TOI-1288 b
TOI-1288 b is a Neptune-like planet orbiting TOI-1288 in the constellation Cepheus. It lies about 375 light-years from Earth and was discovered in 2022 using the transit method.
How Big Is TOI-1288 b?
TOI-1288 b has a radius of 4.97 times that of Earth. Its mass is 44.1 times that of Earth, giving it a density of 1.97 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is TOI-1288 b in the Habitable Zone?
TOI-1288 b orbits inside the inner edge of the habitable zone of TOI-1288. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-1288: 0.642–1.531 AU (conservative: 0.814–1.452 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Temperature on TOI-1288 b
The equilibrium temperature of TOI-1288 b is about 1,203 K (930 °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-1288 b — one full orbit around TOI-1288 — lasts 2.70 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.037 AU — closer to its star than Mercury is to the Sun.
How Was TOI-1288 b Discovered?
TOI-1288 b was discovered in 2022 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-1288 b?
TOI-1288 b is 374.6 light-years (114.9 parsecs) from Earth. Light arriving here tonight left the planet around the year 1652. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 6,592,960 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-1288 b scores 0.15, ranking #4,218 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: TOI-1288
TOI-1288
- Surface temperature
- 5,388 K (Sun: 5,772 K)
- Mass
- 0.96 M☉
- Radius
- 0.96 R☉
- Luminosity
- 0.7000 L☉
- Age
- 6.5 billion years (Sun: 4.6)
The TOI-1288 Planetary System
TOI-1288 b is one of 2 known planets in the TOI-1288 system. Its siblings:
- TOI-1288 c (Cold Gas Giant)
TOI-1288 b — Complete Data
| Radius | 4.968 Earth radii (0.443 Jupiter radii) |
|---|---|
| Mass | 44.10 Earth masses (0.139 Jupiter masses) |
| Density | 1.97 g/cm³ (Earth: 5.51) |
| Orbital period | 2.70 days |
| Orbital distance | 0.037 AU |
| Equilibrium temperature | 1,203 K (930 °C) |
| Earth Similarity Index | 0.15 |
| Distance from Earth | 374.6 light-years (114.9 parsecs) |
| Constellation | Cepheus |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2022 |
Data: NASA Exoplanet Archive, last updated 2024-07-22. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-1288 b
Is TOI-1288 b habitable?
No — TOI-1288 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-1288 b?
TOI-1288 b is about 375 light-years from Earth in the constellation Cepheus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 6,592,960 years to get there.
How big is TOI-1288 b compared to Earth?
TOI-1288 b has 4.97 times the radius of Earth and about 44.1 times its mass.
How long is a year on TOI-1288 b?
One orbit around TOI-1288 takes 2.7 Earth days — short enough that 135 of its years would fit into one Earth year.
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