What is an astronomical unit, a parsec or some other unit of measurment?
Hi there! Let me set the parameters for my answers first: The astronomical unit (AU or au or a.u. or sometimes ua) is a unit of length. It is approximately equal to the mean distance between Earth and Sun. The currently accepted value of the AU is 149 597 870 691 ± 30 metres (about 150 million kilometres or 93 million miles). The symbol “ua” is recommended by the Bureau International des Poids et Mesures, but in the United States and other anglophone countries the reverse usage is more common. The International Astronomical Union recommends “au” and international standard ISO 31-1 uses “AU”. The parsec (symbol pc) is a unit of length used in astronomy. It stands for “parallax of one arc second”. It is based on the method of trigonometric parallax, one of the most ancient and standard methods of determining stellar distances. The parallax of a star is half of the angular distance a star appears to move against the celestial sphere due to the orbit of the Earth around the Sun. As to conv
