Interstellar space is not truly a vacuum devoid of matter. Mixed into vast diffuse clouds of atomic gas are minute grains of silicate and carbonate materials known as 'dust', alongside complex molecules deep in the cold hearts of nebulae. We shall look at how we can detect and observe this tenuous material, through the processes by which dust scatters and absorbs visible light, and emits its own infrared glow. This interstellar matter is of fundamental importance to us all, as it is the reservoir from which all planets form... and any lifeforms living on those planets.

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