Can stars form near supermassive black holes?
It is worth asking if the conditions around supermassive black holes can foster an environment for stars to form and thrive. The search for this answer may quite possibly lie at the center of our Milky Way Galaxy, which harbors the monstrous black hole known as Sagittarius A* (Sgr A*). This region exerts extreme tidal forces and is full of powerful ultraviolet light and X-ray radiation—conditions that theoretically prevent star formation. However, a study published in The Astrophysical Journal Letters found stars dangerously close to Sgr A*.
The Atacama Large Millimeter/submillimeter Array (ALMA) found signs of eleven low-mass protostars within three light-years of the black hole, as per the ALMA Observatory. At this distance, the tidal forces of the massive black hole should be energetic enough to rip apart the star-forming clouds of dust and gas.
What led to the discovery of these protostars was the "double lobes" of material that arrange themselves in the classic hourglass-like shape around each of them. Molecules like those of carbon monoxide present in these lobes appear bright in millimeter-wavelength light, to which ALMA is quite sensitive. This evidence, as surprising as it is, showed how stars can form even in the most unlikely of places, where the conditions are not conducive to their development.
For the stars to form, outside forces have to compress the gas clouds near the galaxy’s center to conquer the violent nature of the region, to make it possible for gravity to take over to form stars. It is speculated that high-velocity gas clouds in the region could help star formation by compressing gas clouds as they make their way through. Another possibility is that jets from the black hole tear through the surrounding gas clouds, compressing material and triggering the star formation bursts.
"The presence of so many dense clumps suggests that star formation could take place in the immediate vicinity of supermassive black holes at the centers of other galaxies," said Yusef-Zadeh, astronomer and lead author of the study. “Future observations will shine more light on this process and help us better understand how this happens and where else we could look for new, young stars."
Interestingly, a more recent study, published in the journal Astronomy & Astrophysics, has only reinforced the idea that Sagittarius A* may not be as destructive as it was previously made out to be. The new observation instrument ERIS (Enhanced Resolution Imager and Spectrograph) at the Very Large Telescope (VLT) facility in Chile found that various "dusty objects" maintain stable orbits around the supermassive black hole Sgr A*. Moreover, the binary star system D9, which was discovered by the research lead Dr. Florian Peissker and team last year, is also defying the immensely powerful tidal forces in the region to remain stable. It now stands as the first known binary system observed so close to a supermassive black hole. "The supermassive black hole at the center of the Milky Way has not only the capability to destroy stars but it can also stimulate their formation or the formation of pretty exotic dusty objects, most likely via mergers of stellar binaries," explained Michal Zajaček from Masaryk University in Brno (Czech Republic).
