An astronomical unit (AU) is equal to the average distance from Earth to the Sun, about 92.9 x 10 mi. A parsec (pc) is the distance at which a length of 1 AU would subtend an angle of exactly 1 second of arc (the figure). A light-year (ly) is the distance that light, traveling through a vacuum with a speed of 186000 mi/s, would cover in 1.0 year. Express the Earth-Sun distance in (a) parsecs and (b) light- years. An angle of exactly 1 second 1 pc- . 1 pc MIAU (a) Number Units (b) Number Units