R Geminorum

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R Geminorum
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Gemini
Right ascension 07h 07m 21.27095s[1]
Declination +22° 42′ 12.7077″[1]
Spectral type S3.5-6.5/6e

R Geminorum (R Gem) is a Mira variable and technetium star in the constellation Gemini. When at maximum light its apparent visual magnitude usually is between 6 and 7, while at minimum light it is typically near magnitude 14.[2] It is located approximately 575 parsecs (1,880 ly) away.[1]

It is one of the brightest known examples of an S-type star, a type that is similar to M-type star, but whose spectra shows zirconium oxide, yttrium oxide and technetium.[3] These exotic elements are formed in the star's core. Technetium has a half-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.[3]


  1. ^ a b c "R Geminorum". SIMBAD Astronomical Database. Centre de Données astronomiques de Strasbourg. Retrieved 20 January 2014. 
  2. ^ "Light Curve Generator". American Association of Variable Star Observers. Retrieved 17 February 2015. 
  3. ^ a b MacRobert, Alan (January 2015). "Weird R Gem Climbs to Maximum". Sky & Telescope. 129 (1): 51.