Epsilon Geminorum marks Castor’s outstretched right leg. It is a supergiant belonging to the spectral class G8 Ib. It has an apparent magnitude of 3.06 and is approximately 840 light years distant.
The star is about 8,500 times more luminous than the Sun and has 19 times the solar mass. The star’s radius is around 105-175 times that of the Sun.
Epsilon Geminorum’s traditional name, Mebsuta, comes from the ancient Arabic MabsÅ«á¹ah, which means “the outstretched paw.” In Arabic culture, Epsilon and Zeta Geminorum represented the paws of a lion. Epsilon Geminorum is also sometimes called Melboula or Melucta.
Gamma Geminorum is another bright star in Gemini. With an apparent magnitude of 1.915, it is easily visible to the naked eye. The star is approximately 109 light years distant from Earth.
Gamma Geminorum is a white subgiant star with the stellar classification A1 IV, It has 2.8 solar masses and 3.3 times the solar radius. It is about 123 times more luminous than the Sun.
The star’s traditional name, Alhenam comes from the Arabic Al Han’ah, which means “the brand,” referring to the brand on a camel’s neck. It is also sometimes known as Almeisan, which is derived from the Arabic Al Maisan, which means “the shining one.”
Castor is the second brightest star in Gemini and the 44th brightest star in the sky. It is a visual binary with a combined apparent magnitude of 1.58. The two components are separated by 6” and have a revolution period of about 467 years.
Each component of the Alpha Geminorum system is in itself a spectroscopic binary star, which makes Castor a four-star system. Castor also has a faint companion about 72” away, an eclipsing binary star system with a period of just under a day.
Both components of the system are red (class M) dwarfs. This makes Castor a sextuple star system, as all six of its components are gravitationally bound together. The third component is classified as a variable star and has the designation YY Geminorum.
The primary component belongs to the spectral class A1 V and its companion is believed to be of spectral type M5 V. The stars of the secondary component have the stellar classifications A2 Vm and M2 V.
Pollux is the brightest star in Gemini and the 17th brightest star in the night sky. It is an evolved orange giant with the stellar classification K0 III. It has an apparent magnitude of 1.14 and is 33.78 light years distant from the solar system.
Beta Geminorum has twice the Sun’s mass and about nine times the solar radius. It is sometimes known as “The Head of the Second Twin,” from the Arabic Al-Ras al-Tau’am al-Mu’akhar.
An extrasolar planet was confirmed to be orbiting the star in June 2006. The planet, Pollux b, has a mass at least 2.3 times that of Jupiter and an orbital period of 590 days.