Picture of the month

NGC 7027

This small planetary nebula, NGC 7027, was first spotted in 1878, only 450 years after the nebula first started expanding. The name “planetary nebula” is a misnomer, however. It dates back to William Herschel, who classified these objects based on their rounded planet-like shape. We now know that planetary nebulae are not related to planets but are instead created as massive stars come towards the end of their lives and eject large amounts of gas due to the high radiation pressure from the dying star. NGC 7027 consists of a neutral gas cloud surrounding an elliptical inner cloud of ionised gas known to emit X-rays. The high temperature of the inner cloud needed to emit X-rays is thought to be a result of an accretion disc surrounding the star in the centre, which is now a white dwarf.

About the author

Compiled by Merlin Kole, Department of Particle Physics, University of Geneva.