Thor's Helmet nebula is actually more like an interstellar bubble, blown as a fast wind from the bright, massive star near the bubble's center sweeps through a surrounding molecular cloud. The central star is an extremely hot giant Wolf-Rayet star, though
Andromeda Galaxy: nearest neighboring major galaxy to our "Milky Way Galaxy". Due to begin a collision with our Milky Way galaxy in about billion years, Andromeda is million light years away from Earth (at the speed of light).
The Horsehead Nebula is a cloud of ionized-hydrogen in the constellation Orion. These clouds are lit from within by young, hot stars. The interstellar dust absorbs the light from part of the ionized cloud creating this beautiful contrast. Image Credit: NA