TOI-5678 b
TOI-5678 b is a Neptune-like planet orbiting the G7 V star TOI-5678 in the constellation Fornax. It lies about 539 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is TOI-5678 b?
TOI-5678 b has a radius of 4.91 times that of Earth. Its mass is 20.0 times that of Earth.
Is TOI-5678 b in the Habitable Zone?
TOI-5678 b orbits inside the inner edge of the habitable zone of TOI-5678. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-5678: 0.645–1.533 AU (conservative: 0.817–1.454 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-5678 b
The equilibrium temperature of TOI-5678 b is about 513 K (240 °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.
Orbit and Year Length
A year on TOI-5678 b — one full orbit around TOI-5678 — lasts 47.7 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.249 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.14).
How Was TOI-5678 b Discovered?
TOI-5678 b 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-5678 b?
TOI-5678 b is 539.4 light-years (165.4 parsecs) from Earth. Light arriving here tonight left the planet around the year 1487. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 9,493,440 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-5678 b scores 0.24, ranking #3,304 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: TOI-5678
TOI-5678
- Spectral type
- G7 V
- Surface temperature
- 5,485 K (Sun: 5,772 K)
- Mass
- 0.91 M☉
- Radius
- 0.94 R☉
- Age
- 8.5 billion years (Sun: 4.6)
Planetary System
TOI-5678 b is the only planet known to orbit TOI-5678 so far.
TOI-5678 b — Complete Data
| Radius | 4.910 Earth radii (0.438 Jupiter radii) |
|---|---|
| Mass | 20.00 Earth masses (0.063 Jupiter masses) |
| Orbital period | 47.73 days |
| Orbital distance | 0.249 AU |
| Eccentricity | 0.140 |
| Equilibrium temperature | 513 K (240 °C) |
| Earth Similarity Index | 0.24 |
| Distance from Earth | 539.4 light-years (165.4 parsecs) |
| Constellation | Fornax |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2023-06-12. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-5678 b
Is TOI-5678 b habitable?
No — TOI-5678 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-5678 b?
TOI-5678 b is about 539 light-years from Earth in the constellation Fornax. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 9,493,440 years to get there.
How big is TOI-5678 b compared to Earth?
TOI-5678 b has 4.91 times the radius of Earth and about 20.0 times its mass.
How long is a year on TOI-5678 b?
One orbit around TOI-5678 takes 47.7 Earth days.
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