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LAWS

  • rayleigh-jeans law » in classical physics, an equation that describes the intensity of blackbody radiation as a function of frequency for a fixed temperature
    • led to the ultraviolet catastrophe
  • wien's law » tells us that objects of different temperature emit spectra that peak at different wavelengths

EQUATIONS

  • distance modulus » m - M
    • the difference between the apparent magnitude (m) and absolute magnitude (M) of a celestial object. provides a measure of the distance to the object, r (in parsec)
  • energy of a photon » E = hc / λ
    • where h is planck's constant, c is the speed of light, and λ is wavelength
  • resolving power » RP = 25,000"(λ / d)
    • where λ is the wavelength of light, d is the diameter of the objective, and resolving power is expressed as an angle

CONSTANTS

  • gravitational constant » 6.67408 × 10 ^ -11 m3 kg-1 s-2
  • planck's constant » 6.63 x 10 ^ -34 js
  • speed of light » 3 x 10 ^ 8 m/s

TERMS

Aa

  • absolute zero » the lowest temperature theoretically possible; 0 degrees kelvin
  • accretion disk » a disk of gas that accumulates around a center of gravitational attraction, such as a white dwarf, neutron star, or black hole
  • albedo » the reflective property of a non-luminous object
    • a perfect mirror would have an albedo of 100% while a black hole would have an albedo of 0%
  • antimatter » matter consisting of particles with charges opposite that of ordinary matter
    • in antimatter, protons have a negative charge while electrons have a positive charge
  • aphelion » the point in the orbit of a planet or other celestial body where it is farthest from the sun
  • azimuth » the direction of a celestial object from the observer, expressed as an angular distance

Bb

  • binary » a system of two stars that revolve around a common center of gravity
  • blackbody » a theoretical ideal radiator and absorber of energy at all electromagnetic wavelength s
    • the term comes from the fact that a cold blackbody appears visually black
  • black hole » the collapsed core of a massive star
    • stars that are very massive will collapse under their own gravity when their fuel is exhausted
    • the collapse continues until all matter is crushed out of existence into what is known as a singularity
  • bolide » a term used to describe an exceptionally bright meteor
    • bolides will typically produce a sonic boom

Cc

  • celestial sphere » an imaginary sphere around the earth on which the stars and planets appear to be positioned
  • circumpolar star » a star that never sets but rather circles the pole star, polaris
  • coma » an area of dust or gas surrounding the nucleus of a comet
  • conjunction » an event that occurs when two or more celestial objects appear close together in the sky

Dd

  • dark matter » a term used to describe matter in the universe that cannot be seen, but can be detected by its gravitational effects on other bodies
  • doppler effect » the apparent change in wavelength of sound or light emitted by an object in relation to an observer's position
    • an object approaching the observer will have a shorter wavelength (blue) while an object moving away will have a longer (red) wavelength

Ee

  • eccentricity » the measure of how an object's orbit differs from a perfect circle
    • a value of 0 is a circular orbit
    • values between 0 and 1 form an elliptical orbit
    • 1 is a parabolic escape orbit
    • greater than 1 is a hyperbola
  • eclipsing binary » a binary system where one object passes in front of the other, cutting off some or all of its light
  • ecliptic » an imaginary line in the sky traced by the sun as it moves in its yearly path through the sky
  • einstein ring » an apparent ring of light caused by gravitational lensing of a distant object when its light passes by a nearer massive object
    • to get the einstein ring requires perfect geometric alignment
  • ejecta » material from beneath the surface of a body such as a moon or planet that is ejected by an impact such as a meteor and distributed around the surface
    • ejecta usually appear as a lighter color than the surrounding surface
  • elliptical galaxy » a galaxy whose structure is shaped like an ellipse. it is smooth and lacks complex structures such as spiral arms
    • more three-dimensional than a spiral galaxy, without much structure, and their stars are in somewhat random orbits around the center
  • event horizon » the theoretical boundary around a black hole beyond which no light or other radiation can escape

Gg

  • galaxy cannabalism » smaller galaxies consumed by collision or by being drawn into a larger galaxy
    • this process may cause changes in the shape and form of the larger galaxy and change its evolutionary pattern
  • gallilean moons » the name given to jupiter's four largest moons: io, europa, callisto & ganymede

Hh

  • head-tail galaxy » a radio galaxy moving through intergalactic space that has its outer portions (where the radio emission comes from) swept backward into the shape of a tail

Rr

  • radio galaxy » a galaxy that emits more energy at radio wavelengths than at visible wavelengths

Ss

  • solar winds » the continuous flow of charged particles from the sun that permeates the solar system
  • starburst galaxy » a class of galaxy characterized by periodic outbursts of star formation over widespread regions in the galaxy

Tt

  • tidal encounter » the nearby passage of a galaxy that stretches its companion by exerting unequal gravitational forces on each side
    • may result in the "grand design" structure of spiral galaxies

Uu

  • ultraviolet catastrophe » the error at short wavelengths in the rayleigh–jeans law for the energy emitted by an ideal black-body

Vv

  • void » vast spaces between filaments (the largest-scale structures in the universe), which contain very few or no galaxies
    • super void » a particularly large void, defined by the absence of rich superclusters
feb 18 2017 ∞
jun 10 2019 +