Editing Hadean Eon (section)

=== Dust ===
'''(Star) dust''' refers to tiny solid particles composed of elements like '''carbon''', '''oxygen''', '''silicon''', '''magnesium''', and '''iron''', often found in the form of compounds or minerals similar to those seen on Earth (silicates, graphite, water ice, and iron oxides). These particles are remnants of previous astrophysical processes, including '''outflows''' from aging stars (when stars at the ends of their lives begin to 'leak' matter and energy), '''supernovas''' (when dying stars explode), and the collision and fragmentation of '''asteroids''' and '''comets''' with other bodies. Dust particles can range in size from a few molecules to micrometers of diameter.

Dust particles act as cooling agents in the ISM by absorbing energy from surrounding gas and re-emitting it at '''infrared''' wavelengths, facilitating the collapse of gas into denser clouds that can eventually form stars (as described above). Dust grains also provide surfaces on which chemical reactions can occur, which can lead to the formation of complex organic molecules, including those essential for life. Dust absorbs and scatters visible and ultraviolet light, affecting the appearance of astronomical objects in a process known as '''interstellar extinction'''; this makes distant stars appear dimmer and redder than they are in reality. Dust is also responsible for nebulae observed in the night sky, as it scatters light from nearby stars or emits light due to its own raised temperature.

Star dust can include '''graphite''' and complex organic molecules, some of which are similar to soot or '''polycyclic aromatic hydrocarbons''' (PAHs); others form large, interconnected structures. Silicates (particles primarily composed of silicon, oxygen, magnesium, and iron) are also common. These are similar in composition to many of the minerals found in Earth's crust but are in the form of very small grains in space. In colder regions of the ISM, dust grains can be coated with ices - water (H2O), methane (CH4), ammonia (NH3), carbon dioxide (CO2), and other molecules can freeze onto the surfaces. Tiny solid particles of metals such as iron, nickel, and magnesium also contribute to interstellar dust.