| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Gemini |
| Right ascension | 07h 07m 21.271s[2] |
| Declination | +22° 42′ 12.75″[2] |
| Apparent magnitude (V) | 6.0 - 14.0[3] |
| Characteristics | |
| Evolutionary stage | AGB |
| Spectral type | S2,9e-S8,9e(Tc)[3] |
| Variable type | mira[3] |
| Astrometry | |
| Radial velocity (Rv) | −45.2[4] km/s |
| Proper motion (μ) | RA: −8.765[2]mas/yr Dec.: 0.665[2]mas/yr |
| Parallax (π) | 1.1795±0.0960 mas[2] |
| Distance | 2,800 ± 200 ly (850 ± 70 pc) |
| Details | |
| Radius | 431[5] R☉ |
| Luminosity | 5,500[5] L☉ |
| Temperature | 2,400[5] K |
| Other designations | |
| BD+22 1577,HD 53791,HIP 34356,HR 2671,SAO 79070[6] | |
| Database references | |
| SIMBAD | data |
R Geminorum (R Gem) is aMira variable andtechnetium star in the constellationGemini. It is located approximately 850 parsecs (2,800 ly) away.
R Geminorum pulsates with an average period of 369.9 days, varying by up to eightmagnitudes at visual wavelengths.[3] When at maximum light its apparent visual magnitude is usually between 6 and 7, while at minimum light it is typically near magnitude 14.[7]
R Geminorum is one of the brightest known examples of anS-type star, a type that is similar toM-type star, but whose spectra showszirconium oxide,yttrium oxide andtechnetium.[8] These exotic elements are formed in the star's core. Technetium has ahalf-life of just 4.2 million years, so it must have been brought up from the core relatively recently. R Gem has an unusual amount of it, even for an S-type star.[8]
