Washington, D.C. - Astronomers using the recently commissioned Gemini
North telescope in Hawaii have discovered a protoplanetary disk orbiting
one of the stars in a newborn quadruple star system. The dusty disk,
about three times the size of Pluto's orbit around the Sun, appears
nearly edge-on when viewed from Earth.
Only about 10 edge-on disks like this one have been discovered to
date. Out of these 10, two are in binary star systems, and this new
object is the first one discovered in a quadruple star system. The
new observations used a technique known as adaptive optics, which partially
corrects for the blurring effects of the Earth's atmosphere in images
of astronomical sources.
"This is a remarkable demonstration that adaptive optics can help
the largest ground-based telescopes reach their full potential," said
Ray Jayawardhana, a Miller Research Fellow at the University of California,
Berkeley. "We now have a powerful tool to probe the evolution of protoplanetary
disks and to look for newborn Jupiter-like planets."
"The new 8- to 10-meter telescopes really need adaptive optics to
achieve the highest possible resolution," said the other team leader,
Kevin Luhman of the Harvard-Smithsonian Center for Astrophysics (CfA).
"Adaptive optics has come of age, and has allowed us to image a protoplanetary
disk in a quadruple star system for the first time."
The findings were reported today (Monday, Jan. 7) in Washington,
DC, at the 199th meeting of the American Astronomical Society by a
team led by Jayawardhana and Luhman. Other members of the team are
Paola D'Alessio of the Instituto de Astronomia, Universidad Nacional
Autonoma de Mexico, and John Stauffer of the Space Infrared Telescope
Facility (SIRTF) Science Center at the California Institute of Technology.
Adaptive optics works by flexing a thin mirror many times a second
into just the right shape to cancel out the effects of roiling air
above the telescope. The technique has become regularly available to
astronomers only in the last few years. When used on large telescopes,
it allows astronomers to obtain images that are as sharp and sensitive
as those from space-based observatories such as the Hubble Space Telescope.
Jayawardhana, Luhman and colleagues combined the University of Hawaii's
Hokupa'a adaptive optics system with the 8-meter Gemini North telescope
to obtain high-resolution infrared images of a wide binary star system.
This binary system is only about 2 million years old, and is part of
a small cluster of stars known as MBM 12, located 900 light years from
In the new high-resolution images, one of the stars is revealed to
be a pair of two closely orbiting stars. What's more, astronomers saw
an additional, much fainter and fuzzier object nearby, with two elongated
lobes that are separated by a dark lane. This morphology is the distinct
signature of a protoplanetary disk that is being viewed edge-on and
is blocking the light from the star at its center. The star's light
reflecting off the top and bottom surfaces of the disk produces faint
nebulosities on either side of the dark lane.
"What we're looking at is an example of a dusty disk that will probably
evolve into a young planetary system over the next several million
years," explains Jayawardhana, lead author of a paper describing these
results submitted to The Astrophysical Journal. "It's the combination
of adaptive optics and a large telescope like Gemini that made this
discovery possible. Thanks to these sharp images, now we can study
the earliest stages of planet formation in remarkable detail."
"We would never have found this object with normal ground-based imaging.
To find something this faint next to a bright star and to resolve its
structure, adaptive optics on a big telescope like Gemini was essential,"
concurs Luhman. "Normally, stars with protoplanetary disks are viewed
from an angle so that we see the star easily but we see little or nothing
of the disk, which is much fainter. Here, we happen to be looking from
an angle where the disk blocks the star and makes its presence known."
By analyzing the infrared images of the edge-on disk and the quadruple
star system, the research team can learn about both the physical properties
of disks from which planets form, and the way in which stars are born
in multiple star systems.
The Gemini Observatory is an international collaboration that has
built two identical 8-meter telescopes. The Gemini North telescope
is located at Mauna Kea, Hawaii, and the Gemini South telescope is
at Cerro Pachon in central Chile. Together they provide full coverage
of both hemispheres of the sky. Both telescopes incorporate new technologies
that allow large, relatively thin mirrors under active control to collect
and focus both optical and infrared radiation from space.
The Gemini Observatory is managed by the Association of Universities
for Research in Astronomy, Inc. (AURA) under a cooperative agreement
with the National Science Foundation. United States participation in
the Gemini Project is coordinated by NSF's National Optical Astronomy
Observatory (NOAO) in Tucson, AZ, through the U.S. Gemini Program.
A Gemini North image of the protoplanetary disk and a composite image
showing a normal ground-based image of the star system plus Gemini
images are available on the Internet at: