TOI-6303 b
TOI-6303 b is a hot Jupiter orbiting TOI-6303 in the constellation Perseus. It lies about 497 light-years from Earth and was discovered in 2025 using the transit method.
How Big Is TOI-6303 b?
TOI-6303 b has a radius of 11.59 times that of Earth, or 1.03 times the radius of Jupiter. Its mass is 2,493 times that of Earth, giving it a density of 8.82 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is TOI-6303 b in the Habitable Zone?
TOI-6303 b orbits inside the inner edge of the habitable zone of TOI-6303. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-6303: 0.232–0.588 AU (conservative: 0.294–0.558 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-6303 b
The equilibrium temperature of TOI-6303 b is about 541 K (268 °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 14.28 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-6303 b — one full orbit around TOI-6303 — lasts 9.49 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.076 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.020).
How Was TOI-6303 b Discovered?
TOI-6303 b was discovered in 2025 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-6303 b?
TOI-6303 b is 496.5 light-years (152.2 parsecs) from Earth. Light arriving here tonight left the planet around the year 1530. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 8,738,400 years to make the journey.
The Host Star: TOI-6303
TOI-6303
- Surface temperature
- 3,977 K (Sun: 5,772 K)
- Mass
- 0.64 M☉
- Radius
- 0.61 R☉
- Luminosity
- 0.0819 L☉
- Age
- 6.4 billion years (Sun: 4.6)
Planetary System
TOI-6303 b is the only planet known to orbit TOI-6303 so far.
TOI-6303 b — Complete Data
| Radius | 11.590 Earth radii (1.034 Jupiter radii) |
|---|---|
| Mass | 2,493.00 Earth masses (7.840 Jupiter masses) |
| Density | 8.82 g/cm³ (Earth: 5.51) |
| Orbital period | 9.49 days |
| Orbital distance | 0.076 AU |
| Eccentricity | 0.020 |
| Equilibrium temperature | 541 K (268 °C) |
| Stellar irradiation | 14.28× Earth |
| Distance from Earth | 496.5 light-years (152.2 parsecs) |
| Constellation | Perseus |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2025 |
Data: NASA Exoplanet Archive, last updated 2025-09-17. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-6303 b
Is TOI-6303 b habitable?
No — TOI-6303 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-6303 b?
TOI-6303 b is about 497 light-years from Earth in the constellation Perseus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 8,738,400 years to get there.
How big is TOI-6303 b compared to Earth?
TOI-6303 b has 11.59 times the radius of Earth and about 2,493 times its mass.
How long is a year on TOI-6303 b?
One orbit around TOI-6303 takes 9.5 Earth days — short enough that 39 of its years would fit into one Earth year.
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