IC 342/Maffei Group

The IC 342/Maffei Group is a nearby group of galaxies behind the Milky Way’s dusty, star-rich plane. Its principal members include the spiral galaxy IC 342 and the Maffei galaxies.

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IC 342: A large nearby spiral galaxy whose disk is viewed through the obscuring plane of the Milky Way. It is the group’s namesake and one of its principal galaxies.
Paolo Maffei: An Italian astronomer who discovered the galaxies Maffei I and Maffei II in infrared observations. His discoveries revealed major galaxies in the group’s previously obscured direction.
Galaxy redshift: The shift of a galaxy’s spectral features toward longer wavelengths, used to measure its motion along the line of sight. Redshifts help distinguish group members from unrelated galaxies behind the Milky Way.
Galaxy peculiar velocity: A galaxy’s motion relative to the uniform expansion of the universe. The group’s motion helps reveal its gravitational influence and relation to nearby structures.
Maffei I: A giant elliptical galaxy discovered in the Milky Way’s Zone of Avoidance. It is a principal group member whose obscured location helped define the group.
Infrared astronomy: The study of astronomical objects through infrared radiation, which penetrates dust better than visible light. Infrared observations exposed galaxies that foreground Milky Way dust concealed.
Neutral hydrogen: Hydrogen atoms that have not been ionized, detectable through their 21-centimeter radio emission. Radio mapping of neutral hydrogen can reveal obscured gas-rich galaxies in the group.
Hubble flow: The general recession of distant galaxies caused by the expansion of the universe. Separating this expansion from local motion is essential for interpreting group velocities.
Maffei II: A heavily obscured barred spiral galaxy in the constellation Cassiopeia. It is another principal member hidden behind the Milky Way.
Milky Way: The barred spiral galaxy that contains the Solar System and dominates the foreground toward this group. Its disk both obscures the group and complicates estimates of its galaxies.