Stellar black hole may be the largest found

Press, 10 January 1983, Page 13

Stellar black hole may be the largest found

NZEA-Keuter Washington A team of astronomers has discovered what it believes is the largest stellar black hole yet detected. The black hole is about 180.000 light years from the Earth, a tiny distance in cosmic terms, and has a mass of between eight and 12 that of the Sun. It was discovered in the Large Magellanic Cloud, the nearest galaxy to the Milky Way, in which the Earth is sited, and has been christened LMC-X3. Black holes are invisible concentrations of matter so compact and dense that they swallow everything, even light, within their gravitational field.

Unlike normal black holes, which are thought to exist at the heart of galaxies, stellar black holes have companion stars which they orbit and suck gases from at extraordinarily high speeds. Roger Bell, a researcher at the National Science Foundation, said, "This is about the best case we have for the actual discovery of a stellar black hole." LMC-X3. which Mr Bell said is believed to be a relatively young black hole at less than 50 million years old. was discovered last November by three astronomers at the Inter-Ameri-can Observatory in Cerro Tololo, a remote district

about 480 km north of Santiago, Chile. Anne Cowley, a researcher at the University of Michigan. and David’ Crampton and John. Hutchings, of the Dominion Astrophysical Observatory in Victoria, British Columbia, came across LMCX 3 while investigating-X-ray sources in the Large Magellanic Cloud.

Using a 158 in optical telescope. they detected a stream of powerful X-rays emitted by hot luminous gases which were being siphoned away from a star in the galaxy, Mr Bell said. They noted that the star had an unusual orbital pattern and concluded that an invisible gravitational force

of tremendous power was nearby, he said. At only seven million miles apart, LMC-X3 and its companion star are extremely close together and are able to orbit each other every 41 hours.

By comparison, the Earth is 93 million miles from the Sun, which it orbits once a year.

A decade ago. scientists using rockets and satellites discovered a stellar black hole for the first time, a source in the Milky Way called Cygnus X-l, thought to be the only other stellar black hole detected, and with a mass estimated at eight times that of the Sun.