# Astronomical and physical constant 
# Planck constant
h = 6.6260755e-27   # erg s
# light speed
c = 2.99792458e10   # cm/s
# Gravitational constant 
G = 6.67259e08      # cm^{-3} g^{-1} s^{-2}
# electron charge 
e = 4.8032068       # esu
# electron mass
m_e = 9.1093897e-28 # g
# proton mass 
m_p = 1.6726231e-24 # g 
# neutron mass 
m_n = 1.6749286e-24 # g
# hydrogen mass 
m_H = 1.6726231e-24 # g 
# Avogadro constant
N_A = 6.0221367e23  # mol^{-1}
# Boltzmann constant
k = 1.380658e-16    # erg K^{-1}
# parsec
1 pc = 3.086e18 cm
# Astronomical unit
1 au = 1.496e13 cm
# light year
1 ly = 9.463e17 cm
# Solar mass
M_sun = 1.99e33 g 
# Solar radius
M_r = 6.96e10 cm
# Solar Luminosity 
L_sun = 3.9e33 erg s-1
# Solar effective temperature 
T_sun = 5780 K
# Hubble constant 
H_0 = 67.80+-0.77 km/s Mpc^{-1}