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Posted by baalke on September 10, 2006, 11:57 pm
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http://pr.caltech.edu/media/Press_Releases/PR12890.html
Jupiter-Sized Transiting Planet Found by Astronomers Using Novel
Telescope Network
Caltech News Release
September 8, 2006
PASADENA, Calif.--Our home solar system may be down by a planet with
the
recent demotion of Pluto, but the number of giant planets discovered in
orbit around other stars continues to grow steadily. Now, an
international team of astronomers has detected a planet slightly larger
than Jupiter that orbits a star 500 light-years from Earth in the
constellation Draco.
Unlike the mythological names associated with the solar system's
planets, the newly discovered planet is known by "TrES-2" and passes in
front of the star "GSC 03549-02811" every two and a half days.
The new planet is especially noteworthy because it was identified by
astronomers looking for transiting planets (that is, planets that pass
in front of their home star) with a network of small automated
telescopes. The humble telescopes used in the discovery consist of
mostly amateur-astronomy components and off-the-shelf 4-inch camera
lenses. This is the third transiting planet found using telescopes
similar to those used by many amateur astronomers.
By definition, a transiting planet passes directly between Earth and
the
star, causing a slight reduction in the light in a manner similar to
that caused by the moon's passing between the sun and Earth during a
solar eclipse. According to Francis O'Donovan, an Irish graduate
student
in astronomy at the California Institute of Technology, "When TrES-2 is
in front of the star, it blocks off about one and a half percent of the
star's light, an effect we can observe with our TrES telescopes.
"We know of about 200 planets around other stars," says O'Donovan, lead
author of the paper announcing the discovery in an upcoming issue of
the
Astrophysical Journal, "but it is only for the nearby transiting
planets
that we can precisely measure the size and mass of the planet, and
hence
study its composition. That makes each new transiting planet an
exciting
find. And because TrES-2 is the most massive of the nearby transiting
planets, it sets a new limit to our understanding of how these gas
planets form around stars."
The planet TrES-2 is also noteworthy for being the first transiting
planet in an area of the sky known as the "Kepler field," which has
been
singled out as the targeted field of view for the upcoming NASA Kepler
mission. Using a satellite-based telescope, Kepler will stare at this
patch of sky for four years, and should discover hundreds of giant
planets and Earth-like planets. Finding a planet in the Kepler field
with the current method allows astronomers to plan future observations
with Kepler that include searching for moons around TrES-2.
And finally, the research team hails the discovery as the second
transiting "hot Jupiter" found with the Trans-Atlantic Exoplanet Survey
(TrES), an effort involving the "Sleuth" telescope at Caltech's Palomar
Observatory in San Diego County, the Planet Search Survey Telescope
(PSST) at Lowell Observatory near Flagstaff, Arizona, and the "STellar
Astrophysics and Research on Exoplanets (Stare) telescope in the Canary
Islands. The name of the planet, TrES-2, is derived from the name of
the
survey.
To look for transits, the small telescopes are automated to take
wide-field timed exposures of the clear skies on as many nights as
possible. When an observing run is completed for a particular
field-usually over an approximate two-month period-the data are run
through software that corrects for various sources of distortion and
noise.
The end result is a "light curve" for each of thousands of stars in the
field. If the software detects regular variations in the light curve
for
an individual star, then the astronomers do additional work to see if
the source of the variation is indeed a transiting planet. One possible
alternative is that the object passing in front of the star is another
star, fainter and smaller.
In order to confirm they had found a planet, O'Donovan and his
colleagues switched from the 10-centimeter TrES telescopes to one of
the
10-meter telescopes at the W. M. Keck Observatory on the summit of
Mauna
Kea, Hawaii. Using this giant telescope, they confirmed that they had
found a new planet. O'Donovan says, "Each of us had spent countless
hours working on TrES at that point, and we had suffered many
disappointments. All our hard work was made worthwhile when we saw the
results from our first night's observations, and realized we had found
our second transiting planet."
TrES-2 was first spotted by the Sleuth telescope, which was set up by
David Charbonneau, formerly an astronomer at Caltech who is now at the
Harvard-Smithsonian Center for Astrophysics and is a coauthor of the
paper. The PSST, which is operated by Georgi Mandushev and Edward
Dunham
(coauthors from Lowell Observatory), also observed transits of TrES-2,
confirming the initial detections.
The other authors of the paper are David Latham and Guillermo Torres of
Harvard-Smithsonian; Alessandro Sozetti of Harvard-Smithsonian and the
INAF-Osservatorio Astronomico di Torino; Timothy Brown of the Las
Cumbres Observatory Global Telescope; John Trauger of the Jet
Propulsion
Laboratory; Markus Rabus, Jos? Almenara, Juan Belmonte, and Hans Deeg
of
the Instituto de Astrof?sica de Canarias; Roi Alonso of the
Laboratoire
d'Astrophysique de Marseille and the Institute de Astrof?sica de
Canarias; Gilbert Esquerdo of Harvard-Smithsonian and the Planetary
Science Institute in Tucson; Emilio Falco of Harvard-Smithsonian; Lynne
Hillenbrand of Caltech; Anna Roussanova of MIT; Robert Stefanik of
Harvard-Smithsonian; and Joshua Winn of MIT.
Contact: Robert Tindol (626) 395-3631 tindol@caltech.edu
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