Why do supernova remnants look like rings rather than spheres? (Intermediate)

When I see supernova explosions depicted on tv i.e. Discovery, tlc etc, the supernovae expansions are shown as a ring. Shouldn't they be in the form of a sphere? Doesn't the result of an explosion go outwards in all directions?

It is spherical, but it looks like a ring. Spherical shells tend to look like rings when projected on the sky. This effect is called "limb brightening". The idea is that if you're looking towards the center of spherical shell, you're not seeing much material along your line of sight, so it's transparent. But along the edges of the shell, you're looking through a lot of material, so it's opaque.

This page was last updated June 28, 2015.

About the Author

Christopher Springob

Christopher Springob

Chris studies the large scale structure of the universe using the peculiar velocities of galaxies.  He got his PhD from Cornell in 2005, and is now a Research Assistant Professor at the University of Western Australia.

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