HIP 41378 c
HIP 41378 c is a mini-Neptune orbiting HIP 41378 in the constellation Cancer. It lies about 347 light-years from Earth and was discovered in 2016 using the transit method.
How Big Is HIP 41378 c?
HIP 41378 c has a radius of 2.51 times that of Earth. Its mass is 6.5 times that of Earth.
Is HIP 41378 c in the Habitable Zone?
HIP 41378 c orbits inside the inner edge of the habitable zone of HIP 41378. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HIP 41378: 1.150–2.674 AU (conservative: 1.456–2.535 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HIP 41378 c
The equilibrium temperature of HIP 41378 c is about 766 K (493 °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. It receives 57.55 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on HIP 41378 c — one full orbit around HIP 41378 — lasts 31.7 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.209 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.07).
How Was HIP 41378 c Discovered?
HIP 41378 c was discovered in 2016 using the transit method, with observations from K2.
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 HIP 41378 c?
HIP 41378 c is 346.7 light-years (106.3 parsecs) from Earth. Light arriving here tonight left the planet around the year 1680. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 6,101,920 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. HIP 41378 c scores 0.25, ranking #3,110 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HIP 41378
HIP 41378
- Surface temperature
- 6,371 K (Sun: 5,772 K)
- Mass
- 1.25 M☉
- Radius
- 1.31 R☉
- Age
- 1.8 billion years (Sun: 4.6)
The HIP 41378 Planetary System
HIP 41378 c is one of 6 known planets in the HIP 41378 system. Its siblings:
- HIP 41378 b (Super Earth)
- HIP 41378 d (Puffy Planet)
- HIP 41378 e (Neptune-like)
- HIP 41378 f
- HIP 41378 g (Super Earth)
HIP 41378 c — Complete Data
| Radius | 2.505 Earth radii (0.223 Jupiter radii) |
|---|---|
| Mass | 6.53 Earth masses (0.021 Jupiter masses) |
| Orbital period | 31.71 days |
| Orbital distance | 0.209 AU |
| Eccentricity | 0.068 |
| Equilibrium temperature | 766 K (493 °C) |
| Stellar irradiation | 57.55× Earth |
| Earth Similarity Index | 0.25 |
| Distance from Earth | 346.7 light-years (106.3 parsecs) |
| Constellation | Cancer |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2016 |
Data: NASA Exoplanet Archive, last updated 2026-05-07. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HIP 41378 c
Is HIP 41378 c habitable?
No — HIP 41378 c orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HIP 41378 c?
HIP 41378 c is about 347 light-years from Earth in the constellation Cancer. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 6,101,920 years to get there.
How big is HIP 41378 c compared to Earth?
HIP 41378 c has 2.51 times the radius of Earth and about 6.5 times its mass.
How long is a year on HIP 41378 c?
One orbit around HIP 41378 takes 31.7 Earth days — short enough that 12 of its years would fit into one Earth year.
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