Learn where the Andromeda Galaxy is, how large it is, why it is moving toward the Milky Way, and what astronomers expect in the distant future.
A galaxy visible to the unaided eye
Under dark skies, Andromeda can appear as a faint smudge. That small patch is actually the combined light of an enormous galaxy located roughly millions of light-years away.
Andromeda is a spiral galaxy
Like the Milky Way, Andromeda has a disk, spiral structure, a central bulge, gas, dust, star clusters, and a surrounding halo. It contains an immense population of stars.
Why it matters to astronomers
Because Andromeda is relatively nearby on cosmic scales, it is an important laboratory for studying galaxy structure and evolution. Astronomers can compare its stellar populations with those in the Milky Way.
The Milky Way and Andromeda are approaching
Measurements show that the two galaxies are moving toward one another overall. Their eventual interaction will unfold over billions of years rather than as a sudden collision.
What happens when galaxies meet
Individual stars are so widely separated that direct stellar collisions are unlikely. Gravity will instead reshape the galaxies, disturb gas, alter stellar orbits, and may eventually produce a merged galaxy.
How to observe Andromeda
A dark sky matters more than high magnification. Binoculars can reveal the bright central region and a wider glow than is usually visible to the naked eye.
Continue with our related Neela Asman guide. For broader science background, visit NASA Science.