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Unit 2 Notes

ASTRONOMY UNIT 6 Notes are missing graphics and formatting is off (website doesn't support use of graphics) 


Everything we know about space we learned by studying Electromagnetic Radiation (wave energy emitted from objects). The Electromagnetic spectrum is the arrangement of radiation in order due to wavelength.


Leading theory, Big Bang Theory states approx. 15 billion years ago the universe began expanding after an enormous explosion. 


After big bang, matter condensed form galaxies. Galaxies - systems containing millions/billions of stars. Earth in Milky Way


  • Photosphere – sun’s lowest layer, were light is given  off
  • Sunspots – area that are cooler than surrounding area
  • Flare - eruptions, can reach earth cause disruptions, particles can be captured by the earth’s magnetic field creating the Aurora Borealis in n. hemisphere or Aurora Australia in S. Hemisphere

Constellations- is a group of stars that form a pattern Ex. Orion


  • Geocentric model –early model explained how solar system was shaped, stated earth was the center and everything else orbited the earth.
  • Heliocentric model – model earth & other objects orbit the sun, Copernicus gave us the first heliocentric model had the orbit of the planets as a perfect circular path. Later Kepler refined model to elliptical paths we use today.


  • Solar System- is a star and bodies that orbit around it.
  • Solar Nebular Theory –formed through condensing of solar nebula by gravity (force of attraction between objects due to mass) 4.6 billion years ago, gravity pulled matter inward, cloud contracted and began to spin, densely packed matter grew extremely hot in center, matter clumped, larger clumps continued to grow through more collisions became planetesimals (became planets), core of the disk grew even denser and hotter, nuclear fusion began in the core our star (sun) was born.



    • Mercury – nearest sun, day 400C night –200C almost no atmosphere composed of O2 and sodium, no moons, 1407.6 hours for rotation Venus –   earth’s twin, dense atmosphere mostly CO2, runaway greenhouse effect temp of 482C, no moons, one d ay is 243 earth days, clockwise spin retrograde), atmosphere CO2 & nitrogen
    • Earth – has water in 3 phases
    • Mars –red planet due irn context in the soil, thin atmosphere, only inner planet with 2 moons phobos & deimos, evidence for once liquid water on Mars, lots of frozen water

Outer Planets (JOVIAN PLANETS)

  • Jupiter – largest, large bands of gases hydrogen and helium, dark bands  sinking gas, light bands rising gas (convection cells) red spot is hurricane, has shortest day in solar system only 10 hours, 4 largest moons called the Galilean
  • Saturn -  has largest ring system, has the lowest density, will float in H2O,  has 7 major ring systems, rings maybe formed as a result of moon breaking apart
  • Uranus – rotates on its side, made mainly of methane gas, has 10 rings
  • Neptune – very blue with large methane content , has more distinctive clouds and atmospheric belts than Uranus  
  • Dwarf Planet Pluto – smallest planet only rocky Jovian planet, low density made of  ice/rock


  • Meteoroid – is a space rock that is still in space
  • Meteor – is a  meteoroid that burns up in the earth’s atmosphere
  • Meteorite – a meteoroid that hits the earth’s surface.
  • Asteroid – rocky/iron ranging mm to km, source of most meteorites. Most between Mars and Jupiter in asteroid belt
  • Comet – a mass of frozen gasses, dusts and rocks particles a dirty snow ball, most comets are located in the Oort cloud which is below Pluto and obits the sun. However, sometimes they come closer and cross our orbit

Sun Earth Interaction
– satellite travels around an object, one revolution around the sun is a year.

Rotation satellite turning on its axis

  • Seasons –regular, short-term change in the climate due to changes in the amount of solar radiation the area receives.
    • Summer solstice – first day of summer in Northern Hemisphere occurs about June 21 , longest day
    • Winter Solstice – Dec 21 shortest day, everywhere N of 66.5 is experiencing 24 hours of darkness
    • Equinoxes – daylight and nighttime are equal
      • Spring equinox – occurs about March 21
      • Autumn equinoxes – occurs about Sept 23


Moon- natural satellites of planets that vary widely in composition


  • Waxing – changes from all dark to all light
  • Waning – changes from all light to all dark


  • Lunar eclipse occurs when the moon passes into Earth’s umbra, only at full moon
  • Solar eclipse – occurs when the moon’s umbra reaches Earth’s surface, only when the moon is closest to the earth, only at new moon phase

Umbra - is the total shadow

Penumbra – is the partial shadow surrounding the umbra


Tides are caused by the gravitational pull of the moon and sun on the ocean.  A tidal change is actually a wave.

A wave is a rhythmic movement that carries energy through matter or space.                                         Spring tide – high tides are especially high and low tides that are especially low

 Neap tide – high tides that are not very high and low tides that are not very low


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