39 Eridani
Star in the constellation Eridanus
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39 Eridani is a wide binary star[3] system in the equatorial constellation of Eridanus. It is visible to the naked eye as a faint, orange-hued star with a combined apparent visual magnitude of 4.87.[2] As of 2015, the components had an angular separation of 6.4″ along a position angle of 143°.[9] The system is moving further from the Sun with a heliocentric radial velocity of +7 km/s.[2]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Eridanus |
| Right ascension | 04h 14m 23.68902s[1] |
| Declination | −10° 15′ 22.6083″[1] |
| Apparent magnitude (V) | 4.87[2] (5.07 + 8.68)[3] |
| Characteristics | |
| Spectral type | K3 III + G2 V[3] |
| B−V color index | 1.156±0.003[2] |
| Astrometry | |
| Radial velocity (Rv) | 6.8±0.8[2] km/s |
| Proper motion (μ) | RA: −7.19[1] mas/yr Dec.: −161.05[1] mas/yr |
| Parallax (π) | 13.46±0.60 mas[1] |
| Distance | 240 ± 10 ly (74 ± 3 pc) |
| Absolute magnitude (MV) | 0.52[2] |
| Details | |
| 39 Eri A | |
| Mass | 1.77±0.49[4] M☉ |
| Radius | 12[5] R☉ |
| Luminosity | 81.3[6] L☉ |
| Surface gravity (log g) | 2.42±0.11[4] cgs |
| Temperature | 4,641±92[4] K |
| Metallicity [Fe/H] | 0.18±0.06[2] dex |
| Rotational velocity (v sin i) | 1.6[5] km/s |
| Age | 1.12+0.36 −0.27[4] Gyr |
| 39 Eri B | |
| Radius | 1.15+0.10 −0.06[7] R☉ |
| Luminosity | 1.369+0.07 −0.06[7] L☉ |
| Temperature | 5,816+168 −223[7] K |
| Other designations | |
| 39 Eri, BD−10°867, GC 5114, HD 26846, HIP 19777, HR 1318, SAO 149478, WDS J04144-1015[8] | |
| Database references | |
| SIMBAD | data |
The magnitude 5.07[3] primary, designated component A, is an aging giant star with a stellar classification of K3 III.[3] This object is more than a billion[4] years old with 1.77[4] times the mass of the Sun. With the hydrogen at its core exhausted, the star has expanded to 12[5] times the Sun's radius. It is a candidate super metal-rich star, showing a significant overabundance of iron compared to the Sun.[10] 39 Eridani A is radiating 81.3[6] times the luminosity of the Sun from its swollen photosphere at an effective temperature of 4,641 K.[4]
The secondary, component B, is a magnitude 8.68[3] G-type main-sequence star with a class of G2 V.[3] It has 1.15[7] times the Sun's radius and shines with 1.37 times the luminosity of the Sun at an effective temperature of 5,816 K.[7]