Abell 21 – The Medusa Nebula


The Medusa Nebula, Abell 21 is a large planetary nebula in the constellation Gemini. It is only 4 light years in diameter (equivalent to the same distance from the Sun to the nearest other star) and is 1,500 light years from us. Despite everything, she is extremely weak and difficult to observe.

A planetary nebula like results from the end of life of a non-massive star that has burned all of its hydrogen and released a shell of colored gases before slowly extinguishing as a white dwarf. This ejection of gas only lasts a few thousand years and represents only a small fraction of the evolution of stars.

Technical details:

Telescope: Celestron Edge HD14 with 0.7x focal reducer
Camera: ZWO ASI 2600MM in bin 2×2 mode
Filters Optolong narrowband in H-alpha, O-III and S-II
Exposure: 49 x 10 minutes.
Processed with PixInsight with  S-II assigned to red, H-Alpha assigned to green and Oxygen III assigned to blue (Hubble palette)