Archive for the ‘Cosmology’ Category
Analysis of galaxies shows local supercluster to be 100 times larger than previously thought.
The supercluster of galaxies that includes the Milky Way has been found to be 100 times bigger in volume and mass than previously thought. The enormous region near the Milky Way has been mapped with newer precion and found that the supercluster that the Milky Way resides in is so much bigger than anyone believe and they the named it Laniakea, which is Hawaiian for ‘immeasurable heaven’.
The new study, which was published in Nature, describes a novel way to define where one supercluster ends and another begins. A team led by Brent Tully, an astronomer at the University of Hawaii in Honolulu, charted the motions of galaxies to infer the gravitational landscape of the local Universe, and redraw its map.
See Nature for the full story:
HZDR’s Michael Anders at the LUNA accelerator in Gran Sasso, Italy. (Courtesy: HZDR/M Anders).
The only three elements created in the early universe, long before stars and galaxies began to form, were hydrogen, helium and lithium. According to Big Bang nucleosynthesis (BBN) theory, protons and neutrons combined to form these three elements just a few minutes after the Big Bang. While the theory does a good job of predicting the observed abundances of hydrogen and helium isotopes in the universe, it fails miserably when it comes to the two stable lithium isotopes: lithium-6 and lithium-7.
As far as lithium-7 is concerned, numerous observations suggest that there is much less of it in the universe than predicted with BBN, with the theory that underlies the prediction having been confirmed in 2006 by experiments done at LUNA by Daniel Bemmerer of Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in Germany and colleagues. Now, Bemmerer and an international team of physicists have turned their attention to lithium-6, which accounts for about 7% of the lithium here on Earth.
Collisions between hydrogen and helium nuclei deep under a mountain in Italy have confirmed a mystery of cosmic proportions: why the amount of lithium-6 observed in today’s universe is so different from the amount that theory predicts was produced shortly after the Big Bang. Working at the Laboratory for Underground Nuclear Astrophysics (LUNA) at Gran Sasso, an international team of researchers has measured for the first time how fast lithium-6 is produced under conditions similar to those when the universe was a few minutes old. The measured rate suggests that almost all lithium-6 was actually produced well after the Big Bang – something that current theories of nucleosynthesis cannot explain.
The production of lithium-6 by BBN should be dominated by one nuclear reaction, namely the collision and subsequent fusion of deuterium (hydrogen-2) with helium-4 to create lithium-6 and a gamma ray. Bemmerer and colleagues have now used the 400 kV accelerator at LUNA to study this interaction at two collision energies that would have occurred in the early universe. They did this by firing an intense beam of helium-4 nuclei at a target of deuterium gas and monitoring the collisions for the gamma rays associated with the production of lithium-6. The probability that this specific fusion process occurs is very low, and so an important experimental challenge for the physicists was to see the weak gamma-ray signal among all the other radiation produced by the collisions, as well as background signals from naturally occurring radioactive materials and cosmic rays. By going deep underground, LUNA’s researchers were able to reduce the cosmic-ray background, while the effect of naturally occurring radon gas was minimized by flushing the experimental area with nitrogen gas.
After carefully analysing the gamma-ray spectra acquired during two experimental runs, the team calculated the rate at which lithium-6 is produced by fusion – finding it to be more or less as was expected. The team then used BBN to calculate the ratio of lithium-6 to lithium-7 that should have been present in the early universe. The result is of the same order of magnitude as previously calculated, albeit a bit smaller, which makes the observation of high levels of lithium-6 in metal-poor stars even more mysterious.
As for the origin of most of the lithium-6 in the universe, this latest measurement reinforces the argument that it could not have been forged in the early universe. One possibility is that the isotope is produced in stellar flares. A much more radical suggestion is that the excess of lithium-6 was created by hitherto unknown physical processes, making cosmic measurements of the isotope a potential probe of physics beyond the Standard Model of particle physics.
The research is reported in Physical Review Letters. http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.113.042501
The most significant news of late is the BICEP2 results – if you are unfamiliar with the result, let me first summarize the results and then offer feedback and alternative viewpoints.
BICEP2 was the second generation BICEP (Background Imaging of Cosmic Extragalactic Polarization) instrument for astronomy located at Earth’s south pole. Possessing a greatly improved focal plane transition edge sensor (TES) bolometer array of 512 sensors (256 pixels) operating at 150 GHz, this 26 cm aperture telescope replaced the BICEP1 instrument, and observed from 2010 to 2012. In March of 2014 a paper emerged suggesting that BICEP2 had detected B-modes from gravitational waves in the early universe. An announcement was made on 17 March 2014 from the Harvard–Smithsonian Center for Astrophysics.
