HD 97658 b
HD 97658 b
confirmed planet • updated: 2023-03-28
HD 97658 b circles the star HD 97658, which is slightly smaller and cooler than our Sun. Scientists found it by measuring the star’s wobble using the radial velocity method at the Keck Observatory.
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 about 8 times Earth’s mass and 2 times Earth’s size, making it similar to Neptune. It orbits its star every 9.5 days, very close in compared to Earth. Its orbit is nearly circular. The planet’s temperature is estimated at around 750 Kelvin (about 475°C or 890°F), based on the star’s brightness and the planet’s distance.
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 97658 b was first reported in 2010 using the Radial Velocity method. The discovery is linked to observations from W. M.
Keck Observatory. Radial-velocity detections come from subtle shifts in the star’s spectrum as it wobbles under the planet’s gravity. The first mass value is often a minimum (m·sin i) unless the orbit’s tilt is known.
The catalog lists an orbital period of about 9.49 days.
The orbit’s eccentricity is 0.05, which describes how stretched the orbit is.
The archive reports a mass scale of 0.0 MJ.
For radial‑velocity work this is commonly m·sin i (a minimum mass) because the orbital tilt is unknown. 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 97658 b orbits HD 97658. The star is classified as K1 V, which is a shorthand for temperature and color.
A temperature near 5212 K places it on the sun-like side of the main sequence. The system is about 70.3 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: semi‑major axis. 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.