(See description below)
Iris Nebula
Through the alchemy of stellar evolution, light elements are converted into heavier elements, and some fraction of these products are expelled from the stars either by gentle stellar winds or by violent explosions. Consequently, the pristine interstellar medium consisting only of hydrogen and helium has been "polluted" over time by elements like carbon and silicon. Combinations of these atoms create tiny particles that astrophysicists call "dust." Such small particles, about the dimension of a visible light wave, scatter blue light much more efficiently than red. Hence interstellar clouds create vivid blue reflection nebulae when they surround a giant blue star.
The Iris Nebula is about 1,300 light-years away and 6 light-years across. It is cataloged as NGC 7023.