Messier 106

Messier 106 (also known as NGC 4258) is an intermediate spiral galaxy in the constellation Canes Venatici.

M106 contains an active nucleus classified as a Type 2 Seyfert, and the presence of a central supermassive black hole has been demonstrated from radio-wavelength observations of the rotation of a disk of molecular gas orbiting within the inner light-year around the black hole.

M106 has a water vapor megamaser (the equivalent of a laser operating in microwave instead of visible light and on a galactic scale) that is seen by the 22-GHz line of ortho-H2O that evidences dense and warm molecular gas.

Water masers are useful for observing nuclear accretion disks in active galaxies.

Before, Cepheid variables from other galaxies could not be used to measure distances since they cover ranges of metallicities different from the Milky Way's.

Composite image features X-rays from Chandra (blue), radio waves from the VLA (purple), optical data from Hubble (yellow and blue), and infrared with Spitzer (red). Two anomalous arms, which are not visible at optical wavelengths, appear as purple and blue emissions.