Magnetism, Not Just Gravity, Makes Black Holes Suck, Study Says

June 21, 2006

Black holes have a reputation for being incredibly dense, sucking in all the light and matter around them thanks to their strong gravitational fields.

But new research suggests it's actually magnetic wind, not just gravity, that makes these massive collapsed stars so impossible to resist.

According to a study appearing in tomorrow's issue of the journal Nature, magnetic fields help matter flow into black holes.

Beyond a certain distance, "matter can orbit black holes pretty much as it would a normal star or in the way things orbit the Earth," said lead author Jon M. Miller of the University of Michigan in Ann Arbor.

"Things already in a stable orbit tend to stay in a stable orbit. We call that angular momentum."

But if a black hole has a neighboring star in close orbit, gas from that star is sucked in. The displaced matter forms a thin bright disk that spirals around the black hole and slowly falls into it.

Some force other than gravity must therefore be exerting itself within the halo of stellar gas—and Miller's team thinks the culprit is magnetic friction.

Mighty Wind

To date, astronomers have identified 20 black holes in the Milky Way and suspect there may be millions more in our galactic neighborhood.

Scientists know a good deal about black holes, including their instrumental role in galaxy formation (related news: "Supermassive Black Hole at Center of Milky Way, Study Hints").

But how the objects seem to defy the law of angular momentum has been a long-standing mystery.

Using NASA's orbiting Chandra X-ray Observatory (gallery: x-ray images from Chandra), Miller's team focused their attention on GRO J1655-40.

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