Most normal matter in the universe isn't found in planets, stars or galaxies – an astronomer explains where it's distributed

An illustration of concentrated dark matter at the heart of a spiral galaxy .

This article was originally published at The Conversation. The publication contributed the article to Space.com's Expert Voices: Op-Ed & Insights.

If you look across space with a telescope, you'll see countless galaxies, most of which host large central black holes, billions of stars and their attendant planets. The universe teems with huge, spectacular objects, and it might seem like these massive objects should hold most of the universe's matter.