Pinwheel Galaxy (M101)

A huge face-on spiral, almost as wide as the full Moon in our sky.

Also called: M101.

🕒 When can I see it?🚀 Travel there

Pinwheel Galaxy (M101) — Drawn, not photographed.

What it is

Spiral galaxy larger than the Milky Way, a prolific 'supernova factory'.

Spiral galaxy: A flat disc of stars wound into arms. Ours is one. Every kind of thing there is →

How to find the Pinwheel Galaxy

Look in the constellation Ursa Major.

It is best placed in the spring if you are north of the equator.

Not visible from most of the Southern Hemisphere.

Star-hop: Low surface brightness despite its large size: needs a dark sky and a wide, low-power eyepiece.

The Planetarium works out where it actually is from your own place and the date — including whether it is above the horizon at all tonight.

Show me the Pinwheel Galaxy in tonight's sky

What you will really see

Through a small telescope, on a good night

A faint fuzzy oval of soft light — the bright core shows; the arms only hint at themselves.

🔭 See it drawn as it looks through a telescope

🖨️ A sheet to print for this

🖨️ Print a sheet and go and look

🖨️ Sheet to take outside →

Worth knowing about the Pinwheel Galaxy

The Pinwheel Galaxy is ~170,000 light-years across — larger than the Milky Way. On that same scale, the Pinwheel Galaxy would be about 21 kilometers away. Light takes 21.0 million years to get here from the Pinwheel Galaxy, so what you are looking at is the Pinwheel Galaxy as it was 21.0 million years ago.

What makes it worth knowing: Has hosted five observed supernovae since 1909, one of the most productive 'supernova factories' astronomers watch. Slightly lopsided arms, likely stirred by past encounters with smaller companions.

How did anyone measure the Earth in the first place?

The numbers