B-mode polarization is a polarization signal in the cosmic microwave background radiation (CBR), in reference to the magnetic component of electromagnetic light in the CBR. The pattern of polarization in the cosmic microwave background can be broken into two components. One, a curl-free, gradient-only component, the E-mode (named in analogy to electrostatic fields), was first seen in 2002 by the Degree Angular Scale Interferometer (DASI). The second component is divergence-free, curl only, and is known as the B-mode.
BICEP2 researchers say that they have found the first evidence of B-mode polarization in the cosmic microwave background. (Courtesy: National Science Foundation)
Cosmologists predict two types of B-modes, the first generated during cosmic inflation shortly after the big bang, and the second generated by gravitational lensing at later times. Its believed that when the universe was very young ~ 10–35 s after the Big Bang – it underwent a period of extremely rapid expansion, ‘inflation’, when its volume increased by a factor of up to 1080 in a tiny fraction of a second. About 380,000 years after the Big Bang, the CMB – the thermal remnant of the Big Bang – was produced on the last surface of scattering, when the universe became transparent to photons. Over the years, the CMB has been measured with great accuracy, but these observations brought some problems: the CMB showed that the entire observable universe seemed to be homogeneous, flat and isotropic, while the physics of the Big Bang suggests that it should be highly curved and heterogeneous.
Further its believed that rather extreme gravitational conditions prevailed during the universe’s infancy. Gargantuan primordial gravitational waves are thought to have propagated through the universe during the first moments of inflation and this would have produced a so-called cosmic gravitational-wave background (CGB). This gravitational-wave background would, in turn, have left its own imprint on the polarization of the CMB – a sort of “curl” component or rotation that is known as the primordial B-mode polarization.
Scientists cannot distinguish between the polarization caused by gravitational waves, which has a tensor component, and that caused by density waves, which have a scalar component, by looking at the temperature variations of the CMB. It’s believed that the primordial B-mode polarization is thought to be much weaker than the E-mode, making it even more difficult to detect. However, certain measurements on the polarization angles that can be detected at each point on the sky provide extra information and allow scientists to differentiate between the tensor and scalar components, providing a “tensor-to-scalar” ratio. This ratio has been measured by BICEP2 to be 0.20 with a statistical significance of about 3σ [3 Sigma]. The possibility that the ratio is zero is ruled out with a statistical certainty of 7σ [7 Sigma]. Read the results here.
A value of 0.20 is considered to be significantly larger than that expected from previous analyses of data from the Planck and WMAP telescopes. If it’s confirmed, it is the first direct evidence not only for inflation, but of a quantum behaviour of space and time. The image of polarization is a relic imprint of roughly a single quanta of graviton action. According to the BICEP2 collaboration, its results suggest that “the long search for tensor B-modes is apparently over, and a new era of B-mode cosmology has begun”.
Sounds pretty exciting but there are some who say, maybe this is not what the BICEP team think it is:
Perimeter Institute director Neil Turok, who worked on an inflationary model of his own with Stephen Hawking in the 1990s, urges caution and says that extensive experimental confirmation is necessary before BICEP2’s results can be considered as evidence for inflation. Paul Steinhardt and Neil Turok were the two loudest critics of cosmic inflation.
Another astrophysicist Peter Coles, who is based at the University of Sussex in the UK, is also cautious about the BICEP2 data interpretations.
Theoretical physicists and cosmologists James Dent, Lawrence Krauss, and Harsh Mathur have submitted a brief paper (arXiv:1403.5166 [astro-ph.CO]) stating that, while ground breaking, the BICEP2 Collaboration findings have yet to rule out all possible non-inflation sources of the observed B-mode polarization patterns and the “surprisingly large value of r, the ratio of power in tensor modes to scalar density perturbations.”
Sir Roger Penrose even goes as far as to suggest that the gravitational waves detected were produced pre-big bang in a previous universe and denies the existence of inflation entirely.
Whatever position you take the results are topical, but still in my mind they need further investigation as to other possible explanations. My biggest concern is that in order to suggest that the Gravitational Waves were produced by inflation, why not asked could have they been produced in the primordial universe without inflation.
Lastly, and more importantly – regardless of inflation – the detection of Gravitational Waves is additional evidence confirming Einstein’s General Theory of Relativity and that to me is the most significant result.
Christof Wetterich, a theoretical physicist at the University of Heidelberg in Germany, posted a paper on the arXiv preprint server, that offers a different cosmology in which the Universe is not expanding but the mass of everything has been increasing over time. Although the paper has yet to be peer-reviewed, none of the experts contacted by Nature dismissed it as obviously wrong, and some of them found the idea worth pursuing. “I think it’s fascinating to explore this alternative representation,” says Hongsheng Zhao, a cosmologist at the University of St Andrews, UK. “His treatment seems rigorous enough to be entertained.”
