TOI-559 b
TOI-559 b is a hot Jupiter orbiting the G V star TOI-559 in the constellation Fornax. It lies about 761 light-years from Earth and was discovered in 2021 using the transit method.
How Big Is TOI-559 b?
TOI-559 b has a radius of 12.23 times that of Earth, or 1.09 times the radius of Jupiter. Its mass is 1,910 times that of Earth, giving it a density of 5.74 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is TOI-559 b in the Habitable Zone?
TOI-559 b orbits inside the inner edge of the habitable zone of TOI-559. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-559: 0.966–2.268 AU (conservative: 1.224–2.151 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-559 b
The equilibrium temperature of TOI-559 b is about 1,180 K (907 °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-559 b — one full orbit around TOI-559 — lasts 6.98 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.072 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.15).
How Was TOI-559 b Discovered?
TOI-559 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-559 b?
TOI-559 b is 760.8 light-years (233.3 parsecs) from Earth. Light arriving here tonight left the planet around the year 1266. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 13,390,080 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-559 b scores 0.08, ranking #4,768 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: TOI-559
TOI-559
- Spectral type
- G V
- Surface temperature
- 5,925 K (Sun: 5,772 K)
- Mass
- 1.03 M☉
- Radius
- 1.23 R☉
- Luminosity
- 1.6880 L☉
- Age
- 6.8 billion years (Sun: 4.6)
Planetary System
TOI-559 b is the only planet known to orbit TOI-559 so far.
TOI-559 b — Complete Data
| Radius | 12.229 Earth radii (1.091 Jupiter radii) |
|---|---|
| Mass | 1,910.15 Earth masses (6.010 Jupiter masses) |
| Density | 5.74 g/cm³ (Earth: 5.51) |
| Orbital period | 6.98 days |
| Orbital distance | 0.072 AU |
| Eccentricity | 0.151 |
| Equilibrium temperature | 1,180 K (907 °C) |
| Earth Similarity Index | 0.08 |
| Distance from Earth | 760.8 light-years (233.3 parsecs) |
| Constellation | Fornax |
| 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-559 b
Is TOI-559 b habitable?
No — TOI-559 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-559 b?
TOI-559 b is about 761 light-years from Earth in the constellation Fornax. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 13,390,080 years to get there.
How big is TOI-559 b compared to Earth?
TOI-559 b has 12.23 times the radius of Earth and about 1,910 times its mass.
How long is a year on TOI-559 b?
One orbit around TOI-559 takes 7.0 Earth days — short enough that 52 of its years would fit into one Earth year.
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