M31 (M32, M101) – the Andromeda Galaxy and its satellite galaxies
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The Andromeda Galaxy (M31 in the Messier catalog) is located in the constellation Andromeda, named after the mythological princess, the daughter of King Cepheus of Ethiopia. Its distance from Earth is approximately 2.52 million light-years.
It is the largest and brightest external galaxy visible in the northern sky. Under favorable conditions—far from the light pollution of urban areas—its brightest central regions can often be seen with the naked eye as a small, slightly fuzzy star or a faint patch of light. However, to fully appreciate its beauty, appropriate optical equipment is required.
The Andromeda Galaxy is classified as an Sb galaxy in Hubble’s classification or SA(s)b in the revised system, meaning it is a spiral galaxy without a central bar, featuring a medium-sized core and well-developed spiral arms. However, scientific reports from 2006 suggest that M31 may have a small bar, which would classify it as SAB(s)b. Additionally, Andromeda is categorized as a Low-Ionization Nuclear Emission-line Region (LINER), placing it in the most common group of galaxies with active nuclei.
The Andromeda Galaxy has a dense double core containing at least one black hole, at least two spiral arms accompanied by a ring of cosmic dust (which may originate from the smaller galaxy M32), and more than 450 globular clusters—some of which are among the densest known.
Interestingly, 14 dwarf satellite galaxies have been identified orbiting Andromeda, the most well-known being M32 and M110.
Observations
August 17, 2018 – Jaworzno (Poland), garden
urban conditions, high level of light pollution
The peak period for observing meteors from the Perseid meteor shower is slowly coming to an end, but that doesn’t mean the night sky above our heads has become any less interesting. On the contrary, late summer and early autumn provide excellent opportunities to observe many fascinating deep-sky objects. One of them is the Andromeda Galaxy.
The photographs below—both the original and its annotated version—were taken without the use of a telescope. I used an older Canon EOS 300D DSLR with a 250mm telephoto lens. The final image is a stack of 10 exposures, each with a 120-second exposure time, resulting in a total exposure of approximately 20 minutes (of course, for stacking purposes, the required number of dark and flat frames was also captured). This was my first photograph of this object, and unfortunately, it is somewhat blurry due to an accidental misfocus while adjusting the camera. Nonetheless, I have great sentimental value attached to this photo.
The photograph shows the Andromeda Galaxy, a beautiful example of a spiral galaxy. Its structural elements are clearly visible, such as the bright central bulge and the galactic disk. Dark bands within the disk (marked with arrows) are also noticeable. Additionally, two other extragalactic star systems—namely the dwarf galaxies M32 and M110—are distinctly visible. Both are satellites of the Andromeda Galaxy, orbiting around it. Slightly below is the star ν Andromedae (Nu Andromedae), a spectroscopic binary star whose components orbit their common center of mass with a period of just over four Earth days.
September 5, 2019 – Jaworzno (Poland), garden
urban conditions, high level of light pollution
Just over a year after my previous attempt at photographing M31, and having upgraded to a newer camera (Canon EOS 60D), I planned another session.
As seen, the image sharpness is significantly better, revealing more details of the galaxy’s structure and the dark lanes within its spiral arms. The longer exposure time helped highlight a greater number of details. The above photograph is cropped; the original image is presented below:
The view of this distant stellar system, suspended in an incomprehensibly vast cosmic void, never fails to make me ponder the mysteries of the universe.
Photo 1 Parameters:
- Total exposure time: 20 minutes (stack of 10 RAW frames at 120s each, using an appropriate number of dark, bias, and flat frames)
- Canon EOS 60D
- ISO: 2500
- Fake colors
- Lens: zoom type (used at fmax = 250mm)
- Aperture: f/4 (the smallest possible for the lens used)
- Mount: equatorial mount with tracking, aligned using the drift method and controlled by a custom-built system
Photos 2 and 3 Parameters:
- Total exposure time: 36 minutes (stack of 36 RAW frames at 60s each, using an appropriate number of dark, bias, and flat frames)
- Canon EOS 60D
- ISO: 800
- Lens: zoom type (used at fmax = 250mm)
- Aperture: f/4 (the smallest possible for the lens used)
- Mount: equatorial mount with tracking, aligned using the drift method and controlled by a custom-built system
Marek Ples