Our Solar System
Our solar system is primarily based on the Sun and the eight planets or objects that revolve around the Sun. The word Solar is derived from the Latin word Sol which means Sun hence, it is termed as Solar System. The Sun is actually a huge star and all the planets revolve around it because of the exertion of gravitational force. The solar system is also comprised of different satellites of the planets, meteors, comets, etc.
The Sun is approximately 109 times bigger than Earth and is a huge ball of gases which makes it a star as it radiates energy at exorbitant rates. It is roughly of spherical shape with consisting of hot plasma and magnetic fields. Three quarters of the Sun consists of Hydrogen gas while the rest of it is Helium. The sun was formed around 4.6 billion years ago with the Bing Bang chiefly responsible for the whole process. Our entire solar system also formed around the same time.
Apart from our planet Earth, there are seven more planets which are present in the solar system and are named Mercury, Venus, Mars, Uranus, Jupiter, Saturn and Neptune. The Jupiter is the largest among all of them and Mercury is considered as the smallest one. Mercury is also the hottest planet because it is situated nearest to the Sun in distance while Neptune is the coldest because it is far away from the Sun.
There was another member in the list of planets orbiting the Sun named Pluto. Now a dwarf planet, Pluto was also considered a planet alongside the above mentioned 8 until 2006 when the International Astronomical Union defined it as a dwarf planet after the discovery of Eris. The Earth is the only planet in our solar system where any form of life is possible. This is due to the favorable temperature that human body can adapt to, while abundance of Oxygen that is necessary for humans to breathe. The Earth is also called the Blue planet because the color of Water which is reflected back when it is viewed from the outer space. Unlike the Sun, and previously though so, the shape of the Earth is not a perfect sphere as it bulges at the Equator and is flat at the poles. The Earth revolves around the sun in approximately 365.25 days and on its own axis too in around 24 hours.
The Solar System is the Sun and all the objects that orbit around it. The Sun is orbited by planets, asteroids, comets and other things. It is billions of years old.
The Sun is a star. It contains 99.9 percent of the Solar System's mass. This means that it has strong gravity. The other objects are pulled into orbit around the Sun. The sun is mostly made out of hydrogen and helium.
There are eight planets in the Solar System. From closest to farthest from the Sun, they are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The first four planets are called terrestrial planets. They are mostly made of rock and metal, and they are mostly solid. The last four planets are called gas giants. This is because they are much larger than other planets and are mostly made of gas.
The Solar System also contains other things. There are asteroids, mostly between Mars and Jupiter. Further out than Neptune, there is the Kuiper belt and the scattered disc. These areas have dwarf planets, including Pluto. There are thousands of very small objects in these areas. There are also comets, centaurs, and there is interplanetary dust.
Six of the planets and three of the dwarf planets are orbited by moons. Furthermore, planetary dust orbits the gas giants. Many other systems like the Solar System have been found. Each of the billions of stars in the Milky Waygalaxy might have a planetary system.
Evolution of the Solar System[change | change source]
Main article: Formation and evolution of the Solar System
The formation and evolution of the Solar System began 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud.
Most of the collapsing mass collected in the centre, forming the Sun, while the rest flattened into a protoplanetary disk of loose dust, out of which the planets, moons, asteroids, and other Solar System bodies formed.
This widely accepted model, known as the nebularhypothesis, was first developed in the 18th (1700's) century by Emanuel Swedenborg, Immanuel Kant, and Pierre-Simon Laplace. Its subsequent development has interwoven a variety of scientific disciplines including astronomy, physics, geology, and planetary science. As our knowledge of space has grown, the models have been changed to account for the new observations.
The Solar System has evolved considerably since its initial formation. Many moons have formed from circling discs of gas and dust around their parent planets, while other moons are believed to have formed independently and later been captured by their planets. Still others, as the Earth's Moon, may be the result of giant collisions.
Many collisions between bodies have occurred, and have been important to the evolution of the Solar System. The positions of the planets often shifted, and planets have switched places. This planetary migration is thought to have been responsible for much of the Solar System's early evolution.
Earth's orbit[change | change source]
The Earth's orbit around the Sun is nearly a perfect circle, but when mapped it is found that the Earth moves around the Sun in a very slightly oval shaped, called an elliptical orbit. The other planets in the Solar System also circle the Sun in slightly elliptical orbits. Mercury has a more elliptical orbit than the others, and some of the smaller objects orbit the Sun in very eccentric orbits.
Discovery and exploration[change | change source]
Main article: History of astronomy
For thousands of years, people had no need for a name for the "Solar System". They thought the Earth stayed still at the center of everything (geocentrism). Although the Greek philosopher Aristarchus of Samos suggested that there was a special order in the sky,Nicolaus Copernicus was the first to develop a mathematical system that described what we now call the "solar system". This was called a new "system of the world". In the 17th century, Galileo Galilei, Johannes Kepler and Isaac Newton began helping people understand physics more clearly. People began to accept the idea that the Earth is a planet and moves around the Sun, and that the planets are worlds with the same physical laws that control Earth. More recently, telescopes and space probes have led to discoveries of mountains and craters, and seasonalmeteorological phenomena such as clouds, dust storms and ice caps on the other planets.
The eight planets[change | change source]
In their order from the Sun:
The planets are the biggest objects that go around Sun. It took people many years of using telescopes to find the objects that were farthest away. New planets might still be found, and more small objects are found every year. Most of the planets have moons that orbit around them just as the planets orbit the Sun. There are at least 173 of these moons in the solar system.
Dwarf planets[change | change source]
Main article: Dwarf planet
Pluto had been called a planet since it was discovered in 1930, but in 2006 astronomers meeting at the International Astronomical Union decided on the definition of a planet, and Pluto did not fit. Instead they defined a new category of dwarf planet, into which Pluto did fit, along with some others. These small planets are sometimes called plutinos.
Structure[change | change source]
There are a few main parts of the Solar System. Here they are in order from the Sun, with the planets numbered, and the dwarf planets marked with the letters a - e.
Inner solar system[change | change source]
The first four planets closest to the Sun are called the inner planets. They are small and dense terrestrial planets, with solid surfaces. They are made up of mostly rock and metal with a distinct internal structure and a similar size. Three also have an atmosphere. The study of the four planets gives information about geology outside the Earth. Most asteroids are also often counted with the inner planets
Outer solar system[change | change source]
Trans-Neptune region[change | change source]
Oort Cloud[change | change source]
The Oort cloud is separate from the trans-Neptune region, and much farther out. It contains the long-period comets.
Ecliptic plane[change | change source]
The plane of the ecliptic is defined by the Earth's orbit around the Sun. All of the planets orbit the Sun roughly around this same orbital plane. The farther away from this plane a planet orbits, the more inclined is its orbit to the ecliptic. If you could look at the solar system "edge on" then all the planets would be orbiting more or less in the plane of the ecliptic.
References[change | change source]
More reading[change | change source]
- Lang, Kenneth R. (2011). The Cambridge guide to the Solar System (2nd ed.). Cambridge University Press. ISBN 9780521198578