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| Question | Answer |
| Solar System | Everything orbiting the sun [8 planets, 5+ Dwarf Planets, Millions of Asteroids, Trillions of comets] |
| Planets | 1. Must orbit sun 2. Must be big enough to pull themselves into a round shape 3. Must have cleared their own orbit of similar objects |
| M V E M C J S U N P H M E | Mercury [Rocky/terrestrial] Venus [Rocky/terrestrial] Earth [Rocky/terrestrial] Mars [Rocky/terrestrial] Ceres [Dwarf] Jupiter [Gas giant] Saturn [Gas giant] Uranus [Gas giant] Neptune [Gas giant] Pluto [Dwarf] Haumea [Dwarf] Makemake [Dwarf] Eris [Dwarf] |
| Moons | - Orbit planets rather than sun - Earth has 1, Jupiter has 60+ |
| Asteroids | - Irregular lumps of rock } 1km -> 500km - Most lie between Mars and Jupiter |
| Comets | - Like asteroids but contain ice + frozen gasses - Mostly exist beyond Neptune in 2 huge clouds [Kuiper Belt + Oort Cloud] -Occasionally get knocked into inner solar system |
| Stars | - Produce own energy [Light, heat, other radiation] - Made of ~75% Hydrogen, ~24% Helium, ~1% other elements - Sun = Ordinary star [Some fainter/brighter] |
| Life of a star | |
| Nuclear Fusion | |
| High Mass stars | When H runs out in a star, core gets hotter + more dense until the He atoms start fusing. Helium -> Carbon -> Oxygen [Now a red giant] Very massive stars can fuse elements heavier than Helium -> Red supergiant. Eventually they become unstable and explode as supernovae. |
| Milky Way | Sun is 1 of 200-300 billion stars in the milky-way. Milky way is a huge island of stars, dust, gas + dark matter. Sun orbits Milky way 250 million years. |
| Milky Way diagram |
Image:
Scan_20140510 (image/jpg)
|
| External galaxies | Beyond the Milky way there are 10's of billions of other galaxies making up the universe. Our closest neighbours form the LOCAL GROUP of ~30 galaxies. [1 of closest = Andromeda - 2.5 million light years] |
| Types of Galaxies | |
| Astronomical Unit | 1AU = 150 million km = average distance of earth to sun. 1 light-year ~ 63000 AU AU not used outside solar system [too small] |
| Stability of stars | 2 forces [gravity (pushing in) + radiation pressure (pushing out)] are balanced. |
| The Universe | Redshift : Waves stretched [appear red] - galaxies moving away Blue shift : Waves compresses [appear blue] - Moving closer |
| Hubble's Law |
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