• 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

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

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



2020-09-102020-10-052021-01-082021-03-07Astrobiology - Exploring Other WorldsCecilia Payne-GaposchkinChandrasekhar limitCoronagraphH-R diagramJohannes KeplerKardashev scaleNew HorizonsOort cloudT Tauri starTycho BraheVoyager missionWien's lawaccretion diskangular momentumangular resolutionasteroid beltasteroidastr-1101astr-1102astronomerastronomical unitastrophysicsatmosphereautumnal equinoxbaryon cyclebetelgeusebig bangbinary starblack dwarfblack holebrown dwarfcarbon nitrogen oxygen cyclecelestial equatorcelestial polecelestial spherecepheid starcereschromospherecometcomparative planetologyconstellationcoriolis forcecoronadark energydark matterdifferentiationdiurnal motiondoppler effectdoppler spectroscopydwarf planeteartheclipseellipseenceladusequinoxerisexospherefoucault pendulumfrost linefusiongalaxiesgalileogeocentric modelgeological processesgiant molecular cloudgiant starglobular clustergravitational collapsegravitational redshiftgravitational wavegravityheavy bombardmentheliocentric modelhelioseismologyhuameahydrostatic equilibriuminstability stripinterstellar extinctioninterstellar mediuminterstellar reddeningjeans instabilityjovian planetjupiterkuiper beltlight curvelight yearlightmain sequence starmain sequencemakemakemarsmass-luminosity relationmercurymeridianmeteor showermeteormeteoritemilky way galaxymolecular cloudmoonmotionnebulaneptuneneutrinoneutron staropen clusteroppenheimer-volkov limitpanspermiaparallaxparsecperiod-luminosity relationphotometryphotosphereplanetplanetary motionplanetary nebulaplutopolarispositronprecessionpulsarradiationrascred dwarfretrograde motionrosetta missionrr lyrae starsaturnsolar systemsolar windspace missionspectroscopystar classificationstar clusterstarstefan-boltzmann lawstellar evolutionstellariumsummer solsticesunsunspotsupergiant starsupernovatelescopeterrestrial planetthe great attractorthe moonthe solar systemtidal forcetransit methodtransit regionuranusvariable starvenusvernal equinoxvulcanwhite dwarfwinter solsticeyellow dwarf