Table of Content
OUR SOLAR SYSTEM is the family of sun including planets, dwarf planets, satellites, asteroids, comets and many other heavenly bodies in its periphery. Its outer boundary lies up to kupier belt. It is located in one of the arms of milky way galaxy, revolving around the galactic center.
Formation of Solar System
Solar system was formed from giant rotating cloud of gas and dust, called as solar nebula. Most of the materials in the nebula collapsed to form sun while other remaining particles formed smaller heavenly bodies which we call as planets, satellites, asteroids, etc.
The age of solar system is estimated to be 4.5 billion years and its mass is 1.0014 times the solar mass. We have got a star (sun) at the center of our solar system around which every components of solar system revolve.
Components of solar system
The sun is the most massive object located in the center of solar system. It constituents more than 99.85% of total mass of solar system. Sun is ultimate source of energy for us and is an active medium sized star.
Sun is made up of hydrogen gas which is continuously being changed into helium atom under extremely high pressure and temperature. The process of nuclear fusion in sun releases vast amount of energy. Thus the center of sun is very hot at about 35,000,000 k and surface temperature of about 6000 k. Sun emits electromagnetic radiations of all wavelengths in the form of radio waves, infra-red, UV-rays, visible light and other radiations.
Life cycle of sun is similar to other stars. It started its journey from nebula and changed gradually into active star. Visit: https://pabitras.com.np/life-cycle-of-a-star/
Solar wind is the stream of charged gaseous ions called plasma. It is emitted continuously by the sun with the speed of about 500 km/s. Sometimes, hot gases also shoot out from sun called prominences.
Planets are the heavenly bodies that revolve around the sun in their fixed path. Greek meaning of planet means ‘wanderer’. There are eight planets in our solar system (sorry pluto 😢). The path in which planets revolve around the sun is called orbit. Orbits are elleptical in shape and the orbits of different planets don’t lie in same plane. They also have their rotation in their own axis.
The definition of planet set in 2006 by the International Astronomical Union (IAU) states that in solar system. a planet is a celestial body that :
- is in orbit round the Sun,
- has sufficient mass to assume hydrostatic equilibirium, and
- has “cleared the neighbourhood” around its orbit.
Planets are classified into two categories: Inner planets and outer planets. Mercury, Venus, Earth and Mars are considered as an inner planet. Jupiter, Saturn, Uranus and Neptune are considered as outer ones. There lies an astronomical belt between Mars and Jupiter which separates outer planets form inner planets.
The four inner or terrestial planets have dense, rocky composition, few or no moons and no ring systems. They are smaller than outer planets and have less duration for a revolution around the sun. These planets have volcanoes, mountains, plains, valleys, etc in their surface. Let’s look over a brief information about them below:
Mercury is the closest planet to solar system and also the smallest one among the eight planets. It is located about 0.4 AU from the sun and weighs only 0.055 earth masses. Because of its small size, it has low gravity in its surface (3.7 m/s²) and no atmosphere. It has got a large number of craters in its surface due to meteor shower and its surface is like that of moon. Mercury has a surface temperature of about 700 k during day and 93 k at night. It is the fastest revolving planet and completes its one revolution in 88 days.
Venus is about 0.7 AU from sun and weighs of about 0.875 earth masses. It is also known as Earth’s twin. It is the hottest planet in solar system due to the presence of large amount of green house gases like carbondioxide. Its temperature rises to about 735 k. It has a regular volcanic eruptions and appears brighter than other planets. Its period of revolution (224.7 days) is nearly equal to that of earth. It also does not have any satellites.
Earth is the largest and densest planet among inner planets, the only one known to have current geological activity, and is the only place in universe where life is known to exist till date. It has one moon, favorable atmosphere and suitable temperature. Its period of revolution around sun is 365 days 4 hours.
Mars is at a distance of 1.5 AU from sun and has 0.107 earth masses. It has its own atmosphere which mainly consists of carbondioxide. There a lot of volcanoes in its surface like Olympus Mons. Mars has two small natural satellites, Phobos and Deimos. There is no sign of life on mars since it has relatively low temperature (223 K). It completes its one revolution sun in 687 days.
