The discovery of a river of gas flowing toward the middle of the Milky Way supports the belief that an infinitely dense speck more massive than 1 million suns lies at the heart of the Earth's galaxy, astronomers say.

The speck is known as a black hole, collapsed stars with such intense gravitational pull that nothing can escape from it, not even light. While many astronomers believe that a massive black hole exists at the core of the Milky Way, this has still not been proven.In research presented Tuesday, astronomers described their discovery of a 90-trillion-mile-long stream of gas that apparently is being sucked across the heavens into the black hole.

Although black holes cannot be seen, astronomers look for other evidence of their existence, such as the tug of their gravity on nearby celestial objects.

Paul Ho, who directed the research at the Harvard-Smithsonian Center for Astrophysics in Cambridge, noted that the galaxy's center is a gravitational well.

"We think that stars drift toward the center," he said. "It's a natural place for a massive black hole to form."

Ho's radio telescope observation was made with astronomers from the Max Planck Institute in Munich and the University of Cologne, both in West Germany, and the Massachusetts Institute of Technology.

The report was presented at a meeting of the American Astronomical Society here.

"This is a complex region," Bonnerd J. Teegarden of NASA's Goddard Space Flight Center in Greenbelt, Md., said of the study. "Results like these are adding a lot to our understanding."

Teegarden said that most astronomers believe that a massive black hole exists at the center of the Milky Way.

He noted that the nature of this and other black holes is one of the most exciting areas of research and speculation in astronomy.

"It pushes hard on the basic concepts of physics," he said. "Physicists don't really know what happens when you collapse a million solar masses of matter down to a point. The laws of physics, as we know them in the laboratory, are inadequate to explain such an extreme situation."

Earlier, astronomers have spotted signs of a massive gaseous cloud spinning around the Milky Way's center, which is 30,000 light years from Earth in the constellation Sagittarius. A light year is 6 trillion miles, the distance light travels in a year.

Scientists believe the cloud is circling a black hole that is 1 million times more massive than the sun. They theorize that parts of the cloud constantly fall into the black hole.

Perhaps the equivalent of one-thousandth of the mass of the sun spirals into the black hole each year. This produces tremendous amounts of kinetic energy, the energy released by motion.

"These black holes could be the most powerful generators that we know about," said Ho.

Astronomers believe that black holes provide the energy of quasars, enormously powerful radio emitters that are the most distant objects in the universe.

The latest discovery suggests that a stream of gas snakes across space, providing the fuel that keeps the Milky Way's black hole going.

Ho believes that a recent stellar explosion, called a supernova, knocked loose part of a large nearby island of gas. This, in turn, was grabbed by the gravity of the black hole and pulled in a stream into its own orbiting cloud.