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93 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Structure of Stars
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A ball of gas, heated by nuclear fusion, no real surface, just a radius at which the gases become transparent
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Mostly hydrogen, with some helium and small amounts of other elements
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Stellar Spectra
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Continuous spectrum formed by hot gases deeper down
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Strength of lines (found at surface) are strongly temperature dependant
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Spectral type
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Surface temperature
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OBAFGKM (90% KM, 99%, GKM)
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Doppler Effect
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Wavelength
Sound Light |
shorter, higher pitch, bluer
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What we can learn from the Stellar Spectra
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line strength
line position line profiles |
temperature, composition
radial velocity rotation, density, magnetic field |
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H-R diagram
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The relationship between temperature (spectral type) and brightness (or absolute magnitude)
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Mass (to a star)
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the temperature of a star is strongly dependent on its mass
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Parallax
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trigonometric--apparent shift
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spectroscopic--inference based on apparent magnitude and absolute magnitude
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Quiet sun
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Core
Photosphere Chromosphere Corona |
energy generate, 15mil deg K, 10% of diameter
apparent surface, 6,000deg K thin layer far into space-eclipse viewing |
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Active sun
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Sunspots
Flares Prominences |
magnetic disturbances-cooler regions
small regions where the temp is high ejections of gas into space |
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Nuclei
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binding energy
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Fusion
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nuclei must be going very fast to override magnetic repulsion
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the gas must therefore be very hot
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Nucleosynthesis
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Proton-Proton Cycle
triple-alpha process CNO cylce |
1H+1H=2H (expels e)
2H+1H= 3HE (expels r) 3He +3He=4He (expels 2x1H) |
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Neutrino
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nearly mass-less (can pass through)
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Caused by nuclear reactions in the sun's core (give insight to the sun's core)
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Stellar evolution
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corresponds to the H-R diagram
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The Birth of Stars
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clouds of dust and gas collapse under the influence of gravity and become hot and dense
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stops collapsing when pressure resulting from the heat generated by the nuclear reactions balances the inward pressure of gravity--it then becomes a star on the main sequence
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Main Sequence
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average life is about 10 billion years
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Life after the main sequence
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balance breaks down (consumed all nuclear fuel)
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red giant (death depends on mass)
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Death of stars like the sun
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after red giant, spews material (planetary nebula)
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the rest becomes a white dwarf (as compressed as it can get
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Death of massive stars
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red supergiants (much hotter and denser)
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Supernovae (violent and rivals galaxy light)
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Neutron Stars
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central part survives the supernovae
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10-20miles across
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Pulsars
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neutron stars conserve angular momentum (go very fast)
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strong magnetic beam
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Black hole
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super-super massive star (same gravity and same angular momentum)
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distorts space (Einstein's general theory of relativity)
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Star Cycle
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stars form-heavy elements produced in stars-said elemnts release by plantary nebula or supernovae-cloud of dust
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Newton's laws
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Gravity
Calculus Optics, including the reflecting telescope Laws of motion-- |
In the absence of external forces, things continue what they were doing
F=ma action= -(reaction) |
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Light
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light as a ray
light as a wave light as a particle |
straight line (abstraction)
visible spectrum (oscillation of electric and magnetic fields) the energy of the photon is related to the wavelength of light |
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Light Spectrum
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Continuous
Line |
black body radiation
activities of free and undisturbed atoms and molecules |
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Blackbody radiation
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Emitted by hot stuff
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smooth spectrum
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Spectral lines
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when an atom changes to a configuration with less or more energy in the electrons
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Spectral line series in the hydrogen atom
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Lyman
Balmer Paschen |
n=1(UV)
n=2(visible) n=3(IR) |
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Temperature-dependence of the lines from other atoms
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the lines for different atoms, ions and molecules appear with different strength int he visible spectrum at different temperatures
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this is an important was to measure the temperature of stars
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Telescope functions
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magnify
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collect lots of light (more important)
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Effects of the atmosphere
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blurs images from ground-based telescopes
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Refracting Telescope
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starlight---lens-----film-----eyepiece
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not used as much
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Reflecting Telescope
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starlight----small mirror-----mirror
I eyepiece |
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Telescope mounting
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altazimuth
equatorial |
up/down//left/right
right ascension/declination |
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Telescope types
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Newtonian Telescope
Cassegrain Schmidt-Cassegrain |
first reflector (big, inconvenient)
curved mirror to move the focus break in the big mirror extra optical correction (lens) |
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Radio astronomy
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large refractor is used (like reflecting telescopes)
use interferometer array (octagons) |
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Solar System (How it got here)
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Cloud of gas and dust gets an initial nudge--gravity takes over and the solar nebula compresses--It flattens and spins faster to conserve AM--the inner portion of the material is the sun, some of the remainder coalesces into planetesimals--planetesimals collide and stick because of gravity--T Tauri wind sweeps light elements our of the inner--rocky planets near the sun, gaseous planets farther out--gravitational interactions among the early planets rearrange their positions and may have ejected most of them from the solar system
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Mercury
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slow rotation
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Craters
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planet got hit by stuff
the surface was solid enough to support craters the impacting objects came in various sizes the craters were, or were not, modified by atmospheric or geological processes the rate, or type, of cratering may have changed over time |
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Atmosphere?
