What is the Pegasus constellation?
He Pegasus (Pegasus) is a constellation in the northern hemisphere named after the mythical Pegasus the winged horse of Greek mythology. It was mentioned in the 1st century AD by Ptolemy in the Almagest and cataloged by William Herschel in 1783. It is one of the 88 modern constellations and one of the 48 Ptolemaic constellations. Pegasus is the seventh constellation in the sky by extension (1,121 square degrees).
Main stars Pegasus
The brightest stars of Pegasus, Markard (α Pegasi), Sheat (β Pegasi), of the 2nd magnitude, and Algenib (γ Pegasi), of the 3rd magnitude, form the horse wing triangle. The body of the horse is made up of a quadrilateral formed by Markab, λ Pegasi, ι Pegasi and ξ Pegasi. The front legs of Pegasus are composed of two stars of the 4th magnitude that do not have a Bayer designation, they have Flamsteed numbers: 1 Pegasi and 9 Pegasi. Enif (ε Pegasi) (of the 3rd magnitude) and Baham (θ Pegasi) form the hind legs. ρ Pegasi and σ Pegasi appear in the tail, but are dim (fifth magnitude). Matar (η Pegasi) (3rd magnitude) and π Pegasi (the snout) form the head of Pegasus. Sadalbari (μ Pegasi) is located at the base of his neck. The three brightest stars of Pegasus form, with Sirrah (α Andromedae), an asterism called the Pegasus square. Sirrah was previously assigned to Pegasus with the designation δ Pegasi.
Enif (ε Pegasi)
Enif (ε Pegasi) is the brightest star in the constellation (and the 84th brightest in the sky). With an apparent magnitude of 2.39, somewhat brighter than Scheat.
Enif is an orange supergiant, about 175 times larger than the Sun and 11 times more massive. It is classified as a variable star, since it ejected a vast amount of matter in 1972 that has temporarily reduced its magnitude to 0.70.
Scheat (β Pegasi)
Scheat (β Pegasi), in the southeast of the constellation, is of apparent magnitude 2.44. Distant 200 light years, it is a red giant at least 200 times larger than the Sun. Like many stars of this type, Scheat is an irregular variable, and its magnitude evolves between 2.40 and 3.00.
Other stars
Another star in the constellation has a name of its own: Homam (ζ Pegasi). It is also notable that a star in this constellation, 51 Pegasi, has the first extrasolar planet to be discovered. It is 0.47 times the mass of Jupiter, orbiting in just 4.23 days, within 0.05 au of the star.
Two other exoplanets, around the stars HD 209,458 and HD216770, have been detected in this constellation.
Pegasus deep sky objects
To Pegasus there are also many celestial objects:
- M15, a globular cluster near Enif.
- NGC 7742, a type 2 Seyfert galaxy.
- Spiral galaxies NGC 7217 and NGC 7331.
- HCG 92, also called «Stephan’s Quintet», is a small cluster of five galaxies: NGC 7317, NGC 7318, NGC 7318B, NGC 7319 and NGC 7320.
- Einstein’s Cross is the best-known example of a gravitational miracle: the image of a quasar, located behind a closer galaxy, appears quadruple, the light of the quasar is deflected and reconcentrated by the galaxy.
- Andromeda VI, also called the Pegasus dwarf spheroidal galaxy (Peg dSph), is a dwarf spheroidal galaxy about 2.7 million light years away in the constellation Pegasus. Andromeda VI is a member of the Local Group and a satellite galaxy of the Andromeda Galaxy (M31). Andromeda VI is a galaxy with primarily metal-poor stellar populations. [ 3 ] Its metal·licitat is [ Fe / H ] ≃ -1.3. [ 4 ] It is located at the correct ascension 23h51m46.30s and declination + 24d34m57.0s in the equatorial coordinate system (epoch J2000.0), and at a distance of 820 ± 20 kpc from the Earth and a distance of 294 ± 8 kpc [ un ] of the Andromeda Galaxy. Andromeda VI was discovered in 1999 by several authors in the films Second Palomar Sky Survey (POSS – II).