Pi Eridani (HIP 17593)

Pi Eridani is a red giant star in the constellation Eridanus. At 510 light years away, it shines at an apparent visual magnitude of 4.42. It is moving through the Galaxy at a speed of 75.6 km/s relative to the Sun.

Sky position: RA 3h 46.1m, Dec -12° 6.1'

Common designations: Pi Eridani, 26 Eridani, HR 1162, HD 23614, HIP 17593, Gaia DR3 5114760146310175488

Pi Eridani has the spectral type M1III. M-type stars are cool red stars below about 3,900 K whose spectra are dominated by titanium oxide molecular bands. Red dwarfs, red giants and red supergiants all fall in this class. Its luminosity class III marks it as a giant: an evolved star that has left the main sequence and swollen to many times its original size.

How to find Pi Eridani in the sky

Pi Eridani lies in Eridanus. With a declination of -12° 6.1', it is visible from the entire Southern Hemisphere and from the Northern Hemisphere up to about latitude 78° 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 Pi Eridani

Astrometry and spectroscopy

Right Ascension (J2000)	56.53556342° (3h 46.1m)
Declination (J2000)	-12.10158848° (-12° 6.1')
Galactic Longitude	201.55388464°
Galactic Latitude	-46.46712841°
Proper motion RA	56.12 mas/yr
Proper motion Dec	59.45 mas/yr
Parallax	6.39 ± 0.17 mas
Spectral Type	M1III
Radial Velocity	45.20 km/s

Photometry

Band	Magnitude	Abs. Mag.
U	8.05	2.08
B	6.04	0.07
V	4.42	-1.55
R	3.08	-2.89
I	2.03	-3.94
J	1.36	-4.61
H	0.47	-5.50
K	0.29	-5.68

Colour index B-V: +1.62

Derivations

Heliocentric distance: 156.39 pc (510 light years) (2.6% margin of error)
Absolute visual magnitude: -1.55
Transverse velocity: 60.6 km/s
Space velocity relative to the Sun: 75.6 km/s
Galactic position (X, Y, Z): -100.2 pc, -39.6 pc, -113.4 pc
Galactic velocity (U, V, W): -75.0 km/s, -7.5 km/s, 6.5 km/s

Data: Extended Hipparcos Compilation (XHIP) and SIMBAD.