Observatoire de Paris
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<-   Temperature, luminosity   ->
The wide variety of stars are illustrated in this diagram. Each point is a star. The temperature is given in abscissa, and the luminosity on the y-axis (total intensity of the radiation emitted by the surface of the star). The colour code indicates the number of stars of the region, as observed by the satellite HIPPARCOS.
Crédit : Paris Observatory / LESIA

In a star like the Sun, the temperature varies from about 5500°C at the surface to more than 15 million degrees at the center. The density varies from less than one millionth gram per cubic centimeter at the surface to approximately 150 grams per cubic centimeter at the center.

However, the Sun is a medium star. Some stars are much more massive (up to 100 times more) or less massive (up to 10 times less). Some are warmer on the surface (up to 25000°C) or cooler (up to 2000°C).

In some stars, the temperature in the center can reach several hundreds of millions of degrees, in others (neutron stars), the density in the center could be one billion tons per cubic centimeter.