Which key constituents form the solid cosmic dust grains within nebulae?
Silicates, Carbonaceous Materials, and Ices.
The composition of the solid component, or cosmic dust, within nebulae is surprisingly complex and mirrors terrestrial materials in some respects. Key constituents include silicates, which are compounds made of silicon and oxygen, similar to rock-forming minerals. Another significant group is carbonaceous materials, which can range from soot-like particles to more complex organic molecules. Furthermore, in very cold and dense regions of the nebula, volatile compounds such as water ($ ext{H}_2 ext{O}$), methane ($ ext{CH}_4$), and ammonia ($ ext{NH}_3$) freeze onto the solid grains, forming icy mantles. These materials are responsible for blocking light (dark nebulae) or scattering it (reflection nebulae).
