| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 23h25m 52.99170s[1] |
| Declination | –20° 36′ 57.6998″[1] |
| Apparent magnitude (V) | +7.74[2] |
| Characteristics | |
| Spectral type | G3V[3] |
| B−V color index | +0.603±0.002[2] |
| Astrometry | |
| Radial velocity (Rv) | +12.30±0.14[1] km/s |
| Proper motion (μ) | RA: –15.328 mas/yr[1] Dec.: –177.593 mas/yr[1] |
| Parallax (π) | 21.3074 ± 0.0236 mas[1] |
| Distance | 153.1 ± 0.2 ly (46.93 ± 0.05 pc) |
| Absolute magnitude (MV) | 4.50[2] |
| Details[4] | |
| Mass | 1.016±0.048 M☉ |
| Radius | 1.068±0.047 R☉ |
| Luminosity | 1.491±0.005[5] L☉ |
| Surface gravity (log g) | 4.360±0.045 cgs |
| Temperature | 5,921±26 K |
| Metallicity [Fe/H] | −0.07±0.10 dex |
| Rotation | ~29 d |
| Rotational velocity (v sin i) | 5.5[6] km/s |
| Age | 4.586±2.487 Gyr |
| Other designations | |
BD–21°6419, GC 32591, HD 220689, HIP 115662, SAO 191898, G 273-43[7] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
HD 220689 is a single[8] star in the equatorial constellationofAquarius. It is a challenge to view with the naked eye, having an apparent visual magnitude of +7.74,[2] but is readily viewed with a pair of binoculars.[9] The star is located at a distance of 153 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +12 km/s.[1] A survey in 2015 has ruled out the existence of any additional stellar companions at projected distances from 26 to 305 astronomical units.[8]
The stellar classification of HD 220689 is G3V,[3] matching a yellow hued G-type main-sequence star that is generating energy through core hydrogen fusion. It is roughly 4.6 billion years old and is spinning with a projected rotational velocity of 5.5 km/s,[6] giving it a rotation period of around 29 days.[4] The star has a similar size, mass, and elemental abundances as the Sun. It is radiating 1.5[5] times the luminosity of the Sun from its photosphere at an effective temperature of 5,921 K.[4]
From 1998 to 2012, the star was under observation from the CORALIE echelle spectrograph at La Silla Observatory. In 2012, a long-period, wide-orbiting exoplanet was deduced from radial velocity variations. This was published in November.[10] The maximum orbital period allowing for dynamic stability of a hypothetical inner planet is 3.9 years.[4] In 2023, the inclination and true mass of HD 220689 b were determined via astrometry.[11]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (years) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 1.2+0.22 −0.11 MJ |
3.433+0.065 −0.064 |
6.23+0.15 −0.14 |
0.053+0.06 −0.037 |
71+13 −18or109+18 −13° |
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