Tuesday, May 27, 2025

Abell 35 is a planetary nebula located in the constellation Hydra, with an apparent diameter of approximately 16 arcminutes. Unlike classical planetary nebulae, Abell 35 displays unusual features — it is believed to be the result of a stellar wind bubble, rather than the typical collapse of a red giant. Its central star is a binary system, composed of a hot sdO subdwarf and a cooler companion, making it similar to other peculiar objects such as Abell 36 and LoTr 5. With an extremely low surface brightness, Abell 35 is invisible to the naked eye or through traditional visual observation, and is revealed only through long-exposure astrophotography. The central region of the nebula is dominated by doubly ionized oxygen (O III) emission, giving the final image a characteristic cyan or blue-green hue.