TOI-2015 b
TOI-2015 b is a puffy low-density planet orbiting the M4 +/- 0.5 star TOI-2015 in the constellation Corona Borealis. It lies about 154 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is TOI-2015 b?
TOI-2015 b has a radius of 3.31 times that of Earth. Its mass is 9.2 times that of Earth, giving it a density of 1.40 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is TOI-2015 b in the Habitable Zone?
TOI-2015 b orbits inside the inner edge of the habitable zone of TOI-2015. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-2015: 0.147–0.386 AU (conservative: 0.186–0.366 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on TOI-2015 b
The equilibrium temperature of TOI-2015 b is about 531 K (258 °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. It receives 13.19 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on TOI-2015 b — one full orbit around TOI-2015 — lasts 3.35 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.029 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.08).
How Was TOI-2015 b Discovered?
TOI-2015 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-2015 b?
TOI-2015 b is 154.4 light-years (47.3 parsecs) from Earth. Light arriving here tonight left the planet around the year 1872. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 2,717,440 years to make the journey.
The Host Star: TOI-2015
TOI-2015
- Spectral type
- M4 +/- 0.5
- Surface temperature
- 3,297 K (Sun: 5,772 K)
- Mass
- 0.30 M☉
- Radius
- 0.33 R☉
- Luminosity
- 0.0322 L☉
- Age
- 5.5 billion years (Sun: 4.6)
The TOI-2015 Planetary System
TOI-2015 b is one of 2 known planets in the TOI-2015 system. Its siblings:
- TOI-2015 c (Super Earth)
TOI-2015 b — Complete Data
| Radius | 3.309 Earth radii (0.295 Jupiter radii) |
|---|---|
| Mass | 9.20 Earth masses (0.029 Jupiter masses) |
| Density | 1.40 g/cm³ (Earth: 5.51) |
| Orbital period | 3.35 days |
| Orbital distance | 0.029 AU |
| Eccentricity | 0.079 |
| Equilibrium temperature | 531 K (258 °C) |
| Stellar irradiation | 13.19× Earth |
| Distance from Earth | 154.4 light-years (47.3 parsecs) |
| Constellation | Corona Borealis |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2025-03-09. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-2015 b
Is TOI-2015 b habitable?
No — TOI-2015 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-2015 b?
TOI-2015 b is about 154 light-years from Earth in the constellation Corona Borealis. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 2,717,440 years to get there.
How big is TOI-2015 b compared to Earth?
TOI-2015 b has 3.31 times the radius of Earth and about 9.2 times its mass.
How long is a year on TOI-2015 b?
One orbit around TOI-2015 takes 3.3 Earth days — short enough that 109 of its years would fit into one Earth year.
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