HD 22946 d
HD 22946 d
confirmed planet • updated: 2023-07-10
HD 22946 d circles the star HD 22946, which is slightly larger and hotter than our Sun. Scientists spotted it when the planet passed in front of the star, causing a tiny dip in brightness — a method called transit.
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.
This planet is larger than Earth but smaller than Neptune — a type sometimes called a sub-Neptune or super-Earth. It orbits close to its star, getting about 18 times more starlight than Earth does. Its surface temperature is estimated at 546 Kelvin (about 523°F or 273°C), which is very hot. The mass is given as a direct value, not a minimum, which is unusual for transit discoveries — but no uncertainty is listed, so we can’t say how precise it is.
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.
HD 22946 d was first reported in 2023 using the Transit method. The discovery is linked to observations from Transiting Exoplanet Survey Satellite (TESS).
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 47.42 days, a semi-major axis near 0.296 AU.
Eccentricity is not provided here; many catalogs omit it when the solution is underconstrained. Because this is a multi‑planet system, stability is ultimately tested with dynamical (N‑body) fits; catalogs can update as models improve.
The archive reports a mass scale of 0.1 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
HD 22946 d orbits HD 22946.
A temperature near 6169 K places it on the hotter side of the main sequence. The system is about 204.8 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: eccentricity. 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.