The Sun is the central star of our Solar system, and has a diameter of approximately 1,392,000 kilometers. This massive star itself forms about 99.86% of the entire Solar System's mass, leaving less than 1% of the solar system to be made up of the planets, asteroids, comets, meteoroids, etc. Thus, from this one can get an idea about the vastness of this star.
What is the Temperature of the Sun?
Determination of the Sun's temperature has been a daunting and herculean task for astronomers. Although measuring the Sun's temperature is quite simple, getting the right reading about a factor called atmospheric absorption is the most difficult part.
In 1837, Sir John Herschel at the Cape of Good Hope, and Claude-Servais-Mathias Pouillet in France observed that the temperature of water, 1.8 cm deep would rise by 1°C/minute if the vertical rays of the Sun were to be completely absorbed. Thus, emerged the problem of atmospheric absorption. However, this problem was solved in 1881, when astronomers compiled unknown information for solar radiation of various wavelengths from the already known data, so as to determine the intensity of each one in the absence of intervening air. This helped to measure the temperature of this star. The temperature is not uniform all over, and varies at different layers and regions of the Sun.
The surface of the Sun is also called the photosphere, which is 340 miles thick and gives off Sun's energy in the form of light and heat. One can view some dark spots, also known as Sunspots that happen to be the only activity visible to us by the naked eye. In fact, most of the sunlight we see is from this photosphere only. The temperature of the Sun's surface is 5,778 K (5,505 °C). This extreme temperature imparts the sunlight its glorious yellow color. Had the temperature been even slightly lower, the Sun would appear reddish. Moreover, had the temperature been slightly higher, sunlight would appear bluish.
The temperature of the Sun at the core region of the Sun is 13,600,000 Kelvin. This is the right range for atoms of hydrogen to fuse together to form Helium by the process called nuclear fusion.
At about 2000 km from the Sun's surface, the temperature rises to about 100,000 kelvin. In fact, temperatures even rises to about 1 million kelvin in various zones of the atmosphere. The range measured in the Sun's corona (outermost layer of the Sun's atmosphere) is about a few million kelvin.
The Sun is an amazing star that radiates light and heat vital for the existence of life on planet Earth. Researchers and astronomers are still to delve into the sea of fascinating facts hidden behind this ball of fire.