Dark Energy
D
Dark energy is the cosmological constant, or that 'nothing weighs something'.
Abell 85
HD
normal :HDと あまり差がない気が・・・
For the first time, astronomers have detected evidence that so-called "dark energy" is stifling growth among galaxy clusters across the cosmos.
"The results are remarkably consistent with those from previous results that measure the expansion of the Universe using distance measurements, revealing that general relativity works as expected on large scales. The cluster work, in combination with other studies, also provides the strongest evidence to date that dark energy is the cosmological constant, or that 'nothing weighs something'. "
http://www.nasa.gov/mission_pages/chandra/multimedia/photosH08-329.html
NASA to Announce New Findings on Dark Energy (2008-12-11)
By: NASA , PR Newswire Association LLC
Astronomers will hold a media teleconference Tuesday, Dec. 16 at 1 p.m. EST to announce important new results on dark energy that were made using NASA's Chandra X-ray Observatory.
The briefing participants are:
Alexey Vikhlinin, astrophysicist, Smithsonian Astrophysical Observatory, Cambridge, Mass.
William Forman, astrophysicist, Smithsonian Astrophysical Observatory
David Spergel, theoretical astrophysicist, Princeton University" EPICOS - News:
http://www.epicos.com/
Dark Energy Constantly With Us / Science News
"By combining the new data with that from several other studies, the team finds that dark energy appears to have maintained the same density over time, resembling Einstein’s cosmological constant."
http://www.sciencenews.org/view/generic/id/39341/title/Dark_energy_constantly_with_us
the voids are not enough to explain away dark energy. "
NASA Jet Propulsion Laboratory - News
"Vanderveld and her colleagues at Cornell University, Ithaca, N.Y., looked more closely at this theory and found a few "holes." The group at Fermi had assumed a bunch of voids would line up between us and the supernovae, but Vanderveld's group said, in reality, the voids would be distributed more randomly -- again like Swiss cheese. With this random distribution, the voids are not enough to explain away dark energy.
There is, however, one other freakish possibility that could mean a void is creating the illusion of an accelerating universe. If our solar system just happened to sit in the middle of a void, then that void would distort our observations. Said Vanderveld, "It's really hard to tell if we're in a void, but for the most part this possibility has been ruled out." "
http://www.jpl.nasa.gov/news/features.cfm?feature=1988
Abell 1689 :First Use of Cosmic Lens to Probe Dark Energy
galaxy cluster Abell 1689を用いて
Cosmological Constraints from Strong Gravitational Lensing in Clusters of Galaxies
Figure 1: The critical lines for a source at z = 3 are overplotted in yellow on the HST ACS image of Abell 1689. The lensing mass model used is the one from which we derived cosmological constraints. In addition to 2 large scale clumps and the BCG, this model includes the contribution of 58 cluster galaxies.
The positions of cluster galaxies are marked with green crosses. Overplotted in white are the 28 multiple images arising from 12 families that we used in this work; the red circles mark the positions of the rejected images.
http://www.spacetelescope.org/static/archives/releases/science_papers/heic1014.pdf
As they conclude in their full paper (warning: not for the fainthearted!), it's a technique that will get even better once observations of ultra-distant objects start rolling in from the forthcoming James Webb Space Telescope.
A New Twist on Dark Energy - SkyandTelescope.com
http://www.skyandtelescope.com/community/skyblog/newsblog/101095989.html
Cosmic Lens Used to Probe Dark Energy for First Time - JPL
the Aug. 20 issue of the journal Science.
http://www.jpl.nasa.gov/news/news.cfm?release=2010-272
First Use of Cosmic Lens to Probe Dark Energy (08/19/2010)HubbleSite - NewsCenter - The Full Story
http://hubblesite.org/newscenter/archive/releases/2010/26/full/
Astronomers use galactic magnifying lens to probe elusive dark energy
http://www.physorg.com/news201427857.html
Astronomers use galactic magnifying lens to probe elusive dark energy
http://www.sciencedaily.com/releases/2010/08/100819141917.htm
Fate of Universe revealed by galactic lens- BBC News
The way in which light is distorted by this cosmic lens depends on three factors: how far away the distant object is; the mass of Abell 1689; and the distribution of dark energy.
The astronomers were able to measure the first two variables using the European Southern Observatory's Very Large Telescope, enabling them to calculate this crucial third factor.
http://www.bbc.co.uk/news/science-environment-11030889
Lambda-CDM model - Wikipedia
ΛCDM or Lambda-CDM is an abbreviation for Lambda-Cold Dark Matter. It is frequently referred to as the standard model
http://en.wikipedia.org/wiki/Lambda-CDM_model
Lambda cold dark matter - Scholarpedia
http://www.scholarpedia.org/article/Lambda_cold_dark_matter
Void that is truly empty solves dark energy puzzle - New Scientist
The trouble is that when physicists use QCD to estimate the condensate's energy density, their calculations suggest it would pack a punch that is 1045 times the cosmological constant that we measure from observations of the universe's expansion.
http://www.newscientist.com/article/mg20727764.100-void-that-is-truly-empty-solves-dark-energy-puzzle.html
Phys. Rev. C 82, 022201 (2010): New perspectives on the quark condensate
http://prc.aps.org/abstract/PRC/v82/i2/e022201
