The Milky Way's Supermassive Black Hole Might Be Flinging Rocks Out Of The Galaxy

Artistic impression of a supermassive black hole. NASA/JPL-Caltech

If you think black holes can mess you up only when you get close to them, I have bad news for you. Researchers from Harvard University have simulated the supermassive black hole at the center of the Milky Way, Sagittarius A*, and it appears to be a cosmic slingshot, shooting out rocks.

The research, presented at the American Astronomical Society conference, focuses on what happens when a star gets too close to Sagittarius A*, something that happens about every 10,000 years. The star is usually stretched and pulled apart by the tremendous gravity, a process called spaghettification, and this material then falls into the black hole.

However, the researchers discovered that the density in this stream of stellar material is high enough for planetary-mass fragments to form, and these can sometimes escape the black hole and fly into the galaxy (sometimes even out of it).

The sophisticated computer simulation uses statistical analysis to work out what happens to these rogue fragments. The team's calculations suggest that the speed of these objects exceeds the 30 million kilometers per hour (20 million mph) needed to escape the gravitational pull of the Milky Way.

The other finding looks at how common these fragments may be in the galaxy. Even knowing that the rate at which stars falls onto Sagittarius A* has not been uniform, there could be hundreds of millions of these fragments that could possibly be even bigger than Jupiter. The nearest of these objects could be just a few hundred light-years away and if we are lucky we could spot one of them. 

"Since the fragments will be moving at several hundred km/s to up to 10,000 km/s, this gives them an increased chance of microlensing despite their rarity as compared to normal free-floating planets, a signal that may be detectable with Large Synoptic Survey Telescope," Eden Girma, who led the research told IFLScience. 

"Because they are planet-like and are not illuminated by a parent star, they will be very cold and dim, but if we're lucky, one may be directly detectable by the James Webb Space Telescope"

It might seem counterintuitive that something can form around (and then escape) a black hole, but it’s not just a question of mass but also a question of space. Spaghettification is about the difference in force between two points on the same body. The heavier a black hole, the larger it is, so the difference becomes smaller.

In the case of Sagittarius A*, the difference in gravity is strong enough to pull a star apart but not enough for an object hundreds of thousands of times smaller.

 

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