Images from Hubble shed light on black holes, but doubts linger

NASA's Hubble Space Telescope has obtained the most convincing photographic evidence yet of the existence of mysterious black holes, astronomers said Thursday.

However, professional doubt over the existence of the gravitational dynamos remains, and even the astronomer responsible for the remarkable images acknowledged that he lacks absolute proof.

"We have not seen a black hole, but we have visualized many of the things that theoreticians who have worried about active galaxies have said must be there," said Walter Jaffe of the Leiden Observatory in The Netherlands.

Specifically, the space telescope photographed a tight swirling disc of dust and gas in the center of an elliptical galaxy in the Virgo Cluster 45 million light years from Earth.

The matter from the disc appears to be feeding a dark core, the theoretical black hole, with a mass 10 million times that of our sun. Emerging from the core are two bright jets of material speeding outward at velocities near the speed of light, Jaffe said.

As explained by physicists, black holes form when certain classes of stars die. As their energy production stops, they collapse to a super dense compact form with a gravitational force so strong that light cannot escape.

For three decades, astronomers have searched for physical proof of the theories that predict the existence of black holes.

The galactic signposts for their observations have been the discs of dust that the theories predict would succumb to the immense gravity and spiral into the black hole and the high-velocity gas jets.

Jaffe surmises that the irregular shape of the disc, which measures about 300 light years across, may actually be the remains of an entire spiral galaxy that passed too close to the black hole and succumbed to its gravitational pull.

The mechanisms for the immense energy produced by a black hole are also not well understood, though astronomers believe they may be the dynamos within quasars, the brightest and most distant objects in the universe.

Dan Weedman, a Pennsylvania State University astronomer and space telescope investigator, challenged the significance of Jaffe's findings.

"I will grant that you have found an incredibly powerful source of gravity," Weedman told colleagues during a NASA presentation of the photographs. "As to what is making that energy, we are a long way from being able to say we understand it."

"I don't like using a word that just passes the buck to something else we don't understand, and that is what I view the word black hole to mean," Weedman added.

According to University of Washington astronomer Bruce Margon, the next step in solving the mystery of Jaffe's discovery will probably have to await the repairs to the Hubble Telescope planned by shuttle astronauts late next year.

The repairs, which correct an optical flaw in the telescope, will also improve the observing powers of the Hubble's faint-object spectrograph.

A high-resolution spectral analysis will enable observers to more accurately compute the speed at which stars in the center of the elliptical galaxy are moving around the core. Using the calculations, the actual mass of the core can be calculated.

"If we discover it's extremely massive, like 100 million times the mass of our sun and extremely compact, then there would probably be no alternative to a black hole," Margon said.