Astronomy

The Solar System a General Overview



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Allow me to introduce you to our solar system. Located about 2/3 of the way to the center of the Milky Way galaxy, our solar system is made up of a star, planets, dwarf planets, asteroids, comets, moons, and numerous other materials. Our star, the sun, is located at the center of this solar system, and is so massive that by itself it makes up more than 99.8% of all the mass in the solar system.

Spreading out from the sun we have the planets Mercury, Venus, Earth and Mars. These four planets are considered to comprise the inner solar system, and are all solid/rocky planets. Beyond Mars is the asteroid belt. After the asteroid belt we find the middle part of the solar system which contains planets known as gas giants. These planets are Jupiter, Saturn, Uranus and Neptune. As we move further out still we reach the region known as the Kuiper Belt which contains the dwarf planets Pluto, Eris, and Sedna, as well as comets that have an orbit of over 200 years.

Let's look at each of these individually. For your reference, all temperatures indicated below are in Fahrenheit.

1. The Sun: Located at the center of the solar system is our home star the sun. The sun has a diameter of 870,000 miles, and at the surface is a scorching 10,000 degrees. As if this weren't hot enough though, the center of the sun is even hotter at over 22 million degrees! The sun is made up of 70% hydrogen and 28% helium. The remaining 2% is made up of materials such as iron, nickel, oxygen, silicon, sulfur, magnesium, carbon, neon, calcium and chromium. Every object in the solar system rotates around the sun.

2. Mercury: Mercury is a tiny planet with a diameter of only 3,032 miles. This planet has a very eccentric orbit which varies its distance from the sun. At its closest, Mercury is 28.6 million miles from the sun, and at its furthest it is 43.4 million miles away. It takes only 88 days for Mercury to make one lap around the sun, and the length of its day is 58.6 Earth days. You might think that being so close to the sun would cause the temperature to be extremely hot all the time. Due to the very thin atmosphere though, Mercury does not retain its heat, and has the most extreme temperature range of all the planets. On the surface you could expect temperatures to be as low as -300 degrees, and as high as 800 degrees. Though Mercury has no moon of its own, it looks much like our moon with a dusty surface, and full of craters.

3. Venus: The second planet is located 67.5 million miles away from the sun. Having a diameter of 7,522 miles, it is almost the same size as Earth. One major difference though is that Venus rotates backwards. The sun rises in the west and sets in the east. It rotates very slowly too, having a single day equal to 243 Earth days. This makes its day longer than its year which is 226 days. Venus is a planet covered in clouds. These clouds cause what is known as a greenhouse effect on the surface. The heat builds up, but is never able to cool off giving a fairly constant surface temperature of 855 degrees. Like Mercury it has no moons.

4. Earth: Our home planet is located 93.2 million miles away from the sun. It has a diameter of 7,926 miles making it the fifth largest planet in the solar system. One day on earth is 24 hours long, and a year is approximately 365 days. Temperatures on Earth range from -128 degrees to 136 degrees. We have one moon named Luna.

5. Mars: The fourth planet in our solar system has an eccentric orbit causing its distance from the sun to vary from 128 million miles at its closest, to 155 million miles at its most distant. Mars is another smaller planet with a diameter of 4,217 miles. One year on Mars is equal to 686 Earth days, but its day is just a little longer than ours at 24.6 hours. There are two moons revolving around the planet named Phobos, and Deimos. The temperature at the surface is just a little colder than we have on Earth ranging from -200 degrees to 68 degrees.

6. Asteroid Belt: Between the inner and outer planets is a region known as the asteroid belt. Most of the asteroid belt is sparsely populated with rocks and debris ranging from grains of sand to dwarf planets over 400 miles in diameter. While many people picture this region as being full of asteroids, it is actually fairly spaced out. Several unmanned spacecraft have made it through the asteroid belt with no issues. Over 50% of the entire mass found in this region is made up of four asteroids named Ceres, 4 Vesta, 2 Pallas, and 10 Hygiea. Ceres has been officially classified a dwarf planet with a diameter of approximately 800 miles. It is believed that the asteroid belt was once a group of planetesimals, the smaller precursors of the planets, but never formed a gravity to pull everything together as a fully formed planet and thus broke up. Collisions between asteroids over the years has resulted in this belt.

7. Jupiter: The first of the gas giants is our fifth planet, and it is indeed a giant. With a diameter of 88,736 miles, Jupiter revolves around the sun at a distance of 460 million miles to 508 million miles. One year on Jupiter is equal to 12 years here on Earth. For as large as it is though, this massive planet rotates quickly having a day that lasts only 9.8 hours. There are 63 known moons surrounding this planet with more possibly waiting to be discovered. Since there is no solid surface, temperatures are measured at the top of the clouds and average around -101 degrees. Like the sun, Jupiter is made up mostly of hydrogen and helium. There is a ring system around this planet, but it is so faint that it wasn't discovered until 1979 by the Voyager spacecraft.

