Astronomy 4 - Solar System

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SOLAR SYSTEM

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* consists of the Sun and many celestial objects held to it by gravity
* Formed 4.6 billion years ago
* has 8 planets, asteroid belt, natural satellites & many SSSB's

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PLANET

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* celestial body that fits these criteria:
- orbits sun
- has enough self-gravity to be round
- has cleared its neighborhood

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DWARF PLANET

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* celestial body that fits these criteria:
- orbits sun
- has enough self-gravity to be round
- has NOT cleared its neighborhood
- is NOT a satellite of another planet

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SMALLER SOLAR SYSTEM BODY

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* All celestial bodies that orbit the sun but are not planets, satellites or dwarf planets
AKA: SSSB
* includes asteroids, comets and meteoroids
* most found in asteroid belt or Oort Cloud

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INNER PLANETS

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* AKA: terrestial (due to what they're made of) or inferior (due to size and location nearest sun)
* consist of Mercury, Venus, Earth & Mars
* rocky w/ solid cores

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OUTER PLANETS

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AKA: gas giants (due to what they're made of), superior (due to size), jovian (because Jupiter is 1 of them)
*consist of Jupiter, Saturn, Uranus & Neptune
* each:
- consist of gas under huge pressure
- has rings
- has many satellites

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NATURAL SATELLITES

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* celestial body that orbits a planet
* AKA: moons
* outer solar system has many more than inner

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DWARF PLANETS

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* examples: Pluto, Ceres, Eris, Sedna
* found in asteroid belt, in trans-Neptunian orbits (beyond Neptune's orbit), or in Oort Cloud

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MAIN ASTEROID BELT

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* found between Mars and Jupiter
* thought to be left over from beginning of S.S.
* Sun's & Jupiter's gravity hold in place

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KUIPER BELT

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* beyond Neptune's orbit
* dough-nut shaped region
* made up of comets
* short period comets come from here (return in 200 years or less)

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OORT CLOUD

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* beyond Pluto and Kuiper Belt
* cloud or spherical region
* made up of comets
* long period comets start here (return in over 200 years)

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COMETS

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* small, icy, celestial body
* orbits sun
* AKA: dirty snowball
* Parts:
- head: brightest part (made up of nucleus & coma)
- coma: fuzzy, gaseous outer layer of head
- nucleus: inner part of coma - frozen ice, dust & gas
- tail: result of sun's heating of head, made up of gas and dust has 2 parts: dust tail (curves) & gas tail (straight)
* tail points away from sun at all times

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SHORT PERIOD COMET

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* returns in 200 years or fewer
* originates in Kuiper Belt

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LONG PERIOD COMET

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* return in over 200 years
* originates in Oort Cloud

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ASTEROIDS

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* rocky, metallic celestial body
* orbits sun
* AKA: planetoid or minor planet
* one thought to have led to dinosaur extinction

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ASTEROID BELT

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* located between Mars & Jupiter
* Jupiter's gravity helps keep them in place

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METEOROIDS

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* chuck of rock or dust in space
* smaller than asteroids

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METEORS

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* meteoroid that has entered Earth's atmosphere
* AKA: falling star, shooting star, fireball
* streak of light = friction btwn it & atmosphere burns it up
* groups of them create meteor showers
* showers occur regularly on specific dates when Earth passes thru trail of dust-gas left by comet

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METEORITE

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* meteor that reaches Earth's surface