A Collision with Another Universe --Are Signs Lurking in the Big Bang Afterglow?
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Sent: 2/12/2014 6:17:27 P.M. Eastern Standard Time
Subj: The Daily Galaxy: News from Planet Earth & Beyond
Posted: 12 Feb 2014 06:44 AM PST
The cosmic microwave background (CMB) is the left-over heat from the Big Bang. This radiation provides a picture of the universe when it was only 400,000 years old. Now, 14 billion years later, it has cooled to microwave frequencies and is nearly uniform. The slight variations of 1 part in 100,000 in its temperature reflect initial inhomogeneities in the matter and radiation that later collapsed to form clusters and galaxies. These fluctuations carry information about the origin, composition and evolution of the universe, and theories of the origin of the universe make detailed predictions about their statistical properties.The CMB is our best hope of uncovering fingerprints of the physics operating at very high-energy scales, inaccessible to Earth-bound particle accelerators. Current cosmological data are, for the first time, precise enough to allow detailed tests of models of the very early universe. The Planck satellite has then dramatically sharpened our view of the early universe, and provided a window into the origin of cosmic structure.
A primordial collision of our Universe with an Exo-Universe would leave a unique imprint in the cosmic microwave background. Physicists in Canada and the US now claim that the prediction can be tested using existing and future space telescopes, contradicting the standard view that the existence of a multiverse is untestable.
Kris Sigurdson of the University of British Columbia in Vancouver and others say they have calculated the detailed features of a "cosmic wake" --if our universe collided with another before our inflation period, the effect would have to erase the wake's evidence similar to the way Earth's tectonics have eliminated evidence of Earth's Early Bombardment Era history. Sigurdson and colleagues calculate that, providing the wake was big enough, it ought to imprint the CMB with a characteristic "double peak": two close rings where the photons sway towards a single polarization state.
Elsewhere, a team led by cosmologist Hiranya Peiris of University College London (below) found clues that this prediction was true. But these predicted features were too vague, say Sigurdson and colleagues, and might have existed in the CMB anyway. Peiris studies the fossilized heat of the Big Bang, the CMB for clues about the physics that governed the very early universe. About 1% of the snow picked up by an untuned television arises from this radiation, generated when the universe was just 0.01% of its present age.
"[Our] features represent the first verifiable prediction of the multiverse paradigm," write Sigurdson and colleagues in their preprint, which they uploaded to the arXiv server last month. "A detection of a bubble collision would confirm the existence of the multiverse, provide compelling evidence for the string theory landscape, and sharpen out picture of the universe and its origins."
If the prediction is correct, it should be possible to test it in upcoming data from the European Space Agency's Planck space observatory and future CMB missions, say the researchers.
Yet Charles Bennett, the principal investigator on NASA's Wilkinson Microwave Anisotropy Probe, a CMB space observatory, thinks the detection of a cosmic wake would nonetheless be "extremely unlikely". NASA's Wilkinson Microwave Anisotropy Probe, known as WMAP, transformed the science of cosmology by establishing the age, geometry, and contents of the universe to astonishing precision.
Bennett says the amplitude of a wake would have to be just right: too small and we wouldn't see it; too big and it would probably have had severe consequences for our universe's structure. The number of collisions would also have to be "fine-tuned", he says. "The claim seems to be that we might see one or two wakes in our sky, but why one or two?" he adds. "Why not none or an infinite number? In fact, if bubble collisions were common we would not be alive to discuss the question."
In his Not Even Wrong blog, Columbia University mathematician Peter Woit reports that in Matthew Kleban’s talk at Columnia this wek, entitled "Testing the Multiverse," the NYU physicist briefly acknowledged that all searches for observable traces left by cosmic bubble collisions in the cosmic microwave background radiation have come up empty. The only prospect for the future mentioned was the polarization data to be released later this year by Planck, which would give some new things to look at, but he seemed unenthusiastic that this would realistically lead anywhere.
Kleban is a theoretical physicist working on string theory and early-universe cosmology, with research interests that include the quantum physics of black holes and gravitational singularities. He came to NYU from the Institute for Advanced Study in Princeton, NJ. Recently he has focused on the possibility of testing theories of fundamental physics with observational cosmology, specifically the multiverse of string theory.
Cosmologist Arjun Berera at the University of Edinburgh, UK, thinks that a positive detection of a multiverse would be "spectacular". "Such a case would offer suggestive evidence in support of string theory," he says. "On the other hand, no evidence in the CMB data for a collision between two universes would not rule out string theory, it would simply extend the widely held belief in the field that string theory is unfalsifiable."
In 1980 Stanford astrophysicist Alan Guth proposed that with the Big Bang, our Universe underwent an explosive burst of growth, ballooning by a factor of 1030 or more within a trillionth of a trillionth of a trillionth of a second. Then this runaway growth spurt abruptly ended; the universe continued to expand but not nearly at the rate of that fleeting surge. NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) produced a survey of the light released soon after the Big Bang in 2003. This radiation, the cosmic microwave background, was incredibly uniform as Guth predicted. But within the overall uniformity was a very slight pattern of variation, and that pattern also closely matched the predictions of inflation.
