Behind a black hole with a mass of 20 million solar masses follows the trail of newborn stars. It has a length of 200 thousand. A light year, so it is twice the diameter of the Milky Way and extends from the black hole to the host galaxy from which it originated. There must be a huge number of newly formed stars in the tail, because all are only half as bright as the host galaxy.
Of course, astronomers can’t see the black hole itself, but they can see the effects of its interaction. So they see a long tail of stars and star-forming material, with the galaxy RCP 28, 7.5 billion light-years away, at one end and a very bright region at the other.
Scientists speculate that this region is either an accretion disk around the black hole, or gas that has been heated to high temperatures due to the black hole rushing into it at a huge speed. “The gas at the top of the black hole is being heated by the shock wave generated by the black hole traveling at supersonic speed,” says Peter van Dokkum of Yale University.
The image was taken by the Hubble Space Telescope
It was a complete accident. I was looking at Hubble images and I saw a little bit of a smudge. I thought cosmic rays were causing the image distortion. However, when we removed the cosmic rays, the smudge was still there. And it didn’t look like anything we’ve seen before,” van Dokkum adds.
Scientists decided to take a closer look at the mysterious phenomenon and used a spectrometer from the WM Keck Observatories in Hawaii. They see a bright structure and after research conclude that it was created by a supermassive black hole that emanated from its galaxy.
According to van Dokkum and his team, black hole ejections are the result of numerous collisions. The first happened about 50 million years ago, when two galaxies merged. Their supermassive black holes formed a binary system and began orbiting each other. After some time, there was a collision with another galaxy. This also contains a supermassive black hole. An unstable system of three black holes formed. About 39 million years ago, one of them took some of the momentum from the other two and was kicked out of the galaxy.
As the individual black hole blasted off in one direction, other black holes spinning in another direction were ejected. On the other side of the galaxy, scientists have observed what may be a receding system of two black holes, and no black hole has been observed at the center of the galaxy.
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