Black holes are as fascinating as they are terrifying not only because of their mysterious dark nature — literally and figuratively — but also because we know so little about them. Heck, we don’t even know how they really look like since one has never been directly seen. All we know is that black holes hungrily gobble up anything that’s unfortunate enough to get near them. Think of it, even light is trapped by a black hole, making this region of spacetime with its extremely powerful gravitational pull quite a destructive force.
But the most surprising thing is that universe’s most mysterious phenomenon may not be as terrifying as previously thought. Thanks to the work of scientists led by Roberto Maiolino from the University of Cambridge, there’s exciting new information showing that while black holes can destroy stars, they can trigger star formation too.
Most galaxies contain supermassive black holes within their cores. When those black holes devour matter from all around, they also heat up the surrounding gas, then expel this heated gas from the galaxy in the form of dense and powerful winds (referred to as outflows).
Using what is probably the world’s most powerful optical instrument — the European Southern Observatory’s Very Large Telescope (VLT) — the research team studied the collision of two galaxies (known collectively as IRAS F23128-5919) located about 600 million light-years away. By concentrating on the colossal outflows being blasted out by one of the galaxies’ supermassive black hole, they were able to see the first evidence that stars can form from within these galactic outflows.
The scientists used two of VLT’s instruments — MUSE and X-shooter — to identify the newly formed stars. Because radiation from young stars has been known to cause surrounding gas clouds to glow in a certain way, they first used X-shooter to rule out the possibility that anything else other than a young star was causing the light emission. They couldn’t find any other explanation, however. Instead, they were able to detect a population of young stars in the outflow. These stars are believed to be less than tens of millions of years old, and are brighter and hotter than stars formed in less extreme conditions.
As Maiolino told Inverse: “The dynamic properties of stars produced in the violent and turbulent winds of a supermassive black hole are completely different than stars that were formed within a galaxy.”
The team studied the population further until they were able to determine the motion and velocity of the young stars. Based on the light from the stars, it appeared that some of the stars are travelling at extremely high speeds away from the galaxy core, which is exactly what’s expected from objects caught in a stream of fast-moving material blasted off from black holes.
Not all of the young stars follow this path, though. According to Maiolino, the fate of the stars depends on where they were formed. Those that form near the center are pulled by the extreme gravity, and this causes the stars to circle around the galaxy and become part of it. On the other hand, those that form far from the center aren’t held back as much, and they can fly away out of the galaxy.
While there’s still much to learn, this discovery is important because it could help answer some of astrophysics’ most basic questions including how galaxies get their shape, where cosmic background radiation comes from, and how space becomes filled up with different kinds of elements.
The results of the study have recently been published in the journal “Nature” under the title “Star formation in a galactic outflow“.