The universe is vast and contains billions upon billions of objects, existing in an immense space-time we humans are only beginning to comprehend. So it’s a curiosity, but not really surprising, when an object thought to be two orbiting stars and thought to be was part of the Andromeda galaxy – next-nearest large galaxy to Earth, only 2.5 million light-years from Earth – is revealed as 1,000 times more distant. New work shows the object known as as J0045+41 is likely not stars at all, but a pair of giant black holes, orbiting one another extremely closely, not millions but billions of light-years away. A paper describing this new result was accepted for publication in the peer-reviewed Astrophysical Journal (preprint online). A November 30, 2017 statement from Chandra X-Ray Observatory said:
It seems like even black holes can’t resist the temptation to insert themselves unannounced into photographs. A cosmic photobomb found as a background object in images of the nearby Andromeda galaxy has revealed what could be the most tightly coupled pair of supermassive black holes ever seen.
Astronomers now believe J0045+41 is around 2.6 billion light-years from Earth, and they’re now estimating the total mass for these two supermassive black holes at about 200 million times that of our sun.
The research team combined the Chandra X-ray Observatory data with spectra from the Gemini North telescope in Hawaii, showing that J0045+41 likely contained at least one supermassive black hole. Using data from the Palomar Transient Factory telescopes in California, the team found repeating variations in the light from J0045+41, a pointer to the presence of two orbiting giant black holes.
If these researchers are correct, the separation between the two giant black holes may be only a few hundred times the distance between our Earth and sun. This corresponds to less than 1/100th of a light-year. By comparison, the nearest star to our sun is about four light-years away. The statement from Chandra said:
Such a system could be formed as a consequence of the merger, billions of years earlier, of two galaxies that each contained a supermassive black hole. At their current close separation, the two black holes are inevitably being drawn closer together as they emit gravitational waves.
And so, bit by bit, our universe becomes more knowable!
Bottom line: Astronomers thought the source known as J0045+41 was a binary star system, part of the nearby Andromeda galaxy, but new work shows the source is 1,000 times more distant and could be the most tightly coupled pair of supermassive black holes ever seen.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.