Scientists believe that the recent detection of a black hole in the constellation Scorpius is the most convincing evidence so far in a 10-year search for the mysterious celestial objects.
The black hole was found by the orbiting satellite Copernicus, which twice has "seen" the invisible black hole in orbit around a star, named V-861, which is 25 times the size of our own sun. Although it's invisible, the black hole was identified when it passed behind the supergiant star V-861 and was momentarily eclipsed from view of X-ray and ultraviolet telescopes aboard Copernicus.
"The "X-rays we were observing dissappeared when the visible star eclipsed its companion star," said Princeton University's Dr. Ronald Polidan, one of a team of five scientists who announced the discovery two weeks ago. "We saw this happen on April 26, then saw it happen again May 28. We plan to observe it a third time July 14 and a fourth time July 22."
Astronomers have long known that V-861 (so named because it is the 861st variable star identified in Scorpius) was the visible half of a binary set whose companion star was too small to see. Small as it is, the companion star exerts a pull that makes the visible supergiant wobble as it moves through the heavens.
The suspects black hole is a mere 6 million miles from its supergiant companion, meaning it's close enough to pull enormous amounts of gas away from the sisible star. The gravitational pull of a black hole is one of the strongest forces in the universe. So densely packed is a black hole that its gravity does not even permit any light to escape it.
What was seen via Copernicus was gas spiraling out of the visible star and into the black hole. The gas leaves the visible star at 1 million miles an hour and doubles it speed by the time it reaches the black hole. The gas heats up to more than 100,000 degrees, centigrade, generating X-rays that were detected by Copernicus.
It was the disappearance of the X-rays each time the invisible star passed behind its visible mate that convinced Princeton's Polidan he had found a black hole. Said Polidan: "The X-rays went from a respectable level to zero, right at the moment of eclipse."
The ultraviolet telescope on Copernicus also witnessed huge amounts of carbon and nitrogen leaving the visible star at 1 million miles an hour. Both fell from sight each time the supergiant eclipsed the black hole.
During the second eclipse, groundbased telescopes were used by astronomers at UCLA to watch for hydrogen gas being sucked away from the visible star by the black hole.
"They confirmed that the hydrogen suddenly changed its appearance at the time of eclipse," Polidan said. "Just before eclipse, the hydrogen line (the spectral lint seen by the telescopes) lost all its strength."
Polidan estimates that the black hole exhausted its nuclear fuel at least 1 million years ago, when it collapsed from the size of a massive star 60 times as big as our own sun to an object no bigger than 30 miles across. Polidan believes the star was no more than 2 million years old when it collapsed.