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A&A press release: First ground-based detection of light from transiting exoplanets (15 Jan. 2009)
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- Published on 12 January 2009
A&A press release
Released on January 15th, 2009
|
First ground-based detection of light from transiting exoplanets |
Based on the articles:
“Ground-based K-band detection
of thermal emission from the exoplanet TrES-3b”, by E.J.W. De Mooij and I.A.G. Snellen
and
“Ground-based secondary eclipse detection of the very-hot Jupiter OGLE-TR-56b”, by D. K. Sing and M. Lopez-Morales
Published in Astronomy & Astrophysics Letters, 2009, vol. 493-2, pp. L31-L38.
This week, Astronomy & Astrophysics
is publishing the first ground-based detections of thermal emission
from transiting exoplanets. Up to now, detections of this kind have
only been made from space. Two independent teams are now presenting
detections with ground-based telescopes of the thermal emission from
transiting hot Jupiters.
Transiting exoplanets
are routinely detected when they pass in front of their parent star as
viewed from the Earth, which only happens by chance. The transit event
causes a small drop in the observed starlight, which can then be
detected. Fifty-five exoplanets have been detected this way since the
observation of the first transiting planet HD 209458 b in 1999. When
the planet revolves around its star or when it goes behind, the light
coming from the system also varies, though the resulting smaller
modulation is much harder to detect. This is mostly due to the small
amount of light emitted by these exoplanets which are believed to be as
dark as coal and reflect little of the incoming starlight. Fortunately,
some of these planets are very hot, thus emitting light, mostly at
infrared wavelengths. Up to now, detections of this kind have only been
made using the Spitzer infrared space telescope. This week, Astronomy
& Astrophysics is publishing the two first
ground-based detections of thermal emission from transiting,
hot-Jupiter exoplanets, from two independent teams of astronomers that
used different approaches.
One team includes Ernst De Mooij and Ignas Snellen (University of
Leiden, Netherlands) who used the William Hershel 4.2 meter telescope
in La Palma (Canary Islands, Spain) to observe the star TrES-3 and its
planet TrES-3b. To be able to detect the light coming from the planet,
they observed the planet exactly at the time when it passes behind the
star. They observed the event at infrared wavelengths, where the planet
is at its brightest compared to the star (even if the planet is still
much fainter than the star!) As they detected the light coming from the
planet, they estimated the temperature of its atmosphere to about 2000
Kelvins. This indicates that the day side of the planet is extremely
hot.
The other team, involving David Sing (IAP, France) and Mercedes
Lopez-Morales (Carnegie Institution of Washington, USA), had a
different approach. They looked at a much fainter star and its planet,
OGLE-TR-56b. This planet is one of the most irradiated planets known so
far, both because the planet is very close to the star and because the
star is very hot. To detect the slight modulation in light that occurs
when the planet passes behind its star, they used the 8 meter Very
Large Telescope (ESO, Chile) and the 6.5 meter Magellan Telescopes (Las
Campanas, Chile) and were able to observe this event at visible
wavelengths. Indeed, the planet OGLE-TR-56b is heated so much by its
star that it emits detectable amounts of light in the visible
wavelengths, and not only in the infrared as TrES-3b does. Hence, Sing
and Lopez-Morales measured the record-high temperature of a planetary
atmosphere: 2700 Kelvins. As in the case of TrES-3b, such a high
day-side temperature indicates that winds cannot redistribute the heat
efficiently from the day side to the night side.
Fig. 1 - Artist's impression of the star OGLE-TR-56 and its planet, as the planet is passing behind the star. © D. Sing (IAP) / A&A.
These two independent results are very interesting for astronomers and planetary scientists because they allow a direct probe of the temperature of these planetary atmospheres, and because they show that such measurements can be made from ground-based observatories, and not only when using space telescopes.
Ground-based K-band detection of thermal emission from the exoplanet TrES-3b, by E.J.W. De Mooij and I.A.G. Snellen. Astronomy & Astrophysics Letters, 2009, volume 493-2, pp. L31. Full article available in PDF format
Ground-based secondary eclipse detection of the very-hot Jupiter OGLE-TR-56b, by D. K. Sing and M. Lopez-Morales. Astronomy & Astrophysics Letters, 2009, volume 493-2, pp. L35. Full article available in PDF format
Contacts:
- Science:
Ernst de
Mooij
Leiden University, Netherlands
Email: demooij (at) strw.leidenuniv.nl
Phone: +31 (0)71 527 8492
Dr.
Mercedes Lopez-Morales
Carnegie Institution of Washington, USA
Email: mercedes (at) dtm.ciw.edu
Phone: +34 922 605 379
Dr.
David. Sing
Institut d'Astrophysique de Paris, CNRS/UPMC, France
Email: sing (at) iap.fr
Phone: +33 (0)1 44 32 80 22
Dr.
Ignas Snellen
Leiden University, Netherlands
Email: snellen (at) strw.leidenuniv.nl
Phone: +31 (0)71 527 5838
- Press office:
Dr.
Jennifer Martin
Astronomy & Astrophysics
61, avenue de l'Observatoire
75014 Paris, France
Email: aanda.paris (at) obspm.fr
Phone: +33 1 43 29 05 41
© Astronomy & Astrophysics 2009