Dragon (constellation)

Dragon constellation
Latin name	Draco
Latin genitive	Draconis
Abbreviation	Dra
Right ascension	09 h 22 m 28 s to  20 h 54 m 49 s
declination	+ 47 ° 32 ′ 51 ″ to  + 86 ° 27 ′ 56 ″
surface	1082.952 deg² rank 8
Completely visible	90 ° N to 1 ° S
Observation time for Central Europe	All year round
Number of stars brighter than 3 mag	3
Brightest star (size)	Etamine (2.23)
Meteor streams	Draconids
Neighboring constellations ( clockwise from north )	Little Bear giraffe Big Bear Bear keeper Hercules lyre swan Cepheus
swell	IAU ,

Dragon , in Latin Draco , is a constellation of the northern sky and for Central Europe it is circumpolar , i.e. a region of the sky that is visible all year round.

description

Pole Star

The constellation Dragon (Draco) as it can appear to the naked eye - the bright North Star belongs to the constellation Little Bear (Ursa Minor)

Draco is a very extensive constellation whose area borders on eight other constellations. The long train of stars of the dragon winds around the Little Bear (Ursa Minor), spanning almost half of the circumpolar sky. The head facing Hercules is represented by four stars, with β ( Alwaid , yellow-green) and γ ( Etamin , red) as the different colored eyes. In the area of ​​the tail, the constellation extends between the Little and the Big Bear (Ursa Maior) to the constellation Giraffe (Camelopardalis) near today's celestial north pole. Five thousand years ago, the earth's axis showed the pole of the northern sky near the star α ( Thuban ); this may be the case again in around twenty thousand years.

On the other hand, the northern ecliptic pole , around which the celestial north pole wanders once in almost 26,000 years as an extension of the earth's axis due to the precession , is located in the front turn of the star formation, the Cat's Eye Nebula (NGC 6543) .

history

The dragon is one of the classic 48 constellations of antiquity mentioned by Ptolemy . In ancient Greek astronomy , the constellation of the dragon also included the little bear's train of stars, which was perceived as the dragon's wing.

Due to the precession movement of the earth, the main star Thuban (α Draconis) was the polar star of the northern sky 5000 years ago. The closest distance to the exact celestial pole was around 2830 BC. Reached with 10 arc minutes .

mythology

There are various stories with a mythological background about this constellation or the figure of a dragon seen in it .

In the Babylonian epic of creation Enūma eliš it is told that Marduk defeated the goddess of salt water Tiamat , depicted as a horned sea serpent, divides her body lengthways, bends one half and thus forms the sky. From the other half of the dragon he creates the earth. In this version, the dragon stretches across the sky with its head and tail diametrically opposite each other.

No dragon-like monster appears in the creation stories of Greek mythology . But in the myths of heroes a dragon has to be overcome. The later city of Thebes can only be founded after Kadmos killed the dragon that lived at this point and sank half of its teeth into the ground. And in the Argonauts legend about Jason , the dragon guarded the Golden Fleece .

In the saga of Heracles it was a question of a hundred-headed dragon, Ladon . Heracles was given the task of stealing the golden apples from the Hesperides , the enjoyment of which promised immortality and eternal youth. The apples were closely guarded by Ladon and the Hesperides. Heracles was finally able to take the apples. According to one version, he is said to have persuaded the titan Atlas to fetch the apples for him - and meanwhile took on the heavy burden of carrying the vault of heaven. According to the other version, Heracles got the apples himself, killing the dragon. Heracles was also immortalized as a constellation. He can be found under the Roman name Hercules near the dragon's head in the sky.

