description HD 209458 Overview
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HD 209458 ranks #29 of 217 in the Star ranking, behind Regulus, ahead of Fomalhaut.
Landmark transiting exoplanet host, atmospheric studies pioneer, strong exoplanet-science reputation.
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Why is HD 209458 b nicknamed Osiris?
HD 209458 b is informally called Osiris, after the Egyptian god associated with death and rebirth. The nickname became especially fitting after astronomers detected hydrogen escaping from the hot planet's atmosphere.
What made HD 209458 b historically important?
In 1999, HD 209458 b became the first known exoplanet observed crossing, or transiting, its host star. Its transits allowed astronomers to determine its radius and study an exoplanet atmosphere directly.
What kind of planet orbits HD 209458?
HD 209458 b is a hot Jupiter, a large gas giant orbiting extremely close to its Sun-like star. It completes an orbit in only a few days, producing regular and measurable dips in the star's light.
Where is the HD 209458 system?
HD 209458 lies in the constellation Pegasus, roughly 150 light-years from Earth. The star is similar enough to the Sun that its transiting giant planet became a benchmark for exoplanet research.
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