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globular star cluster

The Hercules Cluster (M13)

A giant ball of hundreds of thousands of old stars.

Also called: M13, the Great Globular Cluster in Hercules.

🕒 When can I see it?🚀 Travel there
The Hercules Cluster (M13) — Drawn, not photographed.

What it is

One of the best globular clusters in the northern sky, ancient ball of several hundred thousand stars.

Globular star cluster: Hundreds of thousands of ancient stars in a tight ball. Every kind of thing there is →

How to find the Hercules Cluster

Look in the constellation Hercules.

Best placed from the Northern Hemisphere.

Star-hop: A classic bright target for binoculars or any telescope.

Finding it: Along one edge of Hercules's 'Keystone' shape.

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 Hercules Cluster in tonight's sky

What you will really see

With your own eyes

A round, fuzzy ball of light: a hundred thousand old stars swarming round one bright core.

With binoculars

Binoculars show it as a small, soft, grey patch. Not the photograph — and unlike the photograph, it is arriving in your eyes right now.

🔭 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 Hercules Cluster

On the 100-meter-track scale model of the Milky Way, the Hercules Cluster would be about 22 metres from the Sun — roughly the length of a tennis court. Light takes 22 thousand years to get here from the Hercules Cluster, so what you are looking at is the Hercules Cluster as it was 22 thousand years ago.

What it is made of
A globular cluster — a dense, roughly spherical ball of several hundred thousand very old stars.
How we know: Its stars are almost all cool and reddish with no young hot blue stars; models put its age at roughly 11-12 billion years.
What makes it worth knowing
In 1974, the Arecibo Message describing humanity was beamed toward this cluster (won't arrive for 22,000+ years).
The numbers
Distance from us22,200 light-years

Next to it

The Milky Wayspiral galaxyNaked eyeProxima CentauristarWith effortAlpha Centauri A & Bbinary star systemNaked eyeSiriusstarNaked eyeVegastarNaked eyeArcturusstarNaked eye
📖 How the Milky Way fits together

Then go outside

Clear tonight? The Planetarium will show you what is worth a look. Then just go out.

🌙 Plan an evening outside🌌 Everything else in the sky