London, July 24 : Astronomers have spotted evidence of very young stars in a ring of gas close to the heart of the Milky Way, where a massive black hole is thought to reside.
According to a report in New Scientist, these protostars, 6 to 20 light years from the galaxy's centre, are shrouded by so much gas and dust that they can't be seen with telescopes.
The team of astronomers saw strong radio emissions from natural molecular masers. These masers work a little like artificial lasers, but they form naturally within dense, collapsing gas clouds.
Molecules of gas become energized by frequent collisions with other molecules, and then emit the energy as radio waves.
So the presence of these masers suggests that gas is collapsing to form protostars, which will eventually form short-lived stars that are tens of times heavier than the Sun.
Astronomers have known for several years that the ring of gas seemed to be dense enough to form stars. But no one was sure whether the gravitational attraction inside the cloud would be enough to counteract violent tides from the black hole.
"Star formation is something we don't really understand, even if it's not near a black hole," Yusuf-Zadeh told New Scientist.
He added that the find could help fill in our understanding of massive star formation.
The researchers found another line of evidence for young stars in this gas ring.
Newborn stars collect material from the surrounding cloud, but also blast some gas away from their poles in narrow, high-speed jets.
Yusuf-Zadeh and colleagues discovered that the radio emission from the region was distorted in a way that can be explained by the rapid motion of such jets.
These jets only last a few tens of thousands of years, suggesting that the ring of gas that hosts the stars was pulled into orbit around the galactic centre and became dense enough to form stars not long ago.
"Older stars share the same space as these protostars, meaning that clouds may be constantly coming in to form succeeding generations of stars," said Yusef-Zadeh.
This discovery might also explain the presence of some stars even closer to the galaxy's centre, only 2 light years away from the black hole.
Some researchers think these stars formed much further out and were later captured, but these new observations favour an alternative theory - that they formed in collapsing gas clouds near their present location.
To establish the presence of these protostars more solidly, Scoville suggests looking for gas that has been ionized by ultraviolet radiation from the young stars.