Observations indicate that the coldest clouds tend to form low-mass stars, which are first observed via the infrared light they emit inside the clouds, and then as visible light when the clouds dissipate. Giant molecular clouds, which are generally warmer, produce stars of all masses. These giant molecular clouds have typical densities of 100 particles per cm, diameters of 100 light-years (9.5 × 10 km), masses of up to 6 million solar masses (M ☉), or six million times the mass of Earth's sun. The average interior temperature is 10 K (−441.7 °F).