“Dark Stars” of the Early Universe –Were They Powered by Antimattter?



Dark matter stars: not an attempt to destroy the rebels in Star Wars IX, but gigantic stars fueled by the annihilation of dark matter. The "dark star" hypothesis proposes that the very first stars, formed when the universe was far smaller than it is now, had a greater dark matter density to play with.  

Of all the incredibly odd properties dark matter has, one of the most interesting is how it acts as its own antiparticle – if two dark particles hit they'll explode into pure energy.  Why doesn't this cause the entire universe to explode?  Because dark particles are thought to be WIMPs, Weakly Interacting Massive Particles – they find it very hard to even interact with each other, never mind anything else.

Over the past several years, researchers have investigated the properties of dark stars, as well as how these odd stars may help scientists better understand dark matter, black holes, and other astronomical features. 

The phenomena were studied by 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, with Fermilab, who published their results in the New Journal of Physics.

As the team explained, dark stars would represent a new phase of stellar evolution Рthe 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 halos (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.

"Dark Matter" is the invisible, undetectable and utterly transparent mystery matter which apparently has to exist all over the universe for current cosmological theories to not be totally off the mark. Inventing a magic omnipresence to explain the way things are might sound suspiciously religious, but with scientists like Stephen Hawking pursuing proof it might not be nothing.

Dark stars forming in a very dense dark matter region would thus be powered by antimatter annihilation, which converts 100% of the available mass into energy.  Compare this to the wimpy hydrogen fusion which powers the Sun and all life on Earth: a mere 0.7% of the available mass energy, and that's the glorious ideal which we're working towards and dreaming of harnessing.  These dark stars could thus reach sizes millions of times larger than our Sun, and despite their name they'd emit visible light.

It's a fantastic idea: for something almost terminally lacking direct evidence, what more could a dark matterologist dream of than an entire star made of the stuff, glowing brightly (and observably!) and orders of magnitude bigger than even our own Sun!  Even better, it's not just an 'idea', it's backed up by real – if still unsupported – science.

The scientists say such stars could still exist in the further reaches of the universe (albeit with their light doppler-shifted into infrared), or evidence of their passing could be marked by the distribution of supernova-formed elements throughout the universe.  Future observations will confirm if a dark stars really existed.

The Daily Galaxy via physorg.com and the New Journal of Physics 11 (2009) 105014.


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