Chapter 11 The 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 Arizona Meteor Crater in Winslow, Az