Tau-7 Eridani (HIP 17717)

Tau-7 Eridani is a white main-sequence star in the constellation Eridanus. At 260 light years away, it shines at an apparent visual magnitude of 5.24. It is moving through the Galaxy at a speed of 38.3 km/s relative to the Sun.

Sky position: RA 3h 47.7m, Dec -23° 52.5'

Common designations: Tau-7 Eridani, 28 Eridani, HR 1181, HD 23878, HIP 17717, Gaia DR3 5086958032728782848

Tau-7 Eridani has the spectral type A3Vs. A-type stars are white stars with surface temperatures of roughly 7,500 to 10,000 K. Their spectra are dominated by strong hydrogen lines, and many of them rotate rapidly. Its luminosity class V means it is a main-sequence (dwarf) star, still fusing hydrogen into helium in its core like the Sun.

How to find Tau-7 Eridani in the sky

Tau-7 Eridani lies in Eridanus. With a declination of -23° 52.5', it is visible from the entire Southern Hemisphere and from the Northern Hemisphere up to about latitude 66° N. It is bright enough to see with the naked eye under dark skies. It is highest in the sky at local midnight around December, which makes the weeks around that month the best time to observe it.

Tabulated data for Tau-7 Eridani

Astrometry and spectroscopy

Right Ascension (J2000)	56.91520873° (3h 47.7m)
Declination (J2000)	-23.87467746° (-23° 52.5')
Galactic Longitude	218.37179520°
Galactic Latitude	-50.30246506°
Proper motion RA	47.22 mas/yr
Proper motion Dec	48.52 mas/yr
Parallax	12.52 ± 0.09 mas
Spectral Type	A3Vs
Radial Velocity	28.52 km/s

Photometry

Band	Magnitude	Abs. Mag.
B	5.30	0.79
V	5.24	0.72
J	5.14	0.63
H	5.11	0.60
K	5.08	0.57

Colour index B-V: +0.06

Derivations

Heliocentric distance: 79.86 pc (260 light years) (0.7% margin of error)
Absolute visual magnitude: 0.72
Transverse velocity: 25.6 km/s
Space velocity relative to the Sun: 38.3 km/s
Galactic position (X, Y, Z): -40.0 pc, -31.7 pc, -61.4 pc
Galactic velocity (U, V, W): -35.8 km/s, -11.3 km/s, -8.0 km/s

Data: Extended Hipparcos Compilation (XHIP) and SIMBAD.