Tau-9 Eridani (HIP 18673)

Tau-9 Eridani is a white star in the constellation Eridanus. At 327 light years away, it shines at an apparent visual magnitude of 4.66. It is moving through the Galaxy at a speed of 27.3 km/s relative to the Sun.

Sky position: RA 3h 59.9m, Dec -24° 1.0'

Common designations: Tau-9 Eridani, 36 Eridani, HR 1240, HD 25267, HIP 18673, Gaia DR3 5083386372283360000

Tau-9 Eridani has the spectral type ApSi. 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.

How to find Tau-9 Eridani in the sky

Tau-9 Eridani lies in Eridanus. With a declination of -24° 1.0', 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-9 Eridani

Astrometry and spectroscopy

Right Ascension (J2000)	59.98118237° (3h 59.9m)
Declination (J2000)	-24.01621589° (-24° 1.0')
Galactic Longitude	219.64693535°
Galactic Latitude	-47.62455191°
Proper motion RA	11.79 mas/yr
Proper motion Dec	16.74 mas/yr
Parallax	9.97 ± 0.10 mas
Spectral Type	ApSi
Radial Velocity	25.50 km/s

Photometry

Band	Magnitude	Abs. Mag.
U	4.11	-0.90
B	4.52	-0.49
V	4.66	-0.35
R	4.64	-0.37
I	4.77	-0.24
J	4.83	-0.18
H	4.89	-0.12
K	4.80	-0.20

Colour index B-V: -0.14

Derivations

Heliocentric distance: 100.26 pc (327 light years) (1.0% margin of error)
Absolute visual magnitude: -0.35
Transverse velocity: 9.7 km/s
Space velocity relative to the Sun: 27.3 km/s
Galactic position (X, Y, Z): -52.0 pc, -43.1 pc, -74.1 pc
Galactic velocity (U, V, W): -21.5 km/s, -9.6 km/s, -13.8 km/s

Data: Extended Hipparcos Compilation (XHIP) and SIMBAD.