TOI-431 d
TOI-431 d is a puffy low-density planet orbiting TOI-431 in the constellation Lepus. It lies about 106 light-years from Earth and was discovered in 2021 using the transit method.
How Big Is TOI-431 d?
TOI-431 d has a radius of 3.29 times that of Earth. Its mass is 9.9 times that of Earth, giving it a density of 1.36 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is TOI-431 d in the Habitable Zone?
TOI-431 d orbits inside the inner edge of the habitable zone of TOI-431. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-431: 0.406–0.988 AU (conservative: 0.515–0.937 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-431 d
The equilibrium temperature of TOI-431 d is about 633 K (360 °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 TOI-431 d — one full orbit around TOI-431 — lasts 12.5 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.098 AU — closer to its star than Mercury is to the Sun.
How Was TOI-431 d Discovered?
TOI-431 d 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-431 d?
TOI-431 d is 106.2 light-years (32.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 1920. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,869,120 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-431 d scores 0.24, ranking #3,298 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: TOI-431
TOI-431
- Surface temperature
- 4,850 K (Sun: 5,772 K)
- Mass
- 0.78 M☉
- Radius
- 0.73 R☉
The TOI-431 Planetary System
TOI-431 d is one of 3 known planets in the TOI-431 system. Its siblings:
TOI-431 d — Complete Data
| Radius | 3.290 Earth radii (0.294 Jupiter radii) |
|---|---|
| Mass | 9.90 Earth masses (0.031 Jupiter masses) |
| Density | 1.36 g/cm³ (Earth: 5.51) |
| Orbital period | 12.46 days |
| Orbital distance | 0.098 AU |
| Equilibrium temperature | 633 K (360 °C) |
| Earth Similarity Index | 0.24 |
| Distance from Earth | 106.2 light-years (32.6 parsecs) |
| Constellation | Lepus |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2021 |
Data: NASA Exoplanet Archive, last updated 2021-08-16. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-431 d
Is TOI-431 d habitable?
No — TOI-431 d orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-431 d?
TOI-431 d is about 106 light-years from Earth in the constellation Lepus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,869,120 years to get there.
How big is TOI-431 d compared to Earth?
TOI-431 d has 3.29 times the radius of Earth and about 9.9 times its mass.
How long is a year on TOI-431 d?
One orbit around TOI-431 takes 12.5 Earth days — short enough that 29 of its years would fit into one Earth year.
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