TOI-1203.01
TOI-1203.01 is a mini-Neptune orbiting the G3 V star TOI-1203 in the constellation Hydra. It lies about 212 light-years from Earth and was discovered in 2021 using the transit method.
How Big Is TOI-1203.01?
TOI-1203.01 has a radius of 2.92 times that of Earth. Its mass is 7.4 times that of Earth, giving it a density of 1.63 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is TOI-1203.01 in the Habitable Zone?
TOI-1203.01 orbits inside the inner edge of the habitable zone of TOI-1203. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-1203: 0.874–2.062 AU (conservative: 1.108–1.955 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 ›
Temperature on TOI-1203.01
The equilibrium temperature of TOI-1203.01 is about 744 K (470 °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 51.00 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-1203.01 — one full orbit around TOI-1203 — lasts 25.5 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.163 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.032).
How Was TOI-1203.01 Discovered?
TOI-1203.01 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-1203.01?
TOI-1203.01 is 212.0 light-years (65.0 parsecs) from Earth. Light arriving here tonight left the planet around the year 1814. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 3,731,200 years to make the journey.
The Host Star: TOI-1203
TOI-1203
- Spectral type
- G3 V
- Surface temperature
- 5,737 K (Sun: 5,772 K)
- Mass
- 0.89 M☉
- Radius
- 1.18 R☉
- Age
- 12.5 billion years (Sun: 4.6)
The TOI-1203 Planetary System
TOI-1203.01 is one of 4 known planets in the TOI-1203 system. Its siblings:
- TOI-1203 b (Super Earth)
- TOI-1203 c (Super Earth)
- TOI-1203 e (Neptune-like)
TOI-1203.01 — Complete Data
| Radius | 2.918 Earth radii (0.260 Jupiter radii) |
|---|---|
| Mass | 7.39 Earth masses (0.023 Jupiter masses) |
| Density | 1.63 g/cm³ (Earth: 5.51) |
| Orbital period | 25.50 days |
| Orbital distance | 0.163 AU |
| Eccentricity | 0.032 |
| Equilibrium temperature | 744 K (470 °C) |
| Stellar irradiation | 51.00× Earth |
| Distance from Earth | 212.0 light-years (65.0 parsecs) |
| Constellation | Hydra |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2021 |
Data: NASA Exoplanet Archive, last updated 2025-10-02. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-1203.01
Is TOI-1203.01 habitable?
No — TOI-1203.01 orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-1203.01?
TOI-1203.01 is about 212 light-years from Earth in the constellation Hydra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 3,731,200 years to get there.
How big is TOI-1203.01 compared to Earth?
TOI-1203.01 has 2.92 times the radius of Earth and about 7.4 times its mass.
How long is a year on TOI-1203.01?
One orbit around TOI-1203 takes 25.5 Earth days — short enough that 14 of its years would fit into one Earth year.
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