There is a reason why the earth is the only place in the entire solar system where life is present. The rest of the planets can’t support live. Even though scientist have been trying to explore other parts of the solar system and find out whether they can support life, there is none that has been able to get to the level of the earth. Scientists claim that there are microbial or aquatic life forms that live beneath the icy surfaces of Enceladus and Europa. These organisms also exist in the methane lake of Titan. However, as per now, the earth is the only place that has been known to be able to provide the right conditions for the existence of life (Charbonneau, 2014).
The reason why the Earth can support life is that of the sun. The earth lies within the Sun’s Habitable Zone also popularly known as the “Goldilocks Zone”. Being in the Sun’s Habitable zone just means that the earth is in the right spot where it can receive abundant energy from the sun. In other words, the earth is not too far or too close to the Sun like other planets. It is thus able to receive the right amount of light and heat. The big question is how the sun can produce this heat and light that the earth strongly depends on
Delegate your assignment to our experts and they will do the rest.
The best answer is that the sun is a star. Just like all other stars, it is capable of creating energy as a result of a massive fusion reaction. According to scientists, this fusion reaction began when a giant cloud of gas and particles called nebula collapsed due to the force of gravity. The explanation is known as the nebula theory. It created the ball of light at the centre of the solar system. It also triggered a process whereby hydrogen collected at the centre then started fusing thus generating solar energy (Godier, 2000).
Nuclear fusion is the name of the process. It releases an incredible amount of energy in the form of light and heat. For the sun to get that energy from its central part all the way to the earth and beyond, a couple of vital steps are involved. The explanation about how all this process takes place narrows down to the sun’s layers. Each of these layers plays a different role in ensuring that the solar energy gets produced and transmitted.
The Core
The core of the sun is the region that extends from its centre to around 20-25 percent of the solar radius. It is at the centre where energy gets generated by hydrogen atoms (H). These atoms get converted into molecules of helium (He). The process is possible due to the extreme temperature and pressure that exists within the sun’s core Lada, J. (2006). The pressure at this point is estimated to be around 250 billion atmospheres. That is a total of 25.33 trillion KPa. The temperatures are as high as15.7 million, Kelvin. These pressure and temperature figures are beyond comprehension.
The net results entail fusion of four protons (hydrogen molecules) into a single alpha particle i.e. two neurones and two protons bound together into a single particle that is identical to the helium nucleus. The process releases two pisotrons as well as two neutrinos (which converts two of the protons into neutrons), and energy.
The core is the only layer of the Sun that produces an appreciable amount of heat by fusion. 99% of the energy generated by the sun occurs within 24 percent of its radius. By 30 percent, fusion is already over. The rest of the star is heated by transferred energy from its core through the successive layers (Phillips, 1995). It eventually reaches the solar photosphere and escapes into space in the form of sunlight or kinetic energy. It releases energy at a mass-energy conversion rate of 4.26 million metric tonnes per every second. It leads to an equivalent of 38,460 septillion watts (3.846×1026 W)/ second. The above is close to 9.192×1010 megatons of TNT / second (1,820,000,000 Tsar Bombas).
Radiative Zone
The radiative zone is the zone right after the core. It extends out to around 0.7 solar radii. No thermal conversion takes place in the radiative layer. However, the solar material in this layer is extremely high. The material is also very dense such that thermal radiation is all that is required to transfer the heat generated in the core outwards. It entails hydrogen ions and helium emitting photons which travel a short distance before being absorbed by other atoms. Temperatures go down in this layer. They drop from around 7 million Kelvin near the core to approximately 2 million at the boundary. The boundary is simply the convective zone. The density also decreases at this zone. It reduces from 20 g/cm³ near the core to around 0.2 g/cm³ at the upper boundary region. The drop is quite significant (Woolfson, 2000).
Convective Zone
The convective zone is the sun’s outer layer which accounts for everything behold 70 percent of the inner region of the solar radius (or from the surface to around. 200,000 km below). At this zone, temperatures are usually lower than in the radiative zone. The heavier atoms are not ionized fully in this layer. As a result, active heat transport is less efficient at this place. The density of plasma is also low such that it allows convective currents to develop.
The rising thermal cells usually carry most of the heat outwards towards the sun’s photosphere. When these cells rise to just below the photosphere surface, their material cools down. Cooling results in a drop in density. The weight reduction forces them to sink to the bottom of the convective zone again. They pick up more heat from the convective zone, and this cycle continues.
At the sun’s surface, temperatures reduce to about 5,700 K. The turbulent conversion of this area of the sun is what causes an effect that produces magnetic north and south poles all over the sun’s surface. It is also in the convective layer where sunspots occur. Sunspots appear as dark patches when compared to the surrounding parts. The sunspots correspond to concentrations found in the magnetic flux field. These levels inhibit convection thus causing regions on the sun’s surface to drop in temperature as compared to the surrounding material.
Photosphere
The photosphere is the peripheral zone of the sun. It’s the visible layer of the Sun. The sunlight and heat get radiated from this region to the surrounding atmosphere. Temperatures in the photosphere range between 4,500 and 6,000 K (7646 – 10346 °F; 4,230 – 5,730 °C).Since the upper portion of this zone is cooler than the lower part, an image of the sun seems brighter at the centre than on its edge. The limb phenomena are responsible for this difference.
The photosphere layer is tens to hundreds of kilometres in thickness. It is this region of the sun that becomes opaque to the visible light. The reason behind this is the reduction amounting to negatively charged hydrogen ions that absorb visible light easily. The visible light that we see from the earth gets produced when electrons react with hydrogen atoms to give out hydrogen ions.
The energy that gets emitted from the photosphere gets propagated through space up to the earth’s atmosphere and other planets found in the solar system. The earth’s upper layer of the atmosphere (the ozone layer) helps in filtering much of the ultra-violet radiation from the sun. However, it allows some of the UV rays to pass through the surface. The earth then absorbs the energy that it receives. The absorbed energy is responsible for heating land and providing the organism with energy.
The sun is the centre of chemical and biological processes on the earth. The life cycle of plants and animals can’t continue without it. Without the sun, the circadian rhythms of all terrestrial creatures would also end. If this happens, life on earth will cease to exist. The sun's recognition started since prehistoric period. Many cultures viewed it as a deity. During these ancient times, no one knew how it produces energy. The process of how the sun produces energy got discovered a few centuries ago. The discovery was not a single man’s job. It entailed consistent research by physicists, biologists and astronomers. These experts were also able to do the study of the known universe. The study helped them draw a comparison between the sun and other stars. It also helped them discover numerous facts about the sun e.g. the color of the sun, how far the earth is from the sun, characteristic of the sun, etc. A lot of research is still under way about this mysterious star. One of the most interesting ones is about the harvesting of solar power from the space. These discoveries have helped the world move from a world of myths. People can now relate how the sun produces and emits light to its atmosphere. It, therefore, enables them to come up with creative ways of utilizing energy from the sun (Lada, 2006).
References
Charbonneau, P. (2014). " Solar Dynamo Theory". Annual Review of Astronomy and Astrophysics. 52: 251–290.
Godier, S. (2000). " The solar oblateness and its relationship with the structure of the tachocline and of the Sun's subsurface
Lada, J. (2006). "Stellar multiplicity and the initial mass function: Most stars are single".
Phillips, K. (1995). Guide to the Sun. Cambridge University Press. pp. 78–79. ISBN 978-0-521-39788-9.
Woolfson, M. (2000). "The origin and evolution of the solar system". Astronomy & Geophysics. 41 (1): 12.
