The Solar System – Formation And Structure
Astronomers in the medieval times believed that the Earth was at the center of the universe, which was by itself small. This belief during the Middle Ages was a religious dogma, and no one questioned it for fear of personal peril. However, in the 16th century, the Copernican theorychose to change the overall picture which established the motionless sun as the center of the Universe with the Earth and the other planets rotating around it periodically at uniform speeds.
This theory is often considered the starting point of modern astronomy.
The Universe has been in existence for so many years (10 to 20 billion years old) that it dwarfs human lifetimes. It is expanding and is a place that is home of unimaginable violent activity. The universe contains Pulsars, Black Holes, Quasars, and other colliding galaxies.
The galaxy that we live in is called the Milky Way. It is one among the 100 billion others in the Universe that is visible. It is a spiral shaped galaxy with extended arms from the center as in a pinwheel. Our galaxy is in the Orion arm of the galaxy. The sun is just one of the 100 billion stars in the galaxy. The Solar System’s age is approximately 4 to 5 billion years.
Solar System – The Structure
The Sun is at the Solar System‘s center. The nearest planets are Mercury Venus, Earth and Mars and they are rocky in nature. The next four are Jupiter and Saturn (made of hydrogen and helium), and Uranus and Neptune (largely made of ices of water, ammonia, and methane). There lies an asteroid belt in between the orbits of the planets Mars and Jupiter containing Ceres, a dwarf planet. The Kupier Beltis disk-shaped, contains the dwarf planet Pluto and is found beyond Neptune.
Astronomers have discovered Oort cloud and the heliopause that is tear-shaped that are still further. Six of the planets and three of the dwarf planets are orbited by their own satellites called moons. Many other small bodies that include comets and interplanetary dust are found to travel freely between the different regions.
Solar System – Formation and Evolution
The Solar System is believed to have been formed due to the gravitational collapsethat occurred in the inside of a large molecular cloud. This cloud, which was several light years wide, consisted primarily of hydrogen, helium and smaller amounts of heavier elements that were formed when other stars were formed.
The pre-solar nebula, or the area that would later become the Solar System, collapsed and it rotated fast to conserve the angular momentum. A large part of the mass collected at the center and it became hotter. The rotating nebula flattened into a disc with a giant gaseous star (protostar) at the center. Planets were formed when massive objects grew by gravitationally attracting matter in the disc. Many more planets may have existed in the early days but must have been destroyed over time or merged with other bodies.
The metallic elements formed only a small fraction of the nebula and were instrumental in forming the first four smaller planets or the terrestrial planets. The gaseous planets were formed further out at a point where the volatile icy compounds remained solid. These plantes captured large atmospheres of hydrogen and helium. Small leftover material became the smaller dwarf planets, asteroid belt, Oort cloud, etc.
The sun is the Solar System’s main component. It is estimated that the sun can hold up to 1.3 million Earths. The temperature and density in the core of the sunis large enough to cause and sustain nuclear fusion that releases huge amounts of energy. This energy is radiated into space as electromagnetic radiation. Compared to many other stars in the galaxy, the sun is large and bright.
The sun is classified as a G2 yellow dwarf and there are not many other stars that are brighter and hotter than the sun. The red dwarf stars are cooler and dimmer stars. The sun is a star that was born in the later stages of the evolution of the Universe and contains more metals than the older stars.
The planets orbit the sun in oval-shaped elliptical orbits and the sun is located slightly off to the side of the center of each planet’s ellipse.
The Trans Neptunian Region
A band of icy material past Neptune’s orbit is called the Kupier Belt.
It extends to about 30 to 55 times the distance of the Earth to the sun. Comets consisting of ice and rock and other icy bodies that are more than a 100 km wide are found here. From the last decade of the 20th century more than a thousand such objects have been found. The dwarf planet Pluto is found in the Kupier Belt.
The Oort Cloud is found well past the Kupier Belt at about 5000 to 10000 times the distance of the Earth to the sun. It is estimated to be made up of two trillion icy bodies. Sedna is a dwarf planet identified to exist in the Oort cloud. The Solar System’s edge is bounded by the heliosphere, a region in the shape of a teardrop that contains electrically charged particles. The outer limit of the heliosphere is called the heliopause and is at an estimated 15 billion kilometers from the sun.