Sagittarius


Sagittarius


English nameArcher

Major
stars
gamma SagittariiAlnaslmagn. 3,1RA: 18h 05m 48.50sDec: -30 25' 26.3"
delta SagittariiKaus Mediamagn. 2,8RA: 18h 20m 59.67sDec: -29 49' 41.3"
epsilon SagittariiKaus Australismagn. 1,9RA: 18h 24m 10.38sDec: -34 23' 04.6"
zeta SagittariiAscellamagn. 2,7RA: 19h 02m 36.71sDec: -29 52' 49.1"
eta Sagittariimagn. 3,2RA: 18h 17m 37.66sDec: -36 45' 41.8"
lambda SagittariiKaus Borealismagn. 2,9RA: 18h 27m 58.26sDec: -25 25' 17.7"
pi Sagittariimagn. 3,0RA: 19h 09m 45.84sDec: -21 01' 24.9"
sigma SagittariiNunkimagn. 2,0RA: 18h 55m 15.92sDec: -26 17' 48.1"
tau Sagittariimagn. 3,4RA: 19h 06m 56.42sDec: -27 40' 13.0"
phi Sagittariimagn. 3,3RA: 18h 45m 39.37sDec: -26 59' 26.8"

DescriptionConstellation of the zodiac, through which the Sun transits from the end of December to the end of January. It is to the northeast of Scorpius. Sagittarius contains many stars of average magnitude, but it is remarkable in particular for the great quantity of clusters and nebulas.

The principal open clusters are in the northern zone of the constellation. M23 is an ample cluster composed by hundred stars, some of which reach the ninth magnitude: it is visible with good binoculars. M24 is really a zone of the Milky Way in which many stars are assembled in perspective. M25, finally, is a rather diffused cluster, composed by about 50 stars distributed around a yellow supergiant.

To south the of M25 there is M22 a globular cluster of sixth magnitude: seen with small telescopes it appears of elliptical shape, while to resolve the single stars you need a telescope of average power.

M8Near the border with Ophiuchus there is M8, the Lagoon Nebula (on the left): it is visible to the naked eye as an out-of-focus spot; modest M20instrments allow to see a dark trace that cuts into halves the nebula and that gives it the name. A little northwards there is M20, the very beautiful and very famous Trifid Nebula (on the right), which takes the name from the characteristic strips of dust that seem to divide it into three portions. On the border with Scutum and Serpens, finally, there is M17, that because of its circular shape is denominated in many ways: Omega Nebula, Swan Nebula or Horse-shoe Nebula.


Mythology
and history
The constellation is identified with a centaur which bends a bow toward the near Scorpius: it is therefore the second centaur of the sky (the other one is just Centaurus).

According to the version of Eratostenes, instead, the constellation represents Crotus, a satyr son of Pan: the satyrs were fantastic creatures with human bodies, two equine legs, tail and small horns. Crotus was the inventor of the bow (for this reason in the sky he bends a bow) and he loved to spend the time with the nine Muses, the divinities of arts: amused by his company, they asked Zeus to give him a place among the stars.


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