Dragon (constellation)

History

In much of Mythology S, the sinuous form of the constellation was interpreted like a dragon or a Serpent, Déesse sumérienne Tiamat while passing by the dragon which holy Georges killed.

In the Greek Mythology, the constellation would come is dragon which attacked Athéna in the war between the gods of the Olympe and the Titans, is dragon killed by Cadmos close to the place where it founded Thèbes, of that which is kept the Golden Fleece or even of the dragon Ladon which kept the Pommes of gold of the garden of Hespérides and was killed by Héraclès.

Observation of stars

; Localization of the Dragon All in all, the Dragon surrounds the Petite Ourse in direction of Véga. The location of the Dragon can be fact either starting from the Grande Ourse, or starting from the Triangle of summer.

The head of the Dragon is located between Véga of the Lyre and the head of the Petite Ourse, Kochab (β UMi).

One can also locate it starting from the constellation of the Cygne, the two eyes are in the prolongation of the northern wing.

The tail of the Dragon is the not very brilliant star located on alignment between Merak and Dubhe of the Grande Ourse and Polaris (α Ursae Minoris). This alignment is with the bottom of the image. One can notice that it is prolonged to a small star at the extreme edge of the image, which is γ Cep, the point of the hat of Céphée.

; Form constellation The constellation is not very brilliant and rather scattered, one needs good conditions (Mag 4) to trace it correctly.

One sees especially a pair of eyes, which are visible (Mag 2) a long time before the remainder of the constellation. The head of the Dragon forms a Astérisme called the Losange . It is a very lengthened regular rhombus, consisted of the two eyes (β and γ Draconis), mouth (ξ Draconis), and the symmetrical one of the mouth compared to the eyes (ι Her, at the extreme edge of the image).

The tail of the Dragon is parallel to the head of Small Ourse, then turns right towards the heart of the Dragon.

The heart of the Dragon, η Dra, is the relatively brilliant star located in the alignment which form the head of Small Ourse. The heart of the dragon is in the center of a small alignment of three stars, which marks the second direction of the body of the Dragon. This alignment was formerly the belly of the Dragon.

The " body of the dragon" current does not have very clear form, according to the conditions of visibility one can see a rectangle or a very crushed pentagon there.

Formerly, small Ourse belonged to the Dragon, of which it constituted the wing. The Dragon was then much more majestic, with the head of Small Ourse constituting the articulation of the wing and the limit of the body of the Dragon, and chains it towards Polaris marking the edge of the wing.

Principal stars

α Draconis (Thuban)

α Draconis (Thuban) is probably the most known star of the constellation of the Dragon, so much so that l'α was indicated to him by Johann Bayer. However, it is not a question of in no case of the most brilliant star of the constellation (it is only 8th). But, because of the phenomenon of Precession of the equinoxes, Thuban indicated the celestial north pole almost exactly there is 4 700 years, places which fell nowadays to α Ursae Minoris, called for this reason the pole star; consequently, α Draconis was the pole star at the time of the apogee of Egyptian civilization ancient and the Egyptian temples were often built in reference to this star. It is from now on with more 25° pole.

α Draconis is a hot giant star (9 800 K), 300 times more luminous than the Sun and distant of 300 light-years. It is also a star doubles, his/her companion - invisible since the Ground - turns around it in 51 days.

γ Draconis (Eltanin or Etamin)

γ Draconis, or Eltanin, or Etamin is the most brilliant star of the constellation of the Dragon. Its traditional name derives from an Arab word meaning the Snake .

γ Draconis is an orange giantess, 50 times larger than the Sun, 600 times more luminous. Located at 150 light-years of us, it moves in our direction and should pass to less than 30 light-years Solar system in 1,5 million years.

It is while seeking to measure the Parallaxe γ Draconis that James Bradley discovers the Aberration of the light towards 1725.

The Thèbes Greek antique, the “city of the dragon,” had a temple dedicated to this star.

Other stars

β Draconis, sometimes known under the name of Alwaid or of Rastaban, is a Supergéante, 40 times larger than the Sun. Located at approximately 400 light-years, its absolute magnitude is of -2,43, that is to say the glare of 800 suns. Its apparent magnitude is of 2,79. It has a companion located at 450 ua, that is to say nearly 70 billion km.

Nodus Secondus is located at 99 light-years. This star, brilliant like 50 suns, with its absolute magnitude of 0,63, is presented to us with a magnitude of 3,07.

Aldhibah, or Nodus Primus (ζ Dra), is a star apparent magnitude 3,17. Its absolute magnitude of -1,92 corresponds to a glare 500 times higher than that of the Sun. Outdistance: 300 light-years.

ED Asich (ι Dra), 40 times more luminous than the Sun (absolute magnitude 0,81), does not post any more, seen 100 light-years, than a magnitude of 3,29.

η Draconis is a star apparent magnitude 2,73. Its absolute magnitude is of 0,58. It is shining like 50 suns and is located at 88 light-years.

Among the double stars which account this constellation, one can also quote Arrakis (µ Dra), Kuma (ν Dra) including two white components one appreciably the same magnitude (4,87), φ Draconis or Tyl (ε Draconis).

The Dragon also contains two triple systems: 16-17 Draconis and 39 Draconis.

Celestial objects

The Dragon lodges the Nébuleuse planet gear NGC 6543, also known under the name of nebula of the Cats eye. Close to this one is the north pole of the ecliptic.

One also finds there the Galaxie spiral NGC 5866, sometimes indexed under the name of M102 and the Quasar 3C 351, distant of 7 billion light-years.

The galaxies NGC 5981-82-85 and NGC 6503 are there too.

See too

List of stars of the Dragon

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