M94 - Cat's Eye, or Croc's Eye Galaxy
| Polish version is here |
Messier 94, commonly known as the Cat’s Eye Galaxy and sometimes referred to as the Croc’s Eye Galaxy, is a spiral galaxy distinguished by its unusual structure and unique starburst ring. This object is located on the celestial sphere in the constellation Canes Venatici. The Cat’s Eye Galaxy lies approximately 16 million light-years from Earth.
In terms of morphology, M94 is classified as a spiral galaxy whose central region exhibits characteristics typical of active galaxies, although to a moderate degree. Unlike classical Seyfert galaxies, whose nuclei emit intense radiation as a result of strong accretion of matter onto supermassive black holes, M94 has a less active nucleus, often described as a LINER (Low-Ionization Nuclear Emission-line Region). This classification indicates the presence of accretion processes, albeit at much lower intensities, making M94 an excellent example of a transitional object between quiescent spiral galaxies and highly active Seyfert galaxies.
Seyfert galaxies are characterized by strong emission lines in their optical spectra, resulting from the presence of an active nucleus. In the case of M94, observations indicate that while emission intensity is lower, the processes occurring in its center significantly influence the structure and dynamics of the entire galaxy. This makes M94 not only an attractive target for amateur astrophotography but also a subject of detailed scientific studies aimed at gaining a better understanding of the mechanisms governing nuclear activity in spiral galaxies.
Observations
January 31, 2025, around 10:00 PM – Jaworzno (Poland), suburbs
moderate light pollution
The conditions that night proved to be quite favorable—the atmosphere was stable, and the moderate level of light pollution allowed for capturing an image of decent quality. The session utilized long-exposure imaging and frame stacking techniques, enabling the capture of both the bright central ring and the faintly illuminated outer disk, which is relatively challenging to capture for this object.
Two rings were observed within the galaxy’s disk: an inner ring with a diameter of approximately 70 arcseconds (about 5,400 light-years) and an outer ring with a diameter of about 600 arcseconds (around 45,000 light-years). The inner ring, often referred to as the starburst ring, is fueled by gas moving as a result of interactions with an oval structure resembling a bar. A 2009 study revealed that the outer ring is actually a system of spiral arms, which accounts for roughly 23% of the galaxy’s visible mass and is responsible for about 10% of its newly forming stars. The star formation rate in this region is approximately twice as high as in the inner region, suggesting a high efficiency in converting matter into new stars.
On the same night, I also observed the Sunflower Galaxy M63.
Photo 1 Parameters:
- Total exposure time: 90 minutes (stack of 90 RAW frames at 60s each, using an appropriate number of dark, bias, and flat frames)
- ISO: 1600
- Maksutov-Cassegrain telescope (100/1400), prime focus exposure
- A filter was used to reduce the effects of artificial light pollution and atmospheric glow
- Mount: equatorial mount with tracking, aligned using the drift method and controlled by a custom-built system.
Further readings:
- Tonry J. L., Dressler A., Blakeslee J. P., Ajhar E. A., et al., The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances, Astrophysical Journal, 2001, 546(2), str. 681–693
- Karachentsev I. D., Sharina M. E., Dolphin A. E., Grebel E. K., et al., Galaxy flow in the Canes Venatici I cloud, Astronomy and Astrophysics, 2003, 398(2), str. 467–477
- Muñoz-Tuñón C., Caon N., Aguerri J., Alfonso L., The Inner Ring of NGC 4736: Star Formation on a Resonant Pattern, Astronomical Journal, 2004, 127(1), str. 58–74
Marek Ples