Christophe Morisset

Deep in space, there's a cloud of gas that looks like a necklace with bright beads. This is the Necklace Nebula — the remains of a star that once swelled up and swallowed its neighbor. At the center, a pair remains: a small, hot star and its bloated companion, rich in carbon.

The Orion Nebula is a showcase of astrophysics, a laboratory for studying star formation right in our backyard. For over a century, its light has been split into spectra, and each forbidden line whispers its own version of how many electrons per cubic centimeter.