HD 221420
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Octans[1] |
| Right ascension | 23h 33m 19.5789s[2] |
| Declination | −77° 23′ 07.194″[2] |
| Apparent magnitude (V) | 5.81±0.01[3] |
| Characteristics | |
| Evolutionary stage | subgiant[2] |
| Spectral type | G2 IV-V[4] |
| U−B color index | +0.31[5] |
| B−V color index | +0.68[5] |
| Astrometry | |
| Radial velocity (Rv) | 26.48±0.02[6] km/s |
| Proper motion (μ) | RA: +16.306 mas/yr[2] Dec.: +0.736 mas/yr[2] |
| Parallax (π) | 32.1023±0.0325 mas[2] |
| Distance | 101.6 ± 0.1 ly (31.15 ± 0.03 pc) |
| Absolute magnitude (MV) | +3.33[1] |
| Details | |
| Mass | 1.35±0.01[7] M☉ |
| Radius | 1.95±0.01[7] R☉ |
| Luminosity | 4.01±1[8] L☉ |
| Surface gravity (log g) | 4.03±0.03[7] cgs |
| Temperature | 5,830±44[9] K |
| Metallicity [Fe/H] | +0.34±0.07[10] dex |
| Rotational velocity (v sin i) | 2.8±0.5[11] km/s |
| Age | 3.65±0.23[7] Gyr |
| Other designations | |
| 83 G. Octantis, CPD−78°1473, FK5 3887, GC 32742, GJ 4340, HD 221420, HIP 116250, HR 8935, SAO 258154[12][13] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
HD 221420 (HR 8935; Gliese 4340) is a likely binary star system[7] in the southern circumpolar constellation Octans. It has an apparent magnitude of 5.81, allowing it to be faintly seen with the naked eye. The object is relatively close at a distance of 102 light years but is receding with a heliocentric radial velocity of 26.5 km/s.
HD 221420 has a stellar classification of G2 IV-V,[4] indicating a solar analogue with a luminosity class intermediate between a subgiant and a main sequence star. The object is also extremely chromospherically inactive.[4] It has a comparable mass to the Sun and a diameter of 1.95 R☉.[7] It shines with a luminosity of 4 L☉[8] from its photosphere at an effective temperature of 5,830 K,[9] giving a yellow glow. HD 221420 is younger than the Sun at 3.65 billion years.[7] Despite this, the star is already beginning to evolve off the main sequence. Like most planetary hosts, HD 221420 has a metallicity over twice of that of the Sun[7] and spins modestly with a projected rotational velocity 2.8 km/s.[11]
There is a mid-M-dwarf star with a similar proper motion and parallax to HD 221420, which is likely gravitationally bound to it. The two stars are separated by 698 arcseconds, corresponding to a distance of 21,756 AU.[7]
Planetary system
[edit | edit source]In a 2019 doppler spectroscopy survey, an exoplanet was discovered orbiting the star. The planet was originally thought to be a super Jupiter, having a minimum mass of 9.7 MJ.[9] However, later observations using Hipparcos and Gaia astrometry found it to be a brown dwarf with a high-inclination orbit,[7][10][14] revealing a true mass of 23 MJ.[7]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (years) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 22.9±2.2 MJ | 10.15+0.59 −0.38 |
27.62+2.45 −1.54 |
0.14+0.04 −0.03 |
164.0+1.9 −2.6° |
— |
References
[edit | edit source]- ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value). XHIP record for this object at VizieR.
- ^ a b c d e Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value). Gaia DR3 record for this source at VizieR.
- ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ a b c Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ a b c d e f g h i j k l Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value). Gaia DR2 record for this source at VizieR.
- ^ a b c Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
