This very odd galaxy is M94, or Messier 94, a spiral galaxy in the constellation Canes Venatici (hunting dogs).
Messier 94 (M94) was discovered by geodesist Pierre Méchain in 1781, a contribution to Messier’s listing of odd objects that are not comets. In this image we see the bright central part of the galaxy, and then a faint ring around it. It is also known as the Cat’s Eye Galaxy or the Croc’s Eye Galaxy, for obvious reasons. The galaxy’s apparent size is approximately 11 arcminutes in diameter, and is estimated to be at a distance of 16 million light-years away.
Viewed through professional telescopes, especially in infrared wavelengths, the outer rings are seen as spiral arms. They are not closed in a complete ring if viewed in this fashion. Moreover the infrared imaging shows that the outer ring is actively forming stars and is estimated to contain approximately 23% of the galaxy’s mass.
This outermost spiral arm structure (appearing as a halo or ring in my image) may have been caused by this galaxy interacting (and capturing) a small neighbor galaxy. There is a claim that this is a relatively normal halo of stars around a disk with spiral arms. It certainly looks odd.
Looking more towards the center, the outermost area of the bright center is extremely active in star formation, a “starburst” ring of activity.
Perhaps the strangest thing about M94 is the claim that it has practically no dark matter. As a graduate student I was once tasked with computing the dark mass required for a spiral armed disk galaxy to remain stable. All I remember is that the galaxy we looked at would have blown apart without a very large amount of additional force (gravitational attraction of the dark matter) to bind it together. If M94 is stable without such dark mass it is very unusual indeed!
The image of M94 shown was captured at Lac Teeples on April 30, 2022. It represents a combination/stack of 120 one-minute subframes. Equipment was the RASA11 scope with the 6200 Camera.
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