Three small, faint stars, apparently locked in the gravitational
embrace of much larger and brighter companions, have been discovered
in the first light from a new infrared camera with innovative optics
on the 100-inch telescope at the Mount Wilson Observatory in
Pasadena, California.

“This is the first time the historic Mount Wilson telescope has
looked at the universe through this new infrared eye, and already it
is making new discoveries,” says Jian Ge, assistant professor of
astronomy and astrophysics at Penn State and leader of the research
team, which also developed the infrared camera. The discoveries of
the faint stars, to be published in the June issue of Astrophysical
Journal Letters and the July issue of the Astronomical Journal, “mark
the beginning of a new era in the use of the 100-inch telescope for
discovering very interesting faint objects in orbit around brighter
stars, such as brown dwarfs, which are neither stars nor planets,”
says Robert Jastrow, director of the Mount Wilson Institute.

One innovative technique that Ge and his team designed into the new
infrared camera is a specially shaped mask they installed over the
“pupil” of the camera’s eye to allow fainter companions to be seen
around bright objects. The shaped pupil mask that Ge’s team used is
an improvement over the circular masks that astronomers have been
using to block the light from a bright star in an attempt to see a
near-by fainter object, much like the appearance of the corona during
a total eclipse of the Sun. The shaped pupil mask is a solid
light-blocking circle into which Ge and his team have cut a dozen
strategically placed eye-shaped openings. “The image resulting from
the first use of the device revealed areas of greater contrast that
allowed us to find one of the faint dwarf stars,” Ge says. “The
technique potentially improves contrast in images by more than
tenfold compared to current techniques.”

This new technique was proposed in 2001 by David Spergel at Princeton
University, who comments, “This is an exciting and beautiful result.
Jian and his team have done a remarkable job in taking a theoretical
concept and using it to obtain an exciting scientific result. This
type of coronagraph likely will be the principal instrument on the
successor to the Hubble Space Telescope–an instrument capable of
imaging Earth-like planets around nearby stars. Jian’s work at Mount
Wilson is a pathfinder for the Terrestrial Planet Finder being
planned by NASA.”

The dwarf stars Ge and his team discovered are less than one-tenth
the mass of the Sun and give off a dark-red glow that is dimmer than
our hotter Sun’s yellow light. One of the stars is about 50 light
years from Earth, another is about 27 light years away, and the third
is at a distance of about 200 light years. Astronomers consider
these stars to be nearby in our solar system’s corner of the galaxy.
“Our initial conservative estimate is that these are little
very-dark-red dwarf stars,” says Abhijit Chakraborty, a postdoctoral
scholar on Ge’s team. “Their mass is only about 80 to 100 times that
of Jupiter, which itself is a thousand times smaller than our Sun.
They have barely enough mass to burn the hydrogen in their cores, and
are close to the size and luminosity of less-massive brown-dwarf
objects, which don’t have enough mass to ignite into stars at all.”

Astronomers are in need of new techniques for imaging a dim object
such as an Earth-like planet near a bright star like our Sun because,
with current techniques, the star’s brightness hides its dimmer
near-by companions. “This discovery demonstrates that our new
techniques can help reveal dim companions of larger, brighter stars,”
says John H. Debes, a graduate student in Ge’s lab. “These three
first-light discoveries demonstrate the potential to use the Mount
Wilson and similar telescopes to obtain much better images in
high-contrast situations.”

Telescopes at the Mount Wilson Observatory have been used since 1908
to make important discoveries about the expansion of the universe,
the location of galaxies, and the size of stars, paving the way for
the era of modern astronomy. In the mid 1990s, the observatory was
upgraded with advanced “adaptive optics” technology, which
compensates for image distortions caused by the turbulence in the
Earth’s atmosphere. “Adaptive optics takes away the twinkling that
you see when you look up at the stars in the night sky” Jastrow
explains. “Adding adaptive optics made the image quality of the
Mount Wilson telescope ten times sharper–as good as if the telescope
were in orbit above the Earth’s atmosphere.”

But light pollution from nearby Los Angeles limited the telescope’s
capabilities in visible light, so Ge decided to build a camera that
would capture infrared light coming from objects in space. One
advantage of using infrared light is that it cuts right through
optical light pollution. Another advantage is that a comparatively
cool object like a brown dwarf glows most brightly in infrared
wavelengths. “We developed the Penn State IR Imager and Spectrograph
(PIRIS) to be a test bed for new infrared technology to image faint
objects, including planets, for the Terrestrial Planet Finder (TPF)
mission,” explains Ge, who recently joined TPF teams at Princeton
University and Ball Aerospace & Technologies Inc. that are studying
coronagraph technology.

Ge also has invented and developed other instrument technologies that
he and his colleagues at Penn State are in the process of developing
further as part of his lab’s $2-million instrumentation program for
the discovery of extra-solar planets–including Earth-like
planets–and galaxies in the early stages of their formation. “We
are using our PIRIS camera and the 100-inch Mount Wilson telescope to
test a suite of components that we are developing for getting better
images and better spectroscopy from infrared instruments,” Ge says.
The researchers also are working to improve the compactness and
reduce the cost of these instruments so they can be used on space
telescopes, where size and weight are at the highest premium, as well
as on other large ground-based telescopes.

“We hope these observing techniques will help us find and study many
fainter dwarf stars and massive planets in binary systems so we can
learn how planets form within such systems,” Ge says. A tested
theory of planet formation would help to point astronomers toward
stars that are most likely to have Earth-like planets orbiting them.
“None of the planets discovered elsewhere in the universe up to now
have been very much like our Earth,” Ge comments. “The challenge now
is to find Earth-like planets around other stars.”

This research was supported by the National Aeronautics and Space
Administration and the Penn State Eberly College of Science.

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Jian Ge: or +1-814-863-9553

Barbara Kennedy (PIO): or +1-814-863-4682


Robert Jastrow: 310-441-9136, or by e-mail through Kate Barlow:

Bob Eklund (PIO): or +1-310-333-3478