Messier 31, the Andromeda Galaxy: an exceptional image.
The Andromeda Galaxy, also known as Messier 31 and considered the Milky Way’s elder sister, is one of the most important astronomical objects in our sky. We are pleased to share with you an exceptional image, obtained with one of our telescopes.
Messier 31: a deep view.
The image above comes from the sigma clipping combination of 1269, 120-second unguided exposures, for a total of 42,3 hours, remotely taken with the ARTEC250+Paramount ME+C3Pro61000EC robotic unit available as part of the Virtual Telescope Project facility in Manciano, Italy, under the darkest skies of the Italian peninsula.
The huge number of frames used to get the final image above comes from the nova survey we run on the galaxy, which made possible for us to discover a nova candidate in Oct. 2023. It is worth nothing that not all the 1269 images used were of the same quality: at least 1/3 of them was taken with a bright Moon in the sky or under less than ideal sky conditions, so likely it did not contribute to the final result, being excluded by the software producing the integrated image.
Nonetheless, the final image is simply outstanding, honestly revealing the Andromeda Galaxy largely resolved in stars, thanks to the high definition of the picture. Also, some neglected features of the system are here very evident.
For example the satellite galaxy Messier 32 shows very well how its nucleus is off-center respect to its much larger, faint halo, which is clearly elongated off from M 31.
Messier 32 and its elongated halo.
Also Messier 110, on the upper left of our image, is very interesting, showing the dark dusty clouds close to its nucleus, one of the unusual features making this galaxy a peculiar one.
Messier 110.
The Andromeda Galaxy is the most distant object we can see in the sky by unaided eye, under dark skies. It is placed at about 2.5 millions of light years, so looking at it we are looking back in time of 2.5 million of years, that is at the beginning of human evolution.
While visible to the naked eye, the first record of the object as a “little cloud” came around 964CE from the Persian astronomer al-Sufi and only 650 years later the German astronomer Simon Marius described it after looking at the object with a telescope. In 1764 Charles Messier added it to his famous catalogue as the 31st object (hence Messier 31), while about twenty years later William Herschel estimated Messier 31 to be 2000 more distant than the star Sirius, so obviously inside the Milky Way. In 1850 Lord Rosse reported a spiral structure.
Messier 31 has been considered for a long time part of our home galaxy, the Milky Way, even if in the mid-XVIII Century philosopher Pierre Louis Maupertuis conjectured it could be a “island universe”, accordingly with the ideas of Immanuel Kant and about one century later spectroscopy showed it could not be a gaseous nebula.
Messier 31 became a galaxy, in the sense of an outer system, similar (actually larger) to our Milky Way just 100 years ago, at the end of the famous Great Debate between Harlow Shapley (supporting the idea M31 was part of the Milky Way) and Heber Curtis (supporting the extragalactic nature of M31, a galaxy by itself ).
Thanks to the observation of Cepheids in M31, one century ago Edwin Hubble estimated the distance of the object in about 1 million of light years: even if 2.5x times less than the recent estimates, it definitely placed M 31 outside the Milky Way.
The first Cepheid discovered by Hubble in M31 in 1923.
In 1943 Walter Baade detected the stars in the central regions of the galaxy.
It is incredible how much an astronomical object like the Andromeda Galaxy can tell about history, science and philosophy. We are happy that, thanks to such an exceptional image, we could remind us about those important accomplishments by those great scientists.
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