Confirmed planetTOI-700 system
TOI-700 e
A second Earth-sized world in TOI-700's habitable zone, found hiding between the sub-Neptune and the system's first temperate planet.
- Orbital period
- 27.8 days
- Distance from the star
- 0.134 AU · 20.1 million km
- Radius
- 0.953 Earth radii
- Mass
- Not yet measured
- Equilibrium temperature
- About 273 K without an atmosphere
- Discovery
- 2023 · transit
- Host star
- M2.5V red dwarf · about 0.42 solar masses
- Distance from the Sun
- 101.5 light-years
Found on a second look
TOI-700 e was announced in 2023 after astronomers re-examined TESS data and spotted a small, repeating dip between the signals of the sub-Neptune c and the habitable-zone planet d. It is about 95% of Earth's radius and orbits every 27.8 days.
The discovery turned TOI-700 into a system with two Earth-sized planets in the habitable zone, something still rare among known exoplanet systems. Like its companions, e's mass has not yet been measured.
A temperate Earth-sized world
TOI-700 e receives a little less stellar energy than Earth, giving it an equilibrium temperature near 273 K. If it has an atmosphere, surface temperatures could be comfortable for liquid water; without one, it would be cold and airless.
The planet's closeness to the larger c raises interesting dynamical questions. Its orbit appears stable, but studying how the two interact helps astronomers understand how such compact systems settle into long-lived configurations.
What we don't know
Its mass, atmosphere, and surface are all unknown. Weighing it will be difficult because it is small and distant, but future instruments may manage it, and atmospheric searches could follow.
- What is its mass and composition?
- Does it have an atmosphere and surface water?
- How does its orbit interact with the nearby sub-Neptune?
Key publications
| Year | Paper | Venue | Link |
|---|---|---|---|
| 2020 | Gilbert et al., The First Habitable-zone Earth-sized Planet from TESS. I. Validation of the TOI-700 System | The Astronomical Journal 160, 116 | DOI |
| 2023 | Gilbert et al., A Second Earth-sized Planet in the Habitable Zone of the M Dwarf, TOI-700 | The Astrophysical Journal Letters 944, L35 | DOI |
Values compiled from the NASA Exoplanet Archive and the papers listed above.
Worth knowing
It was found in 2023 on a second look at TESS data.
It is about 95% the size of Earth.
It is the second Earth-sized planet in TOI-700's habitable zone.