At the center of our solar system, there is a star (sun), called sun which is almost perfect sphere of hot plasma having convective motion so generating a magnetic field. Even it is far away from us, but it is an important source of energy for earth. Its diameter is 864,000 miles and has mass of 330,000 times than that of earth. It covers 99.86% part of our solar system. Structure of sun is made by such a way that 73% portion of sun consists of hydrogen and remaining 25% is occupied by helium and remaining percentage is taken by the minor amounts of heavier elements like oxygen, carbon, neon and iron.
It was formed around 4.6 billion years ago due to gravitational collapse of matter in large molecular cloud. Maximum part of this matter was gathered at center while other portion formed orbiting disk in solar system. Central mass became too hot and dense that nuclear fusion process started in its core. It is considered that all stars are formed by this process.
According to an estimate, in each second, star (sun) fuses 600 million tons of hydrogen to helium i.e. converting 4 million tons of matter into energy every second. The source of sunlight and heat is the energy in its core which takes 10,000 to 170,000 years to get escaped. Star (sun) is converted into red giant when hydrogen fusion process ends in core, as a result sun doesn’t remain in hydrostatic equilibrium, which results in an increase in temperature and density along with expansion in outer layers.
At an average place on the star (sun) the magnetic field is about 1 Gauss, about twice as strong as the average field on the Earth’s surface (around 0.5 Gauss). Because the atmosphere of the star (sun) is more than 12,000 times greater than that of Earth, the magnetic field of the Sun’s total impact is enormous.
Color of sun
The color of sun seems to be white when viewed from space or when sun is high in sky. If all emitted photons are taken under consideration then more photons lie in green portion of spectrum. When sun is at lower height in sky, then due to atmospheric scattering, sun looks like yellow, red, orange or magenta. Surface temperature of sun is 5,505 degree Celsius.
Structure of Sun
Layers of sun
- Core of sun: Innermost portion of sun with enough temperature and pressure that nuclear fusion can occur over there. In this portion, hydrogen is fused into helium, thus releasing energy. As a result, formed helium slowly accumulates to form core (made of helium).
- Radiative zone: coming out of core, the temperature drops from 7 to 2 million kelvins. This temperature gradient is less than lapse rate so convection can’t occur in this region. So energy is transferred in form of radiation instead of convection.
- Tachocline: a boundary b/w radiative and convective zone.
- Convective zone: in this layer, plasma is not enough dense or hot to transfer heat by radiation instead plasma density is low to allow convective currents to produce ant to transfer sun’s energy on surface.
- Photosphere: the portion of sun which can be observed by visible light i.e. sun becomes opaque to visible light below this layer. Since the outer boundary of sun is not clear so it’s visible parts are divided into photosphere and atmosphere.
- Chromosphere: The Sun’s second-most outer layer is the chromosphere. This is several thousand kilometers deep and sits over the photosphere and beneath the corona. It is relatively transparent due to its low density, resulting in the photosphere being treated as the Sun’s visual surface.
- Corona: The corona of the Sun is the upper most component of the atmosphere of the Earth. Normally the corona is concealed by the blinding illumination of the surface of the Sun. During a complete solar eclipse, though, the corona becomes visible. A blanket of gases, called an atmosphere, covers our Sun.
Atmosphere of sun: The sun’s atmosphere consists of many layers, especially the photosphere, the chromosphere and the corona. It is in such outer layers where the energy of the sun, which bubbled up from the inner layers of the star (sun), is observed as sunlight. Photosphere is the lowest layer of the sun’s atmosphere.
Is sun a star or planet?
The Sun is a star not a planet as there can be no life on sun due to its high temperature. There are lots of stars in our galaxy, but the Sun is the closest one to our planet Earth. It is the center of our solar system and has maximum gravity. It is a hot ball of glowing gases. It keeps our planet warm enough for living things to thrive. It gives us light so we can see.
Photons and neutrinos
Structure of Sun: The high energy gamma ray photons produced in core, due to fusion, are absorbed after travelling up to few millimeters, by solar plasma of radiative zone. Then they are re-emitted with low energy and in random direction. With this series of emission and absorption, radiation takes long time to reach on surface of star (sun). Estimated time of their travelling is 10,000 to 170,000 years, however, neutrinos take only 2.3 second to reach on surface, which contribute about 2% of total energy. In core, as a result of fusion, neutrinos are also produced, but unlike photons, they don’t interact with matter usually, so escape immediately from star (sun).
Facts about sun
- Star (sun) has occupied 99.86 percent mass of solar system.
- One million earth’s can easily fit into sun. However, if earths are squashed in such a way that there is no wasted empty place in sun then 1,300,000 earths can be fit into sun.
- Since sun is burning through helium, it will continue to do so for next 130 million years, but through its hydrogen not helium. So it will expand to a size that it will consume mercury, Venus and earth. At this stage, it will become a red giant.
Energy produced by sun is due to the nuclear fusion reaction in its core, when 4 hydrogen nuclei combine to form a single helium nuclei.
Shape and structure of sun
- Sun is in almost perfect sphere shape.
- The speed at which sun travels is 220 Km/s (24,000 to 26,000 light years from galactic center (center of Milky Way galaxy)). It needs 250 million years to complete an orbit of Milky Way.
- Sun will be converted into white dwarf when it will have formed red giant once. After being red giant, it will collapse by losing its volume but maybe similar mass, so it will be of the size of earth.
- Speed of light is 300,000 Km/s and distance from earth to sun is 150 million Km. light needs millions of years to travel from core of star (sun) to its surface, but takes only 8 minutes and twenty seconds to reach from sun surface to earth.
- For the present time, sun is a yellow dwarf star, which has burnt half of its hydrogen in 4.5 billion years and will continue burning by remaining hydrogen.
- The distance b/w earth and sun is of one astronomical unit (A.u.) as earth orbits in an elliptic path and difference b/w earth and sun’s orbit is 152 million Km.
- Earth rotates from east to west, but sun rotates from west to east: opposite.
- Sun rotates faster on its equator than poles because as the Sun is not a rigid body, unlike the Earth. It consists of a hot spinning plasma and can therefore accommodate various rates of rotation at different latitudes, this is called differential rotation.
The Sun has mighty magnetic field. When the Sun releases magnetic energy during magnetic storms, solar flares occur which we see as sunspots on Earth. Sunspots are mysterious patches on the surface of the Sun caused by magnetic differences. The reason they look dim is that their temperature is significantly lower than that of nearby areas.
Temperature of sun
- In the structure of sun the indoor temperatures can reach 15 million degrees Celsius. Energy is generated in the core of the Sun through nuclear fusion – this is when hydrogen converts to helium – and because objects generally expand, the Sun would explode like a huge bomb if it were not for its tremendous gravity pull.
- Solar Winds are produced by the Sun. These are plasma ejections (extremely hot charged particles) which originate in the Sun’s layer known as the corona, and can travel up to 450 km per second across the solar system.
- Structure of Sun consists of three layers; photosphere, chromosphere and corona make the atmosphere of sun.
The surface temperature of sun is 5000 to 5700 degree Celsius and it is classified as yellow dwarf star.