Astronomical Approximations

Astronomical Constants

Physical Constants

Other Helpful Numbers

1 year	pi · 107 sec	3.15576 · 107 sec
1 mas	5 · 10-9 radians	4.848136811 · 10-9 radians
1 mas/yr	4.74 km/s/kpc	4.7405049 km/s/kpc
1 pc/Myr	1 km/s	0.9778 km/s
1 °	1.75 pc      (at a distance of 100 pc)
1 mas/yr	0.5 km/s     (at a distance of 100 pc)
50 km/s/Mpc	0.18 µas/a	Hubble constant H0

1 pc	3.0857 · 1016 m = 2 · 105 AU = 3.26 ly
1 AU	1.49597870 · 1011 m = 215 RSun
1 MSun	1.9891 · 1030 kg = 1047 MJup
1 RSun	6.96 · 108 m
1 LSun	3.9 · 1026 W
1 Mbol,Sun	4.72 mag
1 MJup	1.90 · 1027 kg = 318 MEarth
1 MEarth	5.976 · 1024 kg

c	2.99792458 · 108 m/s
G	6.6720 · 10-11 m3/kg/s2 = 0.0043 pc/MSun (km/s)2
	= (2 · pi)2 (AU)3/(MSun yr2)
h	6.626 · 10-34 Js
e	1.6021892 · 10-19 C
me	9.1095 · 10-31 kg
k	1.380662 · 10-23 J/K
sigma	5.67032 · 10-8 W/m2/K4

pi	3.1415926535897932...
	41 252 sqare degree	area of the entire sky

Atomic Spectra Database

Airmass calculator

e-mail: sreffert@lsw.uni-heidelberg.de