An object appears to be forming from gas and dust around the star
AB Aurigae.
March 26, 2008
Scientists are one step closer to understanding how
new planets form, thanks to research funded by the National Science
Foundation (NSF) and carried out by a team of astrophysicists at the
American Museum of Natural History.
Ben R. Oppenheimer, assistant curator in the
museum's Department of Astrophysics, and his colleagues have used
the Lyot Project coronograph attached to a U.S. Air Force telescope
on Maui, Hawaii, to construct an image of material that seems to be
coalescing into a body from the gas and dust cloud surrounding AB
Aurigae, a well-studied star. The body is either a planet or a brown
dwarf--something with mass between a star or a planet. Brown dwarfs
have been found orbiting stars since a team that included
Oppenheimer first discovered one in 1995.
The research results, accepted for publication in
June's Astrophysical Journal, represent a significant step
toward direct imaging and the study of exoplanets, which orbit stars
other than the Sun, and may advance theories of planet and brown
dwarf formations.
"The research builds upon Dr. Openheimer's past
successes in the detection of a brown dwarf and several debris disks
and take advantage of an improved, deformable, secondary mirror
which was installed at the telescope facility in 2006," said NSF
Program Manager Julian Christou. "The image produced speaks directly
to the biggest, unresolved question of planet formation--how the
thick disk of debris and gas evolves into a thin, dusty region with
planets." Young stars generally have a lot of material caught in
their gravitational pull--material that organizes itself into a disc
over time. Astronomers believe planets form in this disc.
The image produced by Oppenheimer's team shows a
horseshoe-shaped void in the disc with a bright point appearing as a
dot in the void.
"The deficit of material could be due to a planet
forming and sucking material onto it, coalescing into a small point
in the image and clearing material in the immediate surroundings,"
Oppenheimer said. "It seems to be indicative of the formation of a
small body, either a planet or a brown dwarf."
AB Aurigae is well-studied because it is young,
between one and three million years old, and can therefore provide
information on how stars and objects that orbit them form. One
unresolved question about planet formation is how the initial thick,
gas-rich disk of debris evolves into a thin, dusty region with
planets. The observation of stars slightly older than AB Aurigae
shows that at some point the gas is removed, but no one knows how
this happens. AB Aurigae could be in an intermediate stage, where
the gas is being cleared out from the center, leaving mainly dust
behind.
"More detailed observations of this star can help
solve questions about how some planets form, and can possibly test
competing theories," says Oppenheimer. And if this object is a brown
dwarf, our understanding of them must be revamped as brown dwarfs
are not believed to form in circumstellar materials, Oppenheimer
said.
-NSF-
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