Abell 31 (also known as Sh2-290 or PK 219+31.1[2]) is an ancient planetary nebula in the constellation of Cancer.

Although it is one of the largest planetary nebulae in the sky, it is not very bright.

The central star of the planetary nebula is a white dwarf with a spectral type of DAO.

[3] The white dwarf is the dead remains of a star that existed but had died leaving behind Abell 31 and the white dwarf.

The nebula due to its ancient age has its gas being dispersed into the interstellar medium.