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Reflected Light from a Giant Planet’s Periastron Passage

14 Dec 2015, 22:00 UTC
Reflected Light from a Giant Planet’s Periastron Passage
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HD 20782b is a giant planet with at least twice the mass of Jupiter. What makes HD 20782b bizarre is that its orbit around its host star, a Sun-like star, is the most eccentric orbit known for any exoplanet. HD 20782b takes 597 days to go around its host star once in an extremely elongated orbit with eccentricity 0.956. Once per orbit, HD 20782b swings in for a brief fiery encounter with its parent star. At closest approach (periastron), HD 20782b is only 0.061 AU from its host star, and the planet is 2.73 AU from its host star at its furthest (apastron). The highly elongated orbit of HD 20782b means that the intensity of flux it receives from its host star varies from 3.6 to over 7000 times the intensity of flux Jupiter receives from the Sun. Stephen R. Kane et al. (2015) present evidence for reflected light from HD 20782b during the planet’s periastron passage. The signature of reflected light is indicated as a tiny increase in the brightness of the planet’s host star as reflected light from the planet adds to the overall observed brightness of the host star. Short-period giant planets tends to have relatively low albedos (i.e. ...

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