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Ask A Scientist

How big is the sun and how far is it from the earth?

Asked by: Zachary
School: Vestal Hill Elementary School
Grade: 5
Teacher: Mrs. Morgan
Hobbies/Interests: Games
Career Interest: Video game designer

Answer from Parag Vasekar

Research Scientist

Research area: Solar energy, thin films, materials science
Ph.D. School: Florida Solar Energy Center (University of Florida), Orlando

The Sun is the star at the center of our solar system around which earth and other planets orbit. It’s perfectly spherical like a ball. The diameter of sun is 1,392,000 kilometers which is around 109 times that of earth’s diameter. The mass of sun is 2×1030 kilograms which 330,000 times the mass of earth. More than one million earths could fit inside the space occupied by the sun.  The distance between the sun and the earth varies during the year because of the earth's elliptical orbit around the sun. The average distance from earth to sun is about 150 million kilometers. It takes about eight and half minutes for the light to reach earth from Sun. Of course these scales are beyond our imagination.  Let’s assume for a moment that sun is of the size of a basketball, and then comparatively, the earth will be like a small popcorn seed, which is about hundred feet away from the ‘sun’.

Although only one two-billionth of the sun's radiation reaches the earth, that tiny portion is enough to make life possible. Without the heat of the sun, the earth would be frozen and lifeless.  Although it may appear to be a solid body, the sun is entirely gaseous, since liquids and solids cannot exist at the temperature of even the coolest part of the sun. It consists of very hot plasma and is made of mostly hydrogen (73%) and helium (24%) and the remaining 3% constitutes for oxygen, carbon, nitrogen etc.

The radius of the core of sun is about a quarter of its total radius. The temperature at the core is 13 million degree Celsius. The temperature at the surface of the sun is about 5527 degree Celsius. Most of the energy is generated at the core of the sun by a process known as fusion, which gets transferred outward to the remaining part of the star. That is the reason why the core is the hottest part and as you go outwards towards the surface, the temperature is about 2000 times lower. In the fusion process, every second, 600 million tons of hydrogen species are converted into helium species. This reaction releases a tremendous amount of heat and energy.

The Sun has been shining for about 5 billion years and will continue for at least 5 billion more. The process of converting ‘solar energy’ into other useful forms of energy, which can be directly used in everyday human life, is a hot topic of scientific research, especially here at Binghamton University ‘s Center for Autonomous Solar Power.

Last Updated: 9/18/13