Physics & Math / Cosmology

A recent study led by astrophysicist Marianne Vestergaard of Ohio State University bolsters a revisionist view that black holes— regions of space so dense that even light cannot escape their gravitational pull— are not always destructive. They may also play a creative role, acting as the seeds around which galaxies grow.

Drawing data from various sky surveys, including the Sloan Digital Sky Survey and the Bright Quasar Survey, Vestergaard examined roughly 360 quasars, a class of energetic galaxies that have black holes at their centers. If those dense objects formed by scooping up stars and gas within their host galaxies, the black holes in young quasars should be systematically smaller than those in older ones. Instead, Vestergaard found that even the most youthful quasars contain supersize black holes with up to 100 million times the mass of the sun. "It's striking that in such young galaxies, the central black hole is already quite massive," she says.

The finding implies that black holes formed first, then pulled together the gas that eventually coalesced into galaxies. It is still possible, however, that galaxies spawned black holes that developed much more quickly than their hosts. A third, increasingly popular interpretation is that galaxies and black holes are cosmic twins: When a clump of matter in the early universe grew large enough, it collapsed into a fledgling black hole surrounded by a reservoir of gases and budding stars— the beginnings of a galaxy. Vestergaard hopes to crack this chicken-or-egg question using Kronos, a proposed NASA satellite that would make detailed measurements of the central regions of active galaxies and quasars beginning in 2007.