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Posted by baalke on August 6, 2007, 3:11 pm
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http://www.lowell.edu/media/releases.php?release=3D20070806
FOR IMMEDIATE RELEASE
Largest Transiting Extrasolar Planet Found Around A Distant Star
Lowell Observatory
August 6, 2007
Flagstaff, Ariz.- An international team of astronomers with the
Trans-atlantic Exoplanet Survey announce today the discovery of
TrES-4,
a new extrasolar planet in the constellation of Hercules. The new
planet
was identified by astronomers looking for transiting planets - that
is,
planets that pass in front of their home star - using a network of
small
automated telescopes in Arizona, California, and the Canary Islands.
TrES-4 was discovered less than half a degree (about the size of the
full Moon) from the team's third planet, TrES-3.
"TrES-4 is the largest known exoplanet," said Georgi Mandushev, Lowell
Observatory astronomer and the lead author of the paper announcing the
discovery. "It is about 70 percent bigger than Jupiter, the Solar
System's largest planet, but less massive, making it a planet of
extremely low density. Its mean density is only about 0.2 grams per
cubic centimeter, or about the density of balsa wood! And because of
the
planet's relatively weak pull on its upper atmosphere, some of the
atmosphere probably escapes in a comet-like tail."
The new planet TrES-4 was first noticed by Lowell Observatory's Planet
Search Survey Telescope (PSST), set up and operated by Edward Dunham
and
Georgi Mandushev. The Sleuth telescope, maintained by David
Charbonneau
(CfA) and Francis O'Donovan (Caltech), at Caltech's Palomar
Observatory
also observed transits of TrES-4, confirming the initial detections.
TrES-4 is about 1400 light years away and orbits its host star in
three
and a half days. Being only about 4.5 million miles from its home
star,
the planet is also very hot, about 1,600 Kelvin or 2,300 degrees
Fahrenheit.
"TrES-4 appears to be something of a theoretical problem," said Edward
Dunham, Lowell Observatory Instrument Scientist. "It is larger
relative
to its mass than current models of superheated giant planets can
presently explain. Problems are good, though, since we learn new
things
by solving them."
"We continue to be surprised by how relatively large these giant
planets
can be," adds Francis O'Donovan, a graduate student in astronomy at
the
California Institute of Technology who operates one of the TrES
telescopes. "But if we can explain the sizes of these bloated planets
in their harsh environments, it may help us understand better our own
Solar System planets and their formation."
By definition, a transiting planet passes directly between the Earth
and
the star, blocking some of the star's light and causing a slight drop
in
its brightness. 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 observations are completed for a particular field -
usually over an approximate two-month period - astronomers measure
very
precisely the light from every star in the field in order to detect
the
possible signature of a transiting planet. "TrES-4 blocks off about
one
percent of the light of the star as it passes in front of it," said
Mandushev. "With our telescopes and observing techniques, we can
measure
this tiny drop in the star's brightness and deduce the presence of a
planet there."
Not only is the planet TrES-4 mysterious and intriguing, but so is its
host star cataloged as GSC 02620-00648. Georgi Mandushev explains:
"The
host star of TrES-4 appears to be about the same age as our Sun, but
because it is more massive, it has evolved much faster. It has become
what astronomers call a 'subgiant', or a star that has exhausted all
of
its hydrogen fuel in the core and is on its way of becoming a 'red
giant', a huge, cool red star like Arcturus or Aldebaran."
In order to help confirm they had found a planet, G=E1sp=E1r Bakos of the
Hungarian Automated Telescope Network (HATNet) and Harvard's Guillermo
Torres 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 the TrES
team had indeed found a new planet. In order to measure accurately the
size and other properties of TrES-4, astronomers also made follow up
observations with bigger telescopes at Lowell Observatory and Fred L.
Whipple Observatory in Arizona.
The authors of the paper "TrES-4: A Transiting Hot Jupiter of Very Low
Density", accepted for publication in the Astrophysical Journal, are:
Georgi Mandushev and Edward Dunham of Lowell Observatory; Francis T.
O'Donovan and Lynne Hillenbrand of the California Institute of
Technology; David Charbonneau, Guillermo Torres, David Latham, G=E1sp=E1r
Bakos, Alessandro Sozzetti, and Jos=E9 Fern=E1ndez of the
Harvard-Smithsonian Center for Astrophysics; Mark Everett and Gilbert
Esquerdo of the Planetary Science Institute; Markus Rabus and Juan
Belmonte of Instituto de Astrof=EDsica de Canarias in Tenerife, Spain;
and
Timothy Brown of the Las Cumbres Observatory Global Telescope.
This research is funded by NASA through the Origins of Solar Systems
Program.
FOR MORE INFORMATION
Description of the TrES Network
<http://www.lowell.edu/Research/OtherResearch/index.html>
end
About Lowell Observatory
Lowell Observatory is a private, non-profit research institution
founded
in 1894 by Percival Lowell. The Observatory has been the site of many
important findings including the discovery of the large recessional
velocities (redshift) of galaxies by Vesto Slipher in 1912-1914 (a
result that led ultimately to the realization the universe is
expanding), and the discovery of Pluto by Clyde Tombaugh in 1930.
Today,
Lowell's 19 astronomers use ground-based telescopes around the world,
telescopes in space, and NASA planetary spacecraft to conduct research
in diverse areas of astronomy and planetary science. The Observatory
welcomes 70,000 visitors each year to its Mars Hill campus in
Flagstaff,
Arizona for a variety of tours, telescope viewing, and special
programs.
Lowell Observatory currently has four research telescopes at its
Anderson Mesa dark sky site east of Flagstaff, and is building a 4-
meter
class research telescope, the Discovery Channel Telescope, in
partnership with Discovery Communications.
CONTACT
Steele Wotkyns
(928) 233-3232
steele@lowell.edu
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