Rho2 Arietis
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Aries |
| Right ascension | 02h 55m 48.49800s |
| Declination | +18° 19′ 53.9029″ |
| Apparent magnitude (V) | 5.93 (5.45–6.01) |
| Characteristics | |
| Evolutionary stage | AGB |
| Spectral type | M6 III |
| U−B color index | +1.12 |
| B−V color index | +1.51 |
| R−I color index | +2.17 |
| Variable type | SRb |
| Astrometry | |
| Radial velocity (Rv) | +46.0 km/s |
| Proper motion (μ) | RA: −7.78 mas/yr Dec.: −14.98 mas/yr |
| Parallax (π) | 9.28±0.30 mas |
| Distance | 350 ± 10 ly (108 ± 3 pc) |
| Absolute magnitude (MV) | +0.60 |
| Details | |
| Mass | 1.21 M☉ |
| Radius | 107.9±6.2 R☉ |
| Luminosity | 1,390 L☉ |
| Surface gravity (log g) | 0.5 cgs |
| Temperature | 3,400 K |
| Metallicity [Fe/H] | –0.25 dex |
| Rotation | <909 days |
| Rotational velocity (v sin i) | 6.0±0.5 km/s |
| Other designations | |
| ρ2 Ari, 45 Arietis, RZ Arietis, BD+17 457, GC 3517, HD 18191, HIP 13654, HR 867, SAO 93189, PPM 118672 | |
| Database references | |
| SIMBAD | data |
Rho2 Arietis is an M-type red giant star in the northern constellation of Aries. Its name is a Bayer designation that is Latinized from ρ2 Arietis, and abbreviated Rho2 Ari or ρ2 Ari. The brightness of this star varies from magnitude 5.45 to 6.01, making it faintly visible to the naked eye under good observing conditions. With an annual parallax shift of 9.28 mas, it is approximately 350 light-years (110 parsecs) distant from the Earth. It is drifting further away from the Sun with a radial velocity of +46 km/s.
Rho2 Arietis is classified as a semiregular variable star with periods of 49.9 and 54.8 days. It has the variable star designation, RZ Arietis.
This is a red giant star with a stellar classification of M6 III; it is probably on the asymptotic giant branch, having exhausted its core helium. It is predicted to have started its life with 1.5 times the mass of the Sun, and is now down to 1.2 times the Sun's mass. At its current evolutionary stage Rho2 Arietis has expanded to 108 times the Sun's radius. It is radiating 1,390 times the Sun's luminosity from its photosphere at an effective temperature of 3,400 K.
This star possesses a strong magnetic field, one of the strongest for M-type giants. It also possesses a high lithium abundance, higher than expected from evolutionary models. The strong magnetic field, rapid rotation and unusual lithium abundance suggest this star may have engulfed a planet when it was on the red-giant branch.