Astronomical Units
Convert kilometers, astronomical units, light-years and parsecs, with a solution and the light travel time.
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Enter a whole number, a decimal (2.5), a fraction (1/3) or scientific notation (6.02e23).
The astronomical distance converter converts between kilometers, astronomical units, light-years, parsecs and light time, and shows how long light takes to cover the distance.
Distance units in astronomy
| Unit | Value |
|---|---|
| astronomical unit (AU) | 149,597,870.7 km — the mean Earth–Sun distance |
| light-year (ly) | 9,460,730,472,580.8 km — the distance light travels in a year |
| parsec (pc) | ≈ 3.2616 ly ≈ 206,265 AU |
| light-minute | 17,987,547.48 km |
The speed of light is 299,792.458 km/s. Sunlight reaches the Earth in about 8 minutes 20 seconds, and light from the nearest star, Proxima Centauri, takes 4.24 years.
A parsec is the distance from which the radius of the Earth's orbit (1 AU) is seen at an angle of one arcsecond; it is used for distances to stars and galaxies.
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