TOI-2421 b
TOI-2421 b is a hot Jupiter orbiting TOI-2421 in the constellation Fornax. It lies about 1,070 light-years from Earth and was discovered in 2022 using the transit method.
How Big Is TOI-2421 b?
TOI-2421 b has a radius of 10.37 times that of Earth, or 0.93 times the radius of Jupiter. Its mass is 106 times that of Earth, giving it a density of 0.52 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is TOI-2421 b in the Habitable Zone?
TOI-2421 b orbits inside the inner edge of the habitable zone of TOI-2421. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-2421: 1.252–2.965 AU (conservative: 1.586–2.811 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-2421 b
The equilibrium temperature of TOI-2421 b is about 1,534 K (1,261 °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 924 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-2421 b — one full orbit around TOI-2421 — lasts 4.35 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.
How Was TOI-2421 b Discovered?
TOI-2421 b was discovered in 2022 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-2421 b?
TOI-2421 b is 1,069.6 light-years (327.9 parsecs) from Earth. Light arriving here tonight left the planet about 1,070 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 18,824,960 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-2421 b scores 0.08, ranking #4,572 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: TOI-2421
TOI-2421
- Surface temperature
- 5,607 K (Sun: 5,772 K)
- Mass
- 1.13 M☉
- Radius
- 1.75 R☉
- Luminosity
- 2.7290 L☉
- Age
- 7.5 billion years (Sun: 4.6)
Planetary System
TOI-2421 b is the only planet known to orbit TOI-2421 so far.
TOI-2421 b — Complete Data
| Radius | 10.368 Earth radii (0.925 Jupiter radii) |
|---|---|
| Mass | 105.84 Earth masses (0.333 Jupiter masses) |
| Density | 0.52 g/cm³ (Earth: 5.51) |
| Orbital period | 4.35 days |
| Orbital distance | 0.054 AU |
| Equilibrium temperature | 1,534 K (1,261 °C) |
| Stellar irradiation | 923.60× Earth |
| Earth Similarity Index | 0.08 |
| Distance from Earth | 1,069.6 light-years (327.9 parsecs) |
| Constellation | Fornax |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2022 |
Data: NASA Exoplanet Archive, last updated 2022-08-29. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-2421 b
Is TOI-2421 b habitable?
No — TOI-2421 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-2421 b?
TOI-2421 b is about 1,070 light-years from Earth in the constellation Fornax. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 18,824,960 years to get there.
How big is TOI-2421 b compared to Earth?
TOI-2421 b has 10.37 times the radius of Earth and about 106 times its mass.
How long is a year on TOI-2421 b?
One orbit around TOI-2421 takes 4.3 Earth days — short enough that 84 of its years would fit into one Earth year.
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