Wetterich points out, the characteristic light emitted by atoms is also governed by the masses of the atoms’ elementary particles, and in particular of their electrons. If an atom were to grow in mass, the photons it emits would become more energetic. Because higher energies correspond to higher frequencies, the emission and absorption frequencies would move towards the blue part of the spectrum. Conversely, if the particles were to become lighter, the frequencies would become redshifted. In other words, in the early universe red shifted light would have been emitted as all the mass was smaller and thus the energy of the emitted light was also smaller, and then increasing over time.
Its an interesting idea – go to Nature to read the full article, and there is a link to the paper at the bottom.
Image Credit: Nature & Take 27 LTD/SPL
In November 2012, a new distance record breaker has been weighed in with a photometric redshift of z ~ 10.8 which is roughtly 420 million years after the big bang. This is pretty significant.
The Cluster Lensing and Supernova survey with Hubble (CLASH), and the Spitzer/IRAC has measured the photometric redshift and with the help of Gravitational Lensing has been able to see the object by it’s increased visability and determined its distance.
The paper on the object, together with 2 other distance candidates, can be viewed (in full if you have access) on ApJ: http://iopscience.iop.org/0004-637X/762/1/32 or you can get a pre-print on ArXiv which is almost the same as the ApJ paper: http://arxiv.org/pdf/1211.3663v1.pdf
MACS0647-JD is the one of the three with the largest redshift, and a Lyman Break Galaxy. The light from the relic galaxy, at the time of transmission, was so small and may have been in the first stages of forming a larger galaxy.
This is a Digitized Sky Survey image of the oldest star with a well-determined age in our galaxy. The aging star, cataloged as HD 140283, lies 190.1 light-years away. The Anglo-Australian Observatory (AAO) UK Schmidt telescope photographed the star in blue light. Credit: Digitized Sky Survey (DSS), STScI/AURA, Palomar/Caltech, and UKSTU/AAO
A team of astronomers using NASA’s Hubble Space Telescope has taken an important step closer to finding the birth certificate of a star that’s been around for a very long time.
“We have found that this is the oldest known star with a well-determined age,” said Howard Bond of Pennsylvania State University in University Park, Pa., and the Space Telescope Science Institute in Baltimore, Md.
The star could be as old as 14.5 billion years (plus or minus 0.8 billion years), which at first glance would make it older than the universe’s calculated age of about 13.8 billion years, an obvious dilemma. This is going to be a strom in the cosmology world, as most believe that the univsere 13.7 gigayears (billion years) old – admittedly its only an estimate, but one that will be pushed back.
But earlier estimates from observations dating back to 2000 placed the star as old as 16 billion years. And this age range presented a potential dilemma for cosmologists. “Maybe the cosmology is wrong, stellar physics is wrong, or the star’s distance is wrong,” Bond said. “So we set out to refine the distance.”
The new Hubble age estimates reduce the range of measurement uncertainty, so that the star’s age overlaps with the universe’s age — as independently determined by the rate of expansion of space, an analysis of the microwave background from the big bang, and measurements of radioactive decay.
GOSFORD: Recent examination of supernovae velocities suggests the universe may be expanding non-uniformly in its acceleration, which implies the laws of physics may vary throughout the cosmos.
Physicists working with the Supernova Cosmology Project’s Union2 data set have suggested that the expansion of the universe seems to display a preferred axis, meaning that the universe is expanding faster in one direction than any other.
PERTH: A merger between the infant Milky Way and a smaller galaxy has been detected with the help of a new theoretical model, providing evidence that our galaxy is a barred-spiral galaxy.
The new model simulates a merger between a smaller galaxy and the Milky Way some nine billion years ago and shed light on how the Milky Way was formed, reveals its history of devouring smaller galaxies and may strongly support a new model of the galaxy formation.
NEW METHOD OF MAPPING THE UNIVERSE USING QUASARS -BOSS.
The biggest 3-D map of the distant universe ever made, using light from 14,000 quasars – supermassive black holes at the centers of galaxies billions of light years away – has been constructed by scientists with the third Sloan Digital Sky Survey (SDSS-III).
See the Phyorg article here: http://www.physorg.com/news/2011-05-distant-universe-d-boss-job.html
Or sciencecodex here: http://www.sciencecodex.com/measuring_the_distant_universe_in_3d
THE HUNTING OF DARK MATTER
The race to detect dark matter has yielded mostly confusion. But the larger, more sensitive detectors being built could change that picture soon.
