TOI-558 b
TOI-558 b is a hot Jupiter orbiting the F V star TOI-558 in the constellation Horologium. It lies about 1,313 light-years from Earth and was discovered in 2021 using the transit method.
How Big Is TOI-558 b?
TOI-558 b has a radius of 12.17 times that of Earth, or 1.09 times the radius of Jupiter. Its mass is 1,147 times that of Earth, giving it a density of 3.50 g/cm³ — between that of rocky and gaseous planets.
Is TOI-558 b in the Habitable Zone?
TOI-558 b orbits inside the inner edge of the habitable zone of TOI-558. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-558: 1.351–3.137 AU (conservative: 1.711–2.974 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-558 b
The equilibrium temperature of TOI-558 b is about 1,061 K (788 °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-558 b — one full orbit around TOI-558 — lasts 14.6 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.129 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.30).
How Was TOI-558 b Discovered?
TOI-558 b 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-558 b?
TOI-558 b is 1,313.2 light-years (402.6 parsecs) from Earth. Light arriving here tonight left the planet about 1,313 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 23,112,320 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-558 b scores 0.08, ranking #4,721 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: TOI-558
TOI-558
- Spectral type
- F V
- Surface temperature
- 6,466 K (Sun: 5,772 K)
- Mass
- 1.35 M☉
- Radius
- 1.50 R☉
- Luminosity
- 3.5200 L☉
- Age
- 1.8 billion years (Sun: 4.6)
Planetary System
TOI-558 b is the only planet known to orbit TOI-558 so far.
TOI-558 b — Complete Data
| Radius | 12.173 Earth radii (1.086 Jupiter radii) |
|---|---|
| Mass | 1,147.36 Earth masses (3.610 Jupiter masses) |
| Density | 3.50 g/cm³ (Earth: 5.51) |
| Orbital period | 14.57 days |
| Orbital distance | 0.129 AU |
| Eccentricity | 0.298 |
| Equilibrium temperature | 1,061 K (788 °C) |
| Earth Similarity Index | 0.08 |
| Distance from Earth | 1,313.2 light-years (402.6 parsecs) |
| Constellation | Horologium |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2021 |
Data: NASA Exoplanet Archive, last updated 2022-03-28. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-558 b
Is TOI-558 b habitable?
No — TOI-558 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-558 b?
TOI-558 b is about 1,313 light-years from Earth in the constellation Horologium. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 23,112,320 years to get there.
How big is TOI-558 b compared to Earth?
TOI-558 b has 12.17 times the radius of Earth and about 1,147 times its mass.
How long is a year on TOI-558 b?
One orbit around TOI-558 takes 14.6 Earth days — short enough that 25 of its years would fit into one Earth year.
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