THE SUN IS THE STAR AT THE CENTER of the solar system. It is about five billion years old and will continue to shine as it does now for about another five billion years. The sun is a yellow main sequence star about 1.4 million kilometers in diameter. it consists almost entirely of hydrogen is converted to helium. in the sun's core, hydrogen is converted to helium by nuclear fusion, releasing energy in the process. the energy travels from the core, through the radioactive and convective zones, to the photo sphere (visible surface), where it leaves the sun in the form of heat and light.
On the photo sphere there are often dark, relatively cool areas called sunspots, which usually appear in pairs or groups and are caused by the cooling effect of the magnetic field. Other types of solar activity are flares, which are usually associated with sunspots, and prominence. flares are sudden discharges of high energy radiation and atomic particles.
prominence are huge loops or filaments of gas extending into the solar atmosphere; some last for hours, others for months. beyond the photo sphere is the chromosphere (inner atmosphere) and the extremely rarefied corona (outer atmosphere), which extends millions of kilometers into space. tiny particles that escape from the corona give rise to the solar wind, which streams through space at hundreds of kilometers per second. the chromosphere and corona can be seen from earth when the sun is totally eclipsed by the moon.
EXTERNAL FEATURES AND INTERNAL STRUCTURE OF THE SUN
On the photo sphere there are often dark, relatively cool areas called sunspots, which usually appear in pairs or groups and are caused by the cooling effect of the magnetic field. Other types of solar activity are flares, which are usually associated with sunspots, and prominence. flares are sudden discharges of high energy radiation and atomic particles.
EXTERNAL FEATURES AND INTERNAL STRUCTURE OF THE SUN
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