Bonanza of Black Holes Discovered in Nearby Andromeda Galaxy by NASA

NASA's Chandra X-ray Observatory has made a new discovery. It's found a veritable bonanza of black holes in the Andromeda Galaxy, one of the nearest galaxies to our own Milky Way. Yet these latest findings could just be the tip of the iceberg; there could be a lot more black holes in this galaxy, waiting to be found.

In order to actually discover these black holes, the researchers first made sure that they were stellar mass systems in the Andromeda Galaxy itself, rather than supermassive black holes at the hearts of more distant galaxies. In order to accomplish this, the scientists used a new technique that relied on information about the brightness and variability of the X-ray sources in the Chandra data. In other words, the stellar mass systems change much more quickly than the supermassive black holes.

The next step was actually classifying these Andromeda systems as black holes. The researchers observed that these X-ray systems had special characteristics; they were brighter than a certain high level of X-rays, and also had a particular X-ray color.

In the end, the researchers discovered 26 black hole candidates using more than 150 Chandra observations spread over 13 years. This is the largest number of black holes found to date and brings the total number of black holes in this particular galaxy up to 35.

These black hole candidates actually belong to the stellar mass category, which means they formed in the death throes of very massive stars. These bodies are huge--up to 10 times that of our sun.

"When it comes to finding black holes in the central region of a galaxy, it is indeed the case where bigger is better," said co-author Stephen Murray in a news release. "In the case of Andromeda, we have a bigger bulge and a bigger supermassive black hole than in the Milky Way, so we expect more smaller black holes are made as well."

The findings have given the researchers new insights into the Andromeda Galaxy. They hope to continue their studies, attempting to find more black holes in the galaxy.

The findings are published in The Astrophysical Journal.