The Hubble Space Telescope's apparent confirmation that black holes exist at the core of galaxies is creating new and equally vexing problems for astronomers.
"Not only do we not know how the black hole got there, we don't know what it does," says NASA astrophysics chief Daniel Weedman.
Hubble's Faint Object Spectrograph - repaired last December by spacewalking shuttle astronauts - spied the black hole in the center of M87, a giant elliptical galaxy 50 million light years away in the constellation Virgo. A light year is the distance light travels in a year - about 6 trillion miles.
The spectrograph acted like a radar gun in clocking the speed of the galaxy's center, where scientists suspected a black hole might exist. That allowed them to calculate the mass and determine that it must be a black hole. The discovery clears up more than two centuries of speculation and confirms Albert Einstein's 80-year-old theory of relativity.
Astronomers for the past 30 years have used the black hole concept to explain the power source of active galaxies. Hubble now may help determine if other galaxies also have black holes at their cores.
At least five - including the Milky Way - may have black holes, based on the rapid motions of their central stars. Astronomers know that if the Milky Way has a black hole, it would be far smaller - about the mass of 10,000 suns or less - and less powerful than the M87 giant.
Other data have indicated the existence of black holes several times the mass of the sun, but this is the first evidence of a supermassive black hole at a galactic core.
Astronomers say the black hole is a sort of cannibal that feeds on nearby dust and stars. But they don't know its age, the extent of its appetite or its expected lifetime.
"It will keep eating as long as a meal is around," says astronomer Bruce Margon, University of Washington. The gas around the hole, he says, "is lunch. It's going to fall into the black hole and be gone."
But its predatory powers are limited. "It has an infinite appetite but it can't hunt," says scientist Richard Harms of Applied Research Corp.
Though Johns Hopkins University astronomer Holland Ford is convinced Hubble's measurements amount to "definitive" proof of black holes, he says some scientists may remain doubtful.
"Part of the culture is that scientists are skeptical," he says.
