Oort Cloud
The Oort Cloud is a distant, roughly spherical shell of icy objects believed to surround the Solar System and supply long-period comets.
How big is it?
3.163 ly across
Diameter · approximate
A little perspective
Oort Cloud vs Distance to Proxima Centauri: length comparison
The distance to Proxima Centauri is about 1.34 times the diameter of the Oort Cloud.
The Oort Cloud is a distant, roughly spherical shell of icy objects believed to surround the Solar System and supply long-period comets.
This is the distance from the Sun to Proxima Centauri, the closest known star to our Solar System.
Both rulers start at the same zero and share one linear scale. Artwork keeps its original proportions. A ruler represents the selected distance or a measurement not visible in this view.
Measurements, assumptions & sources +
Oort Cloud
Diameter: 3.163 ly; approximate.
A conceptual 200,000 AU diameter corresponding to a 100,000 AU outer radius. This distant comet reservoir is inferred, with a very uncertain extent. The illustration is a boundary diagram; dots identify objects or regions and do not depict their physical diameters.
The marked diameter is calibrated. Unmeasured illustration details are representative.
Distance to Proxima Centauri
Distance: 4.25 ly; approximate.
Rounded NASA nearby-star distance anchor, 4.25 light-years. The Earth is not at the centre of the galaxy.
NASA — Our nearest celestial neighbour
The marked distance is calibrated. Unmeasured illustration details are representative.
Use the visual comparison to explore its scale, then check the measurements and sources.
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Why this measurement?
Why we use 3.163 ly
We compare the diameter of the Oort Cloud. This is an estimate; check the notes for its rounding and uncertainty.
A conceptual 200,000 AU diameter corresponding to a 100,000 AU outer radius. This distant comet reservoir is inferred, with a very uncertain extent. The illustration is a boundary diagram; dots identify objects or regions and do not depict their physical diameters.
The marked horizontal span follows the measured feature, not the edges of the image. How calibrated comparisons work →
Recorded properties
Dimensions and measurements
| Property | Selected value | Recorded range | Basis |
|---|---|---|---|
| 3.163 ly | Not recorded | approximate |
Around this scale
Explore nearby values.
Compare examples with lower, similar and higher values. Each card names the measurement being compared.
Nearest lower valuePlanets, moons and spacePlanetary Solar System60.22 AUDiameterThe Solar System is the collection of the Sun and all objects gravitationally bound to it, including planets, moons, and smaller bodies.
Nearest higher valuePlanets, moons and spaceDistance to Proxima Centauri4.25 lyDistanceThis is the distance from the Sun to Proxima Centauri, the closest known star to our Solar System.Sources and method
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The source records and measurement method remain available for inspection.
- NASA — Oort Cloud factsThe inferred cloud extends as far as about 100,000 AU from the Sun; it is not a directly mapped hard shell.
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Curated comparisons
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SpaceEarth–Sun distance1 AUThe Earth–Sun distance, or astronomical unit, is the standard measure of separation between Earth and the Sun used in astronomy.
SpaceMilky Way30.66 kpcThe Milky Way is a spiral galaxy containing hundreds of billions of stars, including our Solar System.
SpaceObservable universe28.21 GpcThe observable universe is the region from which light or other signals have had time to reach us since the early universe.SpaceDistance to Proxima Centauri4.25 lyThis is the distance from the Sun to Proxima Centauri, the closest known star to our Solar System.SpaceDistance to Sirius8.6 lyThis is the distance from the Sun to Sirius, the brightest star in the night sky.SpaceNeptune’s orbital distance30.11 AUNeptune’s orbital distance is the average separation between Neptune and the Sun.SpaceDistance to the galactic centre7.972 kpcThis is the distance from the Solar System to the centre of the Milky Way galaxy.SpacePlanetary Solar System60.22 AUThe Solar System is the collection of the Sun and all objects gravitationally bound to it, including planets, moons, and smaller bodies.