24 Eridani (HIP 17457)

24 Eridani is a blue-white subgiant star in the constellation Eridanus. At 709 light years away, it shines at an apparent visual magnitude of 5.25. It is moving through the Galaxy at a speed of 27.9 km/s relative to the Sun.

Sky position: RA 3h 44.5m, Dec -1° 9.8'

Common designations: 24 Eridani, HR 1146, HD 23363, HIP 17457, Gaia DR3 3251365632634326528

24 Eridani has the spectral type B7IV. B-type stars are hot (about 10,000 to 30,000 K), luminous and blue-white. They are massive, short-lived stars, typically only tens of millions of years old, and are common in young clusters and OB associations. Its luminosity class IV marks it as a subgiant: it has exhausted hydrogen in its core and is beginning to expand toward the giant phase.

How to find 24 Eridani in the sky

24 Eridani lies in Eridanus. With a declination of -1° 9.8', it is visible from the entire Southern Hemisphere and from the Northern Hemisphere up to about latitude 89° 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 24 Eridani

Astrometry and spectroscopy

Right Ascension (J2000)	56.12712711° (3h 44.5m)
Declination (J2000)	-1.16309097° (-1° 9.8')
Galactic Longitude	188.32113770°
Galactic Latitude	-41.08483789°
Proper motion RA	3.72 mas/yr
Proper motion Dec	-5.62 mas/yr
Parallax	4.60 ± 0.13 mas
Spectral Type	B7IV
Radial Velocity	27.00 km/s

Photometry

Band	Magnitude	Abs. Mag.
U	4.76	-1.92
B	5.15	-1.53
V	5.25	-1.43
J	5.40	-1.28
H	5.47	-1.22
K	5.43	-1.25

Colour index B-V: -0.10

Derivations

Heliocentric distance: 217.24 pc (709 light years) (2.9% margin of error)
Absolute visual magnitude: -1.43
Transverse velocity: 6.9 km/s
Space velocity relative to the Sun: 27.9 km/s
Galactic position (X, Y, Z): -162.0 pc, -23.7 pc, -142.8 pc
Galactic velocity (U, V, W): -18.9 km/s, -9.8 km/s, -18.0 km/s

Data: Extended Hipparcos Compilation (XHIP) and SIMBAD.