Theta Indi, a white subgiant star in Indus
Theta Indi is a white subgiant star in the constellation Indus. At 99 light years away, it shines at an apparent visual magnitude of 4.48.
Theta Indi (HIP 105319)
Theta Indi is a white subgiant star in the constellation Indus. At 99 light years away, it shines at an apparent visual magnitude of 4.48. It is moving through the Galaxy at a speed of 19.9 km/s relative to the Sun.
Sky position: RA 21h 19.9m, Dec -53° 27.0'
Common designations: Theta Indi, HR 8140, HD 202730, HIP 105319, GJ 9733 A, Gaia DR3 6463748969563201152
Theta Indi has the spectral type A5IV-V. 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. 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 Theta Indi in the sky
Theta Indi lies in Indus. With a declination of -53° 27.0', it is visible from the entire Southern Hemisphere and from the Northern Hemisphere up to about latitude 37° N. Observers poleward of latitude 37° 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 September, which makes the weeks around that month the best time to observe it.
Tabulated data for Theta Indi
Astrometry and spectroscopy
| Right Ascension (J2000) | 319.96662274° (21h 19.9m) |
| Declination (J2000) | -53.44942608° (-53° 27.0') |
| Galactic Longitude | 343.68561905° |
| Galactic Latitude | -43.31973953° |
| Proper motion RA | 106.99 mas/yr |
| Proper motion Dec | -66.46 mas/yr |
| Parallax | 33.05 ± 0.09 mas |
| Spectral Type | A5IV-V |
| Radial Velocity | -8.29 km/s |
Photometry
| Band | Magnitude | Abs. Mag. |
|---|---|---|
| B | 4.64 | 2.24 |
| V | 4.48 | 2.08 |
| R | 5.82 | 3.42 |
| J | 3.43 | 1.03 |
| H | 4.22 | 1.82 |
| K | 4.14 | 1.74 |
Colour index B-V: +0.16
Derivations
- Heliocentric distance: 30.25 pc (99 light years) (0.3% margin of error)
- Absolute visual magnitude: 2.08
- Transverse velocity: 18.1 km/s
- Space velocity relative to the Sun: 19.9 km/s
- Galactic position (X, Y, Z): 21.1 pc, -6.2 pc, -20.8 pc
- Galactic velocity (U, V, W): -17.8 km/s, -8.0 km/s, -3.7 km/s
Data: Extended Hipparcos Compilation (XHIP) and SIMBAD.