Greg L. Bryan and Michael L. Norman (NCSA)

Using X-ray telescopes in Earth orbit, astronomers have discovered that rich clusters of galaxies are immersed in halos of super-hot, million-degree gas. This hot gas is a byproduct of the galaxy formation process and emits large amounts of energy in the form of X-rays. Many of these X-ray clusters are so luminous that they can be seen from many billions of light-years away. By studying the size and distribution of X-ray clusters, astronomers are mapping the large-scale structure of the universe.

Watching clusters form

In this movie, the white square represents the region over which the calculations were performed. Outside the square, the pattern is repeated. Each side of the square is 300 million light-years across (1 light-year equals 6 trillion miles). The calculation begins about one billion years after the Big Bang, when the Universe was more dense and uniform compared to today's Universe. Over time, matter becomes distributed in clusters and clumps, leaving other regions relatively empty. X-ray clusters will form where the largest clumps of matter form; astronomers call the empty regions voids.

Austin Reiter