The Oort Cloud

Far out beyond everything else, a giant shell of icy lumps may wrap around the whole solar system — nobody has ever seen it, but the long comets have to be coming from somewhere! Its edge is halfway to the next star.

What it is

Hypothetical enormous icy shell thought to surround the whole solar system, source of long-period comets.

Suspected, not yet found: Predicted by the maths; not yet seen. Every kind of thing there is →

Can you see it?

Not as one thing, no — the Oort Cloud is a place rather than a sight, and you are already inside it. What you go out and look at are the things in it, one at a time.

Worth knowing about the Oort Cloud

So far away it's almost a quarter of the way to the nearest star — the Sun's light takes over a year to reach the outer edge.

What it is made of: A hypothetical, enormous hollow shell of icy leftover material thought to surround the entire solar system, way beyond even the Kuiper Belt — like an invisible bubble around everything else in the solar system.; How we know: No one has ever directly seen it — telescopes aren't strong enough to spot objects that small and far away. Scientists infer it exists because it would explain where long-period comets (ones that take thousands of years to orbit) come from. Rung 3 of the cosmic ladder — how the solar system is arranged
What makes it worth knowing: Proposed by Dutch astronomer Jan Oort in 1950, based on the orbits of comets.

The numbers

Distance from the Sun, on average	estimated 2,000 to 100,000 AU

What it belongs to

☀️ Everything the Sun holds, in one place 📖 How the solar system fits together

Then go outside

Too big to look at all at once — but the things inside it are not. The Planetarium will show you which are up.

🌙 Plan an evening outside 🌌 Everything else in the sky