Astronomers have seen a distant cluster of galaxies without the expected supermassive black hole at its center, despite the fact that its mass should be between three and 100 billion times that of the sun.
According to NASA observations between 1999 and 2004, the black hole is located in the galaxy cluster Abell 2261, about 2.7 billion light-years from Earth.
More recently, astronomers at West Virginia University used NASA’s Chandra X-ray Observatory and Hubble Space Telescope to explore the area – and couldn’t find the black hole.
Almost every major galaxy in the known universe contains a supermassive black hole. The heavier the galaxy, the larger the black hole. In fact, this particular black hole was predicted to be one of the largest ever.
To put the idea of something a hundred billion times the mass of the sun into perspective, the Milky Way’s central supermassive black hole is estimated to be just four million times the mass of the sun.
But it is missing. To explain that, scientists have provided several explanations.
The first is that the black hole could have been ejected from its host galaxy as a result of the merging of two galaxies to create an even more massive galaxy, also known as a “receding black hole.”
Alternatively, the respective black holes of the two galaxies could have merged into one even larger supermassive black hole, creating a gigantic core at the center of the resulting mega-galaxy. While this phenomenon has not yet been directly observed with black holes on such a scale, astronomers have observed mergers with significantly smaller black holes.
In a paper to be published in the journal American Astronomical Society, a team led by Sarah Burke-Spolaor of West Virginia University put forward two more possible explanations: either there simply isn’t a black hole, or there is indeed a black hole that just isn’t active enough to produce noticeable amounts of X-rays that appear in Chandra observations.
The scientists hope to use NASA’s upcoming James Webb Space Telescope to get a closer look.
READ MORE: On the hunt for a missing giant black hole [NASA]
More about supermassive black holes: Nobel Laureate on Falling Into a Black Hole: “I Would Not Want To”