Gemini (Constellation)

The constellation Gemini (The Twins) can be seen overhead in the evening in spring. Although Castor has the Bayer designation of alpha, Pollux is actually about 0.5 in magnitude brighter than Castor.

Castor (Alpha Geminorum / α Gem)

The second brightest star is Gemini is actually a sextuple star system consisting of three sets of spectroscopic double stars. These are named Castor A, Castor B and Castor C.

Pollux (Beta Geminorum / β Gem)

The brightest star is Gemini is a class K0 red giant with an orbiting planet 2.9 times the size of Jupiter.

Alhena (Gamma Geminorum / γ Gem)

A class A spectral type (hydrogen burning) star. It is also a spectroscopic double and has a companion with an orbital period of 12.6 years.

Wasat (Delta Geminorum / δ Gem)

An F-class sub-giant with a K class companion.

Mebsuta (Epsilon Geminorum / ε Gem)

A cool G-class supergiant star at a distance of 900ly from our solar system.

Mekbuda (Zeta Geminorum / ζ Gem)

A Cepheid-variable supergiant about 1200ly away.

Propus (Eta Geminorum / η Gem)

A semi-regular variable M3 red giant.

Tejat (Mu Geminorum / μ Gem)

A giant irregular M3 class star 232ly away from our solar system.

Alzirr (Xi Geminorum / ξ Gem)

A 3rd magnitude F5 class 'sub-giant'

Gemini contains a number of open clusters of which one has been cataloged by Messier

M35 (or NGC 2168)

A relatively young (150 million years old) and diffuse open cluster of about 2500 stars within a volume of about 30 million light years across.

NGC 2129

An open cluster with an apparent magnitude of 6.7

NGC 2158

Located in the sky close to, and just south-west of M35, NGC 2158 is a much more compact open cluster than M35 and at an age of 1.05 billion years it is also much older.

NGC 2266

At around 1 billion years old this galactic cluster is about 10000ly from Earth.

NGC 2304

An open cluster with an apparent magnitude of 10

NGC 2420

An open cluster with an apparent magnitude of 8.3

IC 2157

An open cluster with an apparent magnitude of 8.4

NGC 2392 (The Eskimo, Clown or Clown Face Nebula)

A 9.1 magnitude planetary nebula with double-shell morphology giving the appearance of and Eskimo's or a clown's face.

NGC 2371-2 (NGC 2371 and NGC 2372)

A double-lobed planetary nebula at an approximate distance of 5000ly. This nebula has two entries in the New General Catalogue.

IC 443 (Jellyfish Nebula or Sharpless 248)

A supernova remnant about 5000ly away

IC 444

An emission/reflection nebula apparantly located close to IC 443

U Geminorum

U Geminorum is the prototype for U-Gem type stars which consist of a white dwarf star in a close binary star system. Detonation of the nova is thought to be caused by instability in the accretion disc.

Gemini shares its borders with the following constellations: Lynx, Auriga, Taurus, Orion, Monoceros, Canis Minor, Cancer

The Astronomical symbol for the constellation Gemini is represented by the Unicode character '♊'