"Stellar eggs" found hatching near the galaxy's central black hole
Supermassive black holes create extremely turbulent environments at the centers of galaxies, and it’s long been presumed that this would disrupt star formation there. But now, astronomers have peered closer at the heart of the Milky Way and discovered several “stellar eggs” in the area – and they appear to be hatching.
Stars are born in dense clouds of dust and gas, when enough of the material gathers in clumps and eventually collapses under its gravity, igniting as a star. For that to happen, though, the space weather needs to be pretty calm and still – which of course are not words you’d use to describe the area around black holes. It’s thought that stars wouldn’t be able to form too close to the supermassive monsters that lurk at the centers of galaxies, since they’d whip the material around instead of letting it settle.
But perhaps that’s not always the case. A team of astronomers has used ALMA to examine the Milky Way’s Central Molecular Zone (CMZ), which extends about 1,000 light-years from the core of the galaxy where the supermassive black hole Sagittarius A* resides.
To their surprise, the team discovered over 800 dense cores of dust and gas in the CMZ, which looked like stellar eggs where stars could begin to form. Whether or not these pockets actually are stable enough to produce stars was another question, though.
So the astronomers investigated further, using ALMA to look for energetic outflows of gas from these eggs, which are “unambiguous evidence” of ongoing star formation, the team says. And sure enough, in 43 of the cores, small, faint outflows were detected.
“It is like hearing babies’ cries in a place we expected to be barren,” says Xing Lu, an author of the study. “It is very difficult for babies to be born and grow up healthily in an environment that is too noisy and unstable. However, our observations prove that even in the strongly disturbed areas around the galactic center, baby stars still form.”
The team says that this small amount of star-forming clouds suggests that the CMZ is at the beginning of its star-forming phase.
“Although a large number of outflows might be still hidden in the regions, our results may suggest we are seeing the beginning of the next wave of active star formation,” says Lu.
This isn’t the first time we’ve found stars being born under “impossible” conditions – a few months ago astronomers reported evidence of star formation in a quasar, a galaxy with a far more active central black hole than our own. Altogether, it seems that star formation is a more stable process than we thought.
The research was published in the Astrophysical Journal.