It Might Be a Planet If... Steve Case North Mississippi NSF GK-8 November 2006.
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Transcript of It Might Be a Planet If... Steve Case North Mississippi NSF GK-8 November 2006.
![Page 1: It Might Be a Planet If... Steve Case North Mississippi NSF GK-8 November 2006.](https://reader035.fdocuments.in/reader035/viewer/2022081513/5697bfed1a28abf838cb8bc2/html5/thumbnails/1.jpg)
It Might Be a Planet If . . .Steve Case
North Mississippi NSF GK-8
November 2006
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What is a planet?
• Until recently, there was no exact definition.
• There were historically five planets.• Uranus, Neptune, and Pluto were discovered after the invention of the telescope.
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Our Nine-Planet Solar System
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Mercury• Closest planet to the Sun
• Very hot and rocky
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Venus
• About the same size as Earth
• Covered with thick clouds
• Farther from the Sun than Mercury, but hotter because of clouds
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Earth
• Our home planet• Contains water necessary for life
• Surrounded by a protective atmosphere
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Mars
• Smaller than Earth
• May have once had surface water
• Planned destination for human exploration
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Jupiter
• Largest planet in the Solar System
• Storms appearing as streaks and bands
• One large storm bigger than Earth: Great Red Spot
• First of the “Gas Giants”
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Saturn
• Known for beautiful rings of rock and ice debris
• Least dense planet (would float in water)
• Farthest planet known to ancient astronomers
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Uranus
• Orbits on its “side”
• Blue color comes from methane in atmosphere
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Neptune
• Most distant of the “Gas Giants”
• Very similar to Uranus in size and composition
• Great Dark Spot similar to Jupiter’s Red Spot
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Pluto
• Until recently, considered farthest planet from the Sun
• Smaller than any other planet
• Too distant to see surface features
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What About A 10th planet?
• In 2005, Eris discovered
• Larger and farther from the Sun than Pluto
• Publicized at first as 10th planet
• More and more objects discovered beyond Pluto
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A New Definition Needed
• If there were many objects about the same size as Pluto located near Pluto’s orbit, should they all be considered planets?
• If Pluto was a planet, why weren’t these new objects planets as well?
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So what is a planet?
• In 2006 the International Astronomical Union came up with three rules for determining whether or not a body is a planet:– Must orbit the Sun– Must have spherical (ball-like) shape– Must clear orbit of other debris
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1. Planets orbit their stars.
• All planets in the Solar System orbit the Sun.
• If a body in the Solar System orbits around something other than the Sun, it is not a planet.
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2. Planets are shaped like a ball (spherical).
• Planets have enough gravity that they were pulled into a spherical shape when they formed.
• If the body does not have a generally spherical shape, it is not considered a planet.
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3. Planets “sweep up” their area around the
Sun.
• Planets have enough gravity to clear their orbits of smaller debris.
• This debris is either captured by the planet and becomes that planet’s moon or else it is pushed out of the planet’s orbit.
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What about Pluto?• Pluto is roughly spherically shaped, and it does orbit the
Sun.• Pluto has not cleared its orbit of other debris.• Scientists have found many other Pluto-like objects near
Pluto’s orbit.• Pluto was given a new classification as a dwarf planet.
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Introducing the Dwarf Planets
• Dwarf planets only fulfill two of the three requirements to be a planet:– They orbit the Sun.– They are roughly spherically shaped.– They have NOT cleared their area of all other debris.
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Our Eight-Planet Solar System
• Scientists now say that our Solar System has only eight planets. Pluto is no longer considered a planet.
• Our Solar System now has three dwarf planets: Pluto, Eris, and Ceres. Pluto and Eris are located beyond Neptune. Ceres is the largest body in the asteroid belt between Mars and Jupiter.
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Other Members of the Solar Family
• Besides planets and dwarf planets, there are many other objects in the Solar System.
• Some of the major non-planet objects include moons, asteroids, and comets.
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Moons• Bodies that orbit other things in the Solar System besides the Sun.
• Many of the planets have moons. Earth has one moon. Mars has two. Jupiter has over fifty.
• Even some smaller objects like dwarf planets and asteroids have moons.
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Asteroids
• Large pieces of rocky debris that orbit the Sun.
• Many are found in the Asteroid Belt between Mars and Jupiter.
• Thought to be debris from a planet that never formed.
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Comets
• Large pieces of rock and ice that orbit the Sun beyond Neptune.
• Occasionally are “bumped” out of orbit and fall in toward the Sun.
• As they approach the Sun, ice and dust is burned off to form a tail stretching away from the Sun.
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Our Solar System:• Eight planets
• Three dwarf planets• Moons
• Asteroids• Comets