Planetary nebula, the Helix, NGC 7293.
Caption: On deep photographs this beautiful planetary nebula has a diameter of about half a degree-the same apparent size as the Moon in the sky. The AAT color picture reveals the various levels of excitation within the shell of matter ejected from the central star, the greenish middle portion being from ionized oxygen, the outer red due to nitrogen and hydrogen. The cloud of gas is extremely tenuous and close inspection will show many faint galaxies of stars in the background. The Helix nebula is about 400 light years away from Earth, or about 100 times more distant than the nearest stars.
Copyright: (c) 1979 Anglo-Australian Telescope Board, photograph by David Malin
Credit: D. F. Malin