K2-31 b
confirmed planet • updated: 2016-11-30
K2-31 b orbits the star K2-31, a yellowish star slightly smaller than our Sun. Scientists found it using the transit method — watching for tiny dips in the star’s brightness as the planet crosses in front.
This page summarizes a catalog entry. If a measurement is missing, it is not shown or guessed. Some values can differ slightly between studies; when that happens, we describe the range rather than picking a favorite without evidence.
Scientific context
Scientific context: This profile layers interpretation on top of archival measurements. Modeled bands appear where direct detections (like spectra or transits) are not listed.
What we can’t claim: surface conditions, biology, or breathable atmosphere without direct spectra.
K2-31 b is a very large planet — about 1.06 times the size of Jupiter and 1.77 times its mass — orbiting extremely close to its star. One full orbit takes just over 1.25 days. Its orbit is likely circular. The planet’s size and mass suggest it’s a gas giant, but we don’t know its exact composition or whether it has clouds or weather.
Glossary (plain English)
- AU: the average Earth–Sun distance.
- Semi-major axis: the planet’s average distance from its star.
- Eccentricity: how oval the orbit is (0 = circle).
- Radial velocity: finding a planet by measuring a star’s tiny “wobble.”
- m·sin i: a minimum mass estimate; the true mass can be higher if the orbit is tilted.
- Equilibrium temperature: a rough estimate from starlight alone, not a surface reading.
K2-31 b was first reported in 2016 using the Transit method. The discovery is linked to observations from K2.
In transit work, astronomers watch for tiny, repeating dips in a star’s light as the planet passes in front of it. Follow-up observations help rule out false positives and refine the orbit.
The catalog lists an orbital period of about 1.26 days, a semi-major axis near 0.022 AU.
The orbit’s eccentricity is 0.00, which describes how stretched the orbit is.
The archive reports a mass scale of 1.8 MJ.
A catalog radius is also listed, which (together with mass) helps constrain density and interior structure.
Why “m·sin i” shows up on RV planets
K2-31 b orbits K2-31. The star is classified as G7 V, which is a shorthand for temperature and color.
A temperature near 5280 K places it on the sun-like side of the main sequence. The system is about 360.5 light‑years away.
Several key parameters are not present in this single catalog row. Missing fields don’t mean the science is unknown—only that this particular snapshot doesn’t carry the values.
In this case the most noticeable gaps are: catalog equilibrium temperature. As new observations arrive, archives often refresh these entries (and sometimes revise earlier numbers).
Scientists keep revisiting systems like this because each new instrument pass can tighten uncertainties: better timing improves the orbit, better spectra improves the star, and better follow‑up can confirm or refute competing solutions. Even when a planet is well‑established, refined stellar properties can shift the inferred planet size, temperature, and habitability context. Transit systems are especially valuable because they can be re‑observed for decades to detect subtle changes in timing or additional planets.