| Subject: Dwarf galaxy companions |
Author:
Blobrana
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Date Posted: 22:10:05 04/07/05 Thu
Astronomers have figured out why a series of small galaxies surrounding the Milky Way are distributed around it in the shape of a pancake.
Theorists believed that the eleven dwarf galaxy companions should have a diffuse, spherical arrangement.
But a University of Durham team used a supercomputer to show how the galaxies could take the pancake form without challenging cosmological theory.
Soon after the Big Bang, cold dark matter should have formed the first large structures in the Universe, which then collapsed under their own weight to form vast halos. The gravitational pull of these halos sucked in normal matter, providing a focus for the formation of galaxies.
This process should leave a tightly bound galaxy at the core, surrounded by a diffuse sphere of smaller satellite galaxies.
But this is not seen with the Milky Way's satellites, which are arranged on a flat circle. This has been a puzzle to astronomers ever since Donald Lynden Bell of Cambridge University published details of the phenomenon in 1982.
Noam Libeskind and Carlos Frenk, from the University of Durham, have used the Cosmology Machine supercomputer, based at the city's institution, to simulate the formation of a galaxy from its building blocks.
Six simulations carried out on the machine not only came up with the correct number of satellites but also showed the same pancake arrangement seen in the Milky Way.
"It explains a cosmic problem. If you sat down and thought about how the galaxy formed, you would never come up with the pancake.” - Professor Carlos Frenk
"It's a major triumph for the cold dark matter model."
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