Posts Tagged ‘dark energy’

How A New Telescope Will Measure The Expansion Of The Universe

For the past several years, scientists at the U.S. Department of Energy’s Lawrence Berkeley National Lab (Berkeley Lab) have been planning the construction of and developing technologies for a very special instrument that will create the most extensive three-dimensional map of the universe to date. Called DESI for Dark Energy Spectroscopic Instrument, this project will trace the growth history of the universe rather like the way you might track your child’s height with pencil marks climbing up a doorframe. But DESI will start from the present and work back into the past.

DESI will make a full 3D map pinpointing galaxies’ locations across the universe. The map, unprecedented in its size and scope, will allow scientists to test theories of dark energy, the mysterious force that appears to cause the accelerating expansion and stretching of the universe first discovered in observations of supernovae by groups led by Saul Perlmutter at Berkeley Lab and by Brian Schmidt, now at Australian National University, and Adam Riess, now at Johns Hopkins University.

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NOAO: Compact Galaxy Groups Reveal Details Of Their Close Encounters

December 18, 2014 Leave a comment

Credit: Dane Kleiner

Credit: Dane Kleiner

Galaxies – spirals laced with nests of recent star formation, quiescent ellipticals composed mainly of old red stars, and numerous faint dwarfs – are the basic visible building blocks of the Universe. Galaxies are rarely found in isolation, but rather in sparse groups – sort of galactic urban sprawl. But there are occasional dense concentrations, often found in the center of giant clusters, but also, intriguingly, as more isolated compact groups (and yes, called Compact Galaxy Groups or CGs). The galaxies in these Compact Groups show dramatic differences in the way they evolve and change with time compared with galaxies in more isolated surroundings. Why is this? Collisions between galaxies in these dense groups are common, leading to rapid star formation, but there seems to be more to the puzzle.

A team led by Dr Iraklis Konstantopoulos of the Australian Astronomical Observatory (AAO) has now obtained spectacular images of some CGs with the Dark Energy camera attached to the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory (CTIO). This camera, constructed at the U.S. Department of Energy’s Fermi National Accelerator Laboratory, is able to image large areas of the sky to unprecedented faint limits. The team aims to combine these images with spectroscopic data from the AAO that will reveal the velocities of the galaxies, leading to a much better understanding of their gravitational interactions.

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Radiation From Early Universe Found Key To Answer Major Questions In Physics

Astrophysicists at UC San Diego have measured the minute gravitational distortions in polarized radiation from the early universe and discovered that these ancient microwaves can provide an important cosmological test of Einstein’s theory of general relativity. These measurements have the potential to narrow down the estimates for the mass of ghostly subatomic particles known as neutrinos.

The radiation could even provide physicists with clues to another outstanding problem about our universe: how the invisible “dark matter” and “dark energy,” which has been undetectable through modern telescopes, may be distributed throughout the universe.

The scientists are publishing details of their achievement in the June issue of the journal Physical Review Letters, the most prestigious journal in physics, which highlighted their paper as an “editor’s suggestion” because of its importance and significance to the discipline.

The UC San Diego scientists measured variations in the polarization of microwaves emanating from the Cosmic Microwave Background—or CMB—of the early universe. Like polarized light (which vibrates in one direction and is produced by the scattering of visible light off the surface of the ocean, for example), the polarized “B-mode” microwaves the scientists discovered were produced when CMB radiation from the early universe scattered off electrons 380,000 years after the Big Bang, when the cosmos cooled enough to allow protons and electrons to combine into atoms.

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One-Percent Measure Of The Universe Constrains Dark Energy

January 10, 2014 Leave a comment

At the January AAS meeting, researchers from the Baryon Oscillation Spectroscopic Survey (BOSS) announced that they have measured the distance to galaxies more than six billion light years away to an accuracy of one percent. Together with information on the rate at which the Universe was expanding, these measurements allow the scientists at the Max Planck Institute for Extraterrestrial Physics to place powerful constraints on the properties of the mysterious Dark Energy. This component is thought to be responsible for the current accelerated expansion of the Universe.

