HU Aqr AB c
HU Aqr AB c
derived planet • updated: 2019-10-18
HU Aqr AB c orbits the binary star system HU Aqr. Scientists detected it using eclipse timing variations — small delays in when eclipses happen — which suggest a third body is tugging on the system.
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 catalog lists a very massive object — about 4.5 times the mass of Jupiter — orbiting at roughly 5.4 astronomical units (Earth-Sun distances) with a highly elliptical path. Because the mass is given as Msin(i)/sin(i), it may reflect the true mass if the orbit is edge-on, but could be higher if tilted. The orbital period is about 4368 days (over 12 years).
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.
HU Aqr AB c was first reported in 2011 using the Eclipse Timing Variations method.
The discovery is linked to observations from Yunnan Astronomical Observatory. Different methods emphasize different strengths: some constrain size, some constrain mass, and some constrain both.
The catalog lists an orbital period of about 4368.00 days, a semi-major axis near 5.400 AU. The orbit’s eccentricity is 0.51, which describes how stretched the orbit is.
A higher eccentricity can imply stronger past interactions or migration, and it can matter for long‑term stability in multi‑planet systems. 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 4.5 MJ.
A rough radius estimate is shown for UI completeness, but it should not be treated as a measurement.
Why “m·sin i” shows up on RV planets
HU Aqr AB c orbits HU Aqr.
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: radius, 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.