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Planets. Ch. 21 Notes. Astronomical Unit. The average distance between the Earth and the sun; approximately 150 million kilometers AU Most useful unit for measuring distances within the solar system. Planets VS. Dwarf Planets. Planets. Dwarf Planets. Must be round Orbit the sun - PowerPoint PPT Presentation
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ASTRONOMICAL UNIT
The average distance between the Earth and the sun; approximately 150 million kilometers
AU
Most useful unit for measuring distances within the solar system
PLANETS VS. DWARF PLANETS
Planets Dwarf Planets Must be round Orbit the sun Have cleared
out the region of the solar system along its orbit
Object that orbits the sun
Has enough gravity to be spherical
Has not cleared the area of its orbit
5 known: Pluto, Eris, Ceres, Makemake, and Haumea
INNER PLANETS
Mercury, Venus, Earth and Mars Small Dense Rocky surfaces Called “Terrestrial Planets” Mercury is the only inner planet without
an atmosphere
MERCURY
• Smallest terrestrial planet• Closest to the sun• Temps. Range from 430 Celsius
to -170 Degrees Celsius• Surface: flat plains• Atmosphere: None
VENUS• Earth’s twin
• Retrograde: spins clockwise
• Atmosphere: think and it is always cloudy, mostly made up of carbon dioxide
• Hottest planet, covered in rock
• Greenhouse effect: the trapping of heat near a
planet’s surface by certain gases in the planet’s atmosphere
EARTH
The only planet in the solar system where you could live easily. Earth has liquid water and a suitable temperature range and atmosphere for living.
Like Venus, Earth experiences a greenhouse effect. Without the atmosphere, Earth would be much cooler.
MARS
“Red planet” Has ice (two polar caps) Atmosphere: 95% Carbon Dioxide Temperatures on the surface range from -
140C to 20 C Volcanoes Mars has 2 very small moons (Phobos and
Deimos)
THE OUTER PLANETS
Jupiter, Saturn, Uranus, and Neptune
Gas Giants Many moons Surrounded by a set of rings
JUPITER
Largest and most massive planet Atmosphere: thick atmosphere made up
of hydrogen and helium Great Red Spot Moons: at least 63
SATURN
2nd largest planet Atmosphere: thick, made up of hydrogen and helium Has the most spectacular rings of any planet
made of ice and rock Moons: at least 61 moons Has the lowest density of any planet. If you
could build a bathtub big enough, Saturn would float!
URANUS
Blue-green in color due to methane in its atmosphere
Surrounded by dark, thin, flat rings Moons: at least 27 Rotates from top to bottom