Detection of Thermal Emission From An Extrasolar Planet
After the confirmation of TrES-1 as a transiting planet, Dr. David Charbonneau
(formally of the STARE team, now of the Harvard-Smithsonian Center for
Astrophysics and a member of the TrES
Network with Sleuth) applied for, and received, observing time
with the Spitzer Space Telescope. Observations in the
infra-red (using the Infrared Array Camera, IRAC) were made while TrES-1
passed behind its parent star. Since the star produces most of its
light in the visible
portion of the spectrum and the planet re-radiates the energy it absorbs at
longer wavelengths, the planet can be 'seen' through the glare of the star
by observing in the infra-red (see figure below).
The observed dimming indicates that the star is blocking light
emitted by the planet itself (see plot below - red line is the best-fit model
eclipse). This is the first ever
direct observation of photons emitted by a planet orbiting another star.
The measured thermal emission was then used to infer the effective temperature
of the planet, 1100 K. The timing of the secondary eclipse was used to infer
that TrES-1 has a negligible orbital eccentricity.
For More Information:
Go to Spitzer Press Release -
www.spitzer.caltech.edu/Media/releases/ssc2005-09/release.shtml
Download preprint accepted by
Astrophysical Journal Letters
(273Kb PDF file).
Visit the STARE web site
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