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Astronomical Unit, Light year , Parsec

Astronomical Unit (AU)

1 AU = 1.50 x 1011 m

This is the average distance of the Earth from the sun.

Light year (lyr)

1 lyr = 9.46 x 1015m

The is the distance travelled by light in a vacuum in one year.

A light year is 5.9 x 1012 miles (approx 6 trillion miles).

Parsec (pc)

1 pc = 3.08 x 1016 m

One parsec (pc) is the distance to a star that subtends and angle of 1 arc second at an arc length of 1 AU.

How to calculate the distance  in parsecs from the parallax angle in seconds.

d = distance in parsecs (pc)
J = the parallax angle in seconds



Methods of determining the distance of objects from Earth.