Spiral Galaxy

Example: Whirlpool Galaxy (M51)

A flat, rotating disc of stars with arms winding out from a bright centre, like a giant pinwheel.

Key facts

Shape: Flat disc with spiral arms and a central bulge
Stars: Young stars in the arms, older stars in the centre
Example shown: Whirlpool Galaxy (M51)
Example’s distance: About 25 million light-years

About the Spiral Galaxy

How to recognise it

Spiral galaxies have a bright central bulge surrounded by a flat disc with curving arms. The arms are full of gas and dust, where new blue stars form, while the centre glows with older, yellower stars. Seen edge-on, a spiral can look like a thin line with no visible arms.

The example: the Whirlpool Galaxy

The Whirlpool Galaxy, also called M51, is about 25 million light-years away in the constellation Canes Venatici. Its arms are dotted with pink clouds where stars are forming. The smaller galaxy at the end of one arm is a companion that is interacting with it.