Introduction

NASA astronomers studying X-ray emissions reported Monday, August 16th, that for the first time they believe they have observed matter being pulled into a massive black hole. Writing in Astrophysical Journal Letters, a team at NASA's Goddard Space Flight Center in Greenbelt, Maryland, reported that the matter was being pulled into what is believed to be a black hole at more than 6 million mph.

100 Million Light-years Away

Team members said they made what they believe is an exciting discovery when looking at X-ray emissions from iron at the center of a galaxy 100 million light-years away. A light-year is the distance light travels in one year at the speed of light, 186,000 miles a second.

"We were looking at one line which is from iron," astrophysicist Paul Nandra, who helped lead the study, said Monday in a telephone interview. "This line, we think, comes from very, very close to the black hole and it comes from matter that is orbiting the black hole in a disk."

In a black hole, the force of gravity is so strong that nothing, not even light, can escape. Some black holes are formed by collapsed stars, but others are "supermassive," containing as much mass as a million to a billion suns compressed into a tiny region known as a singularity. The only way scientists have been able to see them up to now is by looking at the accretion disks Ñ the swirling matter circling around as it is being pulled into the black hole.

Point of No Escape

X-ray telescopes like the one the Goddard team used. Once it gets past a certain point, known as the event horizon, it cannot be seen. Scientists think they have finally seen it. They were looking at the galaxy NGC 3516 using the Advanced Satellite for Cosmology and Astrophysics (ASCA), a Japanese-U.S. X-ray satellite launched in 1993 to look at the superheated gas in the accretion disk. Buried in the X-rays emitted by the gas was a strange feature Ñ energy that has been "red-shifted" in an astronomical Doppler effect.

Just as stretched and compressed sound waves cause the sound of a train's whistle or a truck's horn to rise and fall as they pass an observer, light is stretched, or red-shifted, as it speeds away from the Earth. In this case, Nandra said, an analysis of this altered light indicated the iron was moving at tremendous speeds toward a black hole. This was the first time anyone had reported seeing evidence of matter falling into a black hole.

Quotes provided by microsoft.com