Mars is also called a red planet since its surface is covered with red iron oxide.
These planets lie behind asteroid belt and are also called as giant planets or Jovian planets. Saturn and Jupiter are the big giants of gas like hydrogen and helium while Uranus and Neptune are giants of icy object. They have a ring system around them among which Saturn’s ring is the largest one. A brief description on outer planets:
The largest planet in our solar system, Jupiter, is 5.2 AU from sun and is 318 times the solar masses. It is made up of hydrogen and helium gasses and does not have any solid surface. There are a number of cloud band in its surface and the Great Red Spot is the most popular one. Astronomers have predicted that the red spot is formed due to disorder like atmospheric hurricane. It completes one revolution in 12 years.
It has 79 known satellites. Among them Ganymede is the largest one. It is even larger than Mercury and Pluto! Some other satellites are Callisto, Europa, Lo, Ananke, etc.
Saturn, the planet of ring is 9.5 AU from the sun and is 95 times Earth mass. Its atmospheric condition and combination is similar to that of Jupiter. It is the second largest planet in solar system. Its rings are made up of small ice and rock particles. It completes one rotation in its axis in 10 hours 30 minutes and a revolution around sun in 29.5 Years.
It has 62 confirmed moons. Titan is the largest among them. Some other moons are Enceladus, Mimas, Dione, etc. Titan is large enough to support even its own atmosphere.
Uranus is 19.6 AU from sun and is about 14 solar masses. Its axis is tilted over 90 degrees to the ecliptic. It rotates from east to west, which means that the sun will rise from west and set to east. Its temperature is very low of about 50 k. It has 27 named moons. Some of them are Titania, Ariel, Miranda, etc.
It is the farthest planet from sun. It is 30 AU from sun and is 17 earth masses. It is composed hydrogen, helium, neon, sillicate, water, etc. A great spot have been detected in its surface. It has 13 known satellites. Triton is the largest one. Other satellites are Proteus, Despina, etc.
Asteroids are small Solar System bodies composed mainly of refractory and metallic materials. They are mainly found at the asteroid belt which lies between Mars and Jupiter. There are millions of the asteroids whose size ranges from microscopic to few kilometers in diameter.
Largest asteroid is Ceres, which is large enough to maintain its nearly spherical shape. It has a diameter of 946 Km. It lies in the asteroid belt. Recently, it has been listed in the name of dwarf plant.
Meteoroid is the small rocky or metallic particle in the Solar System. Most of the Meteoroid are the small asteroid, that escapes from its belt. They may also be the fragments of comets.
Those meteoroid that enters the surface of Earth’s (or any other body’s) atmosphere are called Meteor. It looks like the falling star from the surface of Earth and is called the shooting star. The color of these shooting star depends upon their chemical composition. Nitrogen or oxygen contained meteor gives red color. Similarly, iron containing Meteor gives Yellow color. Millions of meteoroid enter Earth’s atmosphere everyday and burn down typically in mesosphere due to friction with air.
There is very less chance of survival of a meteorite up to the surface of Earth. Those meteoroid that reaches the ground and survives impact is called meteorite. Large meteorites have a huge impact in the surface. Since Moon has no atmosphere, a number of meteorites hit moon everyday and large number of craters are formed in its surface.
Comet is the small icy object of solar system with rocks and frozen fluids. It revolves around the sun in highly elliptical orbit. They have a wide range of orbital period ranging from few years to thousands of years.
When comet comes near the sun during its revolution, fluid on its surface evaporates into gases. The gases rush out by rapid vaporization in the form of jets, carrying solid particles with them. This forms the tail of the comet and is headed away from the sun. When comets move away from the sun, all of its gaseous matters disappears and it becomes solid block of icy mass.
Many comets have been observed since ancient times. Some of them are Halley’s Comet, Temple-tutle, Enke, Schwasman-washman, Bennet, Shoemaker Levy, etc.
Satellite is a small heavenly body revolving around the planet. The number of satellite of each planet ranges from 0 to 79. Numbers of satellite of each planets are:
Mercury – 0
Venus – 0
Earth – 1
Mars – 2
Jupiter – 79
Saturn – 62
Uranus – 27
Neptune – 13