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Gliese 221 (GJ 221), also known as BD-06 1339, is a star with an exoplanetary companion in the equatorial constellation of Orion. It is too faint to be visible to the naked eye, having an apparent visual magnitude of 9.70[2] and an absolute magnitude of 8.15.[4] Using parallax measurements, the distance to this system can be estimated as 66.2 light-years. It is receding from the Sun with a radial velocity of +23 km/s.[1] This is a high proper motion star, traversing the celestial sphere at an angular rate of 0.333″·yr−1.[7]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Orion |
| Right ascension | 05h 53m 00.285s[1] |
| Declination | −05° 59′ 41.44″[1] |
| Apparent magnitude (V) | 9.70[2] |
| Characteristics | |
| Spectral type | K7V/M0V[3] |
| B−V color index | 1.321±0.001[2] |
| Astrometry | |
| Radial velocity (Rv) | +22.9±0.4[1] km/s |
| Proper motion (μ) | RA: −1.170 mas/yr[1] Dec.: −346.762 mas/yr[1] |
| Parallax (π) | 49.2485 ± 0.0185 mas[1] |
| Distance | 66.23 ± 0.02 ly (20.305 ± 0.008 pc) |
| Absolute magnitude (MV) | 8.154±0.077[4] |
| Details | |
| Mass | 0.72±0.21[5] M☉ |
| Radius | 0.613±0.064[4] R☉ |
| Luminosity | 0.095±0.01[5] L☉ |
| Surface gravity (log g) | 4.74±0.02[5] cgs |
| Temperature | 4,324±100[5] K |
| Metallicity [Fe/H] | −0.34±0.08[5] dex |
| Age | 4.4±4[5] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
This is a late K-type or early M-type main-sequence star with a stellar classification of K7V/M0V.[3] It has 72% of the mass and 61% of the radius of the Sun.[5] The star is roughly 4.4[5] billion years old and is depleted in heavy elements, containing just 46% of solar abundance of iron.[5] It is an active star and the level of chromospheric activity has been found to vary significantly over time.[3] The star is radiating 10%[5] of the luminosity of the Sun from its photosphere at an effective temperature of 4,324 K.[5]
From 2003 to 2012, the star was under observance from the High Accuracy Radial Velocity Planet Searcher (HARPS). It is becoming less active and this reduced activity allowed for lower-mass planetary measurements to be made.
A super-Venus planet, and an eccentric Neptune / Saturn in the habitable zone, were deduced by radial velocity in January 2013.[8] They were confirmed in May 2013.[9] In January 2014, a candidate planet d was proposed.[10]
The planet Gliese 221b (BD-06 1339 b) is not transiting the disk of the parent star,[11] and its existence was disputed in 2022.[12]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b (disputed[12]) | >8.5806 ± 1.2712 M🜨 | 0.0428 ± 0.0007 | 3.8728 ± 0.0004 | — | — | — |
| c | >54.026 ± 9.534 M🜨 | 0.435 ± 0.007 | 125.94 ± 0.44 | 0.31 ± 0.11 | — | — |
| d (unconfirmed) | 22.246 M🜨 | 1.0947 | 500 | — | — | — |
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