LHS 1478 b
LHS 1478 b is a terrestrial planet orbiting the m3 V star LHS 1478 in the constellation Cassiopeia. It lies about 60 light-years from Earth and was discovered in 2021 using the transit method.
How Big Is LHS 1478 b?
LHS 1478 b has a radius of 1.24 times that of Earth. Its mass is 2.3 times that of Earth, giving it a density of 6.67 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is LHS 1478 b in the Habitable Zone?
LHS 1478 b orbits inside the inner edge of the habitable zone of LHS 1478. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of LHS 1478: 0.069–0.181 AU (conservative: 0.088–0.171 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on LHS 1478 b
The equilibrium temperature of LHS 1478 b is about 595 K (322 °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.
Orbit and Year Length
A year on LHS 1478 b — one full orbit around LHS 1478 — lasts just 46.8 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.018 AU — closer to its star than Mercury is to the Sun.
How Was LHS 1478 b Discovered?
LHS 1478 b was discovered in 2021 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 LHS 1478 b?
LHS 1478 b is 59.5 light-years (18.2 parsecs) from Earth. Light arriving here tonight left the planet around the year 1967. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,047,200 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. LHS 1478 b scores 0.35, ranking #747 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: LHS 1478
LHS 1478
- Spectral type
- m3 V
- Surface temperature
- 3,381 K (Sun: 5,772 K)
- Mass
- 0.24 M☉
- Radius
- 0.25 R☉
- Luminosity
- 0.0072 L☉
Planetary System
LHS 1478 b is the only planet known to orbit LHS 1478 so far.
LHS 1478 b — Complete Data
| Radius | 1.242 Earth radii (0.111 Jupiter radii) |
|---|---|
| Mass | 2.33 Earth masses (0.007 Jupiter masses) |
| Density | 6.67 g/cm³ (Earth: 5.51) |
| Orbital period | 1.95 days |
| Orbital distance | 0.018 AU |
| Equilibrium temperature | 595 K (322 °C) |
| Earth Similarity Index | 0.35 |
| Distance from Earth | 59.5 light-years (18.2 parsecs) |
| Constellation | Cassiopeia |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2021 |
Data: NASA Exoplanet Archive, last updated 2021-04-23. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About LHS 1478 b
Is LHS 1478 b habitable?
No — LHS 1478 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is LHS 1478 b?
LHS 1478 b is about 60 light-years from Earth in the constellation Cassiopeia. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,047,200 years to get there.
How big is LHS 1478 b compared to Earth?
LHS 1478 b has 1.24 times the radius of Earth and about 2.3 times its mass.
How long is a year on LHS 1478 b?
One orbit around LHS 1478 takes 1.9 Earth days — short enough that 187 of its years would fit into one Earth year.
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