When the light of distant galaxies or quasars travels close to massive objects, such as other galaxies or galaxy clusters, it suffers a bending called gravitational lensing.
Under certain conditions (the lens is massive enough and both the lens and the source are sufficiently distant from us), a lens can produce multiple images from the same source, much like a mirage.
A molecular cloud is a type of interstellar cloud whose density and size permits the formation of molecules, most commonly molecular hydrogen (H2).
Stars and planets form inside the densest and coldest regions of molecular clouds from collapsing globules of gas. Dust plays an essential role here, as it shield the gas from external radiation field, thus making the collapse possible.
NGC 3603 is one of the largest star-forming regions of the Galaxy. Surrounding the cluster are natal clouds of glowing interstellar gas and obscuring dust, sculpted by energetic stellar radiation and winds.