Astronomy

• 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

Resources

• Interactive sky charts

Useful Constants

Physical Constants

Name	Value
speed of light ($c$)	$2.9979 \times 10^8 m/s$
gravitational constant ($G$)	$6.674 \times 10^{-11} m3/(kg s^2)$
Planck’s constant ($h$)	$6.626 \times 10^{−34} J-s$
mass of a hydrogen atom ($M_H$)	$1.673 \times 10^{−27} kg$
mass of an electron ($M_e$)	$9.109 \times 10^{−31} kg$
Rydberg constant ($R \inf$)	$1.0974 \times 10^7 m^{−1}$
Stefan-Boltzmann constant (σ)	$5.670 \times 10^{−8} J/(s \times m^2 deg^4)$
Wien’s law constant ($\lambda \max T$)	$2.898 \times 10^{−3} m K$
electron volt (energy) ($eV$)	$1.602 \times 10^{−19} J$
energy equivalent of 1 ton TNT	$4.2 \times 10^9 J$

Astronomical Constants

Name	Value
astronomical unit ($AU$)	$1.496 \times 10^{11} m$
Light-year ($ly$)	$9.461 \times 10^{15} m$
parsec ($pc$)	$3.086 \times 10^{16} m = 3.262 light-years$
sidereal year ($y$)	$3.156 \times 10^7 s$
mass of Earth ($M_{Earth}$)	$5.974 \times 10^{24} kg$
equatorial radius of Earth ($R_{Earth}$)	$6.378 \times 10^{6} m$
obliquity of ecliptic	$23° 26’$
surface gravity of Earth ($g$)	$9.807 m/s^2$
escape velocity of Earth ($v_{Earth}$)	$1.119 \times 10^4 m/s$
mass of Sun ($M_{Sun}$)	$1.989 \times 10^{30} kg$
equatorial radius of Sun ($R_{Sun}$)	$6.960 \times 10^8 m$
luminosity of Sun ($L_{Sun}$)	$3.85 \times 10^{26} W$
solar constant (flux of energy received at Earth) ($S$)	$1.368 \times 10^3 W/m^2$
Hubble constant ($H_0$)	approximately 20 km/s per million light-years, or approximately 70 km/s per megaparsec

Space