NGC 3626

Caldwell 40, also cataloged as NGC 3626, is a medium-sized lenticular galaxy located approximately 70 million light-years away in the constellation Leo. In the cosmic hierarchy, lenticular galaxies like this one occupy the middle ground of the Hubble Sequence; they possess a central bulge and a disk like a spiral galaxy, but they lack the prominent, star-forming arms, giving them a smoother, more aged appearance.

What makes Caldwell 40 particularly fascinating to astronomers is its "counter-rotating" gas. While most of the stars in the galaxy orbit the center in one direction, a significant portion of its neutral hydrogen gas is orbiting in the exact opposite direction. This suggests a turbulent past, likely involving the "cannibalization" of a smaller, gas-rich satellite galaxy or a significant accretion event billions of years ago. Though it appears relatively calm and faint through a small telescope—often seen as a small, bright core with a fuzzy envelope—it is actually a site of complex gravitational history. Its position in the sky makes it a popular target for observers in the spring, residing near the "tail" of Leo.