Unit 12 Lesson 1 What Objects Are Part of the Solar System?
The Solar System Earth, other planets, and the moon are part of a solar system. A solar system is made up of a star and the planets and other space objects that revolve around it.
The Solar System A planet is large, round body that revolves around a star, which, in our solar system, is the sun.
The Solar System There are eight planets in our solar system. The planets in our solar system are very far from one another. The orbits of the planets are oval-shaped, or elliptical.
The Solar System All the planets rotate, or spin, around an axis, which is an imaginary line that goes through the center of the planet. Earth rotates once on its axis every 24 hours, or the length of one day on Earth.
The Solar System
The Inner Planets The four inner planets are Mercury, Venus, Earth, and Mars. The inner planets are 1. Very dense and rocky. 2. Have thin atmospheres 3. Have small diameters. 4. Have large, solid cores 5. Have few moons. 6. Their revolution times are short.
The Inner Planets Mercury
The Inner Planets Venus
The Inner Planets
The Inner Planets Earth
The Inner Planets Mars
The Inner Planets
The Outer Planets The planets farthest from the sun are Jupiter, Saturn, Uranus, and Neptune. These planets are known as gas giants, as 1. They are huge. 2. Made mostly of gases. 3. They don t have a solid surface. 4. Their cores are very small. 5. All have many moons and ring systems.
The Outer Planets Jupiter
The Outer Planets Saturn
The Outer Planets Uranus
The Outer Planets Neptune
The Outer Planets
The Outer Planets
The Outer Planets
Compare Inner and Outer Planets
Compare Inner and Outer Planets
The Flying Objects Moons Moons are small, natural objects that revolve around other objects. Some planets have more than one moon, but Earth has only one. Earth s moon revolves around Earth about every 27 days. Mercury and Venus do not have any moons.
The Flying Objects Moons Moons in our solar system differ from each other. Some moons may contain a lot of ice. Europa, one of Jupiter s moons, may have a liquid ocean under a layer of ice. Some moons have many volcanoes. Io, another one of Jupiter s moons, has the most active volcanoes in the solar system.
Dwarf Planets Pluto was once classified as a planet. Now, it is classified as a dwarf planet. Dwarf planets are nearly round bodies whose orbits cross the orbits of other bodies. Most dwarf planets are found in the Kuiper belt, a region of the solar system, and are very far away and hard to study.
The Flying Objects
Meteoroids, Meteors, and Meteorites Meteoroids are pieces of rock that break off of asteroids and travel through space. Meteor is a term used to describe the streak of light caused when a meteoroid burns up in Earth s atmosphere. If a meteoroid reaches Earth s surface, it is called a meteorite.
The Flying Objects
Asteroids Asteroids are rock and iron objects that orbit the sun. Millions of asteroids are found in the wide region between Mars and Jupiter known as the asteroid belt. Asteroids range in size from as small as a city block to the size of an ocean.
Comets A chunk of frozen gases, rock, ice, and dust is known as a comet. As comets pass close to the sun, part of the frozen surface breaks away and turns into gases and dust. These particles reflect the sun s light and look like long tails that always point away from the sun.
The Flying Objects
The Flying Objects
Space Watch Objects such as comets, meteoroids, and asteroids can hit the surface of other bodies in the solar system. The impact, or hit, from space objects creates impact craters. Scientists keep track of the size, position, and motion of space objects near Earth using telescopes.
Space Watch A comet named Shoemaker-Levy 9 impacted Jupiter in 1994. The comet caused bubbles of hot gas to rise into Jupiter s atmosphere and dark spots to form on its surface. Scientists also believe a huge object impacted Earth 65 million years ago, leading to changes in the environment that killed all the dinosaurs.
Space Watch