Our solar system includes everything that is affected by the sun’s gravity. It includes the sun and everything orbiting around it (the eight planets, moons, asteroids, comets, and other objects).
Inner Planets: The four planets closest to the sun are called the inner planets. They are also called the terrestrial planets, which means that they are rocky like Earth. The terrestrial planets listed from closest to the sun to farthest from the sun are: Mercury, Venus, Earth, and Mars.
Mercury: Mercury has extreme temperatures because it has no atmosphere. Mercury’s day is as long as 58.6 Earth days. Mercury’s year is about 88 Earth days long. It is named after the Roman messenger god and it has no moons.
Venus: Venus is very close in size and mass to Earth. It has an atmosphere made of almost entirely carbon dioxide so it traps heat in a ‘runaway greenhouse effect’. Due to this, Venus’ temperature is around 464oC. Venus is named after the Roman goddess of love and beauty. Venus’ day is about 243 Earth days, and its year is 225 Earth days. This means that it takes longer for Venus to spin around on its axis once than it takes for it to orbit around the sun.
Earth: Earth is the only planet known to support life. Earth has one large moon. Earth’s day is about 23.93 hours and its year is about 365.25 days. Its temperature ranges from -88oC to 58oC. It is named after an old English/German word meaning ‘ground’ or ‘dirt’. Earth’s average distance from the sun is around 149.6 million kilometers and astronomers call this distance one A.U. (astronomical unit).
Mars: Mars looks red because it has a lot of iron oxide (rust) on its surface. It has the largest volcano in the solar system, Olympus Mons. It has two small moons called Phobos and Deimos. Mars is named after the Roman god of war. Its temperature ranges from -153oC to 20oC. Mars’ moons are so small, they aren’t rounded by their own gravity so they are shaped like potatoes. Mars' year is 687 Earth days, and its day is 24.6 hours.
In between Mars and Jupiter there is the asteroid belt. Asteroids are huge chunks of irregularly shaped rocks and are the largest objects in the solar system besides planets and moons.
Outer Planets: The outer planets of our solar system are the planets that are farthest from the sun. The outer planets are gas giants and are MUCH larger than the inner/terrestrial planets.
Jupiter: Jupiter is the largest planet in the solar system. It is named after the king of the Roman gods. It has at least 66 moons, including Ganymede, which is the largest moon in our solar system. Jupiter is made of mostly hydrogen, helium, ammonia, methane, and water vapor. It has an enormous storm on it called ‘The Great Red Spot’. Jupiter’s average temperature is -148oC. Jupiter’s day is about 10 hours and its year is about 12 Earth years.
Saturn: Saturn is the second-largest planet but it has the lowest density. It is made of mostly hydrogen and helium. It has the most complex ring system in the solar system and has at least 60 moons. It is named after the Roman god of agriculture and wealth. One of Saturn’s moons still has active volcanoes. Saturn’s average temperature is -178oC. Its day is 10.7 hours and its year is about 29 Earth years.
Uranus: Uranus is bluish-green in color because of the methane in its atmosphere. It has at least 27 moons. Uranus is special because it rotates parallel to its orbit, meaning that it rotates completely on its side. Its average temperature is -216oC. Its day is 17 hours and its year is 84 Earth years. It was the first planet NOT known to the ancients. It was discovered by William Herschel in 1781. Uranus is named after the Greek god of the sky.
Neptune: Neptune is the farthest planet from the sun and is also bluish-green in color like Uranus. It has at least 13 moons. Its average temperature is -214oC. Its day is 16 hours and its year is 164.8 Earth years. Neptune is named after the Roman god of the sea. Neptune is extra special because it was the first planet to be predicted mathematically before being observed. Urbain Joseph Le Verrier predicted it mathematically and said where it would be in the night sky and Johann Gottfried Galle saw it exactly where it was supposed to be.
Past the outer planets, you have the Kuiper Belt which is like a massive asteroid belt. Then WAY PAST the Kuiper Belt, there is the Oort Cloud which is like a bubble of frozen things around the entire solar system.
Comets: Comets, also called ‘dirty snowballs’ are made of dust, rock particles, frozen gases, and ice that are orbiting the sun. They are sometimes visible to the naked eye.
Meteoroids: Small piece of space dust or rock.
Meteor: A meteoroid burning as it enters the Earth’s atmosphere.
Meteorite: What a meteor is called when it strikes Earth.