Exoplanet Light Curve

August 10, 2008

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Provided by: Anthony Ayiomamitis
Summary Author and Editor: Anthony Ayiomamitis, Jim Foster, Stu Witmer

An exoplanet, or extrasolar planet, is a planet found outside our own solar system. In 2007 a gas giant exoplanet was found orbiting the star known as GSC 03089-00929 in the constellation of Hercules. This planet, named TrES-3, because it is the third exoplanet planet found by The Trans-Atlantic Exoplanet Survey, is much larger than Jupiter and has the density of balsa-wood. Of interest in this discovery is the exoplanet's proximity to its parent star and its degenerative orbit. In other words, because of its orbit, at some point this exoplanet will collide with its star.

What makes the photometry of this exoplanet most challenging is the fact that its host star is quite dim (magnitude 12.17), and the transit depth of 25 milli-magnitude (mmag) translates to very small changes in the overall dimness of the parent star during the exoplanet transit (from 12.170 to 12.195 magnitude).

The brightness of a celestial object as seen from earth is often referred to as its apparent magnitude (m) and is given a numerical value with the brightest stars being first magnitude and sixth magnitude being those just visible to the unaided eye. First magnitude objects are 100 times brighter than those of the sixth magnitude. Venus has an apparent magnitude of about -4, while the Sun is about -27.

The light curve above, during TrES-3's 105-minute transit across the face of its star was captured using only a 6.3" (about 15 cm) apochromatic refractor telescope. One can only wonder how sunrises and sunsets will appear on this foreign world with a 31 hour year, if at all, and whether it has but one moon, similar to our own, or many, and if its atmosphere is a playground for aurorae and meteor showers. Light curve observed in April of 2008 from near Athens, Greece.

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