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massive= stronger gravity and more ability to have an atmosphere
the hotter the planet, the harder it is to hold on to |
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Venus
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atmosphere composed mostly of CO2
Temperature is very high as a result of the greenhouse effect |
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Greenhouse effect
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visible and UV heat the surface but CO2 keeps IR from escaping
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Moon topography
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Maria
Mountains Craters Rays |
smooth areas formed by flowing lava
from impacts from meteor impacts |
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Tides
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earth's oceans pulled by the gravitational attraction of the moon and the sun
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Life on Mars
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Meteorite
May be below the surface Evidence of water in the past |
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Jupiter's Moons
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Io
Europa Ganymede Callisto |
tidal action
covered by ice with liquid water below |
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Saturn's rings
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inside roche limit
see through |
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Saturn's moons
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Titan
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has atmosphere
icy |
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Uranus
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axis rotation of planet and orbits of 5 moons near plane of orbit
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Asteroids
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small, planet like (but not because of equal attraction to Jupiter), cratered, diameter and size using occultations
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Comets
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frozen gases mixed with dust
structure... |
nucleus
coma (cloud) tail (gas tail and dust tail) |
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Meteors
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a small piece of the solar system that hits earth's atmosphere and is heated until it glows
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Cosmic distance ladder
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A sequence of distance-measuring techniques that reach farther and farther from the earth, but generally with less and less reliability
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AUs-Trigonometric Parallax-Spectroscopic Parallax-Cepheid and RR Lyrae variables-Relative brightness of specific structures-size of galaxies-brightness of supernovae-the hubble law
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Types of Galaxies
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Spiral
Elliptical Irregular Peculiar |
large mass, mix of star types, some gas
dwarfs&giants, old red stars, little gas low mass, young blue stars, lots of gas specific strangle characteristics, often radio sources, produced by collisions |
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Radio Galaxies
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radio emission is "nonthermal", meaning that it is not just blackbody radiation from hot gas (like stars). It is usually synchrotron radiation, which is produced by the motion of fast electrons in magnetic fields.
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Often have bipolar of head/tail structure in which the radio emission comes from regions far beyond the visible extent of the galaxy, suggesting that the emission is from jets of material ejected by the galaxy.
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Galaxy clusters
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The speeds of galaxies within clusters are too great for the clusters to e stable without the presence of lots of dark matter. (zone of avoidance)
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Most galaxies are in clusters
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Quasar puzzle
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Are the quasars very distant and producing energy at an enormous rate by some extraordinary process, or is the Hubble Law assumption wrong and the quasars are really more normal objects located much closer to us?
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What are quasars?
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An early phase in the life of a galaxy (we are seeing the past)
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The center is collapsing and swallowing up large amounts of amass. When the available material has been consumed, the quasar fades.
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Where are quasars' energy source?
