Confirmed planetTOI-700 system
TOI-700 b
The innermost world of TOI-700: a hot, Earth-sized rock orbiting its star in just under ten days.
- Orbital period
- 9.98 days
- Distance from the star
- 0.0677 AU · 10.1 million km
- Radius
- 0.914 Earth radii
- Mass
- Not yet measured
- Equilibrium temperature
- About 400 K without an atmosphere
- Discovery
- 2020 · transit
- Host star
- M2.5V red dwarf · about 0.42 solar masses
- Distance from the Sun
- 101.5 light-years
A hot inner rock
TOI-700 b is the closest planet to its star, completing an orbit in 9.98 days. It is slightly smaller than Earth in radius, and its equilibrium temperature is around 400 K, hot enough to rule out surface liquid water under ordinary conditions.
Because it was found by the transit method, only its size is known with confidence. Its mass has not been measured, so its density and composition remain uncertain, though a rocky interior is the natural expectation for a planet this small.
The inner edge of a tidy system
TOI-700 b anchors the inner boundary of a compact, orderly system. Outward from it sit a sub-Neptune and then two Earth-sized planets in the habitable zone. Comparing b with those cooler siblings shows how distance from the star shapes a planet's fate.
At its close orbit, b is likely tidally locked, with one hemisphere facing the star. No atmosphere has been detected, and its surface is expected to be barren and hot.
What we don't know
Future radial-velocity measurements may weigh the planet and reveal whether it is purely rocky or holds a denser, more metallic interior. Its atmosphere, if any, is completely unmeasured.
- What is its mass and composition?
- Does it retain any atmosphere at all?
- Is its rotation synchronised with its orbit?
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
Its year lasts just under 10 Earth days.
It is slightly smaller than Earth.
Its mass has not yet been measured.