Planets and Other Space Rocks First Some Fun Facts about Orbit and Rotation • The Sun, planets, and large moons all orbit and rotate in the same way. • All planets orbit the Sun in the same direction (counterclockwise). • The orbit in elliptical orbits that are almost circular, and in the same plane. • The Sun and most of the planets rotate on their own axis in the same direction, counterclockwise. • Most of the major moons orbit their planet in the same direction the planet rotates. Types of Planets • There are 2 Types of Planets: • Inner or Terrestrial • Outer or Jovian Inner Planets • Inner or Terrestrial Planets- small, rocky planets close to the Sun, and are relatively close together. • These planets are: • Mercury • Venus • Earth • Mars Outer Planets • Outer or Jovian (Gas) Planets- Large, gas-rich planets far from the Sun. they are relatively far apart. • These Planets are: • Jupiter • Saturn • Uranus • Neptune Mercury • The smallest of the planets, and the closest to the Sun. • Made of rock and metal, mostly iron. • It has no moons and no atmosphere. • A year is 87.9 Earth days. • Daytime lasts 3 months and hits temperatures of 425℃. • Nighttime lasts 3 months and is as cold as −150℃. Venus • The only planet in our solar system that is similar to Earth in size. • Covered in thick clouds that make the surface invisible to our eyes. • It is made mostly of rock and metal. • It has no moons. • The atmosphere is thick and heavy, if a human tried to walk on the surface, they would be crushed. • A year is 224.7 Earth days. • It rotates slowly, in the opposite direction of Earth. Each day is 243 Earth days long. • The surface temperatures are 470℃, making it the hottest planet in the solar system.

Earth • Made mostly of rock and metal. • Earth has 1 noticeable moon, which is large in size. • The size of the moon relative to the size of Earth is very unusual for our solar system. • 75% of the surface is covered by water. • It is the only planet that can sustain life on the surface.

Mars • The inner planet that is furthest from the Sun. • It has 2 moons: Phobos and Deimos. • There is evidence of dried lakes and rivers on the planet. • Made mostly of rock and metal. • Its has frozen carbon dioxide on the surface, mostly at the poles. • Just like Earth, the orbit and tilt of the planet allows it to have seasons. • The atmosphere is very thin, it is similar to being at the top of Mount Everest. • There is not enough oxygen for humans to breathe. • A year is 680 Earth days, but a day is only 37 minutes longer than Earth’s. • The daytime temperature is 20℃ (68℉), and nighttime temperature is −140℃ (−220℉) Jupiter • The largest planet in the solar system. • 2-3 Earths could fit inside the Great Red Spot, a giant long-lived storm. The storm has been going on for at least 300 years. It is the largest story in the solar system. • Has thin, faint rings. • Made of hydrogen and helium. • It has no solid surface, it is made entirely of gas. • The increasing gas pressure deeper inside Jupiter would crush you way before you go the core. • Has at least 63 moons, 4 of them are as large as planets. • It is the planet with the most moons. • It year is more than 12 Earth years, but a day is less than 10 hours. • The temperature at the top of the clouds is −148℃. Saturn • Made of hydrogen and helium, and has no solid surface. • It has at least 60 moons, including one with a thick atmosphere covered completely by clouds (Titan). • Mimas, one if its moons looks like the Death Star. • It has the biggest, brightest rings in the solar system that can be seen with a small telescope. • A year is 29.5 Earth years, and a day is 10.2 hours. • The temperature at the top is −178℃. • It has a tilt, so it has seasons like Earth, but they are mild. Uranus • It has faint rings. • Made of hydrogen, helium, water, ammonia, and methane. • Has 5 moons • The planet, rings, and moon orbits are all tipped on their side. • Scientists think this was due to a collision while the planet was being formed. • Its year is 84 Earth years, and day is 17.2 hours. • Because of the tilt, the poles get daylight for ½ of Uranus’ years, and night for the rest of the year. • The temperature at the top is −213℃ Neptune • The furthest planet from the Sun. • Made of hydrogen, helium, ammonia, and methane. • It has faint rings. • It has at least 13 moons. • Triton is the only moon in the solar system that orbits a planet backwards (opposite the direction of Neptune). • Because of this, scientists think it may have been a captured planet. • Its year is just under 165 Earth years, and its day is just over 19 hours. • The temperature at the top is −213℃. • It has a tilt, so it has seasons like Earth, but they are mild. What About Pluto? • As of 2006, Pluto is no longer considered a planet, but it is now a “Dwarf Planet”. • Dwarf Planet- an object orbiting the Sun that is large enough for its own gravity to cause it to be round, but has not cleared out the area in its orbit. • One dwarf planet has been discovered in the asteroid belt, Ceres. • Asteroid Belt is located between Mars and Jupiter. • 4 dwarf planets (including Pluto) have been fount in the Kuiper belt. • The Kuiper Belt is a ring of comets that is located beyond Neptune. What is Planet Nine? • This planet has not actually been discovered yet, but there is evidence that supports its existence. • Scientists noticed that some comets in the Kuiper Belt and the Oort Cloud had odd orbits. • The only explanation for these odd orbits is that they must be orbiting around a planet. • Scientists estimate that the planet is 10 times larger than Earth and 20 times farther from the Sun than Neptune. • It takes 15,000 to 20,000 years for the planet to make one revolution.

http://www.space.com/31670-planet-nine-solar-system-discovery.html What is an Asteroid? • Asteroid- a small rock orbiting the sun. • They are located mostly in the asteroid belt. What are Meteors, Meteoroids, and Meteorites? • Meteoroid- a small asteroid, typically boulder sized or smaller. • Meteor- when a meteoroid hits the Earth’s atmosphere. • Shooting stars are actually meteors that are burning up as they are traveling through the Earth’s atmosphere. • Very bright ones are called fireballs. • Meteorite- a piece of meteor that lands on Earth. A small meteorite left a crater 600 feet deep and 1,200 meters wide. It is located in • Most are small. Winslow Arizona, and is called Meteor Crater. What is a Comet? • Comet- small bodies orbiting the sun. • Mostly made of ice water, ammonia, and methane mixed with rock. • Most are located in the Kuiper Belt beyond Neptune, or farther out in the Oort Cloud (the edge of our Solar System). • Example- Haley’s Comet • Comets don’t get tail until they enter the inner solar system. • This rarely happens.