Chinese astronomers have captured a dramatic cosmic collision on the outskirts of the Milky Way, which offers fresh clues to the birth of stars.
Researchers from the School of Physics and Astronomy at China West Normal University discovered a pair of newly born star clusters located about 45,000 light-years from Earth near the edge of the Milky Way, naming them Emei-1 and Emei-2, after Mount Emei in southwest China.
The clusters are extremely young on cosmic timescales, estimated to be only about 10 million years old, and formed inside high-velocity clouds (HVCs). HVCs are massive streams of gas originated outside the galaxy that plunge into the outer regions of the Milky Way. For decades, astronomers had observed only gas in such clouds and no signs of stars, leading many to view them as inhospitable environments for star formation.
But the new observations suggest that when one of these fast-moving gas clouds slammed into the outer edge of the Milky Way's disk, the violent collision compressed the gas to such an extent that it triggered the birth of stars. The process produced the two young clusters detected by the team, pointing to a previously unknown mechanism for how stars form.
The finding marks the first clear evidence that stars can form within high-velocity clouds, suggesting that other high-velocity clouds could also spark stellar births.
"Contrary to traditional understanding, this proves that star formation is not confined to the interiors of galaxies but can also occur in their outer fringes, effectively identifying a 'blood supply system' that sustains the star life cycle of the galaxies," said He Zhihong, an associate professor from the School of Physics and Astronomy at China West Normal University.
The discovery also offers new insights into how the Milky Way grows. Rather than being a closed system, the galaxy continues to pull in fresh gas from its surroundings. When this incoming material collides with the galactic disk, it can supply the raw ingredients needed to create new generations of stars.
The findings were published on Wednesday in Nature Astronomy.
Chinese scientists find clues to birth of stars at Milky Way's edge
