A few years ago, astronomers discovered a new kind of planet -- a so-called "hot Jupiter," a planet whose mass is similar to that of Jupiter, but whose orbit is very close to its star and whose atmosphere therefore has a temperature of over a thousand degrees kelvin. Besides being fascinating heavenly bodies in their own right, extra-solar planets offer important clues about how our own solar system formed, and why the Earth and the other planets in the solar-system have the properties that they do.
A team of six CfA astronomers, Matthew Holman, David Latham, David Charbonneau, Guillermo Torres, Alessandro Sozzetti, and Jose Fernandez, have been working to improve our understanding of the interior and atmospheric structure of hot Jupiters. Their observational technique is to monitor closely the light of one such object whose orbit fortuitously takes it across the face of its star as seen from the Earth (a "transit"). Using the KeplerCam instrument at SAO's Fred L. Whipple Observatory in Arizona, the team monitored three transits of this known hot Jupiter, whose orbital period is just 2.47 Earth-days. The current observational results on hot Jupiters were puzzling because they implied these planets were larger than the simple models could explain. In their new paper, the scientists report that the radius of the object is 1.222 Jupiter-radii, its mass is 1.198 Jupiter-masses, and the effective temperature of its atmosphere is a scalding 5850 degrees kelvin. Their results, which are consistent with theoretical models, makes this object the most massive known transiting exoplanet, and are significant for refining our knowledge of these strange planets.