• The study of the objects that lie beyond Earth and the process by which these objects interact with one another
    • My definition: The study of celestial objects beyond Earth and how they interact with one another.
  • An observational science
    • Rarely setup traditional experiments
    • Any hypotheses must be tested by observing many samples of the objects being studies
    • We note how different samples vary
  • Light is basically the only information we have access to


Useful Constants

Physical Constants

Name Value
speed of light (cc) 2.9979×108m/s2.9979 \times 10^8 m/s
gravitational constant (GG) 6.674×1011m3/(kgs2)6.674 \times 10^{-11} m3/(kg s^2)
Planck’s constant (hh) 6.626×1034Js6.626 \times 10^{−34} J-s
mass of a hydrogen atom (MHM_H) 1.673×1027kg1.673 \times 10^{−27} kg
mass of an electron (MeM_e) 9.109×1031kg9.109 \times 10^{−31} kg
Rydberg constant (RinfR \inf) 1.0974×107m11.0974 \times 10^7 m^{−1}
Stefan-Boltzmann constant (σ) 5.670×108J/(s×m2deg4)5.670 \times 10^{−8} J/(s \times m^2 deg^4)
Wien’s law constant (λmaxT\lambda \max T) 2.898×103mK2.898 \times 10^{−3} m K
electron volt (energy) (eVeV) 1.602×1019J1.602 \times 10^{−19} J
energy equivalent of 1 ton TNT 4.2×109J4.2 \times 10^9 J

Astronomical Constants

Name Value
astronomical unit (AUAU) 1.496×1011m1.496 \times 10^{11} m
Light-year (lyly) 9.461×1015m9.461 \times 10^{15} m
parsec (pcpc) 3.086×1016m=3.262lightyears3.086 \times 10^{16} m = 3.262 light-years
sidereal year (yy) 3.156×107s3.156 \times 10^7 s
mass of Earth (MEarthM_{Earth}) 5.974×1024kg5.974 \times 10^{24} kg
equatorial radius of Earth (REarthR_{Earth}) 6.378×106m6.378 \times 10^{6} m
obliquity of ecliptic 23°2623° 26’
surface gravity of Earth (gg) 9.807m/s29.807 m/s^2
escape velocity of Earth (vEarthv_{Earth}) 1.119×104m/s1.119 \times 10^4 m/s
mass of Sun (MSunM_{Sun}) 1.989×1030kg1.989 \times 10^{30} kg
equatorial radius of Sun (RSunR_{Sun}) 6.960×108m6.960 \times 10^8 m
luminosity of Sun (LSunL_{Sun}) 3.85×1026W3.85 \times 10^{26} W
solar constant (flux of energy received at Earth) (SS) 1.368×103W/m21.368 \times 10^3 W/m^2
Hubble constant (H0H_0) approximately 20 km/s per million light-years, or approximately 70 km/s per megaparsec

Space astr-1101