R Horologii is a red giant star approximately 1,000 light-years away in the southern constellation of Horologium.[10] It is a Mira variable with a period of 404.83 days,[11] ranging from apparent magnitude 4.7 to 14.3—one of the largest ranges in brightness known of stars in the night sky visible to the unaided eye.[2] The star is losing mass at the rate of 5.9×10−7 M☉·y−1.[7]
 R Horologii (R) in Horologium | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Horologium |
| Right ascension | 02h 53m 52.77465s[1] |
| Declination | −49° 53′ 22.7330″[1] |
| Apparent magnitude (V) | 4.7 - 14.3[2] |
| Characteristics | |
| Spectral type | M5-7e[3] |
| B−V color index | 1.044±0.011[4] |
| Variable type | Mira[5] |
| Astrometry | |
| Radial velocity (Rv) | +60.0±4.4[6] km/s |
| Proper motion (μ) | RA: +125.698[1] mas/yr Dec.: +35.975[1] mas/yr |
| Parallax (π) | 3.1999 ± 0.3632 mas[1] |
| Distance | approx. 1,000 ly (approx. 310 pc) |
| Details | |
| Temperature | 2,200[7] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
