Have you ever stared up into the sky at night and wondered about all you see up there? Us too! One of the things we always were curious about as kids was the planets. What made them planets? How were they different from stars? Is there life on other planets? Can we see any with a telescope? We’ll try to answer all these questions, plus give you a little more info on those great wanderers known as planets, below.
First things first. What makes something a planet? Scientists from all over the world got together in August of 2006 to answer this question. They decided that it has to be something that revolves around the sun, is big and heavy enough for its own gravity to make it fairly round, and has to be big enough to “clear its neighborhood” of smaller objects in its orbit.
There are eight celestial bodies who fit the description, listed in order by their distance to the sun (starting with the closest): Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Here are some interesting facts about them:
- Mercury is composed of mostly heavy metals, which makes it the second densest planet (Earth is first).
- Venus is the hottest planet, with temperature shovering at 863°F. It has a very dense atmosphere, which traps heat really well.
- Venus and Uranus rotate clockwise on their axis. The other planets go counter-clockwise.
- Water has only been found on Earth so far, which is amazing considering we have so much of it—70% of the surface of our planet is water. This also means that Earth is the only planet able to support life.
- Mars is home to the tallest mountain in the solar system: Olympus Mons. It’s 88,600 feet high, and scientists think it could still be an active volcano!
- Jupiter is the largest planet in terms of size and mass.
- Although Saturn is the second largest planet, it is the least dense because it consists mostly of hydrogen.
- Saturn’s rings are small pieces of dust and debris mixed in with billions of tiny particles of ice. The fact that ice is reflective is what makes it visible to telescopes here on Earth.
- Scientists think something collided with Uranus, causing it to rotate the other way. It also has rings, which scientists think is made up of pieces of a moon that was destroyed when something hit it.
- Neptune travels 164.8 Earth years to make its trip around the sun. It has only completed the trip once since it was discovered back in 1846.
- Neptune also has a moon called Triton, which scientists think may have been a dwarf planet that was dragged into Neptune’s orbit, mostly because it orbits in the opposite direction of Neptune. Triton is the coldest known object in our entire solar system, with a -391°F recorded temperature.
So what makes a planet different than a star? We’ll give you two reasons.The biggest is that stars create their own light, while planets reflect it. Stars create this light through nuclear fusion, something planets cannot do. Stars also rotate around the center of their galaxy, unlike our planets (which rotate around the sun, which is a star).
There are a few planets you can see with the naked eye. The big giveaway is this: the light from stars comes to us from so far away that it bends, creating a twinkle effect. Planets are much closer, so they don’t usually twinkle. If you know where to look, you should be able to see Mercury, Venus, Mars, Jupiter and Saturn. If you have really sharp eyes, you might be able to spot Uranus, too!