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Kepler's laws of Planetary motion.
Kepler's laws of Planetary motion.
===Learning objectives===
===Learning objectives===
* The Sun is an immense ball of gases nearly a million miles in diameter, with a mass of more than 300,000 times the mass of the Earth. This happens to be about a thousand times the mass and a thousand times the volume of Jupiter, so the Sun is, like Jupiter, about 30% denser than water. However, unlike Jupiter, which is made of liquid hydrogen and helium, the Sun is entirely gaseous. This difference is caused by the Sun's high temperature, which ranges from a low of 6000 Kelvins (about 10000 Fahrenheit) at the surface to a high of about 15 million Kelvins (almost 30 million Fahrenheit) in the center. These high temperatures tear any molecules or atoms of hydrogen and helium to pieces, and those pieces are much smaller than ordinary atoms, so even at very high densities the materials in the Sun are still gaseous.
* Because of the Sun's high temperature and large size it radiates a tremendous amount of light and to a lesser extent, other kinds of electromagnetic radiation. It gives off approximately 400 trillion trillion watts (4 x 1026 watts) of power, which is created by thermonuclear reactions in its deep interior.
* Despite its immense size, mass and brightness the Sun is actually a fairly average star. There are stars with more than a hundred times the mass of the Sun, and stars with as little as a few percent of its mass. Stars with up to a thousand times the diameter of the Sun, and as little as a hundredth of its diameter. Stars with as much as a few million times its brightness, and as little as one fifty-thousandth of its brightness. And in almost every other respect, whatever properties are discussed for the Sun there are stars with much larger or much smaller values than those which apply to the Sun.
* Despite being a very average star, the Sun is of immense importance to us, because our lives depend upon its light and heat. Without it life on Earth would soon end. In addition, the Sun is very important to astronomers, because being by far the closest star, we can study it in far more detail than any other star.
Explains the main features of the Sun such as Outer and Internal structure of The Sun.
Explains the main features of the Sun such as Outer and Internal structure of The Sun.
