K2-308 b
confirmed planet • updated: 2019-06-07
K2-308 b orbits the star K2-308, which is slightly hotter and larger than our Sun. Scientists found it using the transit method, which detects dips in starlight as the planet crosses the face of its star.
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.
The planet is about 9.9 times Earth’s size (or 0.88 times Jupiter’s size) and orbits its star every 3.39 days. Because it was found by the transit method, we know its size and orbit length, but not its mass — so we can’t say how dense or heavy it is. The star is about 1.09 times the mass of our Sun and has a slightly lower metal content.
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.
K2-308 b was first reported in 2019 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 3.39 days.
Eccentricity is not provided here; many catalogs omit it when the solution is underconstrained.
A measured mass is not available in this row, which limits what we can infer about composition.
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
K2-308 b orbits K2-308.
A temperature near 6100 K places it on the hotter side of the main sequence. The system is about 4287.4 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, semi‑major axis, eccentricity, mass. 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.