HD 63433 d
HD 63433 d is a terrestrial planet orbiting the G5 V star HD 63433 in the constellation Gemini. It lies about 73 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is HD 63433 d?
HD 63433 d has a radius of 1.07 times that of Earth.
Is HD 63433 d in the Habitable Zone?
HD 63433 d orbits inside the inner edge of the habitable zone of HD 63433. So close to its star, surface conditions are far too hot for liquid water.
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 d
The equilibrium temperature of HD 63433 d is about 1,040 K (767 °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 d — one full orbit around HD 63433 — lasts 4.21 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.050 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.16).
How Was HD 63433 d Discovered?
HD 63433 d was discovered in 2023 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 d?
HD 63433 d 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 d scores 0.30, ranking #1,468 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 d is one of 3 known planets in the HD 63433 system. Its siblings:
- HD 63433 b (Super Earth)
- HD 63433 c (Super Earth)
HD 63433 d — Complete Data
| Radius | 1.073 Earth radii (0.096 Jupiter radii) |
|---|---|
| Orbital period | 4.21 days |
| Orbital distance | 0.050 AU |
| Eccentricity | 0.160 |
| Equilibrium temperature | 1,040 K (767 °C) |
| Earth Similarity Index | 0.30 |
| Distance from Earth | 73.1 light-years (22.4 parsecs) |
| Constellation | Gemini |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2024-01-05. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 63433 d
Is HD 63433 d habitable?
No — HD 63433 d orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 63433 d?
HD 63433 d 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 d compared to Earth?
HD 63433 d has 1.07 times the radius of Earth.
How long is a year on HD 63433 d?
One orbit around HD 63433 takes 4.2 Earth days — short enough that 87 of its years would fit into one Earth year.
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