Astrology

• a natural satellite is a celestial body that orbits a planet
• the moon is the Earth's only natural satellite and is the only natural satellite in the solar system
• our solar system includes the sun, planets, and their moons
• the moon does not generate light, instead, it reflects sunlight
• it takes 27 days for the moon to orbit Earth, this is when the moon phases occur
• a moon phase is the lit side of the moon which changes during its orbit around the earth
• the moon rotates its axis at the same rate as it does earth, so we see the same side of the moon
• the moon shape changes bc the sun is constantly lighting up the moon, just not always the side facing us
• a new moon occurs when the lit side is facing away from the Earth, so it appears completely dark
• the observable universe is light that has left its source within the last 13.7 billion years (age of universe, not just milky way - 13.6)

  ** possibly 26.7 billion years (Ottawa prof. Gupta)
• the Earth is 4.5 billion years old, and the Sun 4.6 billion
• observable universe is 93 billion light years across
• objects from beginning of universe are moving away from us

  ** why? think of a balloon expanding (like universe is constantly), images on it would get further apart
• light takes 8 minutes to travel from the sun to the earth

  • so when we see the sun, we are seeing it as it was eight minutes ago
  • for example, when a solar flare happens, we see it later, like looking into the past
• inner planets are closer to the sun and smaller in size

  • mercury
  • venus
  • earth
  • mars
• outer planets, or gas giants, are larger and are beyond the asteroid belt

  • jupiter
  • saturn
  • uranus
  • neptune
• asteroid belt: region between mars and Jupiter made of leftover rock and dust from early development of solar system

  • Jupiter's gravity prevented rocks from forming a planet, leaving them scattered in the belt
• kuiper belt: a region of frozen gas and icy objects (like comets) beyond Neptune

  • formed with leftover material from outer planets
• the main difference between an asteroid and a comet: one is rock and metal, while the other is ice and dust

  shape differences

  • asteroid: rocky, irregular
  • comet: solid core with a glowing tail
• a meteoroid is a smaller asteroid
• a meteor is a meteoroid that enters Earth's atmosphere and burns up

  • burn bc the friction and speed of contact with the atmosphere causes the air in front to compress and heat up
• a meteorite is a leftover space rock from a burned up meteor
• Sedna (2003): one of the furthest objects we know in the solar system

  • dwarf planet
  • Eris is other
  • 8 billion miles away from sun
• the Oort Cloud is a mass of frozen gas and ice particles at the end of the solar system where comets originate from (and Kuiper)
• light year = 63,200 AU