Caligula

History

All the area describes the legend of the princess Andromède, girl of the queen Cassiopée (in north) and of Céphée (a little more in the west), king d' Éthiopie.

Cassiopée always praised beauty of his/her daughter; when she dared to say that she exceeded even the nymph S of the seas. The nymphs required of their father Poséidon, god of the sea, to avenge them. Poséidon irritated and sent a monster (Cetus) with for mission of devastating the coasts of the kingdom. The only way of saving the kingdom was to offer Andromède in sacrifice to alleviate the anger of the monster.

Céphée agreed to sacrifice his/her daughter by connecting it to a rock (the chains of Andromède are in direction of Céphée) to let Cetus devour it.

Fortunately, the hero Persée (in north east), passing by there, killed the Cetus monster by petrifying it (with the head of the Méduse), delivered the beautiful one, and on its beautiful winged horse PEGASE removed it (in the west).

It is also said that for her pride, the Cassiopée queen was connected with her throne, condemned to turn around the North pole and sometimes to hang with back in a way far from worthy.

Observation of stars

Location

The constellation is located starting from Algol and of the great square of PEGASE. On the basis of this square, one sees taking shape immense “a carriage”, three times larger than that of the Grande Ourse, formed by α And, α, β, and λ Peg (the Grand square of PEGASE), then in the prolongation of his diagonal, starting from α And, β And, γ And, and finally Algol (β Persei).

Alignments

This diagonal of Andromède of 60° of amplitude belongs to an immense alignment which makes the turn of the sphere, and which is an axis of major location of the vault of heaven. On the basis of the Grand square of PEGASE it passes by Algol, Capella, Castor and Pollux, Alphard (Hydre, the end of the Voiles then Acrux and Alpha Centauri, Shaula (λ Scorpii), the arc and the head (σ Sgr) of the Sagittarius, then go up by the head of the Capricorne (β Cape), along the axis of the Verseau, to buckle on the diagonal of the Grand square of PEGASE.

Form

The three principal stars of Andromède which appear as of fallen the night located on the large diagonal, and correspond to the head (Alphératz, α, in the square of PEGASE), the hip (Mirach, β And), and the foot (Almach, γ And), all three rather brilliant (mag 2). One rather quickly sees appearing two intermediate stars (mag 3) on this axis, the shoulder and the knee.

The remainder of the members is relatively weak (mag 4): one sees the first alignment perpendicular to the diagonal of Andromède, on the level of the shoulder, which draws the two arms. Southern part, the arm is completed on an alignment of three stars, the third (more external) belongs to the constellation of the Poisson.

Northern side, the arm points on the chain of Andromède, which takes shape slightly (mag 5) between the square of PEGASE and Céphée. The stars a little more brilliant which seem to limit the chain of Andromède form the small constellation of the Lézard.

The northern leg of Andromède leaves the hip towards Cassiopée, and draws a small arc of circle to the right foot (51 And), which almost the hand of Persée touches. Famous the galaxy of Andromède is at the level of the knee, 2° towards outside, and can be seen there whether the conditions of visibility are excellent in the form of a vaguely luminous fog.

Contrary to the departure of the leg of Andromède, and in the same axis, one sees a small intermediate star (which is the point of the constellation of the Triangle), then one fall on the head from the Bélier.

The two feet of Andromède (51 and γ And) are in the alignment of the Western edge of Cassiopée, more in north. Conversely, the base of W of Cassiopée points towards the base of the chain of Andromède before touching the top of the square of PEGASE.

Principal stars

α And (Alphératz/Sirrah)

Most brilliant star of Andromède, α And, called Alphératz, Alpharatz or Sirrah, constitutes with α, β, and λ Peg a Astérisme called the Great Square of PEGASE. This star besides was formerly included in PEGASE: Alphératz means “shoulder of the horse” and Sirrah “navel” in Arab.

It is a very hot star, of color blue-white, shining 110 times more than the Sun. It is also a star doubles, his/her companion not exceeding the Magnitude connect 11,3.

β And (Mirach)

β And, or Mirach, whose name means “the Arabic Belt”, is a red giantess 30 times larger than the Sun.

γ And (Almach)

γ And, or Almach or Alamak (of Arabic Al Anak Al Ard , “the lynx of the desert”), is at the end of the southern leg of “has” constellation. It is beautiful a star doubles with the contrasted, orange and blue colors.

The principal star of the system, γ¹ And, is an orange giantess 80 times larger than the Sun and 2 000 times more luminous than this one. γ ² And is itself a double star. γ ² - is And, magnitude 5,0, and γ ² - B And, of magnitude 5,5, turn around in 61 years according to a elliptic Orbite very strongly . The two stars are both blue. γ ² - has And is itself doubles, his/her companion turning around it in only 2,7 days.

Other stars

υ And has a planetary system with at least three Exoplanète S, 0,71 times, 2,11 times and 4,61 times more massive than Jupiter.

R Andromedae is a star Variable of the type Mira whose magnitude passes from 5,8 to 14,9 according to one 409 days period.

Celestial objects

The most famous object of Andromède is M31, the Galaxie of Andromède, one of the most remote objects visible with the naked eye (M33 is a little more distant). It is about enormous a spiral Galaxie similar to ours. To find the galaxy, one can draw a line between β and μ Andromedae, and continue this line about the same distance since μ.

The object NGC 7640 is another Spiral galaxy of the type barred SBb, rather easy to locate.

The Nébuleuse planet gear NGC 7662 is one of the objects easiest to see with a telescope amateur and reveals an elliptic disc blue-green.

The open Amas NGC 752 covers a rather broad surface. Gathering a hundred stars magnitude 9 to 10, it is located close to 56 Andromedae.

See too

Internal bonds

Constellation
List of stars of Andromède

External bonds

'' Andromeda '' ( The Deep Photographic Guides to the Constellations )

Random links: