Stars ...  The Sun

Stars are those lovely twinkling gems that light up the night sky. In short, a star is an enormous radiant ball of hot gases, mostly hydrogen and helium. There are many different types of stars ranging in size, color, temperature and brightness. Much of what we know about stars is learned through spectral analysis (studying the light of the star). For example, the color of a star gives us information about its temperature much in the same way that the color of a candle’s flame tells us which parts of that flame are hotter.

The closest star to Earth is the Sun. The Sun is a yellow star. Yellow stars have an average temperature of about 6000 (K). In terms of size, the Sun is an average star.  It is about 4.7 billion years old.

Star: The Sun
Distance from Earth: 1 AU (149,597,870 km)
Star diameter: 1,392,000 km

Picture courtesy of the SOHO/EIT consortium.
SOHO is a project of international cooperation between ESA and NASA.