Study Links Star Blast, Black Hole
By MATTHEW FORDAHL
03:42 PM ET 09/08/99
Scientists have found some of the best evidence yet to support the theory that
the cataclysmic explosions of giant stars can lead to black holes, some of the strangest
and least understood objects in the universe. 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 massive celestial objects whose gravity is so powerful that
nothing not even light, can escape from one. 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 onto
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 have long 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 researches 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.''
