Posted on: Thursday, November 11, 2004

Galaxy's black hole to devour lesser one

By Kevin Dayton
Advertiser Big Island Bureau

HILO, Hawai'i — A black hole at the center of the Milky Way galaxy is tugging a smaller black hole and a group of seven stars toward it, and likely will devour them in the next 10 million years or so, astronomers say.

Francois Rigaut, senior scientist at the Gemini North Observatory on Mauna Kea, said scientists aren't exactly sure what happens when one black hole consumes another, but the forces at work will be immense.

"The supermassive black hole at the center of our galaxy is something like 1,000 times heavier, so it's going to be the big one that's going to win, no problem," said Rigaut.

In an article published this year in the scientific journal Astronomy and Astrophysics, Rigaut and other scientists presented evidence of the smaller black hole, demonstrating that its gravitational pull had captured the seven stars, locking them in an orbit around the black hole. The only similar configuration scientists have observed involves the supermassive black hole at the center of the galaxy, which also has trapped stars in its gravitational pull, Rigaut said.

Black holes are objects so dense that matter and even light cannot escape from their gravitational pull. Black holes cannot be seen directly, but astronomers can observe their effects on stars and other objects around them.

Scientists estimate the smaller black hole has a mass equal to that of about 1,300 of our suns, suggesting it is what astronomers classify as a "intermediate mass stellar black hole." The supermassive black hole, known as Sgr A*, has a mass equal to about 4 million suns.

Both black holes are about 28,000 light years from Earth, with each light year equal to the distance light travels in a year, or about 6 trillion miles. The phenomenon of the larger black hole swallowing the smaller one won't affect our solar system.

Scientists studied an area near the center of the galaxy known as infrared source IRS 13 and used data from Gemini and the Canada-France-Hawai'i telescopes on Mauna Kea, the Hubble Space Telescope and the Chandra X-Ray Observatory.

They concluded that the smaller black hole and the stars around it are probably "the wreckage, or remnant core, of a once larger cluster of stars that is now spiraling toward Sgr A* at the galactic center."

The French and U.S. team was led by Jean-Pierre Maillard of the Institut d'Astrophysique de Paris.

Reach Kevin Dayton at kdayton@honoluluadvertiser.com or (808) 935-3916.