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Astronomical Unit Definition:
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An Astronomical Unit (AU) is a unit of length approximately equal to the average distance between Earth and the Sun. It is primarily used to measure distances within our solar system and is defined as exactly 149,597,870.7 kilometers.
The calculator uses the standard AU conversion formula:
Where:
Explanation: This calculation converts any distance in kilometers to its equivalent in astronomical units using the standardized definition.
Details: The astronomical unit provides a convenient scale for measuring distances within our solar system. It helps astronomers compare planetary orbits and spacecraft trajectories using a consistent, Earth-Sun referenced unit.
Tips: Enter any distance value in kilometers. The calculator will automatically convert it to astronomical units. Ensure the input is a positive number greater than zero.
Q1: Why is AU defined as 149,597,870.7 km exactly?
A: This value was adopted by the International Astronomical Union in 2012 as the exact definition to provide consistency in astronomical calculations and measurements.
Q2: How accurate is the average Earth-Sun distance?
A: While the actual Earth-Sun distance varies throughout the year due to elliptical orbit, the AU represents the semi-major axis of Earth's orbit, providing a stable reference point.
Q3: What are typical AU values for planets?
A: Mercury ~0.39 AU, Venus ~0.72 AU, Earth 1 AU, Mars ~1.52 AU, Jupiter ~5.2 AU, Saturn ~9.5 AU, Uranus ~19.2 AU, Neptune ~30.1 AU.
Q4: Is AU used outside our solar system?
A: For interstellar distances, astronomers typically use light-years or parsecs, as AU becomes impractically small for such vast distances.
Q5: How does AU relate to light travel time?
A: Light takes approximately 499.0 seconds (8 minutes 19 seconds) to travel 1 AU, which is the time it takes sunlight to reach Earth.