Facts about the stars

STAR,

A glowing body of gases that also emits heat and other forms of energy that derive ultimately from thermonuclear reactions taking place in its interior. Stars and vast collections of stars known as galaxies are building blocks of the universe. Although the characteristics of individual stars vary greatly, our own sun may be described as a fairly typical star. This article deals with the nature of stars and the ways in which their properties are determined,  the source of stellar energy, and the birth and death of stars. In ancient times the stars were an unresolvable mystery, because no means existed estimating or even guessing at their true nature. It is not surprising that stars were once considered to be lights on a crystal sphere surrounding the earth, or to be holes on a dark surface through which shone the brilliance of a celestial realm. The first solid foundation for the hypothesis that the stars are in fact distant sun's did not exist until the 16th century and the establishment of the copernican concept that the earth revolves around the sun. Toward the end of that century, astronomers such as Tycho Brahe made measurements of the stars that revealed no observable parallax effects. That's is, a given star was observed first from one side of the earth's orbital path and then, half a year later, from the opposite side of the path. When this was done, no shift in the stars position relative to other stars could be observed. The implication was that the star lay at a very great distance from the solar system, just as the most distant objects in a landspace on earth seem to remain fixed relative to small changes in the position of an observer. It was not until the 19th century that more precise instruments enabled the shift in position of a relatively nearby star to be measured for the first time.