areas, showing stars forming throughout the galaxy rather than in clusters. This led to a larger galactic bulge--and a less accurate picture of how Milky Way-like galaxies came into being.
To get the high resolution necessary to make the model work took a great deal of computing power, including 1.4 million processor-hours on NASA’s Pleiades supercomputer as well as additional time on supercomputers at UC Santa Barbara and the Swiss National Supercomputing Center. And at the time, the researchers had no idea if their added resolution would really make a difference.
It turns out it did. The simulated galaxy, Eris, shares the shape, bulge-to-disk ratio, star content, brightness, and various other characteristics with the Milky Way, demonstrating that the “cold dark matter” model can produce spiral-armed disc galaxies like the one we call home after all.
Years After Crash Landing in 2004, NASA’s Genesis Reveals Data About Solar Chemistry
The most recent finding: Earth’s chemistry is quite different from the sun’s. That may sound obvious, but it actually goes against what cosmologists thought. When our solar system formed 4.6 billion years ago, it did so from churning disk of dust and gas. And because everything came from the same stuff, researchers assumed that the inner solar system would have a shared chemistry.
It turns out that’s not entirely the case. According to the researchers still skimming evidence from Genesis’s wreckage, the Earth is enriched with two isotopes of oxygen and one isotope of nitrogen compared with the sun. That shakes up our origin story quite a bit.
To figure all this out, scientists had to invent whole new methods of cleaning the leftovers of Genesis to remove Earthly contamination from the particles captured in space. It wasn’t easy (it took this long), but teams in America and Europe have managed to isolate pristine samples and analyze them, finding that Earth is richer in both oxygen-17 and oxygen-18 than the sun. The nitrogen disparity is even more pronounced: the sun is roughly 40 percent poorer in nitrogen-15 than the Earth.
Now cosmologists have to figure out why. They have some theories, but in the meantime Genesis science continues to slog along slowly. There were 18 measurements researchers planned to analyze from Genesis’s haul before the crash slowed their progress. Seven years later, they’ve checked off about five and are still working on the rest.
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Japanese Neutrino Finding Could Explain Why There Is Matter in the Universe
A new kind of oscillation could be the key to life, the universe, and everything
A primer on neutrinos and why we should care about them: Neutrinos are one of the fundamental building blocks of matter, though they interact very weakly with normal matter (innumerable neutrinos kicked out by the sun pass straight through the earth at any moment, rarely pausing to interact with the planet). They come in three flavors: muon neutrinos, electron neutrinos, and and tau neutrinos. And for the aforementioned reason they are very hard to detect.
Nonetheless, via detectors like T2K (for Tokai-to-Kamioka, as these are the origin and terminus of the nearly 200-mile experiment) we are able to detect and study neutrinos every now and again. T2K fires a beam of muon neutrinos straight through the ground from Tokai on the east coast to the Super-Kamiokande detector 183 miles away. And recently at Super-K, some of the neutrinos detected were electron neutrinos, indicating that they has had shifted mid-flight.
We already knew about two different oscillations (that’s a change from one flavor of neutrino to another) but we’ve never this new, third oscillation: a muon turning into an electron neutrino.
This is significant, because it means that normal neutrinos could have different oscillation characteristics than their antiparticle counterparts (antineutrinos). It’s an example of what physicists term a CP violation, and it could explain why, when all of our models show that the Big Bang should’ve created equal parts matter and antimatter (which would annihilate each other instantly), an excess of matter clearly survived to make up the universe.
That’s big news, but nothing is yet certain. Repairs are underway at T2K’s accelerator, and the experiment will begin churning out data to corroborate (or disprove) the finding later this year.
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Gamma-Ray Burst is the (Latest) Most Distant Object Ever Seen
Just a mere 13.14 billion light-years from Earth
GRB 090429B (the numbered name denotes its April 29, 2009, discovery) is estimated to be some 13.14 billion light years away from Earth. Given that the universe is only estimated to be about 13.7 billion years old, that makes the source of this light really young in a cosmic sense, originating when the universe was just 4 percent of its current age and 10 percent of its present size. It’s also way, way out there, further than any confirmed quasar or galaxy on the books.
Apart from the potential distance record, that makes GRB 090429B extremely interesting from a cosmological standpoint. Whatever galaxy spawned this intense burst of gamma-rays would have to be one of the first galaxies in the universe. And though we can’t see that galaxy with our current observatories, future researchers will know exactly where to point their next-gen telescopes to get a glimpse this GRB’s progenitor.
In the meantime, additional analysis will have to be done to determine if GRB 090429B is indeed the most distant object ever seen in space. Pinpoint accuracy at such distances is understandably hard to come by, but multiple lines of evidence endorse this latest GRB as the current record-holder.
