Simulations showing how giant gas clouds evolve — clouds as large as 100,000 times the mass of the Sun — have demonstrated that stars can form in the neighborhood of supermassive black holes, the kind of black holes found at the center of galaxies. As you would expect, the clouds are disrupted when they move close to the black hole, but only part of the cloud is captured, with the rest contributing to the formation of massive stars that move about the black hole in eccentric orbits. Usefully, the results match what we see near the center of the Milky Way.
These are short-lived stars, says Ian Bonnell (St Andrews University), which in itself may be telling us something:
“That the stars currently present around the Galaxy’s supermassive black hole have relatively short lifetimes of ~10 million years, suggests that this process is likely to be repetitive. Such a steady supply of stars into the vicinity of the black hole, and a diet of gas directly accreted by the black hole, may help us understand the origin of supermassive black holes in our and other galaxies in the Universe.”
The disc that shapes the nascent star, made up of surviving material from the original gas cloud, is itself elliptical in shape. The spiral patterns formed in it by gravitational disruption transfer energy to gas further away from the black hole. Crucial to this work is the modeling of the heating and cooling process within the gas that allows star formation. The work, performed on the Scottish Universities Physics Alliance (SUPA) SGI Altix supercomputer, took over a year of computer time as it modeled the gas clouds in their movement toward the black hole.
Thus we wind up with highly massive stars on eccentric orbits around the huge black hole thought to exist at galactic center. It would take a science fiction writer par excellence (a veritable Benford!) to describe what that scenario would look like from a safe but still relatively close distance. In fact, I’d be interested in hearing from readers about any writers who have tried to model this deeply mysterious part of the Milky Way.
The paper is Bonnell and Rice, “Star Formation Around Supermassive Black Holes,” Science Vol. 321, No. 5892 (22 August 2008), pp. 1060-1062 (abstract).
Talking about astrophysics in Scotland reminds me that this October 8-10, the Royal Observatory Edinburgh will play host to a workshop titled Habitability in our Galaxy, discussing (among other things) exoplanet habitability, possible venues for life in the Solar System, and prospects for SETI. Should be interesting, especially as our ideas of a galactic habitable zone have been undergoing fruitful growth in recent years.