At the center of our galaxy, the Milky Way, sits a mysterious object, an elusive astronomical beast with exotic powers around which the entire galaxy revolves.

It can't be seen with an ordinary telescope because dust clouds and swarms of intervening stars block the view, but it has long been known as a source of unusually strong radio signals.

Astronomers have been pursuing the beast for years in the hope of discovering something that might explain how matter organized itself into vast, wheeling galactic star systems. Presumably each of the 750 billion other galaxies in the known universe has a similar object at its heart.

Now a team of astronomers has discovered evidence that the object, whatever it may be, is spewing vast quantities of energetic particles that collide with a surrounding irregular ring of cold hydrogen gas.

"This rotating, lumpy doughnut provides strong evidence that something exotic is going on deep in the heart of the Milky Way," said Terry Jones, an astronomer at the University of Minnesota who as a member of an international team has been studying the phenomenon. Jones will present the team's findings at the American Astronomical Society's annual meeting next week in Tucson.

Jones said the object at the center could be an unusually bright star that is a thousand times more massive than the sun, or a "spinar," a rapidly rotating star that some astronomers believe may exist, or even a giant black hole. There are special circumstances under which particles falling toward a black hole produce a secondary particle that is ejected in the opposite direction.

The team's observations were made using the world's largest infrared telescope, atop Hawaii's dormant Mauna Kea volcano. The telescope registers infrared, or heat, radiation emanating from objects in deep space and, with the aid of a computer-driven printer, constructs a black-and-white picture of the object that is giving off the infrared radiation.

Jones said the wavelengths of radiation indicate that the ring is a cloud of hydrogen atoms that is too cold to give off enough infrared radiation to be detectable from Earth except around the inside of the ring. This is where the atoms have been "shocked" by collisions with rapidly moving particles flung out from the object in the center.

The Milky Way, an English translation of the Greek galaxias, is a disk-shaped cluster estimated to contain 100 billion stars with a bulge at the center where the greatest numbers of stars are concentrated.

The galaxy has a radius of about 50,000 light years. Each light year, the distance light travels in one year, is about six trillion miles. Our solar system is about halfway between the center and the edge.

As viewed from Earth, the center of the galaxy is in the direction of the constellation Sagittarius. There, hidden beyond all the intervening stars and opaque clouds of dust, is the "beast" Jones and his colleagues are tracking.

"There had been speculation for several years that there is something exotic at our galactic center," Jones said, "and this is further good evidence that indeed there probably is."