Our solar system

1. Our solar system By Mrs. White

2. A theory of the beginning…. Scientists believe the solar system began forming 10 to 12 billion years ago as swirling gas and dust formed a thick core. The core, with most of the mass, collapsed around 5 or 6 billion years ago and later became the sun. The remaining matter swirled into a disk. Some of it crashed together and formed planets. That's the main theory, at least, and though most scientists think that's how it happens, there are a few other explanations.

3. Alternate theory to beginning of Universe • The big bang theory says that the entire universe came to be in a huge explosion about 15 billion years ago. Nobody ever believed this idea until Edwin Hubble discovered the redshift of galaxy light in the 1920s, which seemed to suggest a bigger universe. However, our ability to test this theory and others have gotten better with modern telescopes covering all wavelengths, some of them in orbit. Although many people believe this theory there is no physical proof that it actually happened.

4. As you know, planets are part of our solar system. Comets, asteroids and the planets' moons are part of the solar system, too. These things all orbit around a star we call the sun. And it's all held together by gravity. The planets are often divided into two groups: the four inner planets (Mercury, Venus, Earth and Mars) and the five outer planets (Jupiter, Saturn, Uranus, Neptune and Pluto). A little about our Solar System

5. MERCURY • The diameter of Mercury is 3,031 miles. • It takes the planet 58.6 days to rotate completely 360 degrees. • It takes 88 Earth days for Mercury to rotate around the sun. • Mercury only weighs 5.5% of what earth weighs. • Mercury’s diameter is 38% of what the earth’s diameter is.

6. Mercury is the closest planet to the sun. Because Mercury is so close to the sun (and the sun's glare) it is difficult to spot from Earth. Mercury's gravity is less than half what we have on Earth, so Mercury can hold onto only a small bit of an atmosphere. Since there's not much atmosphere (which on Earth acts like a warm blanket) temperatures on Mercury go crazy. It can be a scorching 750 degrees Fahrenheit during the day, and minus 320 at night! More about Mercury

7. VENUS • The Diameter of Venus is 7,521 miles. • It takes 243 days to rotate 360 degrees completely. • It Takes 225 Earth days to orbit the sun. • It only has 82 % of the mass earth has • Its diameter is about 95% of earths. • It is a 30 percent closer to the sun that the earth.

8. The second planet from the sun bakes under twice as much solar radiation as Earth. Venus reaches temperatures of 895 degrees Fahrenheit! The thick clouds around Venus rotate much faster than the planet itself -- once every four days. Not counting the moon, Venus is the brightest object in the night sky. The surface of Venus is mostly a rocky desert (there are many computer-generated that show lava flows around a place called Sif Mons). Like Mercury, Earth and Mars, Venus is mostly rock and metal. While all of the planets orbit in an ellipse (something like the shape of an egg), Venus' orbit is the closest to a perfect circle. Because it is often brighter than anything in the sky except the moon, Venus is the cause of many UFO reports. More fun facts about Venus

9. EARTH • The Diameter of earth is 7,926 miles. • It takes 23 hours, 56 minutes for the earth to rotate completely. • It takes 365.24 days for the earth to Orbit around the sun.

10. Earth is the third planet from the sun. Like the other three planets of the inner solar system (Mercury, Venus, and Mars) our planet is made up mostly of rock and metal. One of the most important things about Earth is that there's lots of water, which is one important reason why life got started long ago. We're also lucky that Earth's atmosphere has plenty of nitrogen and oxygen, two other things that life needs. It may not feel like it but the ground under your feet is actually moving very, very fast. The Earth's surface is rotating about its axis at 1,532 feet per second at the equator, and the planet zips around the sun at more than 18 miles per second! So all of us are going incredibly fast -- even when we're standing still. Cool facts about Earth

11. MARS • The diameter of Mars is 4,217 miles. • It takes 24 hours and 37 minutes for it to rotate 360 degrees completely. • It takes 687 days for mars to completely orbit the sun. • It only has 5% of the mass that the earth has. • It has 53% of the earths diameter. • It’s 150% further away from the sun than the moon is.

12. The fourth planet from the sun has always made us humans do a lot wondering and hoping. While scientists haven't proven there's any life on Mars, the dusty red planet is still a fascinating place. The surface of Mars is more interesting than most. Like Mercury, Venus and Earth, Mars is mostly rock and metal, but it also has lots of mountains and craters. The dust that gives Mars the reddish color is made of something called iron oxide. Temperatures on Mars can get as cold as -207 degrees Fahrenheit and as high as 80 degrees Fahrenheit on summer days. Mars was probably warm and wet about 3.7 billion years ago. Mars cooled and the water froze. Some of that water still may exist in ice caps at the poles. THE “LOW DOWN” ON MARS

13. JUPITER • Jupiter weighs over 316 times as much as the earth. • It is also 11.12 times larger than the earth. • The fifth planet from the sun is mostly a huge ball of gas. But at Jupiter's center is a core of rock many times the mass of Earth. The whole planet is so massive it could hold all the other planets put together!

14. SATURN • Diameter: 74,900 miles • Time to rotate completely: 10 hours, 39 minutes • It takes 29.5 years for saturn to orbit the sun. • The sixth planet from the sun has a rocky core and a lot of gas on its surface. But Saturn is known for its rings. The mile-thick rings are made of tons and tons of ice that orbit the planet. Some of the ice bits are smaller than marbles, some are bigger than your computer. • Saturn has 18 known moons, each made mostly of ice and rock.

15. URANUS • The diameter of Uranus is 31,763 miles long. • It takes the planet 17 hours and 54 minutes to turn 360 degrees. • It takes 84 years for uranus to orbit the sun. • It weighs 14.5 times as much as the earth • It is 4.1 times heavier than the earth • The seventh planet from the sun is a lot like its neighbors, with a cloudy surface, rapid winds, and small rocky core. • Uranus rotates at an extreme tilt of 98 degrees, sort of on its side. This causes one pole to point toward the sun for decades, giving the planet strange seasons. Scientists think the planet might be on its side because some other large object crashed into it a long time ago.

16. NEPTUNE • The eighth planet from the sun (well, some of the time it's eighth, but more on that later) has a rocky core surrounded by ice, hydrogen, helium and methane. • Like the other gas planets, Neptune has rapidly swirling winds. Its quick rotation causes fierce winds and some very strong storms. The planet has eight known moons. Like Saturn, Neptune has rings. But Neptune's rings are not as thick, and they are hard to spot. • Neptune was discovered in 1846.

17. PLUTO • The mass of pluto is .2% of the earth. • The diameter is only 18% of what the earths is. • Pluto, which is smaller than our moon, is a cold, dark, frozen place. We don't know very much about the tiny planet. Scientists think it is made of rock and ice. It might have a thin atmosphere of nitrogen, carbon monoxide and methane. • Some astronomers think Pluto may have wandered into the system from a more distant place called the Kuiper Belt. In the Kuiper Belt, Pluto-like objects and comets orbit the sun. So maybe Pluto is not a planet at all, but more like a large asteroid or comet. Some scientists say Pluto may be an old moon of Neptune that escaped.

18. REFERENCE PAGE Space kids Big bang theory