temperature

A measure of the average kinetic energy of the atoms or molecules that make up an object. Temperature can be measured in degrees Fahrenheit (oF), degrees Celsius (oC), or in Kelvin (K). The respective freezing and boiling points of water are 32 degrees and 212 degrees F, 0 degrees and 100 degrees C, and 273.16 and 373.16 K. One degree Celsius and one Kelvin measure the same amount of change in temperature.

When referring to the temperature of stars, astronomers usually refer to the effective temperature, or temperature of the photosphere, of a star. In the core however, the temperature is highest around 15 million degrees. In between the core and the surface, the temperature is about 5 million degrees, and at the photosphere, where almost all photons escape, the temperature is 6000 degrees.