Gemini

The Gemini are a Constellation Zodiaque crossed by the Sun June 20th with the July 20th. In the order of the zodiac, the constellation is between the Taureau at the west and the weak Cancer at the east.

It is surrounded by the Cocher and the Lynx hardly visible in north and the Licorne and the Puppy in the south.

Two star S of the constellation are named according to the twins of the legend: Beaver (α  Geminorum) and Pollux (β  Geminorum).

The Gemini are also a sign Zodiaque corresponding to the sector of 30° of the ecliptic crossed by the Sun of the May 21st to the June 20th.

History

For the Greeks, the constellation of the Gemini represented Castor and Pollux, the twin brothers of Helene of Troy. The Romans saw Romulus and Remus there.

The space exploration program Gemini, carried out by NASA in the Sixties, was named according to this constellation.

Observation of stars

; Localization of the constellation The constellation of the Gemini can be located starting from the Grande Ourse: the diagonal of the large carriage points on Pollux, and this alignment is prolonged on the diagonal of Orion.

Conversely, the Gemini can be located starting from Orion: Alignment between Rigel and Bételgeuse passes by the foot of Gémeau (Almeisan, or Alhena, γ Gem) and points on Pollux.

; Form constellation The constellation has a rather clear form, if the conditions of visibility are satisfactory (Mag 4). The stars are distributed along two directions of alignments, one - SO, which goes from the head of the Gemini towards Orion, and the other NO-SE, in the direction marked by the couple Castor/Pollux, which is also that of the wide arms of the two Gemini, that of the knees and the feet. ; Alignments at long distance Pollux is in the beginning many alignments at long distance.

  • the diagonal of Andromède, which passes by Pollux, Capella, α Persei, Andromède, and continues with the Verseau until the Sagittarius.
  • West-south-west alignment, passing by the Bull and the Whale, towards Fomalhaut and the Sagittarius
  • the alignment South-south-west, which passes by Rigel and Bételgeuse, and skirts Éridan to finish on Achernar.
  • the Southern alignment, which pass by Procyon, Sirius, the Colombe and is also completed on Achernar.
  • Contrary to the diagonal of Andromède, alignment is prolonged on Alphard, the extremity of the Voiles, the Cross of the South and the foot of the Centaure, the tail of the Scorpion, and the arc and the head of the Sagittarius.
  • Contrary to the Bull, Régulus of the Lion, Spica of the Virgin , Antarès of the Scorpion, and is completed on the head of the Sagittarius.

Principal stars

See also: List of stars of the Gemini

Beaver (α  Geminorum)

Castor is a white giant star. With a magnitude of 1,58, it is not most brilliant of the constellation (this place returns in Pollux) and its designation “α” gives an account of its position all to the north of the Gemini. It nevertheless remains the 24 {{E}} the most brilliant star of the vault of heaven.

Beaver is in fact a multiple system. In first approach, it is a star doubles. Beaver-HAVe is a white star magnitude 1,98. Beaver-B is also white, magnitude 2,88. They turn one around the other according to a eccentric Orbite in 400 years.

Each one of these two stars is itself doubles. Beaver-HAVe is made up of two stars similar orbiting in 9,2 days to the distance from 0,04 ua. The two stars of Beaver-B achieve a revolution in only 2,9 days.

With approximately 1.000 ua of this double couple Beaver-C orbits, ninth magnitude, which is itself doubles. On the whole, Castor is a sixfold stellar system.

Pollux (β  Geminorum)

The most brilliant star of the constellation is Pollux (β  Geminorum), magnitude 1,16, the 16th most brilliant star of the sky. It is an orange, distant giantess of 34 light-years (enough near to our Solar system, therefore), approximately 10 times broader than the Sun.

Other stars

In the constellation of the Gemini, the other stars bearing a proper name form the body of each twin: Mebsuta (ε  Gem), Tejat Posterior (μ  Gem) and Propus (η  Gem) for the body of Beaver, Wasat (δ  Gem), Mekbuda (ζ  Gem) and Alhena (γ  Gem) for that of Pollux.

Two stars have Exoplanète S: HD  49674 with a planet 0,12 times mass of Jupiter, orbiting to 0,056 8 ua in 4,948 days, and HD  50554, 4,9 times more massive than Jupiter, with 2,38 ua for a 1.279 days revolution.

Celestial objects

The constellation of the Gemini contains, inter alia, the Nébuleuse diffuses IC 443, the open Amas S M35 and NGC 2420 and the planetary nebulas NGC 2371, NGC 2392 and PLN205-14.1.

See too

  • List of stars of the Gemini

Zh-yue: 雙子座

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