description HD 209458 Overview
HD 209458 is a Sun-like G-type main-sequence star located in the constellation Pegasus, approximately 159 light-years from Earth. It hosts the exoplanet HD 209458 b, which was the first exoplanet to be detected by the transit method in 1999. Additionally, the planet holds the distinction of being the first observed outside the solar system to have an atmosphere, identified through spectroscopic analysis.
insights Ranking position
HD 209458 ranks #29 of 212 in the Star ranking, behind Regulus, ahead of Fomalhaut.
help HD 209458 FAQ
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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