HD 209458 b

HD 209458 b, also nicknamed Osiris after the egyptian god, is an exoplanet that orbits the solar analog HD 209458 in the constellation Pegasus,159 light-years (49 parsecs) from the Solar System. The radius of the planet's orbit is 0.047 AU (7.0 million km, 4.4 million mi), or one-eighth the radius of Mercury's orbit (0.39 AU (36 million mi; 58 million km)). This small radius results in a year that is 3.5 Earth-days long and an estimated surface temperature of about 1,000 °C (2,000 °F; 1,000 K). Its mass is 220 times that of Earth (0.69 Jupiter masses) and its volume is some 2.5 times greater than that of Jupiter. The high mass and volume of HD 209458 b indicate that it is a gas giant. HD 209458 b represents a number of milestones in extraplanetary research. It was the first of many categories:
* a transiting extrasolar planet
* the first planet detected through more than one method
* an extrasolar planet known to have an atmosphere
* an extrasolar planet observed to have an evaporating hydrogen atmosphere
* an extrasolar planet found to have an atmosphere containing the elements oxygen and carbon
* one of the first two extrasolar planets to be directly observed spectroscopically
* the first extrasolar gas giant to have its superstorm measured
* the first planet to have its orbital speed measured, determining its mass directly.
Based on the application of newer theoretical models, as of April 2007, it is thought to be the first extrasolar planet found to have water vapor in its atmosphere. In July 2014, NASA announced finding very dry atmospheres on HD 209458 b and two other exoplanets (HD 189733 b and WASP-12b) orbiting Sun-like stars. Further, a magnetic field around HD 209458 b was inferred from the way hydrogen was evaporating from the planet. It is the first (indirect) detection of a magnetic field on an exoplanet. The magnetic field is estimated to be about one tenth as strong as Jupiter's.
Category:Exoplanets