Stephan's Quintet

Stephan's Quintet is a group of five galaxies in the constellation Pegasus, which was discovered on 22 September 1877 by the French astronomer Édouard Jean -Marie Stephan.

The galaxy group consists of the galaxies NGC 7317, NGC 7318A, NGC 7318B, NGC 7319 and NGC 7320th

The galaxies NGC 7317 to NGC 7319 form a spatially close, interactive system in about 300 million light years away. Due to the mutual gravitational effect the spiral arms of galaxies are irregular deformed.

NGC 7320 was originally expected by Stephan at Stephan's Quintet, however, it is in this galaxy due to a significantly lower heliocentric radial relative velocity ( ~ 800 km / s compared to ~ 6500-7000 km / s at the other galaxies ) by a foreground galaxy in just 35 million light -years away, which coincides only by the projection with Stephan's Quintet. Instead, today NGC 7320C is added to the quintet, so that it continues to have five galaxies.

The galaxies of Stephan's Quintet have a brightness of about 13 mag. To watch them you need a telescope with at least 20 cm opening.