1. Please take out your science journals and your envelopes for science vocabulary words.

2. A solar system is a group of objects in space that orbit a star in the center, plus the star itself. In our solar system the objects orbit around the star that we know as the sun. These objects include planets, dwarf planets, asteroids, and comets. We also have moons in our solar system, but they revolve around planets instead of the sun.

3. A planet is a large object that revolves around a star in a clear orbit. There are 8 planets in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The first four are called inner planets, and the last four are called outer planets.

4. The inner planets are the planets that are closest to the sun. These include Mercury, Venus, Earth, and Mars. These planets are similar in the following ways: Rocky surfaces, smaller than most of the outer planets, and none of them have more than 2 moons. They are different in these ways: Mercury is extremely hot, Mars never gets warmer than 70 degrees Fahrenheit, Earth is the only planet in our solar system with liquid water and oxygen in the atmosphere, and Venus has clouds of sulfuric acid that make it very hard to study.

5. An asteroid belt separates the inner planets from the outer planets. It is between Mars and Jupiter. Asteroids are hard and rocky objects that orbit around the sun.

6. Past the asteroid belt, we have the outer planets. These are much further from the sun than the inner planets. The outer planets are Jupiter, Saturn, Uranus, and Neptune. The outer planets are alike in the following ways: they have no known solid surfaces and are made mostly of gases. All of the outer planets have many moons and are surrounded by rings made of dust, ice, or rock. Space ships cannot land on these, but probing machines have. They are different in these ways: Uranus is different from the other outer planets because it orbits on its side. Jupiter is the largest planet in our solar system and has the most moons (at least 63!!). Neptune is the windiest planet in our solar system, and we can see Saturn’s rings from Earth with a telescope.

7. A dwarf planet revolves around a star but its path isn’t clear of other objects. There are 3 dwarf planets in our solar system: Pluto, Ceres, and Eris. Pluto’s orbit sometimes comes inside the orbit of Neptune. Unlike the gaseous outer planets, Pluto is made of ice and rock and it is smaller than Earth’s moon. Eris also revolves beyond the orbit of Neptune in a region with many cometlike objects. Ceres is in the asteroid belt between Mars and Jupiter. Scientists suggest there many be hundreds of dwarf planets in our solar system.

8. Asteroids are bits of rock and metal. Most are located in the asteroid belt and less than 1 kilometer across. A comet is a ball of rock, ice, and frozen gases. Sometimes these comets will get closer to the sun which will melt some of the frozen matter into gas that we may see from Earth as a fiery tail. Most comets are less than 10 kilometers, but the tails can be up to 100,000 kilometers long.