Cosmic Scale
Oort Cloud
Shell of icy bodies around the Sun · Starts ~2,000 AU from the Sun
How big is Oort Cloud?
Oort Cloud is about 3.16 light-years across.
See Oort Cloud in 3D, at true scale
The Oort Cloud is a vast shell of icy bodies surrounding the Solar System, so far out that passing stars can nudge its members loose. Nobody has ever seen it directly — we infer it from the comets that fall inward from every direction.
At a glance
| Diameter | 3.16 light-years |
|---|---|
| Diameter compared with Earth | 2.3 × 10⁹ × Earth |
| Inner edge | About 2,000 AU |
| Outer edge | 50,000–100,000 AU |
| Proposed | 1950, Jan Oort |
| Members | Perhaps trillions |
Good to know
- Its outer edge is roughly a third of the way to Proxima Centauri.
- A comet falling in from there can take millions of years to reach the inner Solar System.
- Voyager 1 will need about 300 years just to reach the inner edge.
- Next smaller: Phoenix A* · 0.06 light-years
- Next larger: Helix Nebula · 5.74 light-years