1-Dec-2010
--New Haven, Conn.—Because red dwarfs are relatively small and
dim compared to stars like our Sun, astronomers hadn't been
able to detect them in galaxies other than our own Milky Way
and its nearest neighbors before now. As such, they did not
know how much of the total stellar population of the universe
is made up of red dwarfs.
Now astronomers
have used powerful instruments on the Keck Observatory in Hawaii
to detect the faint signature of red dwarfs in eight massive,
relatively nearby galaxies called elliptical galaxies, which
are located between about 50 million and 300 million light years
away. They discovered that the red dwarfs, which are only between
10 and 20 percent as massive as the Sun, were much more bountiful
than expected.
"No one
knew how many of these stars there were," said Pieter van Dokkum,
a Yale University astronomer who led the research, which is
described in Nature's Dec.1 Advanced Online Publication. "Different
theoretical models predicted a wide range of possibilities,
so this answers a longstanding question about just how abundant
these stars are."
The team
discovered that there are about 20 times more red dwarfs in
elliptical galaxies than in the Milky Way, said Charlie Conroy
of the Harvard-Smithsonian Center for Astrophysics, who was
also involved in the research.
"We usually
assume other galaxies look like our own. But this suggests other
conditions are possible in other galaxies," Conroy said. "So
this discovery could have a major impact on our understanding
of galaxy formation and evolution."
For instance,
Conroy said, galaxies might contain less dark matter—a mysterious
substance that has mass but cannot be directly observed—than
previous measurements of their masses might have indicated.
Instead, the abundant red dwarfs could contribute more mass
than realized.
In addition
to boosting the total number of stars in the universe, the discovery
also increases the number of planets orbiting those stars, which
in turn elevates the number of planets that might harbor life,
van Dokkum said. In fact, a recently discovered exoplanet that
astronomers believe could potentially support life orbits a
red dwarf star, called Gliese 581.
"There are
possibly trillions of Earths orbiting these stars," van Dokkum
said, adding that the red dwarfs they discovered, which are
typically more than 10 billion years old, have been around long
enough for complex life to evolve. "It's one reason why people
are interested in this type of star."
Contact:
Suzanne Taylor Muzzin
suzanne.taylormuzzin@yale.edu
203-432-8555