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Unveiled: The Most Detailed 3-D Map of Local Universe Ever Created
The project mapped more than 43,000 galaxies picked from the Two-Micron All-SkySurvey (2MASS), which scanned the entire sky in three near-infrared wavelengths. But 2MASS alone offered an incomplete picture. To achieve the third dimension, astronomers needed to know not only how galaxies relate spatially on a flat map, but how far away they are from Earth and each other. So the 2MASS Redshift Survey began measuring the galaxies’ redshifts, one by one, using two telescopes in Arizona and Chile.
Redshifting is the way in which a galaxy’s light is stretched into longer wavelengths by the expansion of the universe. The farther a galaxy is from Earth, the greater its redshift. By analyzing those measurements, the 2MRS was able to achieve that important third dimension, and to produce the map you see above.
But 2MRS isn’t just notable for mapping faraway galaxies. It also made great strides closer to home. Regions nearer the Milky Way tend to be difficult to observe, as they are obscured by the dust and gas in our own galaxy. The near-infrared wavelengths employed by 2MASS are better at penetrating this dust, giving us a better look at our own galactic neighborhood.
A higher res version of the pic is available .
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Largest-Ever Survey of Cosmic History Confirms That Dark Energy Exists, Is Tearing the Universe Apart
The WiggleZ project used NASA’s Galaxy Evolution Explorer space telescope and a massive Australian observatory to peer back 7 billion years in time, equivalent to the cosmic time span that has been dominated by dark energy. It's the first time a single study has looked at such a lengthy period of cosmic history.
Dark energy was first proposed in the 1990s as astronomers discovered supernovae were moving away from us at accelerating speeds. This did not fit with prevailing theories of gravity, so scientists determined a new force called dark energy was to blame. The new survey independently verifies those earlier cosmological expansion observations, according to researchers at NASA and the Swinburne University of Technology in Melbourne, Australia.
The universe is about 13.7 billion years old, according to the best estimates, and for a little more than half that life it was dominated by the influence of gravity. All the baryonic matter, meaning matter with atoms and their constituent parts, was close enough together for gravity to have an influence. It helped form galaxies and galaxy clusters, for instance. But roughly 8 billion years after the Big Bang first flung everything apart, as the universe grew more and more diffuse, gravity’s power apparently succumbed to the increasing influence of dark energy. Galaxy cluster formation slowed down. Things started to fall apart.
To measure this, the researchers used a 3-D map created by NASA’s Galaxy Evolution Explorer, which identified bright, young galaxies in the distant universe. Then the team used the Anglo-Australian Telescope to gather detailed light information about each galaxy. They examined the patterns of distance between pairs of galaxies, which tend to wind up about 490 million light years apart. (This has to do with sound waves left over from the very early universe that resulted in areas of higher or lower pressure.) As the universe has expanded because of dark energy, this pattern has shifted.
The team also measured the rate at which galaxy clusters have been growing, and were able to show that something is counteracting gravity, slowing down the clusters’ formation.
This information was combined with data about how quickly the galaxy pairs are moving away from us, and together that verifies the earlier supernova findings: Yes, they are moving away, and yes, it is happening faster and faster.
Dark energy accounts for about 73 percent of the mass-energy of the universe. Dark matter, which is only slightly better understood, makes up about 23 percent of the universe. The remaining 4 percent is baryonic matter — galaxies, stars, the solar system, and you.
Dark energy will continue to speed up this cosmic expansion, and someday, everything will be so far apart that we won’t be able to see other galaxies or even other stars in the Milky Way. Let's hope we before then.
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Clouds of ‘Impenetrable Gas’ Bounce Off Each Other Like Solids
Strange gases could model processes in neutron stars
The researchers had set out to use lithium gas atoms as stand-ins for electrons in models of strongly interacting systems--that is, systems in which atomic particles are likely to collide with each other. They were trying to study the circumstances that cause electrons and other fermions to form a given state of matter.
What they got instead is a surprising phenomenon that could help model and explain the behaviors of systems like neutron stars, high-temperature superconductors, and the quark-gluon soup that existed right after the Big Bang.
To achieve the impenetrable gas effect (our nomenclature, not theirs) the MIT team cooled their lithium isotopes to about 50 billionths of one Kelvin, or a hair’s breadth from absolute zero. After separating the gas into two clouds with a magnetic field, the team then used a laser light trap to push them together. But instead of diffusing right into one another as is common (and was expected), they bounced off each other.
The gas clouds aren’t exactly impenetrable. They did eventually diffuse into each other, but only after a long second had gone by--which is a pretty lengthy amount of time when you’re working at the atomic scale.
But they do have a research potential beyond just being generally interesting (impenetrable gases!). By confining the lithium gas to two dimensions, researchers could simulate the electrons in high-temperature semiconductors--a key technology for creating long-range electricity transmission lines that are efficient enough to support a renewable energy economy. The discovery could also be used to simulate other strongly interacting systems found at much larger scales in the cosmos, like those in neutron stars that are far smaller in size than our sun but pack many times more mass.
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