CoRoT-21 b
CoRoT-21 b is a hot Jupiter orbiting the F8 IV star CoRoT-21 in the constellation Monoceros. It 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.
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 #5,114 of 5,568 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 |
| 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 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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