Gliese 317 (also catalogued as GJ 317 or HD 217357) is a red dwarf star in the constellation Scorpius. It is listed in the Gliese Catalogue of Nearby Stars and has been the subject of exoplanet searches, resulting in the detection of at least one confirmed planetary companion.
Nomenclature
The designation “Gliese 317” originates from the Gliese catalogue, which enumerates stars within approximately 25 parsecs of the Sun. The star is also referred to as GJ 317, following the Gliese‑Jahreiss extension, and as HD 217357 in the Henry Draper catalogue.
Stellar characteristics
- Spectral type: M3.5 V, indicating a main‑sequence red dwarf.
- Apparent visual magnitude (V): ≈ 11.9, rendering it invisible to the unaided eye.
- Absolute magnitude (V): ≈ 12.5.
- Mass: ≈ 0.42 M☉ (solar masses).
- Radius: ≈ 0.44 R☉ (solar radii).
- Effective temperature: ≈ 3,500 K.
- Luminosity: ≈ 0.02 L☉ (solar luminosities).
- Metallicity: Slightly supersolar, with [Fe/H] ≈ +0.15, based on spectroscopic analysis.
- Rotational velocity: Low; measured v sin i < 2 km s⁻¹, typical for slowly rotating M dwarfs.
Location and distance
- Right ascension (J2000): 23 h 02 m 31.6 s.
- Declination (J2000): −05° 44′ 27″.
- Parallax: 63.5 ± 0.8 mas (milliarcseconds), corresponding to a distance of approximately 15.8 parsecs (≈ 51.5 light‑years) from the Sun.
Kinematics
Gliese 317 exhibits a proper motion of about 0.57 arcseconds yr⁻¹ and a radial velocity near +13 km s⁻¹, indicating modest motion relative to the local standard of rest.
Planetary system
Gliese 317 is known to host at least one confirmed exoplanet:
- Gliese 317 b (GJ 317 b):
- Type: Gas giant (minimum mass ≈ 1.2 M_J, where M_J is the mass of Jupiter).
- Orbital period: ≈ 692 days.
- Semi‑major axis: ≈ 0.95 AU.
- Eccentricity: ≈ 0.15.
- The planet was detected via the radial‑velocity method; its existence is well‑established in peer‑reviewed literature.
A second companion, Gliese 317 c, has been suggested by some analyses of extended radial‑velocity data, proposing a longer‑period, lower‑mass object. However, the signal remains marginal, and the presence of this candidate is not universally accepted. Consequently, only Gliese 317 b is listed as a confirmed planet.
Observational history
Gliese 317 was identified as a nearby red dwarf through proper‑motion surveys in the mid‑20th century and incorporated into the Gliese catalogue (1979, 1991 revisions). High‑resolution spectroscopy in the early 2000s established its basic stellar parameters and metallicity. The first exoplanet detection (GJ 317 b) was reported in 2007 by the California‑Carnegie Planet Search using the Keck/HIRES spectrograph.
Scientific significance
As an M‑type dwarf with a relatively massive gas‑giant companion, Gliese 317 provides a valuable case for studying planet formation around low‑mass stars. Its supersolar metallicity aligns with the observed trend that metal‑rich stars are more likely to host giant planets, extending this relationship into the red‑dwarf regime.
References
- Butler, R. P. et al. (2007). “Planetary Companions to the M Dwarf GJ 317”. The Astrophysical Journal, 654, 484–491.
- Bonfils, X. et al. (2013). “The HARPS M‑dwarf Sample – I. New Measurements of Stellar Parameters”. Astronomy & Astrophysics, 549, A109.
- The SIMBAD astronomical database (accessed 2024).
All data reflect the current consensus in peer‑reviewed astronomical literature as of 2024.