Molecular Clouds
Beyond our solar system, molecules are chiefly found in molecular clouds - regions of space up to 300 light-years wide with a mass of up to 100,000 to 1,000,000 times that of our Sun. (A light-year is the distance light travels in a year, or 9.5 x 1012 km - for comparison, the Sun is 8.3 light-minutes, or 1.5 x 10-5 light-years from Earth.) Any object as large as a molecular cloud is likely to vary greatly from place to place. The gas density in a molecular cloud ranges from 100 to 100,000 atoms or molecules/cm3 and the temperature is approximately 20 K. Molecular clouds are very interesting to astronomers as new stars are formed in these relatively dense regions. The molecular cloud with the richest chemistry that has been observed to date is about 1600 light-years away, near the Orion nebula. An image of this region is shown below.
A view of the Orion Nebula taken with an infrared array