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black holes
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Hubble law (observational evidence)
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most galaxies are moving away from us, and that more distant galaxies are moving away from us faster
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connection to cosmic expansion
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Hubble law (graphical and mathematical description)
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v (velocity of recession of a galaxy) = Ho (Hubble constant) x d (distance of the galaxy)
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approximately linear (suggests that all galaxies were close together at some time in the distant past)
the Ho is key to discovering the age of the Universe |
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The Big Bang evidence
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The Hubble Law
Cosmic background radiation, its spectrum, and its spacial distribution |
CBR--a nearly uniform "bath" of photons that are now at radio wavelengths (essentially perfect blackbody spectrum)
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The "center" of the big bang
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it has no center. the space was created in the big bang--so it occurred everywhere
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Interstallar medium
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Neutral gas
Ionized gas Dust |
Largely H, molecules, "Invisible"
Visible, Line spectrum Seen in silhouette against bright background, causes reddening of starlight |
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Structure of the galaxy
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Arms include clouds of gas and dust, open clusters, hot stars
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globular clusters in a spherical halo
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Motion of the galaxy
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The arms: a density wave that induces star formation
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Generatl rotation (rotation curve) indicates presence of dark matter
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Shape of the sky
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We have no way to personally judge the distance from stars
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Not a sphere
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Constellation/Star names
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Historically figures associated with star patterns
Today, sky divided into sections roughly associated with the historical figures |
Bright stars have many names
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Star brightness
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Brightest stars 1st mag, faintest naked eye stars 6th mag
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the difference of 5 mag corresponds to a factor of 100 in intensity
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NCP/SCP
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the points on the celestial sphere directly above the N & S poles of the earth
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CE
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a circle around the celestial sphere above the earth's equator, 90 degrees from the NCP & SCP
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Sky
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different from Celestial sphere
Zenith Meridian Horizon |
the point directly overhead the semicircle extending from N horizon, through the zenith, to the S horizon the dividing line between earth and sky |
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Circumpolar stars
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the stars that never set as seen from a particular location
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Altitude vs. latitude
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Altitude of the NCP above the N horizon is equal to the observer's latitude
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Declination
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The N/S coordinate measured in degrees from the CE
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Right ascension
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The E/W coordinate measure in hours
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The Spheres
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Earth
Celestial Sphere Sky |
latitude, longitude, N & S pole, equator
declination, right ascension, NCP, SCP, CE horizon, meridian, zenith, altitude |
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Precession
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The direction of the earth's axis of rotation wobbles slightly over time
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the right ascension and declination of stars change over time
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Ecliptic
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the path of the sun around the celestial sphere is a circle that is tilted 23.5 degrees
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When plotted on a flat, rectangular map of the celestial sphere, the ecliptic appears as a sin-like curve
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Equinox/Solstice
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Vernal equinox
summer solstice atumnal equinox winter solstice |
sun on CE going N, first day of spring
sun at max declination, first day of summer sun on CE going S, first day of fall sun at min declination, first day of winer |
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Seasons
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Summer is warmer than winter because the sun is up longer and because it gets higher in the sky
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The sun does not usually rise exactly in the east and set exactly in the west
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Solar/Sidereal day
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time for the sun to return to the meridian
4 minutes longer than the sidereal day |
time for a star to return to the meridian
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Planets' paths
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lie close to the ecliptic
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closer to the sun than the earth move differently than do the planets that are farther away
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Moon's path
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approximately follows the ecliptic
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orbital motion is counterclockwise as seen from above the North Pole
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Phases of the Moon
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the moon is just an object that is illuminated from some direction by a light source
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Eclipses
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Solar
Lunar |
moon passes between the sun and the earth, casting a shadow on the earth
the moon passes directly behind the earth relative to the sun, so the earth's shadow falls on the moon |
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Ptolemaic Model
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geocentric
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sun, moon, planets revolve on epicycles
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Copernican Model
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heliocentric
Evidence-- |
retrograde loops are explained
Kepler's laws of planetary motion work correct phases of the inner planets are observed observation of jupiter's moons stellar parrallax is observed abberation of starlight is observed space probes get where they are supposed to go |
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Brahe
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Careful non-telescopic observations provided the data that Kepler needed
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Kepler
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trial and error
laws-- |
1- planets move in elliptical orbits with the sun at one focus of the ellipse
2-the sun-planet line sweeps out equal areas with equal times. this means that a specific planet moves faster with closer to the sun 3-period squared is proportional to radius of the orbit cubed |
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Galileo's contributions
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Use of telescope for astronomy-
milky way composed of stars sunspots jupiter's moons non-sphericity of saturn topography of the moon phases of the planets |
fundamental physics--
tested theory against experiment free fall relative motion |
