Space.com | Science | 11 Oct 2010
Dark matter that can form dark stars - P Gondolo et alIn the early universe, the first stars may have been made not of regular matter, but of its mysterious cousin, dark matter. But exactly how it all happened remains a mystery, and figuring it out could help astronomers understand dark matter itself.
Dark matter is the pesky substance thought to permeate the universe that stubbornly refuses to show itself to telescopes or any other direct detection method scientists can throw at it. Yet researchers can sense it lurking by the gravitational pull dark matter exerts on normal stars and galaxies.
There are many competing theories about what dark matter is actually made of, and each suggestion comes with slightly different properties and implications. Now, a new study calculated which possible forms of dark matter could lead to so-called dark stars.
Not really dark
"Not all kinds of dark matter would be able to form dark stars," said study leader Paolo Gondolo of the University of Utah. "In this sense dark stars are a tool to understand the nature of dark matter." [Video: Dark Matter in 3-D]
The term dark star is somewhat misleading, he said, because in fact these stars would emit light and would be visible. But the matter that reacts in the star's core to form that light would be dark matter, not regular matter.
Though dark stars have not yet been observed by telescopes, some experts think future observatories like the James Webb Space Telescope, a successor to the Hubble Space Telescope, set to launch in 2014, could be up to the job.
"If we detect evidence of dark stars, or if we can say that there are no dark stars, then they present constraints" on what dark matter is made of, Gondolo told SPACE.com.
What makes a star?
Many dark matter candidate particles are their own antimatter partner, which means if two particles come close enough together, they will annihilate to produce energy, some of which is emitted in the form of light.
Today, with the universe spread out, matter is not packed tightly enough for dark matter particles to be condensed to the point of annihilating. But after the Big Bang when the universe was young and comparatively small, the conditions were right for dark stars.
Dark matter would only form a very small fraction of the total mass of such stars – the rest would be normal matter. But the dark matter annihilation process is very efficient, because colliding dark particles would convert all of their mass to energy via Einstein's equation, E=mc2. Thus dark stars would shine quite bright.
Eventually, when the dark matter supply inside the star was exhausted, normal matter would condense to begin the regular process of nuclear fusion that fuels most stars. Some of these could still be around today.
- Journal of Cosmology and Astroparticle Physics 2010(07) 026 (27 July 2010) DOI: 10.1088/1475-7516/2010/07/026
arXiv.org > astro-ph > arXiv:1004.1258 > 08 Apr 2010 (v1), 09 Apr 2010 (v2)
University of Utah | 03 Dec 2007