Celestial objects

Stars

B.	F.	Names or other designations	Size (mag)	Lj	Spectral class
γ	33	Etamin , Ettanin, Eltanin	2.23	150	K5 III
η	14th	Aldhibain, Al Dhibain	2.74	80	G8 III
β	23	Alwaid , Rastaban, Asuia	2.79	400	G2 II
δ	57	Altais , Al Tais, Nodus Secundus	3.07	100	G9 III
ζ	22nd	Aldhibah , Nodus I.	3.17	300	B6 III
ι	12	Edasich , Ed Asich	3.29	102	K2 III
χ	44		3.57	25th	F7 V
α	11	Thuban	3.65	300	A0 III
ξ	32	Grumium	3.7	about 110	K2 III
ε	63	Epsilon Draconis (Tyl)	3.83	147	G7 + K5
λ	1	Giausar , Giaufar, Juza	3.8	approx. 330	M0 III
κ	5		3.87	400	B8 III
θ	13		4.01	60	F8 IV
φ	43		4.22
ψ	31	Dsiban	4.27	70	F5 + F9
		HR 3751	4.29
τ	60		4.45
	17th		4.5	300	B9 + A1 + B9
ρ	67		4.51
π	58		4.59
i	10	CU	4.65
ο	47		4.66
σ	61	Alsafi	4.7	18.8	K0 V
	39		4.8	150	A1 + A5
ω	28		4.80
υ	52		4.82
	42	Fafnir	4.82	317	K1.5 III
G	18th		4.83
ν 2	25th	Kuma	4.87	120	A5
ν 1	24	Kuma	4.88	120	A6
H	19th		4.89
μ	21st	Alrakis , Arrakis	4.92	85	F7 V + F7 V
	6th		4.94
	4th	CQ	4.95
	54		4.99
	15th		5.00
	30th		5.02
	36		5.03
	35		5.04
c	46		5.04
f	27		5.05
	59		5.13
	2		5.20
	73		5.20
	26th		5.23	50	G0 + K3
	8th		5.24
	3		5.30
	9		5.32
	50		5.35
	51		5.38
	7th		5.43
ψ	34		5.45
	75		5.46
	49		5.48

The names of the stars Ettanin , Thuban and Rastaben are of Arabic origin and are derived from the Arabic name for dragon .

Ettanin, the brightest, is a star 150 light-years away belonging to the spectral class K5 III.

Double stars

system	Sizes (mag)	distance
ε	3.9 / 7.3	3.2 "
ψ	4.6 / 5.8	30.3 "
ν	4.9 / 4.9	61.9 "
39	5.0 / 7.8 / 7.2	3.9 "and 89"
26th	5.3 / 8.0	1.7 "
17th	5.4 / 6.4	3.3 "
μ	5.7 / 5.7	1.9 "

Ny Draconis is a binary star system 120 light years away. Due to the wide angular distance of almost 62 arc seconds, the two components can be resolved into individual stars with prism binoculars .

39 Draconis is a multiple star system 150 light years away with three stars orbiting a common center of gravity.

Variable stars

star	Size (mag)	period	Type
R.	6.7-13	245.5 days	Mira type
T Dra	7.2-13.5	421.2 days	Mira type
RY Dra	6.5-8.0	172 days	semi-regularly changeable

The stars R and T Draconis are pulsation-variable stars of the Mira type . These are bright red giants or supergiants that rhythmically expand and contract again, which can be observed as a clear fluctuation in brightness. During the maximum, R and T become so bright that they can be detected with binoculars. At a minimum, their brightness drops below 13 mag, so that their observation requires a larger telescope.

Messier and NGC objects

Messier (M)	NGC	other	Size (mag)	Type	Surname
102	5866		9	Galaxy
	5907		10	Galaxy
	6503		10	Galaxy
	6543		9	Planetary nebula	Cat's Eye Nebula

NGC 6543 is a planetary nebula , i.e. a star that at the end of its evolution has repelled the outer gas envelope. In the center there is an extremely hot white dwarf star . NGC 6543 appears in the telescope as a diffuse nebula with a faint star in the center. The complex structure of the nebula that gave it the name Cat's Eye Nebula is only visible in long-exposure photographs. The Hubble telescope provided particularly impressive images of the nebula.

The Messier object M 102 is a spiral galaxy of the type S0 at a distance of 30 million light years.

NGC 5907 and NGC 6503 are Sc-type spiral galaxies 30 and 15 million light years away, respectively.

All three galaxies are not very noticeable in the telescope and appear as foggy spots.

See also

• List of constellations

Individual evidence

1. ↑ Jim Tester: A History of Western Astrology. Boydell & Brewer, 1999, ISBN 0-85115-255-4 , p. 121.

Web links

Commons : Dragon (constellation)  - collection of images, videos and audio files

• Astronomie.de: The constellation Dragon
• Astronomie.de: The dragon
• Spektrum.de : Amateur recording of galaxies in dragons