TOI-5398 c
TOI-5398 c is a sub-Neptune orbiting the G V star TOI-5398 in the constellation Leo Minor. It lies about 427 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is TOI-5398 c?
TOI-5398 c has a radius of 3.52 times that of Earth. Its mass is 11.8 times that of Earth, giving it a density of 1.50 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is TOI-5398 c in the Habitable Zone?
TOI-5398 c orbits inside the inner edge of the habitable zone of TOI-5398. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-5398: 0.839–1.966 AU (conservative: 1.063–1.864 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-5398 c
The equilibrium temperature of TOI-5398 c is about 1,242 K (969 °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-5398 c — one full orbit around TOI-5398 — lasts 4.77 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.057 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.14).
How Was TOI-5398 c Discovered?
TOI-5398 c 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-5398 c?
TOI-5398 c is 426.8 light-years (130.9 parsecs) from Earth. Light arriving here tonight left the planet around the year 1600. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 7,511,680 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-5398 c scores 0.19, ranking #3,943 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: TOI-5398
TOI-5398
- Spectral type
- G V
- Surface temperature
- 6,000 K (Sun: 5,772 K)
- Mass
- 1.15 M☉
- Radius
- 1.05 R☉
- Age
- 0.7 billion years (Sun: 4.6)
The TOI-5398 Planetary System
TOI-5398 c is one of 2 known planets in the TOI-5398 system. Its siblings:
- TOI-5398 b (Cold Gas Giant)
TOI-5398 c — Complete Data
| Radius | 3.520 Earth radii (0.314 Jupiter radii) |
|---|---|
| Mass | 11.80 Earth masses (0.037 Jupiter masses) |
| Density | 1.50 g/cm³ (Earth: 5.51) |
| Orbital period | 4.77 days |
| Orbital distance | 0.057 AU |
| Eccentricity | 0.140 |
| Equilibrium temperature | 1,242 K (969 °C) |
| Earth Similarity Index | 0.19 |
| Distance from Earth | 426.8 light-years (130.9 parsecs) |
| Constellation | Leo Minor |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2023-11-06. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-5398 c
Is TOI-5398 c habitable?
No — TOI-5398 c orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-5398 c?
TOI-5398 c is about 427 light-years from Earth in the constellation Leo Minor. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 7,511,680 years to get there.
How big is TOI-5398 c compared to Earth?
TOI-5398 c has 3.52 times the radius of Earth and about 11.8 times its mass.
How long is a year on TOI-5398 c?
One orbit around TOI-5398 takes 4.8 Earth days — short enough that 77 of its years would fit into one Earth year.
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