Source: D4K: “Planets"
Visit the D4K companion Web site to learn more about Planets: D4K: “Planets"
This video segment from IdahoPTV's D4K describes the sun, the center of the solar system, and the planets and asteroid belt of the solar system. It explains why earth is in a favorable spot for life, and the importance of gravity in keeping planets in their orbits. Learn how the planets are alike and different.
JOAN CARTAN-HANSEN: We live on the earth. It's one of the planets in our solar system. Solar means connected to the sun and the sun is the center of our neighborhood.
The sun isn't a planet. It's actually a star and stars are basically big balls of burning gas. The center of the sun or its core is like an enormous furnace, like a bomb that never stops exploding. The heat spreads out from the sun and warms the rest of the solar system and on the surface of the sun, gasses leap up in bright bursts called solar flares.
There are nine planets in our solar system that each revolve around the sun in what's called orbit. Orbit is the path the planet takes around the sun and everything is held in place by a force called gravity. Gravity is also what makes something fall when it's dropped here on earth.
Now let's look at our neighbors. The planet nearest to the sun is Mercury. Now nearest doesn't mean close. Mercury is about 36 million miles from the sun. The next planet is Venus. It's about 67 million miles from the sun. Venus is about the same size as the Earth but its atmosphere or the blanket of gasses that surround the planet is made up of poisonous gasses. It's not at all a friendly place. It's covered with thick clouds which reflect a lot of light. That's why Venus is the easiest planet to see in the night sky.
The Earth is the 3rd planet from the sun. At about 93 million miles away it's just the right distance from the sun to be warm enough and cool enough for life and it has enough gravity to hold on to its atmosphere. The Earth has one moon. Moons are objects that orbit a planet the way a planet orbits the sun.
The next planet in the solar system is Mars. Mars is about half the size of the Earth and is about 141 million miles away from the sun. It has a thin atmosphere. It is known as the red planet. Mars has two small moons. A probe found a giant frozen sea of water there and scientists believe there may be some kind of microbes living in the soil.
These four planets - Mercury, Venus, Earth and Mars are known as the inner planets.
Next comes a big gap called the asteroid belt. Here, asteroids are chunks of rock. Some as small as pebbles, some as big as mountains orbit the sun. And after this gap come the five outer planets.
Jupiter is about 483 million miles from the sun. It's huge. The largest planet in the solar system. 1,300 Earths could fit inside this one planet.
Next comes Saturn. It's 887 million miles from the sun and is known for its rings. The 7th planet is Uranus, about 1.8 billion miles from the sun. It's tipped over on its side. Neptune is the 8th planet in the solar system and Pluto is the 9th - sort of. Pluto is now classified as a dwarf planet. Both Neptune and Pluto are smaller than the Earth and very, very cold - about 11 times colder than your home's freezer.
So what is beyond our solar system? More stars and more planets. Our solar system is part of a bigger galaxy or group of stars so when you look into the sky at night just think what is out there to be discovered.
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