ASTRON 0089: EXAM 1
100 Cards in this Set
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Composition of Elements in the Universe Initially
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Hydrogen 75%, Helium 25%, Metals 0%
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Composition of Elements in the Universe Today
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Hydrogen 70%, Helium 28%, Metals 3%
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Fuse
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To join together
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Star
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Ball of gas that generates its own energy in the core by nuclear fusion
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Planet
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Object that orbits a star
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Moon
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"Rocky or Icy" object that orbits a planet
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Asteroid
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Small rocky object that orbits a star
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Comet
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Small icy object that orbits a star
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Solar System
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Star plus the planets
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Jovian Plantes
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The Gas Planets, Jupiter, Saturn, Neptune, Uranus
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Universe
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All matter and energy
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The Milky Way Galaxy
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Spiral galaxy composed of a highly flattened disk and a central "elliptical" bulge. The disk is about 100,000 light years (30kpc) in diameter.
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How many Stars in the Milky Way galaxy
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100 Billion
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How old is the Milky Way Galaxy
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13 Billion Years
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How far is the Sun from the center of the Galaxy
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27,000 Light Years
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Astronomical Unit
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The average distance between the Sun and the Earth (1.5 x 10^11)
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Light Year
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The distance light travels in one year (3.0 x 10^8 m/s)
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Age of the Universe
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13.75 Billion Years!
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Zenith
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The point directly above you
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Horizon
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A great circle on the celestial field, 90 degrees from the zenith
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Nadir
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The point directly below the zenith
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Meridan
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Great circle moving North-South, and passing through the zenith
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Celestial Sphere
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An imaginary around the Earth on which are "pinned" the sun, the moon, planets, and stars
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60 arcminutes
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1 degree
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60 arcseconds
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1 arcminute
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The planets, the moon orbit
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Anti-clockwise
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Daily Motion
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The Earth rotates once around its axis each day
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Annual Motion
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The Earth rotates around the sun in one year (365 days)
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How far does the sun move in 1 day in regards to the background stars
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1 degree to the east
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Why does the sky look blue
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Because the Earth's atmosphere scatters Blue light better than Red light
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Ecliptic
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The apparent motion of the sun on the celestial sphere
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Celestial Equator
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Intersection of the plane passing through the Earth's equator and the celestial sphere.
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Equinox
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When the sun crosses the celestial sphere
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Summer Solstice
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Sun reaches most northerly point above the celestial equator
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Winter Solstice
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Sun reaches most southerly point below celestial equator
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Seasons are caused by:
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The tilt in the Earth's axis, and orbital motion of the Earth about the Sun
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Solar Day
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Defined by the motion of the Sun
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Mean Solar Day
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Defined as an entire day of 24 hours
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Sidereal
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With respect to the stars
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Solar
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With respect to the Sun
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Sidereal Day
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One complete revolution, 23 hours 56 Minutes
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Sidereal Month
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The moon that completes one revolution around the Earth
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How much the does the Moon move every day
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13 Degrees to the East in regards to the background stars
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Synodic Month
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The completion of a full cycle of the moons phases, takes 29.5 days
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Eclipse
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One one object moves in front of another object
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Solar Eclipse
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When the moon moves in front of the Sun and the Earth
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Total Eclipse
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Hides the moon and only the Corona of the Sun is shown
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Annual Eclipse
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Occurs when the alignment is perfect but the Moons anguladiameter is too small to fully block the Sun
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Lunar Eclipse
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Occurs when the Earth passes in front of the Moon and the Sun, causing Earth's shadow falls on the moon
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The Line of Nodes
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Is the intersection of between the two orbital planes
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Speed of Light
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3.0 X 10^8 m/s
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Photons
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Light particles that have no mass and no charge
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Electromagnetic Radiation
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Varying field of Electric and Magnetic waves in the form of light
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Wavelength (Lambda)
