HIP 41378 b
HIP 41378 b 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 b?
HIP 41378 b has a radius of 2.64 times that of Earth. Its mass is 6.9 times that of Earth, giving it a density of 2.07 g/cm³ — between that of rocky and gaseous planets.
Is HIP 41378 b in the Habitable Zone?
The position of HIP 41378 b relative to the habitable zone of HIP 41378 cannot be precisely determined from the available orbital data.
Habitable zone of HIP 41378: 1.121–2.611 AU (conservative: 1.420–2.475 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 HIP 41378 b — one full orbit around HIP 41378 — lasts 15.6 Earth days, shorter than Mercury's 88-day year. Its orbit is mildly elliptical (eccentricity 0.05).
How Was HIP 41378 b Discovered?
HIP 41378 b 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 b?
HIP 41378 b 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 b scores 0.24, ranking #3,278 of 5,566 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HIP 41378
HIP 41378
- Surface temperature
- 6,290 K (Sun: 5,772 K)
- Mass
- 1.22 M☉
- Radius
- 1.30 R☉
- Age
- 2.1 billion years (Sun: 4.6)
The HIP 41378 Planetary System
HIP 41378 b is one of 6 known planets in the HIP 41378 system. Its siblings:
- HIP 41378 c (Mini Neptune)
- HIP 41378 d (Puffy Planet)
- HIP 41378 e (Neptune-like)
- HIP 41378 f (Cold Gas Giant)
- HIP 41378 g (Super Earth)
HIP 41378 b — Complete Data
| Radius | 2.640 Earth radii (0.236 Jupiter radii) |
|---|---|
| Mass | 6.90 Earth masses (0.022 Jupiter masses) |
| Density | 2.07 g/cm³ (Earth: 5.51) |
| Orbital period | 15.57 days |
| Eccentricity | 0.050 |
| Earth Similarity Index | 0.24 |
| 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 2026-07-16. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HIP 41378 b
Is HIP 41378 b habitable?
HIP 41378 b is not known to orbit within the habitable zone of HIP 41378, and as a mini-Neptune it is an unlikely candidate for life as we know it.
How far away is HIP 41378 b?
HIP 41378 b 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 b compared to Earth?
HIP 41378 b has 2.64 times the radius of Earth and about 6.9 times its mass.
How long is a year on HIP 41378 b?
One orbit around HIP 41378 takes 15.6 Earth days — short enough that 23 of its years would fit into one Earth year.
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