Messier 94 (also known as M94, NGC 4736, Cat’s Eye Galaxy or Croc’s Eye Galaxy) is a spiral galaxy located in the constellation Canes Venatici. It has an apparent magnitude of 8.99, a linear extension of 50000 light years and lies at a distance of 16 million light years from Earth.
Messier 94 is classified as a LINER galaxy, i.e., a galaxy with a low ionization nuclear emission region (LINER). This means that the nucleus of M94 contains ionized gas, but that the gas is only weakly ionized. Some sources classify M94 as a barred spiral, but the galaxy’s “bar” structure appears more oval-shaped.
Messier 94 has two ring structures. The inner ring has a diameter of 70 arc seconds and the outer one, 600 arc seconds. The two rings are found at resonance locations within M94’s disk. The galaxy’s bar-like structure drives gas into the inner ring, triggering star formation in the region. The outer ring of M94 is not a closed stellar ring, as previously believed, but a complex spiral arm structure seen in mid-infrared and ultraviolet wavelengths. In other words, what appears to us as a ring is in fact a structure of two spiral arms that looks like an unbroken ring when seen from Earth.
The outer ring was previously thought to have formed when M94 absorbed a smaller satellite galaxy or as a result of interaction with a star system. However, neither of these theories was supported by research and scientists concluded that the inner disk is an oval distortion which led to the formation of M94’s peripheral disk. The inner starburst ring is a site of intense star forming activity and is believed to have formed in a starburst that occurred less than 10 million years ago.
Messier 94 was discovered by Charles Messier’s colleague Pierre Méchain on March 2, 1781. Méchain reported the discovery to Messier, who found the object, determined its position, and added it to his catalogue of comet-like objects on March 24, 1781.