The Sun- Composition Of Sun

 Key Concepts

• Solar system
• Sun
• Asteroid
• Comet
• Meteoroid
• Meteor
• Meteorite

The Sun and Collection of  Objects 

Introduction: 

People studied the stars before the invention of telescopes. When they observed the sky in the night, they found out that bright lights in the sky changed their position according to other lights. In those days, astronomers called these objects planets. The name planet comes from the Greek word ‘wanderer.’ A planet is a huge body that revolves around a star. A moon is an object that revolves around a planet. Planets and moons are parts of a solar system. A solar system comprises of stars such as the Sun, and all the planets, their moons and other objects revolving around it. 

Sun 

When we see the Sun, it looks like a bright ball of fire. We cannot look directly at the Sun as its brightness can damage our eyes. Thus, astronomers use scientific instruments to study the Sun’s features. Most of the Sun’s energy is produced by nuclear fusion. 

Composition of Sun: 

Approximately 75% of the Sun’s mass consists of hydrogen. Hydrogen and helium together make up 99% of the Sun’s mass. The Sun’s spectrum shows that it comprises trace amounts of other chemical elements. 

The various parts of the Sun are – core, radiative zone, convective zone, photosphere, chromosphere, and corona. 

The Core: 

It is the center part of the Sun. It consists of 25% of the Sun’s total diameter of 1,390,000 km. The temperature of the core is 15,000,000 °C. The core is made up of ionized gas. The most common reaction that occurs inside the Sun is the fusion of hydrogen into helium. 

The Radiation zone: 

It is the surrounding zone of the core. Here the temperature ranges from 2,000,000°C to 7,00,000°C. In this zone, the energy moves outside in the form of electromagnetic radiation or electromagnetic waves. 

The Convection zone: 

This zone is next to the radiation zone, and it forms 30% of the Sun. In this zone, the temperature is about 2,000,000 degrees centigrade. Energy produced in the core region moves through this zone by the process of convection. Convection is the transfer of heat energy by the movement of matter. Around the convection zone is the Sun’s atmosphere. Sun’s atmosphere refers to the uppermost portion of the solar gases. This portion has 3 layers, namely – photosphere, chromosphere, and corona. 

Photosphere: 

It is the innermost layer of the Sun’s atmosphere. The meaning of the photosphere is ‘sphere of light.’ The photosphere is made of gases that come from the convection zone. The temperature of this photosphere is around 6000°C. Much of the energy given out from this sphere is in the form of visible light. The dark spots are cool areas with temperatures of 3800°C and are called sunspots. 

Chromosphere: 

A chromosphere, or color sphere, is a thin layer of gases that glow with light reddish color given off by hydrogen. The temperature of the chromosphere ranges from 6000°C to 50,000°C. 

Corona: 

It is the outermost layer of the Sun’s atmosphere. It is also called a crown. Corona, or crown, is a large area of gas with a temperature above 1,000,000°C. Corona’s magnetic field can stop the escape of many sub-atomic particles into space. 

Solar system: 

• The solar system consists stars, the Sun and everything attached to it by gravity, and the planets such as Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune; dwarf planets like Pluto, moons and many asteroids, comets, and meteoroids.  
• There are many planetary systems orbiting other stars in the milky way. 

Asteroids 

Asteroids are present between the orbits of Mars and Jupiter, called the asteroid belt. They are rocky or metallic objects that move around the Sun. Asteroids are also present beyond Jupiter’s orbit. Asteroids move around the Sun the same as planets do. More than 300,000 asteroids were discovered by astronomers. The largest asteroid, named Ceres, has a diameter of about 1000 km and is also considered a dwarf planet. The closest asteroid to the Sun is about 224 million km from the Sun and is present in the orbit of Mars. Trojan asteroid nearly shares Jupiter’s orbit. 

Composition of Asteroids: 

Based on composition, asteroids are divided into 3 groups. The first group is mainly made up of carbon materials that give a dark color to the asteroid. The second type of asteroid is made up of silicate minerals and looks like Earth rocks. The third type of asteroid is rarest and composed of iron and nickel and has a shiny, metallic appearance, particularly on new or fresh surfaces. 