The Daily Galaxy via Physics World
Image credit: http://lambda.gsfc.nasa.gov/product/map/dr4/sos/5year/
Posted: 12 Feb 2014 07:37 AM PST
Four previously unknown galaxy clusters each potentially containing thousands of individual galaxies have been discovered some 10 billion light years from Earth. Most clusters in the universe today are dominated by giant elliptical galaxies in which the dust and gas has already been formed into stars. "What we believe we are seeing in these distant clusters are giant elliptical galaxies in the process of being formed," says David Clements, from the Department of Physics at Imperial College London.An international team of astronomers, led by Imperial College London, used a new way of combining data from the two European Space Agency satellites, Planck and Herschel, to identify more distant galaxy clusters than has previously been possible. The researchers believe up to 2000 further clusters could be identified using this technique, helping to build a more detailed timeline of how clusters are formed.
Galaxy clusters are the most massive objects in the universe, containing hundreds to thousands of galaxies, bound together by gravity. While astronomers have identified many nearby clusters, they need to go further back in time to understand how these structures are formed. This means finding clusters at greater distances from the Earth.
The light from the most distant of the four new clusters identified by the team has taken over 10 billion years to reach us. This means the researchers are seeing what the cluster looked like when the universe was just three billion years old.
"Although we're able to see individual galaxies that go further back in time, up to now, the most distant clusters found by astronomers date back to when the universe was 4.5 billion years old," explains Clements. "This equates to around nine billion light years away. Our new approach has already found a cluster in existence much earlier than that, and we believe it has the potential to go even further."
The clusters can be identified at such distances because they contain galaxies in which huge amounts of dust and gas are being formed into stars. This process emits light that can be picked up by the satellite surveys.
Observations were recorded by the Spectral and Photometric Imaging Receiver (SPIRE) instrument as part of Herschel Multi-tiered Extragalactic Survey (HerMES). Seb Oliver, Head of the HerMES survey said: "The fantastic thing about Herschel-SPIRE is that we are able to scan very large areas of the sky with sufficient sensitivity and image sharpness that we can find these rare and exotic things. This result from Dr. Clements is exactly the kind of thing we were hoping to find with the HerMES survey"
The researchers are among the first to combine data from two satellites that ended their operations last year: the Planck satellite, which scanned the whole sky, and the Herschel satellite, which surveyed certain sections in greater detail.
The researchers used Planck data to find sources of far-infrared emission in areas covered by the Herschel satellite, then cross referenced with Herschel data to look at these sources more closely. Of sixteen sources identified by the researchers, most were confirmed as single, nearby galaxies that were already known. However, four were shown by Herschel to be formed of multiple, fainter sources, indicating previously unknown galaxy clusters.
The team then used additional existing data and new observations to estimate the distance of these clusters from Earth and to determine which of the galaxies within them were forming stars. The researchers are now looking to identify more galaxy clusters using this technique, with the aim of looking further back in time to the earliest stage of cluster formation.
NGC 7049 shown at the top of the page is a giant galaxy on the border between spiral and elliptical galaxies that spans about 150,000 light-years. It is located about 100 million light-years away from Earth in the southern constellation of Indus. NGC 7049 is the “brightest” galaxy of the Indus Triplet of galaxies (NGC 7029, NGC 7041, NGC 7049), and its structure might have arisen from several recent galaxy collisions.
Bright Cluster Galaxies are among the most massive galaxies in the universe and are also the oldest. They provide astronomers the opportunity of studying the many globular clusters contained within them. NGC 7049 has far fewer such clusters than other similar giant galaxies in very big, rich groups. This indicates to astronomers how the surrounding environment influenced the formation of galaxy halos in the early Universe.
The globular clusters in NGC 7049 are seen as the sprinkling of small faint points of light in the galaxy’s halo. The halo – the ghostly region of diffuse light surrounding the galaxy – is composed of myriads of individual stars and provides a luminous background to the remarkable swirling ring of dust lanes surrounding NGC 7049′s core.
NGC 7049′s striking appearance is primarily due to this unusually prominent dust ring, seen mostly in silhouette. The opaque ring is much darker than the millions of bright stars glowing behind it. Generally these dust lanes are seen in much younger galaxies with active star forming regions. Not visible in this image is an unusual central polar ring of gas circling out of the plane near the galaxy’s center.
The image was taken by the Advanced Camera for Surveys on the Hubble Space Telescope, which is optimised to hunt for galaxies and galaxy clusters in the remote and ancient Universe, at a time when our cosmos was very young.
The research involved scientists from the UK, Spain, USA, Canada, Italy and South Africa. It is published in the Monthly Notices of the Royal Astronomical Society and was part funded by the Science and Technology Facilities Research Council and the UK Space Agency.
The Daily Galaxy via imperial.ac.uk
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