January 14, 1997 in Nation/World

Scientists Believe Nearly Every Galaxy Contains Black Hole

Robert S. Boyd Knight-Ridder
 

New evidence has convinced astronomers that a massive “black hole” lurks at the center of almost every galaxy, including our own Milky Way, gobbling up stars that will never be seen again.

Two teams of astronomers reported their findings about the surprising frequency of these objects - first predicted by Einstein’s Theory of Relativity - at a conference of the American Astronomical Society here Monday.

Black holes consist of matter so dense that nothing, not even light, can escape their tremendous gravity. They are not much bigger than the Sun but many millions of times heavier.

Although they cannot be seen, the presence of black holes can be detected by the violent movement of nearby stars that are about to be swallowed by one of these “cosmic vacuum cleaners,” according to Ramesh Narayan of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

Narayan called the process “the ultimate victory of gravity … What’s inside is completely cut off from the rest of the universe.”

Fortunately, Earth is in no danger of falling into a black hole. The nearest such monster, the one at the center of the Milky Way, is 180 quadrillion miles (30,000 light years) away.

Furthermore, despite its incredible power, a black hole makes up only a tiny fraction, less than 1 percent, of the material in its galaxy.

“The vast bulk of the galaxy is not affected by the black hole in the center,” said Scott Tremaine of the Canadian Institute of Theoretical Astrophysics.

Using different techniques, the two teams of astronomers found two distinct types of black holes.

One group of 12 astronomers, headed by Douglas Richstone of the University of Michigan, Ann Arbor, surveyed 15 nearby galaxies, using the Hubble Space Telescope and the 36-foot Keck telescope on top of a volcano in Hawaii.

At a press conference in Toronto, the astronomers announced the discovery of three massive black holes and strong evidence for a dozen others within 50 million light years (one light year equals 6 trillion miles) of Earth.

Richstone said the “celestial fingerprint” consists of a unique pattern in the velocity of stars spinning around the center of each galaxy, indicating that they are being sucked in by a powerful, invisible object.

Two of the new black holes are in the constellation Leo and the third in Virgo.

According to Richstone, the holes may be the remnants of burned-out quasars, the oldest and most energetic objects in the early universe. “Black holes are dead quasars,” he said.

The second astronomical team, headed by Narayan, the Harvard astrophysicist, observed another, smaller type of black hole created by a pair of stars revolving about each other.

One of the stars in such a system is constantly pulling gas off its partner. The gas becomes tremendously hot - up to a trillion degrees - and radiates X-rays, producing what is known as an “X-ray Nova.”

If the star is less than 40 times as massive as the Sun, it eventually burns to a crisp and becomes a so-called “neutron star.” If it is more than 40 times as massive as the Sun, Narayan said, it apparently forms a black hole.


Thoughts and opinions on this story? Click here to comment >>

Get stories like this in a free daily email