Unit of Measure Conversions

Astronomy

Astronomical Distance Conversions

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Additional Units and Information

Name Symbol Value Description/Notes
astronomical unit AU   Originally defined as the mean distance between the centres of the Earth and Sun
digit   1/12 diameter of the sun or moon Used to denote the extent of an eclipse
light year ly   Distance travelled by light through a vacuum in one Julian year (365¼ days)
lunar distance LD 3.84402 x 108 metres Mean distance between the centres of the Earth and Moon
parsec pc   Originally defined as the distance at which 1 AU subtends an angle of 1 arcsecond
    1.3 parsecs Distance to Proxima Centauri, the nearest star beyond the solar system - a red dwarf

The Solar System

* Relative to the Earth
Object Mean Distance from Sun* Diameter* Mass* Gravity* Known Moons
Sun   109.2 333,000 27.94  
Mercury 0.4 AU 0.383 0.055 0.38 0
Venus 0.7 AU 0.95 0.815 0.91 0
Earth 1.49597871 x 108 km 12,742 km 5.972 x 1024 kg 9.80665 m/s2 1
(Moon)   0.273 0.012 0.17  
Mars 1.5 AU 0.532 0.107 0.38 2
Jupiter 5.2 AU 10.97 317.83 2.53 95
Saturn 9 AU 9.14 95.162 1.07 146
Uranus 20 AU 3.981 14.536 0.89 27
Neptune 30.1 AU 3.865 17.147 1.14 14
Pluto 39.5 AU 0.187 0.002 0.06 5

Useful Approximations

Approximation % Accuracy
1 AU ≈ 15 x 1010 metres, or 150 million kilometres 99.7