Was dark matter hot or cold? - September 17, 2007
The ‘true nature’ of dark matter could be revealed by new computer modelling work (BBC). The modelling, published in Science, suggests in a universe dominated by “warm” dark matter the first stars could have formed from fragments of filaments thousands of light-years long (study abstract, commentary). “The filaments would have been about 9,000 light years long, which is about a quarter the size of the Milky Way galaxy,” according to study leader Liang Gao of Durham University in the UK (press release 1, press release 2). “They would have fragmented in a huge burst of star formation, a spectacular event to contemplate.”
“What is new is we were first to show the properties of these first stars depended so crucially on dark matter,” co-author Tom Theuns, also at Durham, told Reuters. When simulations were run with cold dark matter – the particles of which are less energetic than their warmer brethren – the first stars formed in bunches, rather than in strings. This difference is important as observations could tell us which of the two scenarios is actually true. “If the first constellations can be mapped by future telescopes, the energy of the underlying dark matter may be deduced simply by reading the stars, telling us what dark matter is potentially made of,” says Joanna Baker, associate editor at Science magazine, in AFP’s coverage of the study.
Some of these stars could even be around today – larger stars have shorter life spans but the warm dark matter model predicts that some low mass stars would also be formed. These would still be, as Theuns puts it, “lurking in our galaxy”.
Image: / Science
