Bubble Nebula

Object Type: Emission Nebula
Top image - AP 5" Refractor, 120 min; Bottom image - C-9.25" SCT, 90 min.

The Bubble Nebula (NGC 7635, Sharpless 162, Caldwell 11) is an H II emission nebula in Cassiopeia, near the open cluster Messier 52. The near-perfect 'bubble' is blown by the fierce stellar wind of a hot, massive young star, BD+60 2522 (SAO 20575), estimated at 10-40 solar masses, as it pushes into a surrounding giant molecular cloud that both confines and illuminates the shell. William Herschel discovered it in 1787. The Hubble Space Telescope famously imaged the Bubble for its 26th anniversary in 2016.