101 Must-See Cosmic Objects: The Bubble Nebula

William Herschel first observed NGC 7635 in 1787 as a glow around the magnitude 8.7 star SAO 20575 (cataloged earlier as BD+60°2522). In a telescope, the Bubble Nebula looks more like a comma because the full extent of its spherical shell is so faint that it was only discovered through […]