* Astronomy

Blobrana · L

RE: Dark Energy

Blobrana · L

Radio Astronomers Develop New Technique for Studying Dark Energy

Pioneering observations with the National Science Foundation's giant Robert C. Byrd Green Bank Telescope (GBT) have given astronomers a new tool for mapping large cosmic structures. The new tool promises to provide valuable clues about the nature of the mysterious "dark energy" believed to constitute nearly three-fourths of the mass and energy of the Universe.
Read more

Blobrana · L

But a team of scientists that includes a professor and a graduate student at Carnegie Mellon University has developed a new way to study the expansion that it calls "intensity mapping," a method outlined in an article appearing today in the journal Nature.
Instead of cataloguing thousands of supernovae or galaxies individually and then calculating how much they've changed over time, intensity mapping skips that step and, instead, measures radio waves emitted from hydrogen from thousands of galaxies at the same time, as well as other objects between galaxies, to chart the expansion.
Read more

Blobrana · L

Title: The Possible Detection of Dark Energy on Earth Using Atom Interferometry
Authors: Martin L. Perl

This paper describes the concept and the beginning of an experimental investigation of whether it is possible to directly detect dark energy density on earth using atom interferometry. The concept is to null out the gravitational force using a double interferometer. This research provides a non-astronomical path for research on dark energy. The application of this method to other hypothetical weak forces and fields is also discussed. In the final section I discuss the advantages of carrying out a dark energy density search in a satellite in earth orbit where more precise nulling of gravitational forces can be achieved.

Read more (272kb, PDF)

Blobrana · L

Dark energy may not exist in space

British scientists have claimed that the method used to calculate the make-up of the universe may be wrong.
The universe as we know it - formed of recognisable components such as planets, stars, asteroids and gas - accounts for just four per cent of the cosmos, according to the decades old Standard Model.
The rest is thought to be made up of mysterious dark matter and dark energy. This permeates space and powers the expansion of the universe.
But physicists at Durham University now claim the calculations on which the Standard Model is based could be fatally flawed.
A new analysis of measurements taken by NASA of Big Bang heat radiation in 2001 showed that the heat waves may be far smaller than previously thought.
When the measurements were first taken in 2001 the size of the ripples in the Cosmic Microwave Background radiation led scientists to conclude that the cosmos is made up of four percent "normal" matter, 22 percent "dark" or invisible matter and 74 percent "dark" energy.
Read more

Blobrana · L

Did a 'sleeper' field awake to expand the universe?

In the late 1990s, observations of supernovae revealed that the universe has started expanding faster and faster over the past few billion years. Einstein's equations of general relativity provide a mechanism for this phenomenon, in the form of the cosmological constant, also known as the inherent "dark energy" of space-time. If this constant has a small positive value, then it causes space-time to expand at an ever-increasing rate. However, theoretical calculations of the constant and the observed value are out of whack by about 120 orders of magnitude.
To overcome this daunting discrepancy, physicists have resorted to other explanations for the recent cosmic acceleration. One explanation is the idea that space-time is suffused with a field called quintessence. This field is scalar, meaning that at any given point in space-time it has a value, but no direction. Einstein's equations show that in the presence of a scalar field that changes very slowly, space-time will expand at an ever-increasing rate.
Read more

Blobrana · L

Title: Dark energy from primordial inflationary quantum fluctuations
Authors: Christophe Ringeval, Teruaki Suyama, Tomo Takahashi, Masahide Yamaguchi, Shuichiro Yokoyama

We show that current cosmic acceleration can be explained by an almost massless scalar field experiencing quantum fluctuations during primordial inflation. Provided its mass does not exceed the Hubble parameter today, this field has been frozen during the cosmological ages to start dominating the universe only recently. By using supernovae data, completed with baryonic acoustic oscillations from galaxy surveys and cosmic microwave background anisotropies, we infer the energy scale of primordial inflation to be around a few TeV, which implies a negligible tensor-to-scalar ratio of the primordial fluctuations. Moreover, our model suggests that inflation lasted for an extremely long period thereby favouring a self-reproducing inflationary model. Dark energy could therefore be a natural consequence of cosmic inflation close to the electroweak energy scale.

Read more (20kb, PDF)

Blobrana · L

Expansion of universe due to dark energy

Astronomers have confirmed the mysterious dark energy as the most comprehensive evidence yet for the accelerated expansion of the universe, based on a study of nearly half a million galaxies using the Hubble Space Telescope (HST).
Read more

Blobrana · L

Astronomers confirm Einstein's theory of relativity and accelerating cosmic expansion

University of British Columbia astronomer Ludovic Van Waerbeke with an international team has confirmed that the expansion of the universe is accelerating after looking at data from the largest-ever survey conducted by the Hubble Space Telescope.
The astronomers studied more than 446,000 galaxies to map the matter distribution and the expansion history of the universe. This study enabled them to observe precisely how dark matter evolved in the universe and to reconstruct a three-dimensional map of the dark matter and use this to test Albert Einstein's theory of general relativity.
The findings will appear in a forthcoming issue of the journal Astronomy & Astrophysics. The studys lead author is Tim Schrabback, an astronomer from Leiden University in the Netherlands.
Read more

Blobrana · L

Hubble confirms cosmic acceleration with distorted galaxies

A comprehensive analysis of distorted galaxies from the most ambitious cosmic survey ever undertaken by the Hubble Space Telescope has confirmed the mysterious cosmic acceleration. It has also provided the equivalent of a 3D map of part of the Universe.
A group of astronomers, led by Tim Schrabback of Leiden Observatory, conducted an intensive study of more than 446 000 galaxies within the Cosmological Evolution Survey (COSMOS) field. COSMOS is the largest survey conducted with Hubble, which photographed 575 slightly overlapping views of the same part of the Universe using its Advanced Camera for Surveys. In total, the survey took nearly 1000 hours of observations.
Read more