An Astronomical Unit is a unit of distance used to show the distance between two objects that are separated by a vast distance. An Astronomical Unit is equivalent to 93 Million Miles or 150 Million Kilometers. It is the distance between the Earth and the Sun.
When something is said to be 5.2 A.U. from the Sun, it is essentially saying that the distance is five point two times the distance the Earth is from the Sun. The object that is at that distance from the Sun is Jupiter, bet you knew that.
The distance to Pluto, the once ninth planet of the solar system is about 40 A.U., that's forty times the distance from Earth to the Sun. It is the furthest planet of any sort, gas, rocky or dwarf that has been visited by a man-made object.
Proxima Centauri is 268,142.38 Astronomical Units away from Earth. It is that amount times away from the Sun. An easier way to describe that distance is to use Light Years. Light Years which despite having a unit of time in its name is actually a distance. It is the distance that light travels in a year, that is equivalent to 5.88 trillion miles. Light takes 8 minutes 20 seconds to travel an Astronomical Unit.
The Oort Cloud is estimated to be about 1 Light Year from the Sun. That is roughly about 63241.1 A.U. away from us. The theoretical cloud is where many comets are believed to be located. Every so often, an event will cause an asteroid to come close into the Solar System. It is only theorectical as no one has yet discovered or see it.
The Astromonical Unit term was defined in 1976 by the International Astronomical Union (I.A.U.) and then refined in 2012 to be fixed at 149,597,870.7 km. Britannica.
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