[PHYS 3655-3656 Astrophysics]

[Virginia Tech Department of Physics]

PHYS 3655/3656: Introduction to Astrophysics
J. H. Simonetti

jsimonetti@vt.edu

This page lists useful physical and astronomical constants, in SI units and cgs units.

Physical Constants

Symbol SI value cgs value Name
G 6.673 x 10-11 N m2 kg-2 6.673 x 10-8 cm3 g-1 s-2 Gravitational constant
c 2.99792458 x 108 m s-1 2.99792458 x 1010 cm s-1 Speed of light
μo (mu zero) 4π x 10-7 N A-2 Permeability of free space
εo (epsilon zero) 1/μoc2 Permittivity of free space
e 1.602176462 x 10-19 C 4.803 x 10-10 esu Elementary charge
h 6.62606876 x 10-34 J s6.62606876 x 10-27 erg s Planck's constant
k 1.3806503 x 10-23 J K-11.3806503 x 10-16 erg K-1 Boltzmann's constant
σ (sigma) 5.670400 x 10-8 W m-2 K-45.670400 x 10-5 erg cm-2 s-1 K-4 Stefan-Boltzmann constant
a=4σ/c (=4 sigma/c) 7.565767 x 10-16 J m-3 K-47.565767 x 10-15 erg cm-3 K-4 Radiation constant
me 9.10938188 x 10-31 kg9.10938188 x 10-28 g Electron mass
mp 1.67262158 x 10-27 kg1.67262158 x 10-24 g Proton mass
mn 1.67492716 x 10-27 kg1.67492716 x 10-24 g Neutron mass
mH 1.673532499 x 10-27 kg1.673532499 x 10-24 g Hydrogen mass
u 1.66053873 x 10-27 kg1.66053873 x 10-24 g Atomic mass unit

Astronomical Constants

AU 1.4959787066 x 1011 m 1.4959787066 x 1013 cm Astronomical unit
pc 3.0856776 x 1016 m 3.0856776 x 1018 cm Parsec
ly 9.460730472 x 1015 m 9.460730472 x 1017 cm Light year
Msun 1.9891 x 1030 kg 1.9891 x 1033 g Solar mass
Rsun 6.95508 x 108 m 6.95508 x 1010 cm Solar radius
Lsun 3.839 x 1026 W 3.839 x 1033 erg s-1 Solar luminosity
Mearth 5.9736 x 1024 kg 5.9736 x 1027 g Earth mass
Rearth 6.378136 x 106 m 6.378136 x 108 cm Earth radius
y 3.155692519 x 107 s 3.155692519 x 107 s Tropical year

Useful Info

1 eV = 1.602176462 x 10-19 J = 1.602176462 x 10-12 erg
1 Å = 10-10 m = 10-8 cm
1 arc second = 1/60 arc minute = 1/3600 degrees
1 erg = 1 g cm2 s-2
1 J = 1 kg m2 s-2
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