TOI-444 b
TOI-444 b is a mini-Neptune orbiting the K1/2 V star TOI-444 in the constellation Eridanus. It lies about 187 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is TOI-444 b?
TOI-444 b has a radius of 2.77 times that of Earth.
Is TOI-444 b in the Habitable Zone?
TOI-444 b orbits inside the inner edge of the habitable zone of TOI-444. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-444: 0.493–1.183 AU (conservative: 0.625–1.121 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-444 b
The equilibrium temperature of TOI-444 b is about 609 K (336 °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-444 b — one full orbit around TOI-444 — lasts 18.0 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.133 AU — closer to its star than Mercury is to the Sun.
How Was TOI-444 b Discovered?
TOI-444 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-444 b?
TOI-444 b is 187.2 light-years (57.4 parsecs) from Earth. Light arriving here tonight left the planet around the year 1839. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 3,294,720 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-444 b scores 0.28, ranking #2,424 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: TOI-444
TOI-444
- Spectral type
- K1/2 V
- Surface temperature
- 5,225 K (Sun: 5,772 K)
- Mass
- 0.96 M☉
- Radius
- 0.78 R☉
- Age
- 0.6 billion years (Sun: 4.6)
Planetary System
TOI-444 b is the only planet known to orbit TOI-444 so far.
TOI-444 b — Complete Data
| Radius | 2.770 Earth radii (0.247 Jupiter radii) |
|---|---|
| Orbital period | 17.96 days |
| Orbital distance | 0.133 AU |
| Equilibrium temperature | 609 K (336 °C) |
| Earth Similarity Index | 0.28 |
| Distance from Earth | 187.2 light-years (57.4 parsecs) |
| Constellation | Eridanus |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2023-08-22. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-444 b
Is TOI-444 b habitable?
No — TOI-444 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-444 b?
TOI-444 b is about 187 light-years from Earth in the constellation Eridanus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 3,294,720 years to get there.
How big is TOI-444 b compared to Earth?
TOI-444 b has 2.77 times the radius of Earth.
How long is a year on TOI-444 b?
One orbit around TOI-444 takes 18.0 Earth days — short enough that 20 of its years would fit into one Earth year.
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