Posted by on Aug 30, 2013 in Constellation Of the Month |

The leading constellation of autumn it is an original constellation and honors the winged horse upon which Perseus rode on his way back from his successful Gorgon slaying expedition.

Star Visual Magnitude Spectrum Absolute Magnitude Distance (Lt Years)
ENIF 2.38 K2lbvar -4.19 672
SCHEAT (ver) 2.44 M2II-IIIvar -1.49 199
MARKAB 2.49 B9.5III -0.67 140
ALGENIB (Beta Cephei Var) 2.83 B2IV -2.22 333
MATAR 2.93 G2II-III -1.16 215
HOMAM 3.41 B8.5V -0.62 208
ALPHERATZ (ver) 2.07 B9p -0.30 97

Three of the chief stars of Pegasus, Markab Scheat, Algenib, together with Alpheratz (From the Andromeda constellation) make up the celebrated square. In the night sky the square is actually not so prominent but is easy to locate, as it is high in the southern sky during autumn. Two of the stars of Cassiopeia point to it.

The Square of Pegasus is in the south during the evening and forms the body of the winged horse. The sides of the square are almost 15 degrees across, about the width of a clenched fist, but it contains few stars visible to the naked eye. If you can see 5 then you know that the sky is both dark and transparent!

Three stars drop down to the right of the bottom right hand corner of the square marked by Alpha Pegasi, Markab. A brighter star Epsilon Pegasi is then a little up to the right, at 2nd magnitude the brightest star in this part of the sky. A little further up and to the right is the Globular Cluster M15. It is just too faint to be seen with the naked eye, but binoculars show it clearly as a fuzzy patch of light just to the right of a 6th magnitude star. The most interesting object is the red giant Scheat, which varies between magnitudes 2.25 and 2.75 in a period of 35 days, but is subject to marked irregularities. Its diameter is nearly 150,000,000 miles, but its mass is only 9 times that of the sun, so that like all red giants, it is comparatively rarefied. It’s changed can be followed by using Markab and Algenib as comparison stars.

M15 (NGC 7078)

This is a globular cluster of magnitude 6.4, 34,000 light-years from Earth. It is a Shapley class IV cluster, which means that it is fairly rich and concentrated towards its centre. M15 was discovered in 1746 by Jean Dominique Maraldi

NGC 7331

Is a spiral galaxy, 38 million light-years distant with a redshift of 0.0027. It was discovered by William Herschel in 1784 and was later one of the first nebulous objects to be described as “spiral” by William Parsons.

NGC 7742

A Type 2  Seyfert galaxy. Located at a distance of 77 million light-years with a redshift of 0.00555. Seyfert galaxies are a class of galaxies with nuclei that produce characteristic emission lines from highly ionised gas, moving at high speed around a central black hole.  Named after Carl Keenan Seyfert, who first identified the class in 1943. The centres of Seyfert galaxies form a subclass of active galactic nuclei, and are thought to contain supermassive black holes.

Einstein’s Cross

This is a quasar that has been lensed by a foreground galaxy. The elliptical galaxy is 400 million light-years away with a redshift of 0.0394, but the quasar is 8 billion light-years away. The lensed quasar resembles a cross because the gravitational force of the foreground galaxy on its light creates four images of the quasa

Stephens Quintet

This is another unique object located in Pegasus. It is a cluster of five galaxies at a distance of 300 million light-years and a redshift of 0.0215. First discovered by Edouard Stephen, a Frenchman, in 1877, the Quintet is unique for its interacting galaxies.

Two of the galaxies in the middle of the group have clearly begun to collide, sparking massive bursts of star formation and drawing off long “tails” of stars. Astronomers have predicted that all five galaxies may eventually merge into one large elliptical galaxy.