Article Posted on : - Apr 30, 2010

A nearby starburst galaxy M82 shows Chandra X-ray Observatory data in blue, optical data from the Hubble Space Telescope in green and orange, and infrared data from the Spitzer Space Telescope in red. A Chandra image (Inset) that shows the central region of the galaxy and contains two bright X-ray sources. A NASA Photo by NASA/CXC/Tsinghua Univ./H. Feng et al./JHU/D.Strickland/ESA/STScI/AURA/The Hubble Heritage Team/JPL-Caltech/Univ. of AZ/C. Engelbracht.

ALASKA (BNS): NASA's Chandra X-ray Observatory and ESA's XMM-Newton has brought out fresh evidence about the existence of two mid-sized black holes close to the center of a nearby starburst galaxy.

The black holes, known as "survivor" black holes, avoided falling into the center of the galaxy and could be examples of the seeds required for the growth of supermassive black holes in galaxies, including the one in the Milky Way.

The researchers who were on a look-out for the black holes that are in-between recently found signatures in X-ray data of two mid-sized black holes in the starburst galaxy M82 located 12 million light years from Earth.

"This is the first time that good evidence for two mid-sized black holes has been found in one galaxy," said Hua Feng of the Tsinghua University in China, who led two papers describing the results. "Their location near the center of the galaxy might provide clues about the origin of the Universe's largest black holes – supermassive black holes found in the centers of most galaxies," according to a news release by NASA.

The evidence for these two "survivor" black holes comes from how their X-ray emission varies over time and analysis of their X-ray brightness and spectra, i.e., the distribution of X-rays with energy.

Chandra and XMM-Newton data has shown that the X-ray emission for one of these objects changes in a distinctive manner similar to stellar-mass black holes found in the Milky Way. Thus, the team estimated this black hole's mass is between 12,000 and 43,000 times the mass of the Sun. This mass is large enough for the black hole to generate copious X-rays by pulling gas directly from its surroundings, as per the report.

The black hole is located at a projected distance of 290 light years from the center of M82.

The second object, located 600 light years in projection away from the center of M82, was observed by both Chandra and XMM-Newton.

This result, finally, is one of the strongest pieces of evidence to date for the existence of an intermediate-mass black hole.