Caltech astronomers have taken unprecedented images of the
intergalactic medium (IGM)—the diffuse gas that connects galaxies throughout
the universe—with the Cosmic Web Imager, an instrument designed and built at
Caltech. Until now, the structure of the IGM has mostly been a matter for
theoretical speculation. However, with observations from the Cosmic Web Imager,
deployed on the Hale 200-inch telescope at Palomar Observatory, astronomers are
obtaining our first three-dimensional pictures of the IGM. The Cosmic Web
Imager will make possible a new understanding of galactic and intergalactic
dynamics, and it has already detected one possible spiral-galaxy-in-the-making
that is three times the size of our Milky Way.