Swirling supernova's secret sibling

A companion could be responsible for Puppis A's overlapping rings

- Prof Chris Lintott

The Puppis A supernova remnant is one of the most intriguing and interesting objects in the sky. Slightly overlooked because it's partly hidden behind the nearer Vela remnant, it is the result of an explosion whose light reached Earth about 3,700 years ago. Since then, the bubble of shocked gas has expanded to a diameter of about 100 lightyears, at the centre of which is one of the brightest X-ray sources in the entire sky.

Of particular interest is what lies within the main body of the remnant. In images taken in both X-ray and visible light, there is a set of nested and overlapping rings. Named 'The Swirl' by its discoverer Frank Winkler (making it the object in the sky which most sounds like something a Star Trek captain would encounter), it was originally thought to be the signature of a second supernova taking place within the remnant of the first.