TOI-181 b
TOI-181 b is a hot Jupiter orbiting the K star TOI-181 in the constellation Sculptor. It lies about 314 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is TOI-181 b?
TOI-181 b has a radius of 6.96 times that of Earth, or 0.63 times the radius of Jupiter. Its mass is 46.2 times that of Earth, giving it a density of 0.76 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is TOI-181 b in the Habitable Zone?
TOI-181 b orbits inside the inner edge of the habitable zone of TOI-181. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-181: 0.428–1.034 AU (conservative: 0.542–0.981 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-181 b
The equilibrium temperature of TOI-181 b is about 895 K (622 °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. It receives 102 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-181 b — one full orbit around TOI-181 — lasts 4.53 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.054 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.15).
How Was TOI-181 b Discovered?
TOI-181 b was discovered in 2023 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 TOI-181 b?
TOI-181 b is 313.9 light-years (96.2 parsecs) from Earth. Light arriving here tonight left the planet around the year 1713. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 5,524,640 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. TOI-181 b scores 0.13, ranking #4,301 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: TOI-181
TOI-181
- Spectral type
- K
- Surface temperature
- 4,994 K (Sun: 5,772 K)
- Mass
- 0.82 M☉
- Radius
- 0.75 R☉
- Luminosity
- 0.2980 L☉
- Age
- 5.4 billion years (Sun: 4.6)
Planetary System
TOI-181 b is the only planet known to orbit TOI-181 so far.
TOI-181 b — Complete Data
| Radius | 6.956 Earth radii (0.634 Jupiter radii) |
|---|---|
| Mass | 46.17 Earth masses (0.145 Jupiter masses) |
| Density | 0.76 g/cm³ (Earth: 5.51) |
| Orbital period | 4.53 days |
| Orbital distance | 0.054 AU |
| Eccentricity | 0.154 |
| Equilibrium temperature | 895 K (622 °C) |
| Stellar irradiation | 102.43× Earth |
| Earth Similarity Index | 0.13 |
| Distance from Earth | 313.9 light-years (96.2 parsecs) |
| Constellation | Sculptor |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2023-03-15. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-181 b
Is TOI-181 b habitable?
No — TOI-181 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-181 b?
TOI-181 b is about 314 light-years from Earth in the constellation Sculptor. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 5,524,640 years to get there.
How big is TOI-181 b compared to Earth?
TOI-181 b has 6.96 times the radius of Earth and about 46.2 times its mass.
How long is a year on TOI-181 b?
One orbit around TOI-181 takes 4.5 Earth days — short enough that 81 of its years would fit into one Earth year.
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