Astronomers think that our Milky Way galaxy is home to about 100 million of these objects, which are so dense that not even light can escape them. Now, for the first time, scientists have published strong proof that they found one of these fast-moving black holes that don’t belong.
This kind of black hole is made when a star that is about 20 times as heavy as the sun explodes and collapses into an object that is very close together. It’s how things in our universe change over time.
“These are just stars that move around. Those stars that move around become black holes that move around “Astronomer Kailash Sahu from the Space Telescope Science Institute told Mashable that he led one of the studies about this discovery.
It might seem crazy that there are about 100 million of these rogue black holes moving through the galaxy. But it makes good sense. Stars die. There are a lot of stars in the sky. “That seems like a lot, but our galaxy has 100 billion stars,” Sahu pointed out. There are other dramatic ways black holes are made, but stars falling apart is a common one.
“The Milky Way should be full of black holes,” agreed Fabio Pacucci, an astrophysicist at the Center for Astrophysics at Harvard and Smithsonian who wasn’t involved in the new research.
Importantly, there may be a lot of black holes in our galaxy, but they are still pretty far from our solar system because space, like our galaxy, is huge. About 5,000 light-years away is this rogue black hole (one light-year is nearly 6 trillion miles). Researchers say that based on statistics, the most nearby rogue black hole should be about 80 light-years away. For comparison, Proxima Centauri, the star closest to us, is four light-years, or about 24 trillion miles, away.
Even though these black holes move around, it’s important to remember that we do, too. Our solar system moves at more than 500,000 mph (828,000 km/h) around the center of the Milky Way, where there is a supermassive black hole called Sagittarius A*.
Sahu said, “Everything kind of moves around, nothing is really still.”
But these rogue black holes have been given a good kick, which sends them on a more random path through the galaxy. They were created by very powerful explosions. If a traveling black hole came close to a solar system, it might throw off the orbits of the planets in that system. But black holes don’t take everything in the universe with them. Douglas Gobeille, an astrophysicist and black hole researcher at the University of Rhode Island, said earlier this year, “They are not vacuum cleaners. If they were, we would be in one.”
The rogue black hole detection
Astronomers did something smart to make this observation over a number of years. Space bends around black holes, which are very dense things, like a bowling ball sitting on a mattress. The research team carefully watched through the Hubble Space Telescope, which is about the size of a school bus, for a very dense object (like a black hole) to pass in front of a faraway star. The passing black hole bent and twisted the starlight as it cut through this area of space. This is called “microlensing,” and it is a type of observation.
Also, the Hubble telescope then looked at tiny changes in light to figure out how much light the black hole reflected. Hubble is a great tool for making this kind of sensitive observation because it orbits above Earth. This means that our atmosphere doesn’t blur and distort its views.