LIFE OF THE STARS
PROPERTIES OF STARSHow can we find out what the stars are really like? Once we know the distance to a particular star, we can work out how bright the star is and begin the to learn other things about it, such as its size, mass, age. We find tiny white dwarfs about the size of the Earth and supergaints big enough to engulf much of our Solar System. Some stars are only a few million years old, while others are almost as ancient as the Universe itself.
The masses of stars are not usually measured in kilograms or tonnes, but in relation to the mass of the Sun. the lightest stars are less than one-tenth of a solar mass, while the heaviest may be more than 50 solar masses. Like pebbles on a beach, there are uncountable small stars, but few really big ones.
LUMINOSITTY AND ABSOLUTE MAGNITUDE
A stars real brightness, compared with the Sun, is
called its virtual luminosity: stars range from 100,000 times to 1/100,000 times to the
Suns brightness. Astronomers also refer to luminosity in terms of a stars
absolute magnitude, which is the magnitude the star would appear if it were 10 parsecs
(32.6 light years) from the Earth.