HN Peg b
HN Peg b
confirmed planet • updated: 2014-05-14
HN Peg b was spotted directly by the Spitzer Space Telescope in 2006, making it one of the few exoplanets seen as a separate point of light rather than inferred from its star’s behavior.
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 object is extremely massive — about 22 times the mass of Jupiter — and roughly 1.05 times Jupiter’s size. It orbits at a very wide distance from its star, about 773 times farther than Earth is from the Sun. Because it was found by direct imaging, we don’t yet know how long it takes to complete one orbit or how elliptical its path 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.
HN Peg b was first reported in 2006 using the Imaging method. The discovery is linked to observations from Spitzer Space Telescope.
Direct imaging tries to separate faint planetary light from the glare of the host star. It works best for young, warm planets far from their stars.
The catalog lists a semi-major axis near 773.000 AU.
Eccentricity is not provided here; many catalogs omit it when the solution is underconstrained.
The archive reports a mass scale of 22.0 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
HN Peg b orbits HN Peg.
The star is classified as G0 V, which is a shorthand for temperature and color. The system is about 59.1 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, orbital period, 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.