Tau7 Eridani

Tau⁷ Eridani is a solitary star in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude of 5.235.^[2] Using the parallax method, the distance to this star can be estimated as around 251 light years.^[1]

For other star systems with this Bayer designation, see Tau Eridani.

τ⁷ Eridani

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Eridanus
Right ascension	03h 47m 39.65058s[1]
Declination	−23° 52′ 28.8352″[1]
Apparent magnitude (V)	5.235[2]
Characteristics
Spectral type	A3 Vs[3]
U−B color index	+0.168[2]
B−V color index	+0.067[2]
Astrometry
Radial velocity (Rv)	28.4±0.5[4] km/s
Proper motion (μ)	RA: +47.46[1] mas/yr Dec.: +49.10[1] mas/yr
Parallax (π)	13.00±0.28 mas[1]
Distance	251 ± 5 ly (77 ± 2 pc)
Absolute magnitude (MV)	+0.81[5]
Details
τ7 Eri A
Mass	2.03[6] M☉
Luminosity	37.6[7] L☉
Surface gravity (log g)	3.86±0.2[8] cgs
Temperature	8,740±200[8] K
Rotational velocity (v sin i)	18[8] km/s
Age	387[6] Myr
Other designations
τ7 Eridani, τ7 Eri, 28 Eridani, CD−24°1877, HD 23878, HIP 17717, HR 1181, SAO 168836[9]
Database references
SIMBAD	data

This is an A-type main sequence star with a stellar classification of A3 Vs,^[3] where the 's' indicates it has narrow absorption lines. It may be a chemically peculiar Am star, which means it displays unusual abundances of certain elements in its surface layers. Tau⁷ Eridani appears to be a low amplitude variable that displays slight fluctuations in luminosity over a period of 7.17 days. It is slowly rotating with a projected rotational velocity of 18 km/s,^[8] and is around 387 million years old.^[6]