If you did yet get this PDF now is a good time to download it
Article on Nature website: http://www.nature.com/news/2011/110323/pdf/471433a.pdf
THE NEW MOST MASSIVE OBJECT – CURRENT TITLE HOLDER ANYWAY:
The most massive known object in the young universe, a galaxy cluster dubbed SPT-CLJ2106-5844, is also a probe of conditions in the young universe. This image combines optical and infrared images with intensity contours from the Chandra X-ray Observatory.
Phyorg article here: http://www.physorg.com/news/2011-04-massive-distant.html
SUPER LUMINIOUS SUPERNOVA
Images of SN 2008am obtained with the Keck I telescope’s Low Resolution Imaging Spectrometer (LRIS).Credit: D. Perley & J. Bloom / W.M. Keck Observatory
The Keck I Telescope has played a key role in unraveling the mysteries of one of the brightest supernovas ever discovered.
DOES DARK MATTER LINK GAMMA RAYS TO GALACTIC HAZE?
Annihilating dark matter at the heart of the Milky Way could account for signals detected by two space telescopes, according to a pair of US physicists.
IOP website: http://physicsworld.com/cws/article/news/45804
ANITMATTER DETECTOR READY
A heavyweight, and controversial, cosmic-ray detector is set to head for the International Space Station.
The Alpha Magnetic Spectrometer will seek antimatter in deep space, and measure cosmic rays closer to home
Nature website: http://www.nature.com/news/2011/110428/full/news.2011.260.html
THE MAGNETIC UNIVERSE
We live in a magnetic universe, but much about magnetism at cosmic scales remains unknown.
The magnetic field at the Milky Way’s core is at least 10 times stronger than that of the rest of the galaxy.
Another universe tugging on ours? Maybe not, researchers say
A new study from the University at Buffalo contradicts the dark flow theory, showing that exploding stars in different parts of the universe do not appear to be moving in sync. Working with data on 557 such stars, called supernovae, UB scientists deduced that while the supernovae closest to Earth all shared a common motion in one direction, supernovae further out were heading somewhere else. An article announcing the research results will appear in a forthcoming edition of the peer-reviewed Journal of Cosmology and Astroparticle Physics.
Astronomers mull merger of missions
Cosmic-origins scientists convene with exoplanet hunters.
NASA’s constrained budget is encouraging some creative pairings. This week, scientists eager to find other habitable worlds explored the possibility that a future space telescope for probing the origins of stars and galaxies could serve their needs as well.
Xenon100: ‘We hope to detect the largest proportion of the matter in space’
The underground laboratory at Gran Sasso in Italy is the home of the Xenon100 experiment, which is being conducted as an international collaboration that includes the Heidelberg-based Max Planck Institute for Nuclear Physics to detect the mysterious particles directly. The researchers recently published the evaluations of one hundred days of measurement time. The result: although there is no significant signal for dark matter as yet, the world’s best limits for the masses and interaction strengths of the WIMPs have been obtained, and already noticeably reach into the predicted range.
Scientists suggest spacetime has no time dimension
The concept of time as a way to measure the duration of events is not only deeply intuitive, it also plays an important role in our mathematical descriptions of physical systems. For instance, we define an object’s speed as its displacement per a given time. But some researchers theorize that this Newtonian idea of time as an absolute quantity that flows on its own, along with the idea that time is the fourth dimension of spacetime, are incorrect. They propose to replace these concepts of time with a view that corresponds more accurately to the physical world: time as a measure of the numerical order of change.
Planck’s version of the CIB is quite startling as well – as I am sure many of you have seen some of the photos by now, for there is more information as Planck looks through voids in the milky way to see deeper…
Every spot in these images of the sky represents a point of light seen by Planck. On the left are objects within our own Galaxy, while on the right are other galaxies. On the left, the Galactic sources are almost all in the disc of our Galaxy, which is seen edge-on from Earth and lies across the centre of the image. There are loops and wisps of gas and dust above and below the Galactic Plane, which are generally parts of the Galaxy much closer to Earth. On the right, the Extragalactic sources are distributed all over the sky, though they cannot be seen through the Galactic Plane due to the gas and dust within our own Galaxy. The large spots below-right of the centre are the Magellanic Clouds, which are nearby, small galaxies which orbit our own. The background image in each is the Planck full-sky map, and the size of the points represents how bright they are when seen by Planck. Image credit: ESA/Planck Collaboration.
This image shows the location of the first six fields used to detect and study the Cosmic Infrared Background. The fields, named N1, AG, SP, LH2, Boötes 1 and Boötes 2, respectively, are all located at a relatively high galactic latitude, where the foreground contamination due to the Milky Way’s diffuse emission is less dramatic.
One of the areas of the Galaxy where Planck has seen the anomalous microwave emission. Image credit: ESA/Planck consortium.