8. Saturn: This giant yellow planet with its enormous ring system has a diameter of 74,500 miles. It has a year that is equal to 29.5 Earth years because it is located from 840 million miles to 938 million miles away from the sun. There are a total of 59 known moons revolving around Saturn with more still being discovered. Like Jupiter, Saturn spins quickly giving it a day that is 10.7 hours long. The temperature at the cloud tops is a frigid -274 degrees.

9. Uranus: This is the seventh planet in the solar system, and the first to be found in "modern" times. At a distance of 1.8 billion miles from the sun, Uranus is not visible on Earth with the naked eye. It was first recorded in 1690 by John Flamsteed, but was not known to be a planet until Sir William Herschel observed it on 13 March 1781. Uranus has a diameter of 32,000 miles. Its year is 84 Earth years, and its day is 17.24 hours in length. There are 27 known moons around the planet. The temperature at the cloud tops is -328 degrees. Uranus is unique in that its axis is tilted so far that it is rotating sideways. The south pole is facing the sun. Like Jupiter and Saturn, Uranus has a ring system. It is different than the other two planets though, and even has a ring arc, or partial ring surrounding it.

10. Neptune: The last of our gas giants, and the eighth planet is a distant 2.8 billion miles from the sun. Neptune is only slightly smaller then Uranus with a diameter of 30,760 miles. It takes 165 years to revolve around the sun, and its day is only 17.24 hours. There are 13 known moons surrounding Neptune, and it too has a ring system. Unlike all of the other planets thus far, Neptune was discovered using math. Discovered on September 23, 1846, Neptune was found noticing unexpected changes in the orbit of Uranus. This led astronomers to postulate the effects of an unknown planet. Neptune was found within a degree of the predicted position. The temperature at the cloud tops is -346 degrees.

11. Pluto: What once was considered the ninth planet, Pluto is now classified as a dwarf planet because of its 1,485 mile diameter. Located within the inner fringes of the Kuiper Belt, Pluto is another planet with an eccentric orbit bringing it as close as 2.76 billion miles from the sun, and taking it as far out as 4.6 billion miles. For 20 years of its 248 year orbit, Pluto is actually closer to the sun than Neptune. This planet rotates slowly so that its day lasts 6.4 Earth days. There are three moons revolving around Pluto named Charon, Nix, and Hydra. Nix and Hydra have only been discovered within the past few years. Pluto is solid and rocky, like the inner planets, and has a surface temperature of -387 degrees. This planet was discovered in 1930 by Clyde Tombaugh. He was searching specifically for a planet because mathematical theory suggested that there still might be a ninth planet. He found Pluto by comparing pictures of stars taken over several years. One of those "stars" appeared to move over the years and was discovered to be Pluto.

12. Kuiper Belt: Like the asteroid belt, the Kuiper Belt consists mainly of small bodies, but while the asteroid belt is composed primarily of rock and metal, the Kuiper belt objects are made up largely of frozen "ices", such as methane, ammonia and water. The first object in this belt was discovered in 1992, though in 1951 Gerard Kuiper said that some kinds of comets with an orbit of over 200 years might come from the Kuiper Belt. The Kuiper Belt was named after Gerard Kuiper. It starts just outside of Neptune and extends out to over 4.6 billion miles away.

13. Eris: This dwarf planet wasn't discovered until 2005. With an orbit that is even more eccentric than Pluto, Eris ranges from 3.5 billion miles away from the sun all the way out to over 9 billion miles. It is so far away that it is hard to distinguish its rotation, but it is believed to have a day anywhere from eight to ten hours. Eris is 27% larger than Pluto with a diameter of 1,553 miles. It takes 557 years for this dwarf planet to circle the sun. Eris has one moon, Dysnomia.

14. Sedna: Having the most eccentric orbit of all, Sedna ranges in distances from 7.1 billion miles to 90.1 billion miles away from the sun. This gives it a year estimated to be between 10,500 and 12,000 Earth years. With Sedna being so far away it is hard to measure its actual size, but it is estimated to be 730 to 1120 miles in diameter. Being so far from the sun, the surface temperature never reached above -400 degrees. Because of its extreme orbit, scientists are still debating whether or not to consider Sedna a Kuiper Belt object, or an Ort Cloud object.

This is a general overview of our solar system. It is a large and fascinating place that we haven't even scratched the surface of understanding. As technology grows we will gain even more knowledge about this, our solar neighborhood.

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