Dark Matter Stars Could Hold Secrets to the Universe

[rhoenix]

[quote="PhysOrg.com"](PhysOrg.com) -- The first stars in the universe may have been very different from the stars we see today, yet they may hold clues to understanding some of the mysterious features of the universe. These "dark stars," first theorized in 2007, could grow to be much larger than modern stars, and would be powered by dark matter particles that annihilate inside them, rather than by nuclear fusion. In the early universe, dark stars would have emitted visible light like the Sun, but today their light would be redshifted into the infrared range by the time it reaches us, and so dark stars would be invisible to the naked eye.

Over the past two years, researchers have further investigated the properties of dark stars, as well as how these unusual stars may help scientists better understand dark matter, black holes, and other astronomical features. In a new study, the group of scientists that originally theorized dark stars has presented a review of the research on dark stars and predicted future areas of research. Katherine Freese of the University of Michigan; Paolo Gondolo of the University of Utah; Peter Bodenheimer of the University of California, Santa Cruz; and Douglas Spolyar, currently with Fermilab, have published their results in a recent issue of the New Journal of Physics.

As the scientists explain, dark stars would represent a new phase of stellar evolution - the first phase, occurring just 200 million years after the big bang. At that time, dark matter densities in the early universe were higher than they are today, and the first stars are predicted to have formed in the middle of dark matter haloes (which are precursors to galaxies) as opposed to today’s stars that are scattered about the edges of a galaxy. According to the theory, these early stars grew larger by accreting mass from their surroundings, pulling in dark matter along with the surrounding gas.

Inside these stars, weakly interacting massive particles (WIMPs), a candidate for dark matter, could accumulate. Since WIMPs can be their own antiparticles, they could annihilate to produce a heat source. If the dark matter density was high enough, this heating would dominate over other heating (or cooling) mechanisms, such as nuclear fusion. Compared with fusion, WIMP annihilation is a very efficient power source, so that only a small amount of dark matter is required to power the star.

“Dark stars are a natural consequence of WIMPs as dark matter particles ... although it took us a while to put the necessary ingredients together to realize this!â€