June 1
Astronomers using the Trans-atlantic Exoplanet Survey (TrES) network of small telescopes are announcing today their discovery of a planet twice the mass of Jupiter that passes in front of its star every 31 hours. The planet is in the constellation Hercules and has been named TrES-3 as the third planet found with the TrES network.
The new planet is the 15th transiting planet discovered so far-in other words, it is a planet that passes directly in front of its home star as seen from Earth.
When a transiting planet passes directly between Earth and the star, the result is 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. When TrES-3 is in front of the star, it blocks off about 2.5 percent of the star's light, which is an effect observed with the TrES telescopes.
TrES-3 is an unusual planet as it orbits its parent star in just 31 hours.That is to say, the year on this planet lasts less than one and a third Earth days. This means it is very close to the star--much closer than Mercury is to the Sun--and so is heated by the intense starlight to about 1,500 degrees Kelvin. The planet is about 1,500 light-years from Earth.
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--astronomers measure very precisely the light from every star in the field in order to detect the possible signature of a transiting planet.
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