Summer constellations

Summer constellations

During the summer season, the silvery band of the Milky Way will be a precious guide in the search for the constellations. In the hemisphere boreal, we shall look for first of all a group of stars called the triangle of summer orientation. It is a formed  asterism In astronomy, an asterism is a remarkable figure drawn by particularly brilliant stars. by the most brilliant three stars which, in the north hemisphere, appear the first ones between June and September, from the fallen night.

These three stars are Altair of the constellation of the Eagle (Aquila, Aql), Deneb of the constellation of the Swan (Cygnus, Cyg) and Vega of the constellation of the Lyre (Lyra, Lyr). On bottom of Milky Way, this triangle is very easily recognizable, and often serves as point of departure to find the other constellations or track down some objects of the deep sky, as M27 or M57.

Image: By agreement the names of the stars of a constellation are prefixed by a Greek letter followed by the first 3 letters of the constellation, the example: α Ori, β Ori,... (Greek letters: α β γ δ ε ζ η θ ι κ λ μ ν ξ ο π ρ ς σ τ υ φ χ ψ ω).

Lyre constellation (Lyra)

The Lyre is a small constellation and it possesses a characteristic shape of parallelogram. It is very recognizable thanks to the most brilliant star of the summer sky Vega.
The Lyre is except the most brilliant band of the Milky Way, but in a zone still very rich in stars.
The antique civilizations in the Middle East and in India saw a vulture there. The Greek astronomers saw a lyre (or rather a "kithara") there and the oldest astronomical charts represent it generally held in the claws of a vulture.
Under the shape of a vulture, this constellation is hung on on Hercules's legend which, for its 6th work, killed the birds of the lake Stymphale.

The constellation is moreover close to the Swan and to the Eagle. The lyre was the musical instrument of Orpheus.

The constellation recognizes in its shape in rhombus and Vega its most brilliant star, is in the point of a young " V " which reminds its name. Under a wider angle, the constellation is on the adaptation which leaves the small She-bear, by way of the head of the Dragon, to come to get Vega. Vega is one of the summits of the big summer, easily locatable triangle.

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Swan constellation (Cygnus)

The Swan is big and brilliant one constellation, sometimes called the Cross of the North in opposition to the Cross of the South, because its stars are mainly arranged according to a big cross.
Crossed by the Milky Way, it contains several brilliant stars and numerous heavenly objects.
In the constellation of the Swan, the star Deneb is on the tail of the Swan, which its spread wings flies away southward, along the Milky Way.
The stars of the Swan possess the shape of a big cross and Deneb, the star placed at the top of this cross, is the most brilliant of the constellation.

According to the Greek mythology, one of the legends tells that the god Zeus had disguised as swan to seduce Leda, whose Gemini and Hélène of Troy he had child.
He could also represent Orpheus, transformed in swan after his murder and placed in heavens next to his lyre. The star Deneb (α Cyg) marks one of the angles of the summer, visible triangle from the night fallen (mag 1).
Three stars of the summer triangle, Deneb is the least brilliant, the summer triangle is formed by Deneb, Vega and Altair.

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Eagle constellation (Aquila)

The Eagle is a constellation situated about on the heavenly equator.
Easily recognizable and endowed with rather brilliant stars, it was listed by Ptolemee from the 2th century. This small equatorial constellation is on the Milky Way, below the Swan and on the West below this one in the evening. The main star names Altair, with its two companions Tarazed and Alshain the constellation shows only 3 stars of average brilliancy aligned.

The constellation of the Eagle, with its characteristic, visible asterisms since the latitudes of the Mediterranean Basin, was naturally listed by Ptolemee in its Almageste, but under the naming " Antinoos and its eagle ", Antinoos being a Greek slave who became the favorite of the emperor Hadrian.
Antinoos was definitively joined into the Eagle by Johann Bode.

Arrow constellation

We find also in the South of the Swan, the very former small constellation of the Arrow. It is situated in the Milky Way, in the North of the star Altair of the Eagle where, according to the legend, the Arrow reminds Hercules's fight against the vulture. The main star has for name Sham and it is a great giant.
The Arrow contains only a relatively brilliant opened heap. It is in mountain and on nights without the Moon that we can best observe this constellation. The legend says that the Arrow would have been thrown by Hercules in the direction of the Swan or of the Eagle. He could also involve the Cupid's dart, or even that of the Sagittarius.

The Arrow is in the summer triangle, in the North of the constellation of the Eagle. It is halfway between the head of the Swan and Vega.
The Arrow is a weak constellation but of rather characteristic shape, formed by four stars in adaptation. Most in the East (γ Sge) Is the most brilliant.
That of the middle (δ Sge) is hardly less brilliant than the first one. The less brilliant empennage of the Arrow is formed of α et β Sge.

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Hercules constellation

The constellation of Hercules globally little brilliant, is not far from the star Vega de la Lyre and under the head of the Dragon. We can also find it between the Boreal Crown and the Lyre. Hercules's adaptation reminds literally K inverted. Hercules's main star has for name Ras Algethi. It is a red giant whose diameter equals 800 times that of the Sun.
It is in fact about a double star the other constituent of which is also a giant. Hercules contains a beautiful spherical heap named Messier 13.

This one is just on the verge of visibility of the eye and contains an incredible number of stars. Messier 13 is situated in approximately 25000 light years of the Earth. Hercules also counts another spherical heap. It is about Messier 92, who is smaller and more concentrated than Messier 13.

Boreal Crown constellation

Between Hercule and the Cattleman is the constellation of the Boreal Crown. This one is small, but of well bounded shape. Indeed, 7 stars gather here to form a sort of diadem Diadem: Incomplete crown concerned the front of the head, the sign of a major power.. Gemma so called The Pearl or Alphekka is the most brilliant star of this group of stars and the study of its specter demonstrated that a star partner turns around her it a period of 14 days. It is effectively formed by stars arranged in an arc of circle, and the northern counterpart of the southern Crown.

The constellation is weak, but collected, and gives a pleasant spectacle when the conditions of observation are good. The boreal crown finds a way rather easily between Vega and Arcturus, and in the continuation of " sleeve of the pan " that forms the Great Bear.
Its shape in crown is rather net, contrary to that of its counterpart southern.

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