‘Arrested development’ at work in the Universe December 17, 2008Posted by Sarah in science.
Tags: astronomy, chandra, cosmology, dark energy, nasa
A cross-continental team of astronomers led by Andrei Vikhlinin have used data from the American X-ray space telescope Chandra to help pin down the nature of the most enigmatic stuff in the Universe, dark energy. By observing clusters of galaxies over a range of different ages, the team were able to track how their masses have evolved over the history of the Universe. Using the statistics of this evolution and comparing them with results from several other complimentary studies, they have significantly narrowed the constraints on the precise nature of dark energy.
Dark energy is the slightly nebulous name given to the energy that causes the Universe’s expansion to accelerate, thought to represent almost three quarters of all mass-energy in the Universe. The term was first coined about 10 years ago, when distant supernovae were found to be further away than predicted, suggesting some unknown and invisible repulsive force. Using observations from several other studies, such as the cosmic microwave background results from WMAP, scientists have repeatedly confirmed the presence of this extra anti-gravitational push.
So in a way, this study tells us nothing new – only that we’re on the right track, and that our current if vague understanding is becoming increasingly plausible over other exotic theories. But the method Vikhlinin and his colleagues used is very neat, and the paper has a lot of very interesting information. Clusters of galaxies are the largest gravitationally bound structures in the Universe, and without the gravity-opposing force of dark energy, we would expect bigger and bigger clusters to form as the Universe evolves. But as dark energy begins to win the fight with gravity, the formation of clusters gradually switches off. And that’s exactly what was observed.
Sean Carroll, a man who knows much more about it, gives a nice overview with some of the paper’s graphs, over on Cosmic Variance. CV has lots of posts about dark energy and the like, so go and link-hop to explore.
Phil Plait weighs in here.
Update: Disco Dave has a nice compilation of blog posts and info sources on dark energy.