M82 and M81 in the Integrated Flux Nebula (IFN)

Description:

We usually see photos of M82, the Cigar Galaxy, or M81, Bode’s Galaxy, in a tight frame showing them alone or in a well-framed pair.

This photo shows them in a wider field of view and with long exposures that reveal the nebulosity in which they are immersed. This nebulosity is called an integrated flux nebula, and this faint veil is not easy to photograph.

These nebulae are similar to reflection nebulae, but are not. Reflection nebulae are nebulae that are illuminated by one or more nearby stars. However, in the case of integrated flux nebulae, there are no nearby stars illuminating them.

So what illuminates integrated flux nebulae? These nebulae (composed of interstellar dust) are actually illuminated by the luminous halo of our entire galaxy, the Milky Way. In scientific terms, we would say that these nebulae are illuminated by the integrated visual and UV flux of the Milky Way…which explains their name “Integrated Flux Nebulae”.