LHS 1903 d
LHS 1903 d is a mini-Neptune orbiting the M star LHS 1903 in the constellation Lynx. It lies about 116 light-years from Earth and was discovered in 2026 using the transit method.
How Big Is LHS 1903 d?
LHS 1903 d has a radius of 2.50 times that of Earth. Its mass is 6.0 times that of Earth, giving it a density of 2.09 g/cm³ — between that of rocky and gaseous planets.
Is LHS 1903 d in the Habitable Zone?
LHS 1903 d orbits inside the inner edge of the habitable zone of LHS 1903. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of LHS 1903: 0.177–0.455 AU (conservative: 0.224–0.432 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on LHS 1903 d
The equilibrium temperature of LHS 1903 d is about 442 K (169 °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 6.35 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on LHS 1903 d — one full orbit around LHS 1903 — lasts 12.6 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.086 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.11).
How Was LHS 1903 d Discovered?
LHS 1903 d was discovered in 2026 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 1903 d?
LHS 1903 d is 116.4 light-years (35.7 parsecs) from Earth. Light arriving here tonight left the planet around the year 1910. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 2,048,640 years to make the journey.
The Host Star: LHS 1903
LHS 1903
- Spectral type
- M
- Surface temperature
- 3,664 K (Sun: 5,772 K)
- Mass
- 0.54 M☉
- Radius
- 0.54 R☉
- Age
- 7.1 billion years (Sun: 4.6)
The LHS 1903 Planetary System
LHS 1903 d is one of 4 known planets in the LHS 1903 system. Its siblings:
- LHS 1903 b (Super Earth)
- LHS 1903 c (Mini Neptune)
- LHS 1903 e (Super Earth)
LHS 1903 d — Complete Data
| Radius | 2.500 Earth radii (0.223 Jupiter radii) |
|---|---|
| Mass | 5.96 Earth masses (0.019 Jupiter masses) |
| Density | 2.09 g/cm³ (Earth: 5.51) |
| Orbital period | 12.57 days |
| Orbital distance | 0.086 AU |
| Eccentricity | 0.112 |
| Equilibrium temperature | 442 K (169 °C) |
| Stellar irradiation | 6.35× Earth |
| Distance from Earth | 116.4 light-years (35.7 parsecs) |
| Constellation | Lynx |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2026 |
Data: NASA Exoplanet Archive, last updated 2026-02-26. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About LHS 1903 d
Is LHS 1903 d habitable?
No — LHS 1903 d orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is LHS 1903 d?
LHS 1903 d is about 116 light-years from Earth in the constellation Lynx. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 2,048,640 years to get there.
How big is LHS 1903 d compared to Earth?
LHS 1903 d has 2.50 times the radius of Earth and about 6.0 times its mass.
How long is a year on LHS 1903 d?
One orbit around LHS 1903 takes 12.6 Earth days — short enough that 29 of its years would fit into one Earth year.
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