CoRoT-21 b
CoRoT-21 b is a hot Jupiter orbiting the F8 IV star CoRoT-21 in the constellation Monoceros. It lies about 4,562 light-years from Earth and was discovered in 2012 using the transit method.
How Big Is CoRoT-21 b?
CoRoT-21 b has a radius of 14.57 times that of Earth, or 1.30 times the radius of Jupiter. Its mass is 718 times that of Earth, giving it a density of 1.36 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is CoRoT-21 b in the Habitable Zone?
CoRoT-21 b orbits inside the inner edge of the habitable zone of CoRoT-21. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of CoRoT-21: 1.642–3.832 AU (conservative: 2.080–3.633 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Orbit and Year Length
A year on CoRoT-21 b — one full orbit around CoRoT-21 — lasts 2.72 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.042 AU — closer to its star than Mercury is to the Sun.
How Was CoRoT-21 b Discovered?
CoRoT-21 b was discovered in 2012 using the transit method, with observations from CoRoT.
The transit method watches a star for the tiny, regular dip in brightness that occurs when a planet crosses in front of it. The depth and timing of these dips reveal the planet's size and orbital period.
How Far Away Is CoRoT-21 b?
CoRoT-21 b is 4,562.4 light-years (1,398.8 parsecs) from Earth. Light arriving here tonight left the planet about 4,562 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 80,298,240 years to make the journey.
Earth Similarity Index
The Earth Similarity Index (ESI) scores how physically similar a planet is to Earth, from 0 to 1, based on radius, density, escape velocity and surface temperature. CoRoT-21 b scores 0.06, ranking #5,111 of 5,565 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: CoRoT-21
CoRoT-21
- Spectral type
- F8 IV
- Surface temperature
- 6,200 K (Sun: 5,772 K)
- Mass
- 1.29 M☉
- Radius
- 1.95 R☉
- Age
- 4.1 billion years (Sun: 4.6)
Planetary System
CoRoT-21 b is the only planet known to orbit CoRoT-21 so far.
CoRoT-21 b — Complete Data
| Radius | 14.572 Earth radii (1.300 Jupiter radii) |
|---|---|
| Mass | 718.30 Earth masses (2.260 Jupiter masses) |
| Density | 1.36 g/cm³ (Earth: 5.51) |
| Orbital period | 2.72 days |
| Orbital distance | 0.042 AU |
| Earth Similarity Index | 0.06 |
| Distance from Earth | 4,562.4 light-years (1,398.8 parsecs) |
| Constellation | Monoceros |
| Discovery method | Transit |
| Discovery facility | CoRoT |
| Discovery year | 2012 |
Data: NASA Exoplanet Archive, last updated 2018-12-03. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About CoRoT-21 b
Is CoRoT-21 b habitable?
No — CoRoT-21 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is CoRoT-21 b?
CoRoT-21 b is about 4,562 light-years from Earth in the constellation Monoceros. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 80,298,240 years to get there.
How big is CoRoT-21 b compared to Earth?
CoRoT-21 b has 14.57 times the radius of Earth and about 718 times its mass.
How long is a year on CoRoT-21 b?
One orbit around CoRoT-21 takes 2.7 Earth days — short enough that 134 of its years would fit into one Earth year.
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