What is the Sun?
Sun is the parent star of the solar system and accounts for more than 99% of the total mass of the solar system. All planets revolve around the sun in their planetary orbit. The mass of the sun is 1.988 435×1030 kgs which is equal to the total mass of 332,946 Earths. It is believed that the Sun is about 5 billion years old.
The main component of the Sun is Hydrogen which constitutes nearly 74% of the total mass of the Sun. Helium constitutes 25% of the total mass of the Sun and the rest is made up of trace quantities of heavier elements.
The Sun is the closest star to Earth, at a mean distance of 149.60 million kilometers. The Sun is held together by gravitational force, producing high pressure and temperature at its core. The Sun has six regions - the core, the radiative zone & the convective zone in the interior and the photosphere, the chromosphere & the corona (outermost region) in the exterior.
The energy produced in the core of the Sun at a temperature of about 15 million degrees C, is responsible for producing all the heat & light t the Earth receives. The process of photosynthesis is dependent on sunlight and sunlight is ultimately the source of all food and fossil fuel. The connection & interactions between the Sun & Earth cause the seasons, ocean currents, weather and climate. It takes approximately 8 minutes for sunlight to reach the Earth’s surface.
Most of the Sun’s radiation escapes from the Photosphere which is a 500 kilometer thick region on the surface of the Sun. The temperature of the photosphere is about 5,500 degrees Celsius (10,000 degrees Fahrenheit).
The chromosphere and the corona lie above the photosphere. Visible light from these regions is usually too weak to be seen against the brighter light from the photosphere. However, during total solar eclipses, when the photosphere is covered by the Moon, the chromosphere can be seen as a red rim and the corona forms a white circle of light around the Sun.
Sunspots in the photosphere are areas with strong magnetic fields that are cooler, and thus darker, than the surrounding region of the Sun.
Sun and Eye Damage:
Sun should never be viewed directly because of a potential danger of damaging the retina. The Ultra Violet (UV) index of sunlight can heat up the retina and can result in the formation of cataracts (an eye-disease).
During a partial solar eclipse, the moon covers the sun almost completely excluding the photosphere of the sun. The Photosphere has the same intensity of sunlight as compared to other regions of the sun. Viewing of the solar eclipse with the naked eye can damage the retina permanently and can result in permanent blind spots. Children, especially, should not be allowed to see a partial solar eclipse with naked eyes as there is no immediate perception of pain.
When the moon passes in front of the Sun and hides it fully or partially, it is termed as a Solar Eclipse. This phenomenon can occur only at Full Moon.
Eclipse Eclipse Shadow on Earth
There are four types of solar eclipses:
* A partial solar eclipse occurs when the Moon hides the Sun only partially.
* A total solar eclipse occurs when the Moon completely hides the Sun. The Sun’s corona is visible only during a total eclipse.
* An annular (ring-formed) eclipse
* A hybrid eclipse