| Gravitational constant | G = 6.672(4)*10^-8 cm^3 g^-1 sec^-2 |
| Velocity of light (vacuum) | c = 2.99792458*10^10 cm s^-1 (by definition !) |
| Planck's constant | h = 6.62618(4)*10^-27 erg s hbar = 1.054589(6)*10^-27 erg s |
| Boltzmann's constant | k_B = 1.038066(4)*10^-16 erg K^{-1} |
| Electron charge | e = 4.80324(1)*10^-10 esu e = 1.602189(5)*10^-19 Coulomb |
| Proton mass | m_p = 1.6726949(9)*10^-24 g |
| Electron mass | m_e = 9.10953(5)*10^-28 g |
| Stefan-Boltzmann constant | sigma = pi^2 k_B^4/(60 hbar^3 c^2) sigma = 5.6703(7)*10^-5 erg s^-1 cm^-2 K^-4 |
| Thomson cross section | sigma_T = 8 pi e^4/(3 m_e^2 c^4) sigma_T = 6.65245(6)*10^-25 cm^2 |
| Astronomical Unit | 1 AU = 1.49597892(1)*10^13 cm |
| Light-Year | 1 ly = 9.4608953536(1)*10^17 cm |
| Parsec | 1 pc = 648,000/pi AU (by definition) 1 pc = 3.08567802(2)*10^18 cm 1 pc = 3.26150740(2) ly |
| (Siderial) Year (1900) | 1 yr = 3.1558149984*10^7 s |
| Solar Mass | M_sun = 1.989(2)*10^33 g G * M_sun = 1.32712497(1)*10^26 cm^3 s^-2 |
| Solar radius | R_sun = 6.9599(7)*10^10 cm |
| Bolometric Solar Luminosity | L_sun = 3.826(8)*10^33 erg s^-1 |
| Escape velocity from Sun | v_* = 617.5 km s^-1 |
| Absolute Solar Magnitude | M_v = +4.83 M_B = +5.48 |
| Earth Mass | M_earth = 5.976(4)=10^27 g |
| Hubble constant | H0 = 60..75 km s^-1 Mpc^-1 H0 = 18..23 km s^-1 Mly^-1 H0 = 1.9..2.4 *10^-18 s^-1 |
| Hubble Time | H0^-1 = 4.1..5.2*10^17 s H0^-1 = 13.0..16.3*10^9 yr |
Values in parentheses give inacuracy in preceding digit.
Useful approximate relations:
1 km/s ~ 1 pc per million y (1.023)
M_sun/L_sun ~ 0.5 in cgs units (0.52)
1 radian = 206,265" , 1 pc = 206,265 AU (648,000/pi)