Astronomical Constants + Approximations

Astronomical Approximations

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

Astronomical Constants

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

Physical Constants

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

Other Helpful Numbers

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

Atomic Spectra Database
Airmass calculator


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