Stars are really just distant suns, even the nearest star is too far to be seen as more than a point of light in the biggest telescope. The distance of the stars is so great that none is known to have a heliocentric parallax (difference in apparent position as observed from the earth and the sun) of as much as 1".
Stars are different in size from giants having diameters greater than that of the orbit of the earth, to small ones which may be no larger than the major planets. The size and density cover wide ranges. The color of stars vary with the temperature, a hot star is bluish-white, and a colder star, is a faint red. ln Orion, blue Rigel and red Betelgeuse, are located on opposite sides of the belt, and look noticeable different.
Under ideal viewing conditions, the dimmest star that can be seen with the unaided eye is of the sixth magnitude. In the entire sky there are about 6,000 stars of this magnitude or brighter. Half of these are below the horizon at, about 2,500 stars are visible to the unaided eye at any time. When looking for stars for a sight I have about 15 of the brighter ones that I use and keep track of where they are in the sky.
Stars which have a change of magnitude are called variable stars. A star which suddenly becomes several magnitudes brighter and then gradually fades is called a nova. A real bright one is called a supernova.
Two stars that look close together are called a double star,if more than two stars are included in the group, it is called a multiple star, and if a large number appear in a spherical shape, it is called a globular cluster. The Pleiades and some stars of the Big Dipper are examples of open clusters. A group of stars which appear close together, are called a constellation, particularly if the group forms a striking configuration. The ancient Greeks recognized 48 constellations covering only certain groups of stars. Today astronomers recognize 88 constellations.
Stars rotate on their axes, and revolve around the center of their galaxy, Motion of a star through space like any celestial body is called space motion. Stars are great for viewing during the winter because their are so many neat ones showing, you just have to have a clear night to enjoy them.
