Astronomers often describe Solar System distances in astronomical units, or AU. One AU is about the average Earth–Sun distance. Neptune orbits roughly 30 AU from the Sun, so the outer planets need much more space in a distance model.
Space · Discover & try
How big is our Solar System?
Reading level 3 of 5 · IndependentChange
Word help
Scale
A consistent relationship between model measurements and real measurements.
Astronomical unit
A length of about 150 million kilometres, close to the average Earth–Sun distance.
Diameter
The distance across an object through its centre.
Watch · Try · Explain
See how it works
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Average orbital distances and planet diameters, shown on separately labelled scales. This is not a live positions map.
What to look for
- Compare the inner-planet gaps with the outer-planet gaps.
- Switch between the size and distance views.
- Read whether planet symbols share the distance scale.
Explain what you noticed
Why are planets often enlarged in a Solar System distance diagram?
Keep this idea: Planet size and distance are different measurements and need explicit scales.
Follow the sources
- NASA — How Big Is the Solar System?
- NASA Jet Propulsion Laboratory — Make a Scale Solar System
- NASA Jet Propulsion Laboratory — Solar System Sizes and Distances: Reference Guide
Source material checked 2026-10-28. Explanations and activities by Nepedia. Agency source links do not imply endorsement.
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