(Photo by P. Marenfeld & NOAO/AURA/NSF)

Kitt Peak National Observatory at dusk.

A new spectrograph is coming to Kitt Peak National Observatory, near Tucson.

The Dark Energy Spectroscopic Instrument, or DESI, just got formal approval from the US Energy Department. It’ll help answer some long-standing questions about the universe’s expansion, among other things.

With me to explain is Risa Wechsler, she’s a professor at Stanford and one of the spokespeople for this project.