Astronomical distances can be mind boggling. Our closest neighbor, the Moon, is a quarter of a million miles away — equal to about 10 trips around Earth’s equator. The closest planet, Venus, is always at least a hundred times farther. And the closest neighboring star, Proxima Centauri, is about a million times farther still. Yet even that is just a hop compared to the distance to the most remote object that’s easily visible to the unaided eye. The Andromeda Galaxy is more than half a million times farther than Proxima Centauri — two-and-a-half million light-years. Right now, the galaxy stands in the east-northeast, about half-way up the sky, at nightfall. It looks like a faint patch of light about as wide as the Moon. Binoculars bring it into better view. Like our home galaxy, the Milky Way, Andromeda is a wide, flat disk. The visible part of the disk spans more than a hundred thousand light-years. But powerful telescopes reveal that stars taper off into space well beyond that, making