The new distance measurements were presented at the meeting of the American Astronomical Society by Harvard University astronomer Daniel Eisenstein, the director of SDSS-III. They are detailed in a series of articles submitted by the BOSS collaboration last month and available online. “Determining distance is a fundamental challenge of observational astronomy,” said Eisenstein. “You see something in the sky — how far away is it?”

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GREAT3 Challenge Seeks New Methods For Measuring Weak Gravitational Lensing

November 28, 2013 Leave a comment

Image courtesy of NASA, ESA, S. Beckwith (STScI) and the HUDF Team

Image courtesy of NASA, ESA, S. Beckwith (STScI) and the HUDF Team

Think you can figure out a way to unlock one of the biggest secrets of the universe? The recently launched third Gravitational Lensing Accuracy Testing challenge (GREAT3) is giving researchers the opportunity to do just that.

GREAT3, which is led by Carnegie Mellon University’s Rachel Mandelbaum and UCL’s (University College London’s) Barnaby Rowe, invites researchers from many fields, including astrophysics, statistics and machine learning, to test new and existing methods for measuring weak gravitational lensing. Weak gravitational lensing is one of the most direct – but also most difficult – ways scientists have to learn about the mysterious invisible dark matter and dark energy that dominates our universe.

“In previous challenges, people have come up with entirely new methods for measuring weak gravitational lensing that we are using in practice today. We’re excited to think about what people will come up with in this challenge, and to think about what new information we’ll learn about existing methods for measuring weak lensing,” said Mandelbaum, who is an assistant professor of physics and member of the McWilliams Center for Cosmology at Carnegie Mellon.

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UK Scientists Begin 5 Year Quest To Solve Cosmic Detective Puzzle

September 3, 2013 1 comment

A five year quest is underway (3 September 2013) looking to solve the cosmic detective puzzle of why the expansion of the universe is speeding up. UK physicists and astronomers working alongside colleagues from around the world, from an observatory in Chile, are using the world’s most powerful digital camera – the Dark Energy Camera – to try and answer some of the most fundamental questions about our universe.

For hundreds of nights over the next five years, the researchers taking part in this Dark Energy Survey (DES) aim to find out not only why the growth of the universe is accelerating, instead of slowing down due to gravity, but also to probe the mystery of dark energy, the force believed to be causing that acceleration.

Scientists on the survey team will systematically map one-eighth of the sky (5000 square degrees) in unprecedented detail. The start of the survey is the culmination of ten years of planning, building, and testing by scientists from 25 institutions in six countries, including the Universities of Cambridge, Edinburgh, Nottingham, Portsmouth, Sussex and University College London in the UK.

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On The Trail Of Dark Energy: Physicists Propose Higgs Boson ‘Portal’

August 12, 2013 Leave a comment

One of the biggest mysteries in contemporary particle physics and cosmology is why dark energy, which is observed to dominate energy density of the universe, has a remarkably small (but not zero) value. This value is so small, it is perhaps 120 orders of magnitude less than would be expected based on fundamental physics.

Resolving this problem, often called the cosmological constant problem, has so far eluded theorists.

Now, two physicists – Lawrence Krauss of Arizona State University and James Dent of the University of Louisiana-Lafayette – suggest that the recently discovered Higgs boson could provide a possible “portal” to physics that could help explain some of the attributes of the enigmatic dark energy, and help resolve the cosmological constant problem.

In their paper, “Higgs Seesaw Mechanism as a Source for Dark Energy,” Krauss and Dent explore how a possible small coupling between the Higgs particle, and possible new particles likely to be associated with what is conventionally called the Grand Unified Scale – a scale perhaps 16 orders of magnitude smaller than the size of a proton, at which the three known non-gravitational forces in nature might converge into a single theory – could result in the existence of another background field in nature in addition to the Higgs field, which would contribute an energy density to empty space of precisely the correct scale to correspond to the observed energy density.

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