TOI-251 b
TOI-251 b is a super-Earth orbiting TOI-251 in the constellation Sculptor. It lies about 325 light-years from Earth and was discovered in 2021 using the transit method.
How Big Is TOI-251 b?
TOI-251 b has a radius of 2.74 times that of Earth. Its mass is 318 times that of Earth.
Is TOI-251 b in the Habitable Zone?
TOI-251 b orbits inside the inner edge of the habitable zone of TOI-251. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-251: 0.680–1.598 AU (conservative: 0.861–1.515 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Orbit and Year Length
A year on TOI-251 b — one full orbit around TOI-251 — lasts 4.94 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.057 AU — closer to its star than Mercury is to the Sun.
How Was TOI-251 b Discovered?
TOI-251 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 TOI-251 b?
TOI-251 b is 324.6 light-years (99.5 parsecs) from Earth. Light arriving here tonight left the planet around the year 1702. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 5,712,960 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-251 b scores 0.23, ranking #3,571 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: TOI-251
TOI-251
- Surface temperature
- 5,875 K (Sun: 5,772 K)
- Mass
- 1.04 M☉
- Radius
- 0.88 R☉
- Luminosity
- 0.8310 L☉
- Age
- 0.2 billion years (Sun: 4.6)
Planetary System
TOI-251 b is the only planet known to orbit TOI-251 so far.
TOI-251 b — Complete Data
| Radius | 2.740 Earth radii (0.244 Jupiter radii) |
|---|---|
| Mass | 317.83 Earth masses (1.000 Jupiter masses) |
| Orbital period | 4.94 days |
| Orbital distance | 0.057 AU |
| Earth Similarity Index | 0.23 |
| Distance from Earth | 324.6 light-years (99.5 parsecs) |
| Constellation | Sculptor |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2021 |
Data: NASA Exoplanet Archive, last updated 2020-12-10. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-251 b
Is TOI-251 b habitable?
No — TOI-251 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-251 b?
TOI-251 b is about 325 light-years from Earth in the constellation Sculptor. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 5,712,960 years to get there.
How big is TOI-251 b compared to Earth?
TOI-251 b has 2.74 times the radius of Earth and about 318 times its mass.
How long is a year on TOI-251 b?
One orbit around TOI-251 takes 4.9 Earth days — short enough that 74 of its years would fit into one Earth year.
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