Thus, the frequency spectrum shown by reflection nebulae is similar to that of the illuminating stars.
The latter two are often aligned with the galactic magnetic field and cause the scattered light to be slightly polarized.
The supergiant star Antares, which is very red (spectral class M1), is surrounded by a large, yellow reflection nebula.
In 1922, Edwin Hubble published the result of his investigations on bright nebulae.
One part of this work is the Hubble luminosity law for reflection nebulae, which makes a relationship between the angular size (R) of the nebula and the apparent magnitude (m) of the associated star: where k is a constant that depends on the sensitivity of the measurement.