We cannot see our own Galaxy – the Milky Way – from the outside, and there is nothing we can do about it. But we can look at other galaxies – more or less similar to our star city, and draw indirect conclusions about its structure. Fortunately, there are plenty of galaxies around us suitable for such study.
One of these galaxies – very similar to the Milky Way, at least in appearance, is the M100 galaxy, also known as NGC 4321, or as the “Mirror Galaxy” (“Mirror Galaxy” – not to be confused with the popular smartphone from Samsung!)
If someone intelligent from the M100 galaxy and equipped with a suitable optical instrument looked in our direction, it is quite possible that they would see the same thing that we see – practically their own reflection (perhaps that is why they called this galaxy “Mirror”). But it is worth making a clarification that our Galaxy is slightly more populated with stars (more than 200 billion) than its “mirror image” (about 100 billion stars). But both galaxies are almost equal in size – about 100 thousand light years across.
M100 has an intermediate position between those galaxies that we consider close and those that are considered already very distant. There are approximately 55 million light years of intergalactic void between us. But still, from such a distance, the astronomer was able to resolve the outer regions of the spiral arms into individual stars, and find among them several variable stars – Cepheids, and from the Cepheids they were already able to determine the distance to the “Mirror Galaxy”. It does not correspond to the one previously determined by its redshift – the error was approximately 2 times. And this once again warns us that the speed of galaxy recession is a universal trend, and not a strict law, and we can only rely on this amazing phenomenon on a metagalactic scale.
Looking at the M100 galaxy, we see one of the largest galaxies in the Virgo cluster, although cartographically this galaxy is located in the constellation Coma Berenices, but not far from the border with Virgo, and galaxies and their clusters know nothing about our constellations and their boundaries, because all the stars of our constellations belong to our Galaxy – the Milky Way. It turns out that all other galaxies are located behind all the constellations… but this is, well, a philosophical digression.
There is another cluster of galaxies in the constellation Coma Berenices – it is even called a Supercluster. But it is several times farther from us than the Virgo cluster (which contains the heroine of today’s story – the M100 galaxy), and is several times more populated by galaxies that, in ground-based and space telescopes, no longer break up into individual stars – they are much more difficult for us to study . And the galaxies of the Virgo cluster (and in particular the “Mirror Galaxy”) are still quite easy to study. And this is not surprising, because we ourselves—the Milky Way Galaxy and the surrounding Local Group galaxies—also belong to the Virgo cluster. True, it is believed that we “live” on the very edge of this agglomeration of star cities.
The M100 galaxy has been known to humanity for just over two centuries. Its discoverer is considered to be the French astronomer Pierre Mechain, who was only a month ahead of Charles Messier with the discovery of this nebulous-looking object. For telescopes of that time, this was an object close to the limit of visibility. And for a long time, astronomers could not discern anything but a foggy spot here. Nowadays this galaxy is accessible for observation with the simplest telescopes. But to discern its spiral structure, you need a professional instrument, and dividing it into individual stars (and then only in places) is only possible with such powerful observational instruments as the Hubble Telescope and the James Webb Telescope.
However, over the last century, this galaxy has pleased astronomers with numerous supernova explosions, which provided additional information about this galaxy and made it possible to clarify the distance to it. According to various sources, during this period from 5 to 7 supernovae were observed here – this is almost a record frequency of outbreaks… although this may just be luck.
At the same time, the galaxy M100 has very high nuclear activity, which apparently indicates the presence of a supermassive black hole. According to some estimates, its mass can be about 5 million solar masses – this practically corresponds to the mass of the black hole that exists in the center of the Milky Way. But our galactic black hole is “dormant,” and the “mirror” one has awakened and is actively absorbing interstellar gas and dust, partially spewing it outward, creating a strong “stellar wind” that drives a shock wave ahead of itself. The immediate consequences of such activity are very active star formation (maybe that’s why there are many supernovae in a row – this is an echo of its beginning, when many suddenly born giant stars have already completed their stellar journey). The more distant consequences of the activity of the galactic core will lead to the depletion of hydrogen in the “Mirror Galaxy”, and star formation in it will come to naught.
The M100 galaxy has at least two companion dwarf elliptical galaxies, which makes it similar to the Andromeda Galaxy. Although, in this case, most likely, these satellites in the past had their own spiral branches, but were mercilessly gnawed by the strong gravity of the “Mirror Galaxy”.
Videoattached to this post, is based on amateur astrophotography by Drew Evans (Drew Evans). This photo is recognized “best astrophotography of the day” May 2, 2024.
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