For decades, astronomers treated the interstellar medium as a static backdrop to the goings-on of the universe. Now, a wave of 3D mapping is bringing the interstellar medium’s dynamic nature into focus.

In 2010, the Hubble Space Telescope released this image of a pillar of gas and dust in the Carina nebula that’s about 3 light-years — roughly 18 trillion miles — tall.

NASA

Introduction

You might imagine space to be empty. But the seeming void contains a barely perceptible fog of hydrogen and other neutral atoms. In 2020, NASA’s New Horizons spacecraft, having passed the orbit of Pluto, measured a proxy for the amount of hydrogen around it.…