Washington, Jun 13:

Astronomers have discovered 26 new black holes in the Andromeda Galaxy, one of the nearest galaxies to the Milky Way, using data from NASAs Chandra X-ray Observatory.

Using more than 150 Chandra observations, spread over 13 years, researchers identified 26 black hole candidates, the largest number to date, in a galaxy outside our own.

Many consider Andromeda (M31) to be a sister galaxy to the Milky Way. The two ultimately will collide, several billion years from now.

While we are excited to find so many black holes in Andromeda, we think its just the tip of the iceberg, said Robin Barnard of Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, and lead author of the study.

Most black holes wont have close companions and will be invisible to us, Barnard said.

The black hole candidates belong to the stellar mass category, meaning they formed in the death throes of very massive stars and typically have masses five to 10 times that of our Sun.

Astronomers can detect these otherwise invisible objects as material is pulled from a companion star and heated up to produce radiation before it disappears into the black hole.

The first step in identifying these black holes was to make sure they were stellar mass systems in the Andromeda Galaxy itself, rather than supermassive black holes at the hearts of more distant galaxies.

To do this, the researchers used a new technique that draws on information about the brightness and variability of the X-ray sources in the Chandra data. In short, the stellar mass systems change much more quickly than the supermassive black holes.

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NASA’s Chandra detects blackhole bonanza next door