Tau1 Eridani

HR 818

Observation data Epoch 2000      Equinox 2000
Constellation	Eridanus
Right ascension	02h 45m 06.18710s
Declination	−18° 34′ 21.2149″
Apparent magnitude (V)	4.46
Characteristics
Spectral type	F7V
U−B color index	+0.00
B−V color index	+0.48
Astrometry
Radial velocity (Rv)	+25.9 km/s
Proper motion (μ)	RA: +334.20 mas/yr Dec.: +37.19 mas/yr
Parallax (π)	70.32 ± 1.83 mas
Distance	46 ± 1 ly (14.2 ± 0.4 pc)
Orbit
Period (P)	958 d
Eccentricity (e)	0.45
Periastron epoch (T)	39391.9
Argument of periastron (ω) (secondary)	180°
Details
Mass	1.15 M☉
Surface gravity (log g)	4.34 cgs
Temperature	6,231 K
Metallicity [Fe/H]	−0.08 ± 0.06 dex
Rotational velocity (v sin i)	28.02 km/s
Database references
SIMBAD	data
Other designations
1 Eridani, BD−19 518, GJ 111, HD 17206, HIP 12843, HR 818, SAO 11557.

Tau¹ Eridani (τ¹ Eri) is a binary star in the constellation Eridanus. It has an apparent magnitude of 4.46, making it visible to the naked eye in suitably dark conditions. This a spectroscopic binary with an orbital period of 958 days. It is located about 46 light years from the Earth.

Debris disk

A moderate far-infrared excess was observed for this star system, in the 12μm, 25μm, 60μm and 100μm wavelengths, by the Infrared Astronomical Satellite (IRAS), and published in 1993. This discovery was subsequently interpreted as indicating a debris disk with a radius near to 500 AU. It was further speculated that, if the star system had been observed at longer wavelengths, it was likely the debris disk would have been seen to have a radius considerably wider than 500 AU.

Later observations made by the Spitzer Space Telescope, published in 2004, detected no substantial infrared excess around the stars, within the 14-35μm range of wavelengths.