Observatoire de Paris
<-   The states of matter in the Universe   ->

The interstellar medium (ISM)

The interstellar medium is made up of gas, between 10 and 100K. The chemistry there is slow.

The stars

The stars are made up of dense ionized gas. The temperature on the surface of the stars is between 3000 and 50000K. At this temperature, the atoms are separated into plasma (ion soup).

The giant planets

The giant planets are made up of gas with a liquid and/or solid core. The giant planets of the Solar System are between 100 and 200K.

The terrestrial planets

The terrestrial planets are made up of solid materials and an atmosphere. Nearer to the Sun than the giant planets, their temperatures are between 200 and 500K. The combined effect of the effective temperature and the greenhouse effect maintains a temperature interval which enables water to be in the liquid state (0-100 degrees Celsius or 273-373K), a favorable medium for the emergence of life.

The main difference between terrestrial and giant planets concerns their density : one cubic centimeter of a terrestrial planet weights between 4 and 6 grams whereas one cubic centimeter of a giant planet weighs between 1 and 2 grams.