A Stunning Portrait of Messier 31: Exploring the Marvels of the Andromeda Galaxy

The Andromeda Galaxy, also referred to as Messier 31 and regarded as the elder sister of the Milky Way, is among the most significant celestial objects visible in our sky. We are delighted to present to you an extraordinary image, captured using one of our telescopes.

The image displayed above is the result of the sigma clipping combination of 1269 unguided exposures, each lasting 120 seconds, totalling 42.3 hours, remotely captured using the ARTEC250+Paramount ME+C3Pro61000EC robotic system available at the Virtual Telescope Project facility in Manciano, Italy, under the darkest skies on the Italian peninsula.

The substantial number of images utilized to produce the final image above stems from the nova survey we conducted on the galaxy, which enabled us to identify a nova candidate in October 2023. It is important to note that not all 1269 images employed were of identical quality: at least one-third were taken with a bright Moon in the sky or were under less than optimal sky conditions, thus likely not contributing to the final outcome and being excluded by the software that generated the integrated image.

Nevertheless, the final image is absolutely remarkable, vividly showcasing the Andromeda Galaxy richly populated with stars, owing to the high resolution of the photograph. Furthermore, certain previously overlooked features of the system are now very clear.

For instance, the satellite galaxy Messier 32 clearly illustrates how its nucleus is offset in relation to its much larger, faint halo, which is distinctly elongated away from M 31.

Moreover, Messier 110, located in the upper left of our image, is quite intriguing, exhibiting the dark dusty clouds close to its nucleus, which are among the unusual features that make this galaxy unique.

The Andromeda Galaxy is the furthest object observable with the naked eye, under clear skies. It is approximately 2.5 million light-years away, thus when we gaze at it, we are peering back in time by 2.5 million years, to the dawn of human evolution.

Though visible to the unaided eye, the initial record of the object as a “small cloud” dates back to around 964 CE by the Persian astronomer al-Sufi, and it was only 650 years later that the German astronomer Simon Marius described the object after observing it through a telescope. In 1764, Charles Messier included it in his well-known catalogue as the 31st entry (thus called Messier 31), while about twenty years later, William Herschel estimated that Messier 31 was 2000 times more distant than the star Sirius, thus clearly placing it outside the Milky Way. In 1850, Lord Rosse noted a spiral structure.

Messier 31 has long been viewed as part of our home galaxy, the Milky Way, even though in the mid-18th Century, the philosopher Pierre Louis Maupertuis speculated that it could be an “island universe,” in alignment with the ideas of Immanuel Kant. Roughly a century later, spectroscopy demonstrated that it could not be a gaseous nebula.

Messier 31 was classified as a galaxy, in the sense of an external system, akin to (actually larger than) our Milky Way, only about 100 years ago, following the conclusion of the famous Great Debate between Harlow Shapley (who supported the idea that M31 was part of the Milky Way) and Heber Curtis (who advocated for M31’s extragalactic identity as a standalone galaxy).

Thanks to the observation of Cepheids in M31, one century ago, Edwin Hubble estimated the distance to the object at about 1 million light-years: although this was 2.5 times less than contemporary estimates, it certainly established M 31 as separate from the Milky Way.

In 1943, Walter Baade observed the stars in the core regions of the galaxy.

It is remarkable how much an astronomical entity like the Andromeda Galaxy can reveal about history, science, and philosophy. We are delighted that, due to such an extraordinary image, we can reflect upon those significant achievements by these great scientists.

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