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Spacing between crests, measured in nm
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Frequency
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The number of waves that pass an observer in 1 second, measured in Hz
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C=
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(Wavelength)x(Frequency)
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Frequency=
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((Planck's Constant)x(C))/(Wavelength)
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Spectrum
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Light split into its own separate components or colors
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Spectroscopy
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The splitting of light into its component wavelength's
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Refraction
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The change in the direction of light as it travels from one medium to another
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The different types of visible light
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Red (Longest Wavelength), Orange, Yellow, Green, Blue, Indigo, Violet (Shortest Wavelength)
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Types of Electromagnetic Radiation, Highest to Lowest Energy
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Gamma, X-Ray, Ultraviolet, Visible, Infrared, Radio
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As radiation passes through a COLD gas it produces (Krichoff Law)
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An Absorption Line Spectrum
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As radiation passes through a HOT gas it produces (Krichoff Law)
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An Emission Line Spectrum
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Continuous Spectrum
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Intensity of visible light changes smoothly with wavelength
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Emission Line Spectrum
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Light emitted at only a few wavelength's because the intensity of electromagnetic radiation at that wavelength is greater than neighboring wavelength's
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Absorption Line Spectrum
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A continuous spectrum in which dark bands are seen because the intensity of electromagnetic radiation at that wavelength is less than that of neighboring wavelength's
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Blackbody
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Perfect absorber and emitter of electromagnetic radiation, which is a function of temperature and wavelength only, emits a continuous spectrum
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A real stellar spectrum
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Not a perfect blackbody, it contains absorption lines and/or emission lines
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As a blackbody gets hotter
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It moves further to shorter wavelength's
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Wein's (Displacement) Law
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Lambda(max)= Constant (2.9 x 10^6 nm K)/Temperature
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As a Blackbody gets hotter
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More radiation is emitted at all wavelength's
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Stefan-Boltzmann Law
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L= 4(pi)(R)^2(sigma)(T)^4
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Sigma=
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5.7x10^-8
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Neutral Atom
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An atom with equal protons and neutrons, no charge
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Ground State
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ALL electrons are in their lowest energy level
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Excited State
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Added energy allows electrons occupy a higher energy level
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A photon is emitted when
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Electrons jump to a higher energy level, emission line is produced
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A photon is absorbed when
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Electrons jump to a lower energy level, absorption line is produced
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Lyman Series
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The transition between the ground and the excited state
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Balmer Series
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Transition from the 1st energy level to higher energy levels
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The Doppler Effect
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(Lamba)-(Lambdao)/(Lambdao)
The Change in Wavelength/The Wavelength measured at the source
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Chromatic Aberration
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The light of different colors are focused at different lengths
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Parabolic and Spherical Mirrors
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Suffer from Aberrations
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The collecting area of a single telescope
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.25(pi)(diameter)^2
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Refracting Telescope
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Collects Electromagnetic Radiation by Lenses
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Disadvantages of Refracting Telescopes (4)
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1) Costly, 2) Suffer from Chromatic Aberrations, 3) Difficult to mount large lenses, 4) Difficult to make large lenses
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Advantages of Refracting Telescopes (1)
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Long focal length gives good plate scale for astronomy
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Reflecting Telescopes
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Focus light using mirrors which are parabolic in shape
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Advantages of Reflecting Telescopes
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1) No Chromatic Aberration 2) Easy to build 3) Easy to mount
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Disadvantages of Reflecting Telescopes
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1) Small fields due to Coma, 2) Resolution used to be limited (Not anymore) (Adaptive Optics)
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Schmidt Telescopes
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Focus light using Mirrors and Lenses
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Resolution in Radians
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1.22(Wavelength/Diameter)
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Resolution in arcseconds
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2.52 x 10^5 (Wavelength/Diameter)
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Interferometry in Radio Telescopes
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To improve resolution, two or more telescopes can be used simultaneously
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Kepler's First Law of Planetary Motion
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Each planet's path around the sun is an ellipse with the sun at one of the focal points
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Kepler's Second Law of Planetary Motion
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A planet moves along its elliptical path with a speed that changes in such a way that a line from a planet to the Sun sweeps out equal areas in equal intervals of time
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Kepler's Third Law of Planetary Motion
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The ratio of a cube of a planet's Semi Major Axis, a, to the square of its orbital p, is the same for each planet
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Cosmic Ray
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High energy protons coming from outer space, not electromagnetic radiation
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Composition of the Universe
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Atoms= 4.6%, Dark Matter= 23%, Dark Energy= 72%
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