s Eridani (HIP 12413)

s Eridani is a white main-sequence star in the constellation Eridanus. At 145 light years away, it shines at an apparent visual magnitude of 4.75. It is moving through the Galaxy at a speed of 30.8 km/s relative to the Sun.

Sky position: RA 2h 39.8m, Dec -42° 53.5'

Common designations: s Eridani, HR 789, HD 16754, HIP 12413, Gaia DR3 4946915263923114368

s Eridani has the spectral type A1Vb. 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 s Eridani in the sky

s Eridani lies in Eridanus. With a declination of -42° 53.5', it is visible from the entire Southern Hemisphere and from the Northern Hemisphere up to about latitude 47° N. Observers poleward of latitude 47° S see it as circumpolar: it never sets. It is bright enough to see with the naked eye under dark skies. It is highest in the sky at local midnight around November, which makes the weeks around that month the best time to observe it.

Tabulated data for s Eridani

Astrometry and spectroscopy

Right Ascension (J2000)	39.94989709° (2h 39.8m)
Declination (J2000)	-42.89181086° (-42° 53.5')
Galactic Longitude	255.67309107°
Galactic Latitude	-62.98086826°
Proper motion RA	118.80 mas/yr
Proper motion Dec	-1.52 mas/yr
Parallax	22.56 ± 0.53 mas
Spectral Type	A1Vb
Radial Velocity	18.00 km/s

Photometry

Band	Magnitude	Abs. Mag.
B	4.81	1.58
V	4.75	1.52
J	4.68	1.45
H	4.62	1.39
K	4.46	1.23

Colour index B-V: +0.06

Derivations

Heliocentric distance: 44.32 pc (145 light years) (2.4% margin of error)
Absolute visual magnitude: 1.52
Transverse velocity: 25.0 km/s
Space velocity relative to the Sun: 30.8 km/s
Galactic position (X, Y, Z): -5.0 pc, -19.5 pc, -39.5 pc
Galactic velocity (U, V, W): -17.6 km/s, -24.5 km/s, -5.9 km/s

Data: Extended Hipparcos Compilation (XHIP) and SIMBAD.