Where does this come from, and can I check it?

It began as the Earth-Sun distance and is now a defined constant. The figure is taken from IAU, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.

Is this really a space fact?

Yes. It sits on the Space shelf, one of 2,600 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.

What else can I read about it?

The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.

Mondo Knows Facts

An astronomical unit is 149.6 million kilometres

It began as the Earth-Sun distance and is now a defined constant The International Astronomical Union fixed the value exactly in 2012, removing the last dependence on measurement. It is used as the yardstick for distances inside the solar system. Light covers one astronomical unit in about 8 minutes 19 seconds. It sits in Mondo's space collection, one of 200 facts that each trace back to the reference below.

Where this comes from

IAU

Facts that can change over time are reviewed and updated. If something here looks wrong, Mondo would rather know than be confidently incorrect.

Go further

Science trivia

More facts like this

A light year is 9.461 trillion kilometresIt measures distance, not time, and the nearest star is over four away A parsec is a parallax measurement, not a timeIt is the distance at which Earth's orbit subtends one arcsecond The SI rests on seven base unitsMetre, kilogram, second, ampere, kelvin, mole and candela anchor every measure SI prefixes scale measurements by powers of tenKilo multiplies by a thousand and milli divides by the same amount Standard gravity is fixed at 9.80665The agreed value describes free fall at sea level and 45 degrees latitude Minus forty is the same in both scalesThe Celsius and Fahrenheit scales meet at exactly minus 40 degrees

Tags: units, distances, solar-system

An astronomical unit is 149.6 million kilometres: the short answers

Where does this come from, and can I check it?: It began as the Earth-Sun distance and is now a defined constant. The figure is taken from IAU, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.
Is this really a space fact?: Yes. It sits on the Space shelf, one of 2,600 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.
What else can I read about it?: The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.