39 Crucis, a blue-white giant star in Crux
39 Crucis is a blue-white giant star in the constellation Crux. At 844 light years away, it shines at an apparent visual magnitude of 4.94.
39 Crucis (HIP 61966)
39 Crucis is a blue-white giant star in the constellation Crux. At 844 light years away, it shines at an apparent visual magnitude of 4.94. It is moving through the Galaxy at a speed of 32.9 km/s relative to the Sun.
Sky position: RA 12h 41.9m, Dec -59° 41.1'
Common designations: 39 Crucis, CH Crucis, HR 4823, HD 110335, HIP 61966, Gaia DR3 6059642884074103936
39 Crucis has the spectral type B5III. 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 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 39 Crucis in the sky
39 Crucis lies in Crux. With a declination of -59° 41.1', it is visible from the entire Southern Hemisphere and from the Northern Hemisphere up to about latitude 30° N. Observers poleward of latitude 30° 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 April, which makes the weeks around that month the best time to observe it.
Tabulated data for 39 Crucis
Astrometry and spectroscopy
| Right Ascension (J2000) | 190.48570493° (12h 41.9m) |
| Declination (J2000) | -59.68582068° (-59° 41.1') |
| Galactic Longitude | 301.73221068° |
| Galactic Latitude | 3.16380698° |
| Proper motion RA | -24.46 mas/yr |
| Proper motion Dec | -4.23 mas/yr |
| Parallax | 3.86 ± 0.08 mas |
| Spectral Type | B5III |
| Radial Velocity | 12.50 km/s |
Photometry
| Band | Magnitude | Abs. Mag. |
|---|---|---|
| U | 4.55 | -2.51 |
| B | 4.91 | -2.15 |
| V | 4.94 | -2.12 |
| J | 4.86 | -2.21 |
| H | 4.93 | -2.13 |
| K | 4.79 | -2.27 |
Colour index B-V: -0.03
Derivations
- Heliocentric distance: 258.78 pc (844 light years) (2.1% margin of error)
- Absolute visual magnitude: -2.12
- Transverse velocity: 30.5 km/s
- Space velocity relative to the Sun: 32.9 km/s
- Galactic position (X, Y, Z): 135.9 pc, -219.8 pc, 14.3 pc
- Galactic velocity (U, V, W): -18.6 km/s, -26.6 km/s, -5.6 km/s
Data: Extended Hipparcos Compilation (XHIP) and SIMBAD.