CHARACTERISTICS OF STARS

A star is a massive ball of plasma that emits light throughout the universe. A star can be defined by five basic characteristics-brightness, color, surface temperature, size and mass.                                                             BRIGHTNESS-----Two characteristics define brightness-luminosity and magnitude. Luminosity is the amount of light that a star radiates. The size of the star and its surface temperature determines its luminosity. Apparent magnitude of a star is its visible brightness, factoring in size and distance, while absolute magnitude is its true brightness irrespective of its distance from Earth.                                                                              COLOR___A star's color depends on its surface temperature. Cooler stars tend to be redder in color, While hotter stars have a bluer appearance. stars in the mid ranges are white or yellow such as our sun. stars can also blend colors, such as red-orange stars or blue-white stats.                                                             SURFACE TEMPERATURE____Astronomers measure a star's temperature on the kelvin scale is equal to-273.15 degrees Celsius. The coolest, reddest stars are approximately 2,500 K, Our sun is about 5,500 k.                                                                                                                                                                   SIZE___Astronomers measure the size of a given star in terms of our own sun's radius. Thus, a star that means that measure 1 solar radii would be the same size as our sun. The star Rigel, which is much larger than our sun, measures 78 solar radii. A star's size, along with itsa surface temperature determines its luminosity.   MASS___A star's mass is also measured in terms of our own sun, with 1 equal to the size of our sun. for instance, Rigel, which is much larger than our sun, has a mass of 3.5 solar masses.Two stars of a similar size may not necessarily have the same mass, as stars can vary greatly in density.                     BETELGEUSE, THE BRIGHT STAR ON ORION'S TOP-LEFT SHOULDER, IS SO BIG THAT IF IT WAS PLACED WHERE THE SUN IS, IT WOULD SWALLOW UP EARTH MARS AND JUPITER;                                                                                                                                                It's  estimated  that the number of star's in the universe  is greater than the number of grains of sand on all the beaches in the world;