September: In the heart of the swan
In the middle of the constellation of the Swan lies the star Sadir ( Cygni), the second brightest star in the centre of the asterism. This field lies right in the disc of our galaxy, which is why we cannot see any distant galaxies, but we can see numerous dark nebulae and HII regions. It is also a field rich in planetary nebulae and supernova remnants, although the single most prominent object is the Crescent Nebula (NGC 6888), an emission nebula around a Wolf-Rayet star, where the outer layers of the star that were blown away by the solar wind are ionised by ultraviolet radiation from the star itself. This is a phase prior to its death as a supernova.
Author: Daniel López / IAC (Astrograph STC - UC3)