Exoplanet
Nicknamed 'Osiris,' the first exoplanet observed transiting its star and the first found to have an atmosphere.
| Type | Exoplanet |
|---|---|
| Orbits | HD 209458 |
| Distance from Earth | 159 ly |
| Diameter | 193,000 km |
| Mass | 1.39 × 10²⁷ kg |
| Temperature | 1,186°C |
| Orbital period | 4 days |
| Apparent magnitude | 7.65 |
| Hemisphere | Northern |
| Discovered | 1999 |
Every exoplanet here was found indirectly, by the wobble or the dimming it causes in its own star, since none is close enough to photograph in real detail.
At 193,000 km across, HD 209458 b is 15 times the diameter of Earth.
Its mass is 232 times the mass of Earth.
A single orbit takes 3.5 days.
The light reaching us from HD 209458 b tonight left it around 159 years ago.
An average temperature of 1,459 K works out at 1,186 degrees Celsius, warmer than the 15 degrees Earth averages.
It has been on record since 1999.
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