Answer:
Material thrown out in the space because of a death of a star.
Step-by-step explanation:
Most of the gas and dust found in the interstellar clouds come from death of a star. Either that star exploded (Supernova Explosion) or blew off its outer layers and thus sending this material into interstellar region. This gas and dust can be observed in IR spectrum as they radiate heat after absorbing the visible and UV light.