description Abell 31 Overview
Abell 31 is a large, faint planetary nebula in the constellation Cancer and is also cataloged as Sh2-290. It consists of ionized gas expelled by a dying star, with an old, diffuse shell that is interacting with and dispersing into the surrounding interstellar medium. Because its light is spread across a broad area and has low surface brightness, it is primarily a target for astrophotographers and observers using sensitive imaging equipment.
help Abell 31 FAQ
What is Abell 31?
Abell 31 is a large, faint planetary nebula in the constellation Cancer, also cataloged as Sharpless 2-290. It consists of ionized gas shed by a dying star, with an old, diffuse shell dispersing into interstellar space.
How large is Abell 31 in the sky?
It spans on the order of 16 arcminutes, making it one of the largest planetary nebulae in apparent size — roughly half the apparent width of the full Moon. Despite that size, its surface brightness is very low, so it is a challenge rather than a showpiece.
Why is this nebula called Abell 31?
It comes from astronomer George Abell's catalog of planetary nebulae, compiled from Palomar Sky Survey photographic plates in the 1950s and 1960s. Many large, old, low-surface-brightness planetary nebulae like this one carry Abell numbers.
How can amateur astronomers observe Abell 31?
It requires genuinely dark skies, a narrowband OIII or UHC filter, and a wide-field telescope at low power to pick up its faint glow around 6th-magnitude region in Cancer. Visually it usually appears as a very dim, smooth haze rather than showing structure.
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