by Astronomers study the supermassive Milky Way black hole have found “compelling evidence” that may finally explain his mysterious past.
Sagittarius A* is located 26,000 light-years away at the center of our galaxy. It is a giant rip in space-time with a mass four million times that of our Sun and a width of 23.5 million kilometers.
But how did the black hole form and why is it like that? surprisingly fast spinning and its orientation with the rest of the galaxy, remain unknown. Now, data from the telescope that took the first picture of the black hole in 2022 has revealed a clue: The Sagittarius A* we see today formed billions of years ago from a catastrophic merger with another giant black hole — and it still shows the effects of that violent collision. The researchers published their findings Sept. 6 in the journal Nature Astronomy.
“This discovery paves the way for our understanding of how supermassive black holes grow and evolve,” said the study’s lead author. Yihan Wangan astrophysicist at the University of Nevada, Las Vegas (UNLV), said in a statement“The misaligned high spin of Sgr A* indicates that it may have merged with another black hole, dramatically changing the amplitude and orientation of its spin.”
Despite only accounting for 0.0003% of the Milky WayWith its mass, Sagittarius A* is a powerful engine that periodically sucks in matter and then spews it out at almost the speed of light, creating a feedback process that has shaped our galaxy since its inception.
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Scientists believe the giant black hole started out like others, born from the collapse of a giant star or gas cloud before feeding on anything that came too close. After swelling to monstrous proportions, black holes can even feed on other supermassive black holes.
Supermassive black holes merge when entire galaxies merge. Bumps and kinks in the Milky Way’s disk indicate that it probably collided with at least a dozen galaxies over the past 12 billion years. But astronomers are still unsure how important black hole mergers are in creating supermassive black holes, or whether these rips in spacetime can grow to such mind-boggling proportions simply by consuming gas and dust.
To find direct evidence for the origins of Sagittarius A*, the researchers behind the new study used data from the Event Horizon Telescope to model the black hole’s behavior over time. In a series of simulations, the astronomers found that the black hole’s unusual spin — which is completely out of alignment with the rotation of our galaxy — was best explained by a massive merger event with another galaxy’s supermassive black hole.
“This merger likely occurred about 9 billion years ago, after the Milky Way. merger with the Gaia-Enceladus galaxyco-author of the study Bing Zhanga professor of physics and astronomy at UNLV, said in the statement. This merger not only provides evidence for the idea that black holes can grow larger by swallowing their own kind, but also offers “insights into the dynamical history of our galaxy,” Zhang added.
To find more evidence of merging giant black holes in the universe, the researchers say they are waiting for the construction of gravitational wave space telescopes, such as those from NASA and ESA. Laser Interferometer Space Antenna (LISA) projectWhen LISA is launched into space in 2035, it will detect the shock waves that space-time when supermassive black holes collide.
