Astronomers using the Hubble Space Telescope have gotten their closest look yet at a suspected "black hole," and the chief scientist on the project says "it's a whopper."
Tod R. Lauer, of the National Optical Astronomy Observatories, said yesterday that Hubble has revealed a densely packed region of stars at the center of a galaxy called M87, about 52 million light years from Earth in the constellation Virgo.
The sharply increasing density of stars toward M87's core, revealed by Hubble for the first time, conforms "dead-on" to theoretical black hole models proposed in 1978 by the late Caltech astronomer Peter Young.
And if it's really there, the titanic black hole at M87'score has a mass equal to 2.6 billion suns. Suspected black holes in other relatively nearby galaxies have masses estimated at only 1 million to 10 million suns.
But Lauer was not prepared to say his photographs prove the black hole exists.
"It looks like a duck," he said, "but we haven't heard it quack yet."
That proof may come with future spectrographic studies of M87 to measure the speed of the stars circling the galactic core. Once they know the speed and distance of the stars from the core, scientists can calculate the mass of the object they are orbiting.
If it's massive enough, it must be a black hole.
The discovery was to be announced today at the 179th meeting of the American Astronomical Society in Atlanta,by Lauer and C. Roger Lynds, of NOAO; Sandra M. Faber of the University of California at Santa Cruz; and members of the Space Telescope Science Institute's Wide Field Planetary Camera imaging team in Baltimore.
Black holes are the unimaginably dense remnants of collapsed stars, with mass and gravitation so powerful that nothing, not even light, can escape. That's why none has ever been seen directly.
The photographs sent back to Earth by Hubble's Wide Field Planetary Camera show what looks like a single bright automobile headlamp shining through a dense, glowing fog of stars.
The central "lamp" is believed to be an intense pinpoint of energy much smaller than it appears. It is thought to be produced by the nuclear emissions from a superhot disk of gas and stellar material cascading down into the black hole itself.
"The central structure of M87 is a striking departure from what the normal core of a giant elliptical galaxy would look like," said Lauer. In fact, the density of stars there is 300 times what astronomers would expect.
The estimated mass of M87's black hole -- 2.6 billion masses -- is staggering. "It's the kind of black hole you would need to power a quasar," Lauer said.
Quasars, or quasi-stellar objects, are enormously powerful energy sources seen only at the farthest reaches of the universe, and therefore are thought to have existed only at the universe's beginnings.
It's possible, Lauer said, that M87's black hole is itself a former quasar.
Theorists suggest that M87's black hole began as a "seed black hole" with the collapse of a star billions of years ago in the galaxy's infancy.
Fed by gas and other material sucked from passing stars, the black hole would have grown more and more massive, until stars farther and farther away began to be drawn by its growing gravitational pull toward an increasingly crowded galactic center.
To a being on a planet circling one of those stars today, Lauer said, the night sky "would be spectacular," with 1,000 times the number of stars visible from Earth.
Confirming the existence of a black hole is one of the primary missions of the Hubble Space Telescope. And giant M87 has been a favorite place to look.
Even backyard astronomers have long been fascinated by M87. It is one of the brightest galaxies in the "local" universe, and in a small telescope it looks like a fuzzy star.
Actually, astronomers say M87 is an elliptical system of more than 100 billion stars, analogous to our own spiral Milky Way galaxy. It resides in a still-larger system, or cluster of 3,000 galaxies known as the Virgo cluster, averaging about 65 million light years from Earth.
Astronomers using ground telescopes had already discovered a powerful plume or "jet" of hot gases being ejected from the core of M87, and that jet was found to be a strong source of radio and X-radiation.
But with the Hubble's Planetary Camera -- 10 times better than anything on the ground -- Lauer and his team looked deep into M87's core for evidence to support the black-hole theory.