Andromeda is the main actress of a Greek myth cycle, which includes many of the autumn sky constellations, including Pegasus, Perseus, Cassiopeia, Cepheus and Cetus, the Whale. Its distinctive star chain, which starts at the Square of Pegasus, is easy to find.

GX Andromedae is also known as Groombridge 34 and an unremarkable physical double star of two red dwarf stars. The two stars are 8.2 and 10.6m bright and about 40 arc seconds apart – it is not a particularly conspicuous object which can be found 15 arc minutes north of the 6.1m bright 26 Andromedae. The two stars belong to the closest neighbors of our Sun – they are only 11.2 light-years away from Earth and change their position within 20 years by about one minute of arc. Although the two stars are under observation since 1860, it is still unknown how long a complete orbit will take – an estimation from 1957 is 3,000 years. 160 astronomical units separate the two stars from each other – one AU is the distance between Sun and Earth.

The Andromeda Galaxy M 31 is probably the most well-known galaxy and has disappointed many observers when they were looking through their telescopes. The 12,000 light-years large central bulge appears 20 arcmin wide, corresponding to two thirds of the full Moon diameter. The entire Andromeda Galaxy spans nearly 3° – only a few telescopes have such a large field of view. In binoculars, the 4.3m bright galaxy is, however, more than striking. Although no individual stars can be resolved, the elliptical shape of the galaxy, which is inclined by 15° to the line of sight, is clearly evident, and any 10 × 50 should be able to distinguish the central area, spiral arms and halo.

Während der Zentralbereich von M 31 leicht zu erkennen ist, sind die Spiralarme nur auf Fotografien deutlich zu sehen.
While the central bulge of M 31 is clearly visible, its spiral arms are prominent in photographs – or in binoculars.

Under good conditions, M 31 is clearly visible with the naked eye. It was first mentioned in the year 902 AD in the „Book of the Stars“ by the Arab astronomer Al Sufi as a „small cloud“. Edwin Hubble revealed its true nature as a Galaxy by observing variable stars (the Cepheids) in 1923, and in 1944, Walter Baade found two different classes of stars in M 31, which he divided into Population I and Population II stars – this classification is still used today.

Just like our own Milky Way with the Magellanic Clouds, M 31 also has two larger companion galaxies – M 32 and M 110. The shape of the Andromeda galaxy is clearly disturbed in the vicinity of M 32 by the mass of its companion galaxy. With a diameter of 150,000 light-years, M 31 is larger than our Milky Way. Its luminosity equals that of 73 billion Suns. The 2.5 to 3.2 million light-years distant galaxy is 3.2 times brighter than our Milky Way and even brighter than all the other members of the local group together.

M 32 is a 5.2 million light-years distant satellite galaxy of M 31 and only 6,000 light-years across. Therefore, it appears at low magnification almost like a star, but it is easy to see in 10 × 50 binoculars. M 32 is 9.1m bright and only seven arcmin in diameter. It is an elliptical galaxy, which contains mainly older stars, while gas and dust clouds are rare in it. M 32 probably has lost some of its mass to M 31.

The second companion of the Andromeda nebula is M 110. The only one million light-years distant galaxy appears 12 × 20 arc minutes large and is quite hard to see because it has a rather low surface brightness. Therefore it usually remains invisible in smaller devices, but at least with a 10 × 50 it should not be too hard to find. With a diameter of 12,000 light-years, it is twice as big as M 32, although it has only a tenth of the extent of the Andromeda galaxy. It contains old, red stars as well as younger stars.

The 3,400 light-years distant open cluster NGC 752 contains in an area with 50 minutes of arc in diameter nearly 100 stars, of which two dozen are visible in binoculars. It is located 5° south-southwest of γ Andromedae, which is itself a pretty double star for the telescope that resembles a miniature version of Albireo in Cygnus. Its center is marked by a 7.1m bright star, while two stars of sixth magnitude shine in the southwest of the star cluster. However, these stars do not belong to NGC 752 – the brightest stars of the cluster only reach 8.0m, its overall brightness is 5.7m.

It is over a billion years old and probably originated in the peripheral regions of the Milky Way. Nowadays, it is above the galactic plane. NGC 752 shows both characteristics of an open cluster and a globular cluster.

The Blue Snowball NGC 7662 is a 1,800 light-years distant planetary nebula, which appears in binoculars only as an 8.2m bright star. NGC 7662 requires nearly a 100x magnification to see it as a disk and its blue-green color is the best way to identify it. It is one of the brightest planetary nebulae and has an extremely hot central star – the 13.2m bright stellar remnant has a surface temperature of about 135,000° F (75,000° C).

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