Basics of Our Solar System
Our Solar System - What's In It?
If the Milky Way galaxy were shrunk down to the size of North America, our solar system would fit inside a coffee cup. Our solar system is made up of a star that we call the Sun , along with eight or nine planets (more on that later): Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and the most controversial: Pluto. The solar system also includes the satellites of these planets, numerous comets, asteroids, and meteoroids.
Our Solar System - How Many Planets?
It has long been taught that our solar system contains nine planets, but that number was cast into doubt in 2006 when the International Astronomical Union voted to reclassify Pluto as a dwaft planet. The reason for it's demotion has to do with Pluto not being "gravitationally dominant" in its orbital zone. What does that mean? For an object to be gravitationally dominant it must exert a gravitational pull on the objects surrounding it. For example, the earth has a stronger pull on the Moon than the Moon has on the earth. That means the earth is gravitationally dominant. There are two other dwarf planets in our solar system besides newly demoted Pluto: Ceres and Eris.
Our Solar System - How Big is It?
In order to get a good visual of the relative sizes of our solar system, imagine a model that has been reduced by a factor of one billion. That means the Earth is now the size of an olive. The Moon is a pepper corn orbiting about a foot away. The Sun is now the height of a man and about a city block from Earth. Jupiter has just become the size of a large grapefruit and is five blocks away from the Sun. Saturn, the size of an apple, is ten blocks away, Uranus and Neptune, both lemons, are twenty and thirty blocks away. A human on this scale is the size of an atom and the nearest star is more than 24,850 miles (40,000 km) away.
Our Solar System - How Was It Created?
The question of how our solar system - and also our universe - were created is a seriously contentious issue! There is a chance that we might never know entirely, but there some well-researched theories as to how it was created. The most famous and believed by astronomers is the Big Bang theory. The theory goes that about 14 billion years ago, the entire universe was thousands of times smaller than a pinhead. It was incredably hot and dense. At some point the micor-universe exploded, the blast made all this debris in the universe. The planets, moons and asteroids today are the survivors from that explosion and our Sun is the central star and the universe is still expanding to this day.
- Drop us a line if you know something cool about our solar system. It is a great subject for a science project at school.
- Space Term Glossary
- Planet Overview - Earth
- Planet Overview - Mars
- Planet Overview - Neptune
- More About the Solar System