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The strange center of the Andromeda galaxy has occupied the specialist world for decades. Now a research team claims to have found an answer. It has it all.
Boulder / Frankfurt – The Andromeda Galaxy (M31) is the most distant object in the sky that can be seen in good conditions see with the naked eye* can. It is a spiral galaxy similar to the Milky Way. But there is something about the galaxy that surprised astronomers: “When researchers first examined Andromeda, they expected to see a supermassive black hole surrounded by a relatively symmetrical cluster of stars,” explains astrophysicist Ann-Marie Madigan from the University of Colorado at Boulder. “Instead, they discovered a large, elongated mass.” What this strange cluster of stars in the center of the Andromeda Galaxy was about remained a mystery for decades – but now a research team claims to have found an answer.
The starry region in the center of the Andromeda Galaxy* Has a strange oval shape, like someone “stretched out a bunch of plasticine,” according to a University of Colorado release. Researchers call this an “eccentric core disk”. But how did this formation come about? To find out, the group used computer simulations to track what happens when two supermassive black holes collide – after all, the popular theory is that the Andromeda Galaxy formed billions of years ago from two galaxies that collided.
Andromeda Galaxy was created by the collision of two galaxies with black holes
The computer simulation showed the team that a violent collision of two supermassive black holes can change the orbits of stars near the galactic center – and create an elongated mass of stars. “When galaxies merge, their black holes eventually become a single black hole,” explains the study’s lead author, Tatsuya Akiba. “We wanted to know: What are the consequences?”
In their study, Akiba and Madigan explain what happens when two black holes merge. When galaxies collide, the black holes in the center of the galaxies begin to rotate around each other, explains Akiba. They move faster and faster until they eventually collide, causing gravitational waves that can be detected by special instruments on earth. “These gravitational waves carry the momentum away from the black hole and there is a recoil, like the recoil of a weapon,” says Akiba, summarizing his findings.
Andromeda Galaxy: Black holes merge – gravitational waves cause “recoil”
But what can this recoil do within a radius of around 30 trillion kilometers around the center of a galaxy? Madigan and Akiba have recreated galaxy centers with hundreds of stars on the computer and found that the gravitational waves that are created by the merging of two black holes do not directly affect the stars in the galaxy. Instead, the recoil throws the remaining supermassive black hole through space – at unimaginable speeds that can reach several million kilometers per hour. “A black hole that moves at thousands of kilometers per second can escape its galaxy,” emphasizes Madigan.
Black hole is thrown out of the galaxy – or changes star orbit
Black holes that do not leave their galaxy in this way can “pull” on the orbits of the stars in their vicinity and cause their orbits to expand. The result is similar to the center of the Andromeda Galaxy. In the next step, the two experts want to enlarge their computer simulations so that they can compare their computer results directly with the real galaxy core – in which there are significantly more stars.
The findings of Madigan and Akiba were made published in The Astrophysical Journal Letters. They assume that their study results can also help other scientists. “When you’re in orbit around a central object and the object suddenly flies away – you can scale that idea down to examine many different systems,” Madigan emphasizes. Planets orbiting neutron stars are an example. (tab) *fr.de is an offer from IPPEN.MEDIA.
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