Astronomy Packet: 6
With all this talk about comets, we need to discuss what a comet is. Comets are very fast moving objects made up of a lot of ice and a little bit of rock. They move much faster than asteroids, making it much more dangerous for a comet to hit the Earth than an Asteroid.
Short term comets, such as Halley's Comet which comes near the Earth every 76 years, originate from the Kuiper Belt. Long term comets, which take thousands of years to circle the Sun, come from the Oort Cloud.
The End of the Solar System:
Where does the Solar System end? Once we get out past the Oort Cloud there are few rocks, or comets, but this is not the end of the Solar System. The Solar System officially ends when the Sun's Solar Winds begin to blend in with the stellar wind of other stars.
The Sun produces a wind which blows outward in all directions. This wind is what blew away the cloud of dust and gas the Sun originally formed in. This solar wind can be felt for trillions of miles. Once the wind gets too weak and begins to mix with the winds of other stars, this is where we say the Solar System ends.
A Few Moons:
There are many worlds in our Solar System. This is because we don't just count the planets as worlds, we also count all the moons as worlds. Some of the moons are even bigger than Mercury and Pluto.
First of all, what makes a moon a moon? In order for a world to be called a moon it has to orbit a planet. The planets orbit the Sun, while the moons orbit the planets. This is the only difference between the planets and the moons.
The moons in our Solar System are not all the same. There are many that are like Earth's moon, but there are many that are very unique. It is mostly the moons of Jupiter that are the most interesting. Jupiter's moon Io is covered with violent volcanoes that erupt quite often. Another of Jupiter's moons is larger than both Mercury and Pluto. It is also believed that this moon, along with another of Jupiter's moons, may have a liquid water ocean under its icy surface.
Saturn's moons are also quite interesting. For example, Titan is the second largest moon in the Solar System and is larger than Mercury, Pluto and Earth's moon. Scientists are unable to study Titan up close because Titan's atmosphere is so thick that satellites cannot see the surface of the planet. Many of Saturn's other moons have very unique surfaces because they have been hit by comets or asteroids in the past.
Assignment # 2:
Click Here to find the answers to the following questions:
1. How many worlds are there in the Solar System?
2. Is a moon always smaller than a planet?
3. What is the only difference between what we call a moon, and what we call a planet?
4. Which moon has a very thick atmosphere?
5. Which moon or moons might have a liquid water ocean?