He stayed until 1942, studying a class of active galaxies now called Seyfert galaxies.

Several lines of dialogue hint that it is a galaxy called Dimension X:

The galaxy, called NGC4622, is 140 million light-years away.

The blob-shaped galaxy, called GN-108036, is the brightest galaxy found to date at such great distances.

Ponman and Bertram's work concerns the compact group of four galaxies called HCG62.

The newfound galaxy is located in the center of an even larger clump, a cluster of some 1,000 galaxies called Abell 2029.

Except for the plane of our own galaxy, the brightest far-infrared object in the sky is central region of a galaxy called Messier 82.

The Clan had been called primitive by many in the settled galaxy, called unevolved, underevolved, even devolved.

The winner is a group of galaxies called Arp 274.

Some galaxies, called active galaxies, emit huge amounts of energy in the form of radiation.