L 168-9 b
L 168-9 b is a super-Earth orbiting the M0.5 V star L 168-9 in the constellation Tucana. It lies about 82 light-years from Earth and was discovered in 2020 using the transit method.
How Big Is L 168-9 b?
L 168-9 b has a radius of 1.63 times that of Earth. Its mass is 4.1 times that of Earth, giving it a density of 5.18 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is L 168-9 b in the Habitable Zone?
L 168-9 b orbits inside the inner edge of the habitable zone of L 168-9. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of L 168-9: 0.219–0.558 AU (conservative: 0.277–0.529 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on L 168-9 b
The equilibrium temperature of L 168-9 b is about 998 K (725 °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.
Orbit and Year Length
A year on L 168-9 b — one full orbit around L 168-9 — lasts just 33.6 hours, shorter than Mercury's 88-day year. It orbits at an average distance of 0.021 AU — closer to its star than Mercury is to the Sun.
How Was L 168-9 b Discovered?
L 168-9 b was discovered in 2020 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 L 168-9 b?
L 168-9 b is 82.0 light-years (25.1 parsecs) from Earth. Light arriving here tonight left the planet around the year 1944. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,443,200 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. L 168-9 b scores 0.29, ranking #1,717 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: L 168-9
L 168-9
- Spectral type
- M0.5 V
- Surface temperature
- 3,842 K (Sun: 5,772 K)
- Mass
- 0.61 M☉
- Radius
- 0.60 R☉
- Luminosity
- 0.0723 L☉
Planetary System
L 168-9 b is the only planet known to orbit L 168-9 so far.
L 168-9 b — Complete Data
| Radius | 1.630 Earth radii (0.145 Jupiter radii) |
|---|---|
| Mass | 4.07 Earth masses (0.013 Jupiter masses) |
| Density | 5.18 g/cm³ (Earth: 5.51) |
| Orbital period | 1.40 days |
| Orbital distance | 0.021 AU |
| Equilibrium temperature | 998 K (725 °C) |
| Earth Similarity Index | 0.29 |
| Distance from Earth | 82.0 light-years (25.1 parsecs) |
| Constellation | Tucana |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2020 |
Data: NASA Exoplanet Archive, last updated 2024-08-30. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About L 168-9 b
Is L 168-9 b habitable?
No — L 168-9 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is L 168-9 b?
L 168-9 b is about 82 light-years from Earth in the constellation Tucana. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,443,200 years to get there.
How big is L 168-9 b compared to Earth?
L 168-9 b has 1.63 times the radius of Earth and about 4.1 times its mass.
How long is a year on L 168-9 b?
One orbit around L 168-9 takes 1.4 Earth days — short enough that 261 of its years would fit into one Earth year.
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