Upsilon-1 Eridani, an orange giant star in Eridanus
Upsilon-1 Eridani is an orange giant star in the constellation Eridanus. At 125 light years away, it shines at an apparent visual magnitude of 4.51.
Upsilon-1 Eridani (HIP 21248)
Upsilon-1 Eridani is an orange giant star in the constellation Eridanus. At 125 light years away, it shines at an apparent visual magnitude of 4.51. It is moving through the Galaxy at a speed of 57.6 km/s relative to the Sun.
Sky position: RA 4h 33.5m, Dec -29° 46.0'
Common designations: Upsilon-1 Eridani, 50 Eridani, HR 1453, HD 29085, HIP 21248, Gaia DR3 4878920537149380992
Upsilon-1 Eridani has the spectral type K0+IIIbFe-0.5. K-type stars are orange stars with surface temperatures of about 3,900 to 5,300 K. Their spectra are rich in neutral metal lines and, in the cooler examples, molecular bands. 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 Upsilon-1 Eridani in the sky
Upsilon-1 Eridani lies in Eridanus. With a declination of -29° 46.0', it is visible from the entire Southern Hemisphere and from the Northern Hemisphere up to about latitude 60° 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 Upsilon-1 Eridani
Astrometry and spectroscopy
| Right Ascension (J2000) | 68.37730105° (4h 33.5m) |
| Declination (J2000) | -29.76649185° (-29° 46.0') |
| Galactic Longitude | 229.85817912° |
| Galactic Latitude | -41.58765234° |
| Proper motion RA | -114.74 mas/yr |
| Proper motion Dec | -272.06 mas/yr |
| Parallax | 26.03 ± 0.09 mas |
| Spectral Type | K0+IIIbFe-0.5 |
| Radial Velocity | 20.62 km/s |
Photometry
| Band | Magnitude | Abs. Mag. |
|---|---|---|
| U | 6.20 | 3.28 |
| B | 5.49 | 2.57 |
| V | 4.51 | 1.59 |
| R | 3.76 | 0.84 |
| I | 3.22 | 0.30 |
| J | 2.85 | -0.07 |
| H | 2.28 | -0.64 |
| K | 2.20 | -0.72 |
Colour index B-V: +0.98
Derivations
- Heliocentric distance: 38.42 pc (125 light years) (0.3% margin of error)
- Absolute visual magnitude: 1.59
- Transverse velocity: 53.8 km/s
- Space velocity relative to the Sun: 57.6 km/s
- Galactic position (X, Y, Z): -18.5 pc, -22.0 pc, -25.5 pc
- Galactic velocity (U, V, W): 37.0 km/s, -25.2 km/s, -36.2 km/s
Data: Extended Hipparcos Compilation (XHIP) and SIMBAD.