M31: A Deep Dive

M31, the Andromeda Galaxy, is one of the most stunning objects in the night sky and is the closest spiral galaxy to our own Milky Way. Located just 2.5 million light-years away in the constellation Andromeda, it spans over 220,000 light-years in diameter—making it larger than our galaxy. This image captures its bright core, intricate dust lanes, and even some of its satellite galaxies, including M32 and M110. Andromeda is unique in how large it is due to it's proximity. This annotated image shows the many other galaxies present in the photo.

Remarkably, this image was captured from downtown Guelph in our very own Bent Nail Observatory. We do have significant light pollution. Despite these challenging conditions, the use of careful imaging techniques and narrowband filters allowed me to cut through the urban glow and reveal the fine structure of Andromeda.

To create this image, I collected a total of 346 x 3-minute exposures for the RGB data and an additional 621 x 5-minute exposures, plus 13 x 10-minute exposures for narrowband data, using Hydrogen, Sulfur, and Oxygen filters. This lengthy integration time allowed me to pull out the fine details, such as the vibrant regions of star formation and the delicate structure of the galaxy’s spiral arms.

With the narrowband filters, I was able to highlight the galaxy’s H-alpha emission regions, which trace areas of intense star formation. These regions, visible as faint pinkish hues across the arms, reveal ongoing stellar birth in Andromeda. The sulfur and oxygen data add depth and highlight the different processes at work within the galaxy.

Andromeda’s proximity and size make it a popular target for astrophotographers, but what makes this image particularly special is the integration of both broadband and narrowband data, which brings out the richness of the galaxy’s structure. The narrowband data, often used for nebulae, is especially effective in isolating emission regions, giving us a more detailed view of Andromeda’s activity.