Near-Earth Asteroids: 

Many asteroids have orbits that sometimes bring them close to Earth, and these asteroids have wide, elliptical orbits that bring them close to Earth’s orbit. Hence, they are termed Near-Earth Asteroids. These asteroids make up a very small percentage of the total number of asteroids in the solar system. 

Other objects in the solar system 

The other objects in the solar system are comet, meteor, meteoroid, and meteorite.  

Comet: 

Comets are small bodies of ball of rock, ice, and cosmic dust that revolve around the Sun. Halley’s comets are very famous, and it passes by Earth every 76 years. It passed by Earth in 1986 and will come back in 2061. 

Structure of comets: 

The comet consists of a core or nucleus, coma, and tail. The core (Nucleus)comprises rock, metals, and ice. Coma is present around the core(nucleus). Coma is a round cloud that consists of gas and dust. Coma can extend very far, maybe 1 million km from the nucleus. The nucleus and coma form the head of the comet. 

The tail is a very interesting part of the comet. Comets come from the outside borders of the solar system. When a comet moves towards the Sun, the heat of sunlight warms the ice of the comet, which causes the sublimation of ice; that is, ice turns from solid to gas and forms a cloud of gas and dust. The radiation from the Sun and sunlight pushes the clouds away, and this results in the formation of a gas tail that points away from the Sun. The second tail of a comet is the dust tail and is made up of dust and curves backwards along the comet’s orbit. 

The Kuiper belt: 

There are small objects beyond the orbit of Neptune. These objects, along with comets from a ring of icy bodies called the Kuiper belt, which is located just outside Neptune’s orbit. The dwarf planets such as Pluto and Eris are situated in the Kuiper belt. 

The Oort cloud 

According to astronomers, most comets come from the Oort cloud. The Oort cloud is a round cloud of dust and ice that lies beyond Neptune’s orbit and that comprises nuclei of billions of comets. The Oort cloud encircles the solar system and reaches halfway to the nearest star. 

Meteoroids 

• These are small, rocky, or metallic objects that move around the Sun in both the regions (inner and outer regions) of the solar system. The craters present on the Moon were created by the collision of meteoroids. According to scientists, the many meteoroids are pieces of matter that got detached from the passing by comets. Large meteoroid may be formed as a result of a collision between the asteroids. 

Meteor  

• When a meteoroid enters the Earth’s atmosphere, friction between the object and the air molecules creates heat. That heat heats the surface of a meteoroid and as a result of this friction and heat, meteoroids burn in the atmosphere. So, when a meteoroid burns up in Earth’s atmosphere, it produces a streak of bright light called a meteor. Meteors are also called shooting stars. When large numbers of small meteoroids enter the Earth’s atmosphere in a very short time, a meteor shower takes place. 

Meteorite 

• When many meteoroids enter Earth’s surface, some of them do not burn up completely because of their huge size. So, these meteoroids fall to Earth’s surface and are called meteorites. Many meteorites are small, but large meteorites sometimes hit the Earth’s surface with great force, and these impacts cause craters that can be seen in many places on Earth. 
• Meteorites are of three types – stony, iron, and stony-iron. The composition of Stony meteorites is the same as the composition of rocks present on Earth. Some stony meteorites consist of carbon compounds. Iron meteorites have a peculiar metallic appearance. Stony iron meteorite consists of iron and stone. But these types of meteorites are very rare. 

Summary

• Planets and moons are parts of a solar system. A solar system comprises a star as the sun, and all the planets, moons and other objects revolving around it.The various parts of the Sun are – core, radiative zone, convective zone, photosphere, chromosphere, and corona.
• Solar system consists of stars, the Sun and everything attached to it by gravity and the planets such as Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune; dwarf planets like Pluto, moons and many asteroids, comets, and meteoroids.
• Kuiper belt is located just outside Neptune’s orbit.
• The Oort cloud is a round cloud of dust and ice that lies beyond Neptune’s orbit and that comprises nuclei of billions of comets.
• Meteoroids are small, rocky, or metallic objects that move around the Sun in both the regions (inner and outer regions) of the solar system.
• Meteorites are of three types- stony, iron and stony-iron.