Star power: Astronomers have found stars forming just a few light-years from the Milky Way's center, despite the powerful gravitational tides generated by the central black hole.
Credit: NASA, ESA, and A. Schaller (for STScI)
BRISBANE: Stars can form much closer to the Milky Way's central black hole than was previously thought possible, new research has found.
Signs of two protostars were detected just seven and 10 light-years from the black hole, a distance close enough to excite researchers from the Smithsonian-Harvard Centre for Astrophysics in Cambridge, U.S., and the Max Planck Institute for Radio Astronomy in Bonn, Germany.
The astronomers made the find using the Very Large Array of radio telescopes in New Mexico, and announced their discovery at last week's meeting of the American Astronomical Society in California.
Torn nurseries
The finding of the two protostars where they were is surprising, since the gravitational force from the central black hole should be stretching and tearing apart nearby molecular clouds capable of acting as stellar nurseries - preventing stars from forming close to it.
Although astronomers had observed young stars in the region before, including one protostar, it was previously thought that they had drifted into the area after forming.
"People really thought that stars should not be able to form there," said Elizabeth Humphreys, an astronomer at Centre for Astrophysics who presented the research.
Caught in the act
Though clouds of gas and dust around the centre of the Milky Way block visible light, making the area difficult to study, Humphreys' team was able to detect 'water masers', radio signals produced by protostars still in their birth cocoons.
"We literally caught these stars in the act of forming," she said.
The evidence of star formation so close to the core of the Milky Way suggests the molecular gas at our galaxy's centre must be denser than previously thought, Humphreys said.
This deduction is made on the basis that a higher density would allow the gas enough self-gravity to hold together under the pressure of the black hole's damaging gravitational tides, and to later collapse under this gravity to form new stars.
The last place you'd look
Stuart Ryder, an astronomer at the Anglo-Australian Observatory in Sydney, Australia, said that the work was very exciting. "It's almost the very last place we'd look for young stars," he said.
Although it was possible that the masers were being emitted by something other than a protostar, Ryder said, it seems most likely that stars really are forming in the centre of the galaxy.
"If these stars do turn out to be real stars forming… it would mean that stars could form in places where we thought that was impossible," Ryder said. "It forces us to rethink out current paradigm for star formation. We might have to think again about how stars like our own are formed."
Humphreys' team plans to continue their research, and are looking for more signs of protostars using the Submillimetre Array in Hawaii.
