Stars forming just beyond black hole's grasp at galactic center

WASHINGTON, Jan. 5 (Xinhua) -- New stars can, in
fact, form very close to the Milky Way's central black hole, according to a
recent study published by the Harvard-Smithsonian Center for Astrophysics.

The center of the Milky Way is wracked with powerful
gravitational tides stirred by a gigantic black hole. Those tides should rip
apart molecular clouds that act as stellar nurseries, preventing stars from
forming in place. Yet the alternative -- stars falling inward after forming
elsewhere -- should be rare occurrences.

Using the Very Large Array of radio telescopes,
astronomers from the Harvard-Smithsonian Center for Astrophysics in the United
States and the Max Planck Institute for Radio Astronomy in Germany have
identified two proto-stars located only a few light years from the galactic
center.

"We literally caught these stars in the act of
forming," said Smithsonian astronomer Elizabeth Humphreys, who presented the
finding Monday at a meeting of the American Astronomical Society in Long Beach,
California.

The center of the Milky Way is a mysterious region
hidden behind intervening dust and gas, making it hard to study. Visible light
does not make it out, leaving astronomers no choice but to use other wavelengths
such as infrared and radio, which can penetrate dust more easily.

Humphreys and her colleagues searched for water
masers - radio signals that serve as signposts for proto-stars still embedded in
their birth cocoons. They found two proto-stars located seven and 10 light years
from the galactic center.

Combined with one previously identified proto-star,
the three examples show that star formation is taking place near the Milky Way's
core.

Their finding suggests that molecular gas at the
center of our galaxy must be denser than previously believed.

A higher density would make it easier for a molecular
cloud's self-gravity to overcome tides from the black hole, allowing it to not
only hold together but also collapse and form new stars.

The discovery of these proto-stars corroborates
recent theoretical work, in which a supercomputer simulation produced star
formation within a few light years of the Milky Way's central black hole.

"We don't understand the environment at the galactic
center very well yet," Humphreys said.

"By combining observational studies like ours with
theoretical work, we hope to get a better handle on what's happening at our
galaxy's core. Then, we can extrapolate to more distant galaxies," she
said.