Saturday, March 31, 2012

Ancient sound waves sculpted galaxy formation

Sound waves that rang out in the early universe sculpted its structure. The best measurement yet of their imprint on galaxies is a boon to dark-energy studies.

About 30,000 years after the big bang, matter collapsed around dense seeds of dark matter. Outward pressure from photons caused the collapsing matter to rebound, creating acoustic waves, like ripples in a pond. These ripples expanded until the universe cooled to a certain temperature, stalling the waves. More matter existed at the centres and edges of these ripples, and therefore should have led to more galaxies there.

This is exactly what the Baryon Oscillation Spectroscopic Survey (BOSS) sees in a study of 265,000 galaxies. When the BOSS team measured the distance between pairs of galaxies between 4.5?billion and 6.3?billion light years from Earth, they found an excess of galaxy pairs separated by 500 million light years (arxiv.org/abs/1203.6594).

That is the expected radius of the sound waves?? if the universe's expansion has been accelerated in line with the leading model of dark energy. Called the cosmological constant, the model suggests that the amount of energy in a given volume of space does not vary with time.

If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.

Have your say

Only subscribers may leave comments on this article. Please log in.

Only personal subscribers may leave comments on this article

Subscribe now to comment.

All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.

If you are having a technical problem posting a comment, please contact technical support.

melasma jimmy rollins jimmy rollins let it snow jason trawick jerry lewis tampa bay bucs

No comments:

Post a Comment

Note: Only a member of this blog may post a comment.