Exploring Our Solar System Planets and Space
Our Solar System Have you ever looked up into the sky and wonderedwhat was there? Higher than the birds, past the clouds, and farther than the moon, a wholehost of fascinating objects spin in outer space. Let's imagine for a moment that we can leavethe earth behind, and explore the solar system that surrounds it.
We call it the solar system because everythingin it is centered around the sun, and solar means something to do with the sun. The sunis a star, just like many of the stars that you can see in the night sky - just many timescloser to us. Still, the sun is very, very far away from the earth; almost 93 millionmiles away: that's why it looks so small, even though it's the biggest object in thesolar system. In fact, the sun makes up more than 99 percent of the mass in the solar system.If you put all of the planets, moons, asteroids, comets, and everything else in the solar systemtogether, they would make up less than one quarter of a percent of it.
The sun is so big that it's more than 100times wider than the earth, and if it were a giant jar you could fit more than one millionearths into it. More than that, the sun is what holds thesolar system together. Its massive gravity is what keeps the earth and all the otherplanets circling around it instead of drifting off into space. The sun is also what allows us to live onEarth. Without the sun, there would be no heat.
There would be no light. Plants couldnot grow, water would freeze, and nothing could survive. The sun gives us heat and lightbecause it is always burning: it is a giant ball of gas, mostly hydrogen and helium, andit burns at millions of degrees in its center. Let's leave the sun now to explore the planets. As we move away from the sun, the first planetwe will encounter is mercury. Mercury is the smallest planet in the solar system, muchsmaller than earth, and one of only five planets you can see from earth using nothing but youreyes. Of course, it won't look much like a planet.
It looks more like a bright star,and many nights you can see it close to the horizon near sunrise and sunset. Mercury is a lot like our moon. It's smalland has a rocky surface with craters on it. It has no moon of its own, and no air to breathe.You probably wouldn't enjoy a visit to mercury, since temperatures are boiling hot in thesun and freezing cold in the shade. Something interesting about mercury is that it is thefastest planet to go around the sun - it only takes 88 days. Next is Venus, the second planet. Some peoplecall venus earth's sister, because the two planets are very close in size and gravity,but they are very different on the surface. First of all, it is very hot. Venus is thehottest planet in the solar system.
It's not as close to the sun as mercury, but its thickatmosphere of carbon dioxide helps it to trap the heat and stay warmer than its neighbor.It has a thick atmosphere, but it is not one you could breathe. It is mostly made of carbondioxide and there are clouds of sulfuric acid! Venus might not be fun to visit, but it isbeautiful to lok at. It is the second-brightest object in the night sky - the only thing brighteris the moon. If you are looking at a sunrise or a sunset and suddenly notice what lookslike a very bright star, you are probably looking at Venus. After Venus comes Earth, the third planetfrom the sun. Of course, you know all about Earth, because that's the planet where welive! Earth is what's called a 'goldilocks planet,' because it's not too hot, and nottoo cold - it's just right. As far as we know, Earth is the only planet to have living things.
Let's leave earth again for a moment, though,and visit Mars, the fourth planet from the sun. Mars is known as the 'red planet,' becauseiron oxide (a material like rust) in the soil gives it a reddish color. Mars is smallerthan Venus and the earth, but larger than mercury. It is cold and rocky, with a thinatmosphere made of carbon dioxide and oxygen. There is water ice on mars. Scientists are very interested in mars becausethey think that people could live there with the help of some special equipment. Rocketsand probes have already been sent there to gain more information about the planet.
Rightnow, there are two special robots exploring the surface of mars, sending information backto earth. Mars is the first planet we've visited todaybesides Earth to have its own moons. It has two, although they are not big and round likeour moon. Mars's moons are small and irregular. Scientists think they may be captured asteroids.Maybe they came from the big asteroid belt that is between mars and jupiter. An asteroidbelt is a big ring of asteroids, or rocky objects, orbiting the sun. Jupiter comes next, the fifth planet in thesolar system. Jupiter is the largest planet and is something called a 'gas giant.' Itis called this because it is really big and made mostly of gasses.
Jupiter is so big thatyou would have to place 11 earths end to end just to stretch across its middle. Jupiter is also the third brightest objectin the night sky; only venus and the moon are brighter. You can usually find Jupiterhigher in the sky than venus, since Jupiter is away from the sun and not towards it. Jupiter has at least 67 moons that circlearound it, but 55 of them are very small, only about as big as a mountain, or smaller.Some of its moons are very large, and at least two of them are about the same size as theplanet Mercury.
One of its moons is the largest moon in the solar system. Someof these large moons can be seen from earth in your backyard with a telescope. People cannot land on Jupiter because it ismade of gas - there is no ground to land on! Even if there was somewhere to land, Jupiteris covered by terrible storms, much stronger than even the strongest storms on earth. Onestorm that we know about can be seen from earth. We call it the great red spot becausethat's what it looks like - and it has been going on for at least 200 years! After Jupiter comes Saturn, another gas giant.Saturn is famous for its beautiful rings. Although they look solid from a distance,the rings are actually made from many, many small ice particle, as well as rocks and dust. Saturn also has more than sixty moons orbitingaround it, some as large as the planet mercury, and many smaller. Something interesting about Saturn is thateven though it is very large, it is not very dense. That means that if you could find abathtub large enough to put saturn in, it would float instead of sink! Saturn is the farthest planet that can beseen from earth without the help of a telescope. After saturn comes uranus, the seventh planetfrom the sun.
Uranus is another gas giant, but it is much smaller than Saturn and Jupiter.Unlike any other planet in the solar system, it is tilted so much that it actually spinssideways! Uranus has rings around it, although they are much smaller than saturn's, and 27known moons. Uranus is covered in blue clouds made of methane, which give it its lovelycolor. Very similar to uranus is Neptune, the eighthplanet from the sun. Neptune is another gas giant, and like uranus it has methane in itsatmosphere so it also looks blue. Neptune is a darker blue than uranus and scientistsaren't sure why. Neptune has a few thin rings and 14 moons that we know about. Because neptune is so far out in space, ittakes it a very, very long time to go around the sun.
Remember Mercury, that only takes88 days to go once around the sun? Poor neptune takes over 164 YEARS to finish an orbit aroundthe sun. The last time that neptune was in the same place it is now was before the AmericanCivil War, before computers, phones, airplanes, or cars had been invented! Neptune has thelongest orbit of any planet in the solar system. Now, you may think that I've forgotten someone- Pluto. Pluto was discovered in 1930 and was listed as the ninth planet in the solarsystem. As it was studied longer, scientists realized how small it is. It is much smallerthan any other planet in the solar system, and even smaller than many other moons.
Plus,people started to discover other small, rocky planet-like objects in space near pluto. Someof them were even bigger than pluto! In 2006, after 76 years being listed as a planet, Plutowas declared a 'dwarf planet' to show that it was something that was like a planet, butmuch smaller. There are at least 6 dwarf planets in the solar system, and possibly many, manymore. That leaves us with 8 official planets inour solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. I hope you enjoyed exploring the solar systemwith me today. Goodbye till next time!