Preprint : Press Release : TrES : Finding TrES-2 : TrES-2 Details : TrES-2 Press
TrES-2 and the Transatlantic Exoplanet Survey
The Transatlantic Exoplanet Survey (TrES) is a network of telescopes, Sleuth, PSST and STARE, that is used to search the skies for gas giants orbiting other stars that occassionaly cross the disk of the stars. The TrES team had our first successful detection of such a transiting planet with the discovery of TrES-1. We are pleased to announce the discovery of our second planet, TrES-2, which is the most massive of the known transiting planets within ~750 light years.
TrES-2 was identified from observations made with the 10-cm telescopes, Sleuth and PSST, pictured above. When the brightness of the star TrES-2 was monitored over several months, numerous 1.4% transits of the star were detected. The light curve derived from these TrES observations is shown below (click for a larger version). Also shown are the light curves from more recent observations of TrES-2, made at various optical wavelengths. These follow-up observations show a consistent transit depth, independent of the wavelength. (A wavelength-dependent depth would indicate that the eclipsing system was in fact an multiple-star system, not a planet orbiting a star.)
Confirmation of the planet required the use of one of the 10-m Keck telescopes, the world's largest optical telescopes. This diagram (Credit: Scott Kardel, Palomar Observatory) illustrates the much larger light gathering area of the Keck mirrors. The wobble of the star caused by the presence of a massive companion was measured, and proved to be consistent with a planetary companion (a radial velocity semi-amplitude of 182 m/s).
Much about the new planet is novel. It is the most massive (1.28 Jupiter masses) of the known transiting planets that orbit around nearby, bright stars. It crosses the star at a high stellar latitude (see illustration below; click for an animation). It is the first transiting planet to be found in the 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.
The images above show you how to find TrES-2. Click on each to get an enlarged image.
The image on the left is a 45 degrees x 45 degrees map of the sky around TrES-2, centered on the star TrES-2. You can see the constellations Cygnus, Lyra, Draco and Hercules, as well as very bright stars, like Debeb and Vega. Only stars brighter than V = 6.5 magnitudes are shown. With V = 11.4 magnitudes, the star TrES-2 is 100 times fainter than the faintest star shown!
The image on the right is a Digitized Sky Survey image, which is 15 arcminutes on a side. Again, the image is centered on the star TrES-2, which here is visible. The area shown is 1/32400 that of the image on the left.
Position: 19h 07m 14.03s +49d 18m 59.3s (J2000)
V Magnitude: 11.4 magnitudes
Spectral Type: G0V
Mass: 1.08 solar masses
Radius: 1.00 solas masses
Orbital Period: 2.47063 days
Semi-Major Axis: 0.0367 AU = 5.5 million kilometers
Orbital Inclination: 83.9 degrees
Mass: 1.28 Jupiter masses
Radius: 1.24 Jupiter radii
TrES-2 Press