What does this number measure?
The reference unit for distances in the Solar System. The astronomical unit is defined as exactly 149 597 870 700 metres. It is close to the mean Earth–Sun distance without being their instantaneous separation.
Compare the stated dimensions
The comparison uses the number in each fact sheet: altitude, height, diameter, length or distance, depending on the reference. Two values in metres do not necessarily describe the same property.
Source and limitations
Catalogue order of magnitude; a source is provided, but this measurement has not been individually audited.
Astronomical unit: reference distance shown schematically along a Sun–Earth axis; the celestial bodies are enlarged, with no common scale for their diameters.