Astronomical Units

On astronomy scale distances are very large, hence comfortable units are:

Unit	Symbol	Value SI
parsec	${\rm pc}$	$3.0857 \times 10^{16 } {\rm\; m}$
megaparsec	${\rm Mpc}$	$3.0857 \times 10^{22} {\rm \;m}$
lightyear	${\rm ly}$	$9.4605 \times 10^{15} {\rm \;m}$
astronomical unit	A.U.	$1.496 \times 10^{11} {\rm \;m}$
degree	$^\circ$	$17.4532925 {\rm \; mrad}$
arcsecond	$^{\prime\prime}$ (double prime)	$0.000277778^\circ$
arcminute	$^\prime$ (prime)	$0.0166667^\circ$

Constants

Name	Symbol	Value
Earth Radius	$R_{\oplus}$	$6.378 \times 10^6 {\rm \; m}$
Sun Radius	$R_\odot$	$6.961 \times 10^8 {\; m}$
Earth Mass	$M_\oplus$	$5.975 \times 10^{24} {\rm \; kg}$
Sun Mass	$M_\odot$	$1.989 \times 10^{30} {\rm \; kg}$
Sun Luminosity	$S_\odot$	$3.85 \times 10^{26} {\rm \; W}$