CD Cet b
CD Cet b is a super-Earth orbiting the M5.0 V star CD Cet in the constellation Cetus. It lies about 28 light-years from Earth and was discovered in 2020 using the radial velocity method.
Is CD Cet b in the Habitable Zone?
CD Cet b orbits inside the inner edge of the habitable zone of CD Cet. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of CD Cet: 0.044–0.118 AU (conservative: 0.056–0.111 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on CD Cet b
The equilibrium temperature of CD Cet b is about 464 K (191 °C) — hotter than anywhere on Earth. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 8.60 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on CD Cet b — one full orbit around CD Cet — lasts 2.29 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.019 AU — closer to its star than Mercury is to the Sun.
How Was CD Cet b Discovered?
CD Cet b was discovered in 2020 using the radial velocity method, with observations from Calar Alto Observatory.
The radial velocity method measures the subtle wobble of a star caused by the gravitational pull of an orbiting planet, visible as periodic shifts in the star's light spectrum. The size of the wobble reveals the planet's minimum mass.
How Far Away Is CD Cet b?
CD Cet b is 28.1 light-years (8.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 1998. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 494,560 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. CD Cet b scores 0.40, ranking #455 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: CD Cet
CD Cet
- Spectral type
- M5.0 V
- Surface temperature
- 3,130 K (Sun: 5,772 K)
- Mass
- 0.16 M☉
- Radius
- 0.18 R☉
- Luminosity
- 0.0029 L☉
- Age
- 3.0 billion years (Sun: 4.6)
Planetary System
CD Cet b is the only planet known to orbit CD Cet so far.
CD Cet b — Complete Data
| Mass (best estimate) | 3.95 Earth masses |
|---|---|
| Orbital period | 2.29 days |
| Orbital distance | 0.019 AU |
| Equilibrium temperature | 464 K (191 °C) |
| Stellar irradiation | 8.60× Earth |
| Earth Similarity Index | 0.40 |
| Distance from Earth | 28.1 light-years (8.6 parsecs) |
| Constellation | Cetus |
| Discovery method | Radial Velocity |
| Discovery facility | Calar Alto Observatory |
| Discovery year | 2020 |
Data: NASA Exoplanet Archive, last updated 2021-11-02. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About CD Cet b
Is CD Cet b habitable?
No — CD Cet b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is CD Cet b?
CD Cet b is about 28 light-years from Earth in the constellation Cetus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 494,560 years to get there.
How long is a year on CD Cet b?
One orbit around CD Cet takes 2.3 Earth days — short enough that 159 of its years would fit into one Earth year.
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