HIP 41378 d
HIP 41378 d is a puffy low-density planet 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 d?
HIP 41378 d has a radius of 3.54 times that of Earth. Its mass is 4.6 times that of Earth, giving it a density of 0.56 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is HIP 41378 d in the Habitable Zone?
The position of HIP 41378 d relative to the habitable zone of HIP 41378 cannot be precisely determined from the available orbital data.
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 d
The equilibrium temperature of HIP 41378 d is about 367 K (94 °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 3.01 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on HIP 41378 d — one full orbit around HIP 41378 — lasts 278.4 Earth days, between the years of Mercury (88 days) and Earth (365 days).
How Was HIP 41378 d Discovered?
HIP 41378 d 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 d?
HIP 41378 d 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 d scores 0.52, ranking #231 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 d is one of 6 known planets in the HIP 41378 system. Its siblings:
- HIP 41378 b (Super Earth)
- HIP 41378 c (Mini Neptune)
- HIP 41378 e (Neptune-like)
- HIP 41378 f
- HIP 41378 g (Super Earth)
HIP 41378 d — Complete Data
| Radius | 3.540 Earth radii (0.316 Jupiter radii) |
|---|---|
| Mass | 4.60 Earth masses (0.014 Jupiter masses) |
| Density | 0.56 g/cm³ (Earth: 5.51) |
| Orbital period | 278.36 days |
| Equilibrium temperature | 367 K (94 °C) |
| Stellar irradiation | 3.01× Earth |
| Earth Similarity Index | 0.52 |
| 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 2025-09-17. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HIP 41378 d
Is HIP 41378 d habitable?
HIP 41378 d is not known to orbit within the habitable zone of HIP 41378, and as a puffy low-density planet it is an unlikely candidate for life as we know it.
How far away is HIP 41378 d?
HIP 41378 d 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 d compared to Earth?
HIP 41378 d has 3.54 times the radius of Earth and about 4.6 times its mass.
How long is a year on HIP 41378 d?
One orbit around HIP 41378 takes 278.4 Earth days.
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