Supermassive black holes are usually seen as the end of stars. They either eat them or they are responsible for heating up hydrogen gas so much that they can’t form anymore. Astronomers have long suspected that in some cases they can actually help form new stars. Now, for the first time, they have found evidence of this.
Using the Very Large Telescope, a group of European astronomers has observed stars forming in the winds produced by a supermassive black hole. This one is located inside a galaxy that is currently colliding with another one, a system collectively known as IRAS F23128-5919.
“Astronomers have thought for a while that conditions within these outflows could be right for star formation, but no one has seen it actually happening as it’s a very difficult observation,” team leader Roberto Maiolino from the University of Cambridge, said in a statement. “Our results are exciting because they show unambiguously that stars are being created inside these outflows.”
The winds are moving really fast and this could lead to sudden compression of gas. This can start episodes of star formation, even in extreme environments like black hole winds. Depending on where these stars form they might end up in different regions of the galaxy, or even outside of it.
“The stars that form in the wind close to the galaxy centre might slow down and even start heading back inwards, but the stars that form further out in the flow experience less deceleration and can even fly off out of the galaxy altogether,” co-author Helen Russell added.
The work, published in Nature, shows that this population of stars is very young, just a few tens of millions of years old, and the preliminary results suggest that they are brighter and hotter than stars formed in less extreme environments.
This discovery, while confirming some ideas about galaxy evolution, also challenges others.
“If star formation is really occurring in most galactic outflows, as some theories predict, then this would provide a completely new scenario for our understanding of galaxy evolution,” Maiolino concluded.
More observations of this and other galaxies might push the envelope on understanding the complicated and interconnected lives of black holes and star formation in galaxy mergers.
