TOI-1221 b
TOI-1221 b is a super-Earth orbiting TOI-1221 in the constellation Volans. It lies about 451 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is TOI-1221 b?
TOI-1221 b has a radius of 2.91 times that of Earth. Its mass is 1,112 times that of Earth.
Is TOI-1221 b in the Habitable Zone?
TOI-1221 b orbits inside the inner edge of the habitable zone of TOI-1221. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-1221: 0.733–1.735 AU (conservative: 0.928–1.645 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-1221 b
The equilibrium temperature of TOI-1221 b is about 440 K (167 °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 6.06 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-1221 b — one full orbit around TOI-1221 — lasts 91.7 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.387 AU — comparable to the inner Solar System. Its orbit is mildly elliptical (eccentricity 0.21).
How Was TOI-1221 b Discovered?
TOI-1221 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-1221 b?
TOI-1221 b is 451.4 light-years (138.4 parsecs) from Earth. Light arriving here tonight left the planet around the year 1575. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 7,944,640 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-1221 b scores 0.38, ranking #594 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: TOI-1221
TOI-1221
- Surface temperature
- 5,592 K (Sun: 5,772 K)
- Mass
- 0.93 M☉
- Radius
- 1.03 R☉
- Age
- 10.0 billion years (Sun: 4.6)
Planetary System
TOI-1221 b is the only planet known to orbit TOI-1221 so far.
TOI-1221 b — Complete Data
| Radius | 2.910 Earth radii (0.260 Jupiter radii) |
|---|---|
| Mass | 1,112.40 Earth masses (3.500 Jupiter masses) |
| Orbital period | 91.68 days |
| Orbital distance | 0.387 AU |
| Eccentricity | 0.210 |
| Equilibrium temperature | 440 K (167 °C) |
| Stellar irradiation | 6.06× Earth |
| Earth Similarity Index | 0.38 |
| Distance from Earth | 451.4 light-years (138.4 parsecs) |
| Constellation | Volans |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2023-05-16. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-1221 b
Is TOI-1221 b habitable?
No — TOI-1221 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-1221 b?
TOI-1221 b is about 451 light-years from Earth in the constellation Volans. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 7,944,640 years to get there.
How big is TOI-1221 b compared to Earth?
TOI-1221 b has 2.91 times the radius of Earth and about 1,112 times its mass.
How long is a year on TOI-1221 b?
One orbit around TOI-1221 takes 91.7 Earth days.
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