HD 63433 c
HD 63433 c is a super-Earth orbiting the G5 V star HD 63433 in the constellation Gemini. It lies about 73 light-years from Earth and was discovered in 2020 using the transit method.
How Big Is HD 63433 c?
HD 63433 c has a radius of 2.69 times that of Earth. Its mass is 15.5 times that of Earth, giving it a density of 4.63 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is HD 63433 c in the Habitable Zone?
The position of HD 63433 c relative to the habitable zone of HD 63433 cannot be precisely determined from the available orbital data.
Habitable zone of HD 63433: 0.658–1.560 AU (conservative: 0.833–1.479 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HD 63433 c
The equilibrium temperature of HD 63433 c is about 679 K (406 °C) — hot enough to melt many metals. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C.
Orbit and Year Length
A year on HD 63433 c — one full orbit around HD 63433 — lasts 20.5 Earth days, shorter than Mercury's 88-day year.
How Was HD 63433 c Discovered?
HD 63433 c was discovered in 2020 using the transit method, with observations from Transiting Exoplanet Survey Satellite (TESS).
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 HD 63433 c?
HD 63433 c is 73.1 light-years (22.4 parsecs) from Earth. Light arriving here tonight left the planet around the year 1953. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,286,560 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. HD 63433 c scores 0.26, ranking #2,758 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 63433
HD 63433
- Spectral type
- G5 V
- Surface temperature
- 5,553 K (Sun: 5,772 K)
- Mass
- 0.96 M☉
- Radius
- 0.93 R☉
- Luminosity
- 0.7480 L☉
- Age
- 0.4 billion years (Sun: 4.6)
The HD 63433 Planetary System
HD 63433 c is one of 3 known planets in the HD 63433 system. Its siblings:
- HD 63433 b (Super Earth)
- HD 63433 d (Terrestrial)
HD 63433 c — Complete Data
| Radius | 2.692 Earth radii (0.240 Jupiter radii) |
|---|---|
| Mass | 15.54 Earth masses (0.049 Jupiter masses) |
| Density | 4.63 g/cm³ (Earth: 5.51) |
| Orbital period | 20.54 days |
| Equilibrium temperature | 679 K (406 °C) |
| Earth Similarity Index | 0.26 |
| Distance from Earth | 73.1 light-years (22.4 parsecs) |
| Constellation | Gemini |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2020 |
Data: NASA Exoplanet Archive, last updated 2025-10-30. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 63433 c
Is HD 63433 c habitable?
HD 63433 c is not known to orbit within the habitable zone of HD 63433, and as a super-Earth it is an unlikely candidate for life as we know it.
How far away is HD 63433 c?
HD 63433 c is about 73 light-years from Earth in the constellation Gemini. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,286,560 years to get there.
How big is HD 63433 c compared to Earth?
HD 63433 c has 2.69 times the radius of Earth and about 15.5 times its mass.
How long is a year on HD 63433 c?
One orbit around HD 63433 takes 20.5 Earth days — short enough that 18 of its years would fit into one Earth year.
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