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Chapter 11The Structure of the solar system
Distances in Space
• Distances are sol large in the Solar System that you can’t just use meters or kilometers.
• Astronomical unit- AU- the average distance from Earth to the Sun
• 150 million km
Motion of Planets
• Rotation- the time it takes to make one rotation on its axis
• Revolution- the period it takes for the planet to make a full orbit around the Sun
Planetary orbits and speeds
• Do not move in circles
• Pattern is elliptical or oval- shaped
• An ellipse had two points inside it called foci ( pl) a focus is the singular
• Foci are equal distance from the center of the ellipse
• The Sun is one foci and the other foci is empty space
• Planet speed changes- closer to Sun speed increases
• Farther from sun- speed decreases- Why
What is a solar system
• Planets moving according to the ancient Greeks
• Planet means wanderer
• Solar system- the Sun and the group of objects that orbit the Sun
• The first objects identified were 5 planets- Mercury, Venus, Mars, Jupiter and Saturn
The Sun
• A star
• Ten times the diameter of the largest planet
• Made of hydrogen gas
• Nuclear fusion produces an enormous amount of energy.
• Sun emits some of the energy as light which shines on the planets
• Sun applies gravitational force on the planets so they orbit.
Objects that orbit the sun
• Planets
• Dwarf planets
• Asteroids
• Comets
Planets
• Nearly spherical shape
• Total mass must be greater than other objects near it
• 8 planets- divided into two groups
• Inner planets- Mercury, Venus, Earth and Mars
• Outer planets- Jupiter, Saturn, Uranus, Neptune
Dwarf planets
• Spherical object that orbits the sun
• It is not a moon of another planet
• It is in a region of the solar system where there are many objects orbiting near it
• DOES NOT HAVE MORE MASS THEN OTHER OBJECTS NEAR IT
• Made of rock and ice
• Ceres, Pluto, Makemake
Dwarf planets continued
• In 2006, the International Astronomical Union adopted a new category- the dwarf planet
• Definition- an object that orbits the Sun, has enough mass and gravity to form a sphere, and has objects similar in mass orbiting or crossing its orbital path
Pluto
• Two thirds the size of the Moon
• Period of revolution is 248 years
• Pluto is so cold it is covered with frozen nitrogen
• Has three known moons
Asteroids• Small rocky objects that orbit the Sun in the Asteroid belt
between Mars and Jupiter
• Usually not spherical
Asteroids continued
• Also made of ice
• Largest asteroid is Pallas- 500 km in diameter
• Similar in composition to the inner planets
Comets
• A comet is made of gas, dust, ice and rock and it moves around the sun in an oval shaped orbit.
• Solid, inner part is the nucleus
• As it moves closer to the Sun, it absorbs energy and has a bright tail-
• The coma is the glowing nucleus
Comets continued
• Short period- takes less than 200 Earth years to orbit the sun.
• Most short period come from the Kuiper belt
• Long period- take more than 200 years to orbit
• Most long period comets come from the Oort cloud
Meteoroid
• Meteoroid- a small rocky particle that moves through space
• Most are the size of a grain of sand
• A meteor- “shooting star” as a meteoroid moves through the atmosphere it begins to glow- most burn up
• If a meteor were to make it to Earth then it is a meteorite
• Meteorites can strike a planet causing impact craters.
Impact crater from a meteorite in ArizonaMeteor Crater in Winslow, Az