Birds do, bees do it, stars do it
It’s usually nice to have a companion. And in the lonely, dark expanse of the early universe, even some of the first stars had soul mates, new simulations reveal.
Previous studies had indicated that the first stars were extraordinarily massive — at least 100 times as heavy as the sun — but were also loners (SN: 6/8/2002, p. 362). Now, more detailed modeling, including a careful consideration of how atomic and molecular hydrogen interact at low densities, reveals that at least 5 percent and perhaps as many as half of these heavyweights were gravitationally bound to similar-mass companions, says Tom Abel of Stanford University He and his colleagues, Matthew Turk of Stanford and Brian O’Shea of Michigan State University in East Lansing, report their findings online July 9 in Science.
Pairs of massive stars are intriguing, notes Abel, because each star will probably collapse into a black hole. The coalescence of the two black holes would be a key source of gravitational waves, ripples in space-time predicted by Einstein’s theory of general relativity but never directly detected.
A second star’s presence could also enhance the production of distant gamma-ray bursts, flashes of high-energy light that have long-lasting afterglows and provide a window on the early universe. Gamma-ray bursts are produced when a single, massive star that crunches down into a black hole generates powerful jets of particles. A companion star can spin up its partner, and such rapid rotation may help generate the energetic jets, Abel says.
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