Smallest-known black hole observed

GREENBELT, Md., Dec. 15 (UPI) -- Astronomers say data from a U.S. X-ray satellite has revealed the "heartbeat" of the smallest-known black hole.

The evidence gathered by NASA's Rossi X-ray Timing Explorer is in the form of a specific type of X-ray pattern, nicknamed a "heartbeat" because of its resemblance to an electrocardiogram, a release from the space agency said Thursday.

The black hole is part of a binary system with a normal star, and the system is named IGR J17091-3624 after the astronomical coordinates of its sky position.

Researchers say the black hole may weigh less than three times the sun's mass, near the theoretical mass boundary where black holes become possible.

Based on its X-ray "heartbeat" captured by the RXTE satellite, astronomers say IGR J17091 must possess a minuscule black hole.

"Just as the heart rate of a mouse is faster than an elephant's, the heartbeat signals from these black holes scale according to their masses," said Diego Altamirano, an astrophysicist at the University of Amsterdam in the Netherlands.

Launched in late 1995, RXTE is second only to Hubble as the longest-serving of NASA's operating astrophysics missions, the space agency said.