Tau5 Eridani
Star in the constellation Eridanus
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Tau5 Eridani, Latinized from τ5 Eridani, is a binary star system in the constellation Eridanus. It is visible to the naked eye with a combined apparent visual magnitude of 4.26.[2] The distance to this system, as estimated using the parallax technique, is around 293 light years.[1]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Eridanus |
| Right ascension | 03h 33m 47.27613s[1] |
| Declination | −21° 37′ 58.3830″[1] |
| Apparent magnitude (V) | 4.26[2] |
| Characteristics | |
| Spectral type | B0 V + B9 V[3] |
| U−B color index | 0.35[2] |
| B−V color index | −0.09[2] |
| Astrometry | |
| Proper motion (μ) | RA: +44.94[1] mas/yr Dec.: −28.16[1] mas/yr |
| Parallax (π) | 11.12±0.21 mas[1] |
| Distance | 293 ± 6 ly (90 ± 2 pc) |
| Absolute magnitude (MV) | −0.51[4] |
| Orbit[5] | |
| Period (P) | 6.2236 d |
| Eccentricity (e) | 0.2 |
| Periastron epoch (T) | 2424446.548 JD |
| Argument of periastron (ω) (secondary) | 313° |
| Semi-amplitude (K1) (primary) | 107 km/s |
| Semi-amplitude (K2) (secondary) | 103 km/s |
| Details | |
| τ5 Eri A | |
| Mass | 3.30+0.24 −0.20[6] M☉ |
| Radius | 3.2[3] R☉ |
| Luminosity | 188[7] L☉ |
| Surface gravity (log g) | 4.00±0.15[6] cgs |
| Temperature | 12,514±425[8] K |
| Rotational velocity (v sin i) | 55±8[3] km/s |
| Age | 157+23 −45[6] Myr |
| τ5 Eri B | |
| Radius | 2.6[3] R☉ |
| Rotational velocity (v sin i) | 50±8[3] km/s |
| Other designations | |
| τ5 Eridani, τ5 Eri, 19 Eridani, BD−22°628, HD 22203, HIP 16611, HR 1088, SAO 168634[9] | |
| Database references | |
| SIMBAD | data |
Tau5 Eridani is a double-lined spectroscopic binary system.[10] The two stars orbit each other closely with a period of 6.2 days and an eccentricity of 0.2.[5] On average, the two stars are separated by around 0.183 AU.[3]
The primary component is a B-type main sequence star with a stellar classification of B0 V.[3] It is around 157 million years old and is spinning with a projected rotational velocity of 55 km/s.[3] The star has around 3.3[6] times the mass of the Sun and 3.2[3] times the Sun's radius. It radiates 188[7] times the solar luminosity from an outer atmosphere at an effective temperature of 12,514 K.[8]
The secondary component has a stellar classification of B9 V.[3] It is slightly smaller, with an estimated size equal to 2.6 times the radius of the Sun.[3]
Although τ5 Eridani has no bright visual companion stars, the galaxy IC 1953 is less than 10' away. It is one of the brighter members of a loose group of galaxies called the Eridanus Group scattered around the components of τ Eridani.