Astronomy

• Big Bang Theory


  Creation of the universe
• 13.7 billion years ago is when the "Big Bang" occurred
• Big Bang Singularity


  Where/how the universe began, space was shrunk down to a very small area and then began to stretch out rapidly
• At the time of the Big Bang, space was compressed down so much that it was incredibly hot and dense, and our current mathematical models don't work beyond that point
• Two major scientific discoveries that provide strong support for the Big Bang Theory


  • Hubble's discovery of the relationship between a galaxy's distance from Earth and its speed in the 1920s
  • Cosmic microwave background radiation discovered in the 1960s
• How we know the universe is expanding

  1. Edwin Hubble measured the distances of objects in space

  2. The speed that objects move away from each other is proportional to the distance apart

  3. The farther objects are away from Earth, the faster they are moving away from us
• Cosmic microwave background radiation (CMBR)


  Leftover radiation from the Big Bang
• Solar Nebular Theory


  Creation of the Solar System
• The Solar System is made up of the Sun, planets and their moons, and billions of other smaller celestial objects, all held together/orbiting by the Sun's gravitational force
• How the Solar System formed

  1. A cold spinning cloud of gas called a solar nebula

  2. Gravitational pull condensed gas towards the centre, increasing the speed of rotation and flattening the cloud

  3. Growing force of gravity continued to pull matter to the centre, increasing pressure and temperature until it created a star

  4. Matter outside the star started to clump together to create protoplanets, with lighter gases pushed farther away
• Nebular Hypothesis


  • Explains why planets and the star they orbit usually spin in the same direction and lie in the same plane
  • Explains the arrangement of planets with rocky ones nearest to the sun and gas giants farther away
• The sun formed about 4.5 billion years ago
• Composition of the sun

  • 91% hydrogen
  • 8.9% helium
  • Rest is heavier elements
• The elements in the sun are in a plasma phase
• The sun contains 99.8% of all mass in our solar system
• The sun's gravitational pull keeps the solar system together
• The sun's magnetic field (heliosphere) protects our entire solar system from cosmic radiation
• Structure of the sun

  1. Core

  2. Radiative Zone

  3. Convection Zone

  4. Photosphere

  5. Chromosphere

  6. Corona
• Core


  Where thermonuclear fusion occurs which releases enormous amounts of energy
• Radiative Zone


  Energy moves slowly outward taking more than 170,000 years to radiate through this layer
• Convection Zone


  Energy continues to move towards the surface through convection currents of heated and cooled gas
• Photosphere


  The visible surface of the Sun. It can have sunspots which are created by high magnetic fields
• Chromosphere


  Thin layer that has magnetic field to restrain the electrically charged solar plasma. Can create solar flares and prominences which extend out into the corona and may eject material away from the Sun
• Corona


  The Sun's atmosphere. It glows in x-ray and extreme UV wavelengths
• If the Sun were to disappear right now

  • For 8 minutes, we wouldn't know since the sun is 8 light minutes away
  • The sun's gravitational pull would also still last for 8 minutes
  • The Earth would travel in a straight line
  • Photosynthesis would stop
  • We would have enough oxygen for 1000 years
  • It would be cold (Freezing temp.)
• Earth is the perfect distance from the Sun to support life
• • Any closer to the Sun and we would be scorched (too hot)
  • Too far, and we'd freeze (too cold)
• The Earth's magnetic field deflects most of the solar wind from entering the atmosphere
• Ozone and other gases in the Earth's atmosphere help protect us from the Sun's harmful x-rays and UV rays
• Other gases help trap heat near the surface of the Earth that would otherwise go back into space – this allows minimal change in temperature
• Stars


  • Giant balls of dust and gas (hydrogen and helium) that emit large amounts of energy in the form of light and heat
  • Gigantic balls of plasma, which is ionized gas, held together by gravity
  • Work because of thermonuclear fusion in the core, where hydrogen atoms fuse into helium atoms
• Stars


  • Vary in size and mass
  • Categorized by temperature, brightness, composition, and mass
• Temperature of stars


  The colour of the star tells us the approximate temperature of the star's surface and its life stage
• Hertzsprung-Russell (HR) Diagram


  • Shows the relationship between luminosity, size, and temperature of stars
  • 90% of stars plotted on the HR diagram fit into a diagonal band known as the main sequence
  • Main sequence stars fuse H to He in their cores
• Brightness of stars


  • Depends on how much energy a star produces and gives off
  • Luminosity is the total amount of energy produced by a star each second
• Composition of stars


  • The elements that make up a star
  • Can be an indicator of the star's temperature
  • Can be determined using spectral analysis
• Life cycle of stars

  1. Starts from a stellar nebula, a cloud of dust and gases (mostly hydrogen and helium)

  2. Gravitational forces pull gas and dust particles together forming a protostar

  3. Pressure in the core rises and nuclear fusion begins, combining hydrogen atoms to form helium and light
• The more massive the star, the shorter the life cycle
• Impact Hypothesis


  Origins of the Moon
• Origins of the Moon

  1. An object the size of Mars hit a fully formed Earth

  2. Matter from Earth flung into space

  3. Matter eventually came together to form the Moon