 |
~
Solar System |
|
Solar System Our solar system is made up of the Sun and all the objects that travel around it. The objects that travel around the Sun include the planets, moons, asteroids, meteoroids, comets, and interplanetary dust and gas. Our solar system is shaped like a disk. Some scientists think that our solar system might have a tenth planet, a Planet X. The Sun is one of only billions of stars in the universe. Long ago, people believed the Earth was at the center of the solar system. Today, however, we know the planets, moons, and Earth all revolve around the Sun. Some of the other stars in the universe might have planets similar to those in our solar system. Our solar system is about one light-day across. In contrast, the Milky Way is 100;000 light-years across. Distances within our solar system are measured in Astronomical Units (AU). One AU is the distance from the Earth to the Sun. Pluto, for example, is the farthest planet from the Sun at 39.44 AU. Scientists believe the Milky Way is at least twice as old as our solar system. Our Sun is the only star we know that has such a large system of planets. There is much debate over whether there is life anywhere else in our solar system. Most scientists, however, believe that there is no intelligent life elsewhere in our solar system. Over the years, there have been several different theories formulated to explain the origin of our solar system. However, each of them has been proven flawed. Because our solar system encompasses such a great distance and because it was formed so long ago, it is very hard to find evidence to test these theories. In fact most early theories were only based upon the following facts: most of the objects in our solar system spin in the same direction on their axes; most objects in the solar system orbit the Sun in the same direction that it spins; most moons orbit their planets in the same direction that the planets orbit the sun; from the sun outward, the distance between the planets' orbits increases; the solar system is disc-shaped. Today, our most important information comes from space probes. Current theories concerning the origin of our solar system can be considered either monistic or dualistic. Monistic theories state that the objects in our solar system were formed from a solar nebula, a flat cloud of gas. Some monistic theories state that the objects in our solar system were formed at the same time. Others state that the Sun was formed first and then the rest of the solar system was formed form the gas that was left over. Most astronomers support monistic theories. An example of a monistic theory is the Protoplanet Theory. Gerard P. Kuiper and Thomas Chrowder Chamberlain formulated the Protoplanet Theory. The theory states that a solar nebula was formed when a large cloud of interstellar matter came together. Next, the solar nebula developed a dense center. That dense center was the protosun. Then, gravity caused the matter from the outer part of the cloud to form clusters. These clusters became protoplanets. Next, gravity caused the protosun to contract. This caused the Sun to heat up and blow most of what remained of the cloud into space. Finally, enough matter was left to come together and form the planets. Protomoons became moons as protoplanets became planets. Dualistic theories state that our solar system was formed when an immense object passed the Sun. The object's gravity pulled a long stream of gas out from the Sun and the planets and other objects in our solar system formed from that gas. Scientists believe that the future of solar system depends on the future of the Sun. They think the Sun will remain the way it is for the next four or five billion years. Then, however, it will exhaust its supply of hydrogen. When this happens, the Sun will have nuclear reactions involving helium and heavier atoms. Next, the Sun will become a bigger and brighter red giant, expand beyond Venus' orbit, and possibly engulf our planet. Then, after much time has passed, the Sun will exhaust all of it nuclear fuel and begin to cool down. Finally, our sun will become a white-dwarf star, and as it cools down, it will become a dense, dark black dwarf. Those planets that are not engulfed will freeze and orbit the black dwarf.
|
||
