Andromeda Galaxy Gets ‘Photobombed’ By Supermassive Black Hole Binary In New Photos


As it turns out, it’s not just us humans who surprise photographers by inserting themselves into the pictures they take. A series of new photos shows the nearby Andromeda galaxy getting a “cosmic photobomb” from two supermassive black holes that might also be the closest such pairing ever observed.

According to a press release from NASA, the discovery was made using the space agency’s Chandra X-ray Observatory, with supporting data from two ground-based telescopes, Hawaii’s Gemini-North and the California Institute of Technology’s Palomar Transient Factory. Originally, the astronomers were looking for a “special” type of star in the Andromeda galaxy, which is located about 2.5 million light-years away from Earth. And while it was originally thought that the object was within Andromeda, the data from the telescopes revealed that the object was much more distant than expected, at about 2.6 billion light-years from our planet.

“We were looking for a special type of star in M31 and thought we had found one,” said Trevor Dorn-Wallenstein of the University of Washington, lead author of a paper describing the Andromeda galaxy photobomb.

“We were surprised and excited to find something far stranger!”

That “something far stranger” was what appeared to be a pair of supermassive black holes orbiting each other in very close proximity. Both black holes are believed to have a combined mass about 200 million times greater than that of our sun and were previously identified by a separate team of researchers as a pair of stars that orbited around each other every 80 days or so.

That theory was proven incorrect by Dorn-Wallenstein and his colleagues, as the intense X-ray source spotted by the Chandra observatory suggested one of two things — the star system codenamed J0045+41 was a binary system with a neutron star or black hole sucking in material from a companion star, or a far more distant system featuring at least one supermassive black hole.

It was the former star system that Dorn-Wallenstein had first suspected as being responsible for the so-called Andromeda galaxy photobomb. But since J0045+41 was not located inside Andromeda, the researchers used the Gemini-North telescope in Hawaii to conclude that there was at least one supermassive black hole inside J0045+41, and that the system was much farther away than suspected.

As noted by the International Business Times, further analysis of the spectrum from Gemini-North revealed that there was what looked to be a second black hole inside the star system and that it moved at a different pace than the first. With Caltech’s Palomar Transient Factory spotting periodic light variations, these features matched existing models of two supermassive black holes orbiting each other.


As they are separated by only less than a hundredth of a light-year, the two objects in the Andromeda galaxy photobomb are believed to be the tightest pair of supermassive black holes ever spotted. According to study co-author and fellow University of Washington researcher John Ruan, there’s a chance that the pairing will merge at some point in the future, possibly as soon as the 24th century.

“We’re unable to pinpoint exactly how much mass each of these black holes contains. Depending on that, we think this pair will collide and merge into one black hole in as little as 350 years or as much as 360,000 years,” said Ruan, who is also affiliated with the University of Washington.

Although J0045+41 seemingly features two supermassive black holes orbiting in extremely close proximity to each other, NASA’s press release noted that any gravitational waves emitted would likely not be detectable via conventional means. Instead, Dorn-Wallenstein said that the slow changes in gravitational waves from such a star system could be detected by a “Pulsar Timing Array,” a completely different gravitational wave facility from the ground-based LIGO and Virgo facilities.