The Helix Nebula, NGC 7293

This faint object is the nearest planetary nebula to the Sun and on deep photographs has a diameter of about half a degree -- the same apparent size as the Sun in the sky. The AAT colour picture shows the various ionisation levels within the shell of matter ejected from the central star, the greenish middle portion being evidence of excited oxygen atoms, the outer red due to nitrogen and hydrogen. The smallest of the radial blobs inside the red shell are about 150 astronomical units across (150 times the Earth-Sun distance) and they give this beautiful object its alternative name, the Sunflower Nebula. The Helix is about 400 light years away, or about 100 times more distant than the nearest stars.

Entry from NGC 2000.0 (R.W. Sinnott, Ed.) © Sky Publishing Corporation, 1988:

NGC 7293  Pl 22 29.6  -20 48 s  Aqr  12.8        ! pF, vL, E or biN