TOI-1278 b
TOI-1278 b is a cold gas giant orbiting the M0 V star TOI-1278 in the constellation Cygnus. It lies about 247 light-years from Earth and was discovered in 2021 using the transit method.
How Big Is TOI-1278 b?
TOI-1278 b has a radius of 12.22 times that of Earth, or 1.09 times the radius of Jupiter. Its mass is 5,880 times that of Earth, giving it a density of 18.00 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is TOI-1278 b in the Habitable Zone?
TOI-1278 b orbits inside the inner edge of the habitable zone of TOI-1278. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of TOI-1278: 0.202–0.516 AU (conservative: 0.256–0.489 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 ›
Orbit and Year Length
A year on TOI-1278 b — one full orbit around TOI-1278 — lasts 14.5 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.095 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.013).
How Was TOI-1278 b Discovered?
TOI-1278 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-1278 b?
TOI-1278 b is 246.5 light-years (75.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 1780. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 4,338,400 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-1278 b scores 0.20, ranking #3,860 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: TOI-1278
TOI-1278
- Spectral type
- M0 V
- Surface temperature
- 3,799 K (Sun: 5,772 K)
- Mass
- 0.54 M☉
- Radius
- 0.57 R☉
- Luminosity
- 0.0614 L☉
Planetary System
TOI-1278 b is the only planet known to orbit TOI-1278 so far.
TOI-1278 b — Complete Data
| Radius | 12.218 Earth radii (1.090 Jupiter radii) |
|---|---|
| Mass | 5,879.83 Earth masses (18.500 Jupiter masses) |
| Density | 18.00 g/cm³ (Earth: 5.51) |
| Orbital period | 14.48 days |
| Orbital distance | 0.095 AU |
| Eccentricity | 0.013 |
| Earth Similarity Index | 0.20 |
| Distance from Earth | 246.5 light-years (75.6 parsecs) |
| Constellation | Cygnus |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2021 |
Data: NASA Exoplanet Archive, last updated 2021-08-03. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About TOI-1278 b
Is TOI-1278 b habitable?
No — TOI-1278 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is TOI-1278 b?
TOI-1278 b is about 247 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 4,338,400 years to get there.
How big is TOI-1278 b compared to Earth?
TOI-1278 b has 12.22 times the radius of Earth and about 5,880 times its mass.
How long is a year on TOI-1278 b?
One orbit around TOI-1278 takes 14.5 Earth days — short enough that 25 of its years would fit into one Earth year.
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