Study: Stars Spawn Black Holes

New evidence supports the theory that the explosive death throes of giant stars can lead to the formation of black holes, the strange celestial objects where gravitation is so strong that nothing -- including light -- can escape the pull.

Researchers analyzed the gases near a star that wobbles around a suspected black hole and concluded that the chemicals could have originated only in the blast of a neighboring supernova.

The findings were published in Thursday's issue of the journal Nature.

Black holes are super-dense dead stars whose gravity is so powerful that nothing can escape from them. Since even light is trapped, scientists cannot actually see a black hole, but they can infer its existence from the effects on the orbits of nearby stars.

Black holes are believed to form in two different ways: when a star runs out of fuel and collapses, or when a dying star explodes. The debris from such a blast falls back on itself to create a black hole.

"We were able to establish the physical conditions of the star that ended in a supernova and provide a connection between the supernova and black hole formation," said Rafael Rebolo, study co-author and researcher at the Institute of Astrophysics of the Canary Islands.

Astronomers suspected that a black hole and a visible star existed side-by-side in the constellation Scorpius about 10,000 light-years from Earth. Large bursts of X-rays evidence of matter swirling around a black hole were detected nearby.

Rebolo and his colleagues analyzed the spectrum of the visible star to try to decipher its chemical composition. They found an overabundance of oxygen, magnesium, silicon and sulfur -- elements that could not have been produced by the visible star. Instead, the researchers speculated that the elements were spewed during the explosion of its now-dark neighbor.

"The only way you can produce an excess of these elements is through several billions of degrees," Rebolo said. "The only way to reach these temperatures is when a star goes to a supernova situation."

The former star was probably about 40 times more massive than the sun before it exploded an estimated 1 million years ago, he said. Such a blast might have been visible from Earth.

Astronomers said the Spanish researchers are the first ever to offer convincing evidence of the birth of a black hole from a supernova explosion.

"The explanation offered by the researchers is the most straightforward and logical one," said John Cowan, professor at the University of Oklahoma in Norman. "There could be some other explanation, but it would have to be more convoluted."

But the theory requires a delicate balance between the explosion and the fallback of material, said Alex Filippenko, an astronomy professor at the University of California, Berkeley.

"The outer parts of the star seemingly got expelled, but the inner parts colapsed to form a black hole," he said. "It requires a delicate balance between the explosion energy and the amount of material in the star."