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