Stars (Important Facts) {Part-7}

STARS ARE BODIES of hot,glowing gas that are born in nebulae. They vary enormously in size, mass, and temperature: diameters range from about 450 times smaller to over 1,000 times bigger

Star

than that of the Sun; masses range from about a 20th to 50 solar masses; and surface temperatures range from about 3,000^oC to over 50,000^oC. The color star is determined by its temperature: the hottest stars are blue and the coolest are red. The Sun, with a surface temperature of 5,500^oC, is 

Hottest star (Blue in color)

Coolest Star (Red in Color)

between these extremes and appears yellow. The energy released by a shining star is usually produced by nuclear fusion in the star's core. The brightness of a star is measured in magnitudes - the brighter

Nuclear fusion in the star's core

the star, the lower is magnitude. There are two types of magnitude;

(i) Apparent Magnitude:-Brightness seen from Earth (of the stars)

(ii)Apparent Magnitude:-Brightness seen from a standard distance of 10 parsecs (32.6 light years)

The light emitted by a star may be split to form a Spectrum containing a series of dark lines (absorption lines).  The patterns of lines indicate the presence of particular chemical elements,

Birth of Star

Star spectrum

enabling astronomers to deduce the composition of the star's atmosphere. The magnitude and spectral type (color) of stars may be plotted on a graph called a Hertzsprung-Russell diagram, which shows stars tend to fall into several well-defined groups. The principal groups are main sequence stars

Hertzsprung-Russell diagram

(those are fusing hydrogen to form helium), giants, supergiants, and white dwarfs.

Star Color Chart