The constellation Unicorn (Monoceros-Mon)

The name, the story, the myth


The constellation of the Unicorn was introduced by Jakob Bartschius, or Bartsch, son-in-law of Kepler, in 1624 although some believe that Plancius already introduced it in 1613 with the intention of raising to heaven the famous animal with the only horn, synonymous of purity and often mentioned in the Bible.


In his Bestiary, Guillaume le Clerc (13th century) informs us that to calm and capture the Unicorn, the presence of a virgin was necessary. The unicorn was also seen as a symbol of Christ, her horn would represent the truth of the Gospel. The animal, probably a rhinoceros whose description has been loaded with symbolism, is mentioned - as said - in the Bible, 3rd century BC, with the Greek translation of the Old Testament. When the scribes had to translate the word re' em, they coined the neologism monoceros. In fact, both Ideler and Olbers suggested that the constellation was older, and that Plancius had merely traced a presence already found in Persian sky maps. The origins of the Unicorn are therefore to be found in the East, more specifically between India and China. An ancient description of the Unicorn is in fact found in the great book Li-Ki together with those of the turtle, the Dragon and the Phoenix considered beneficial creatures. Since many centuries ago, Li-Ki describes the Unicorn in a very different way from how it is depicted now: its features are those of a big deer with a five-coloured back and yellow belly; it has the hooves of a horse, the tail of an ox and a big horn on its forehead. A first probable representation of the Unicorn can be found in an animal inside the Caves of Lascaux in France dating back to the Upper Palaeolithic, in which a very long horn can be found on the head and hair under the snout.


A mythical animal

The unicorn is an imaginary animal, practically a horse, usually white, with a horn in the middle of its forehead: it is also called liocorn and is found in some heraldic coats of arms. In short, an animal linked to not very well known traditions that see it as a symbol of generosity and strength. My contribution: a unicorn appears in the science fiction masterpiece Blade Runner , once as origami built by policeman Gaff and another time (but only in a particular version) live, in the form of a dream by policeman Deckard (the mythical Harrison Ford).

On the subject Blade Runner I could talk for hours and hours, but duty calls me and then we discover first of all, for those who do not know, where the Unicorn is in the sky: thanks to Stellarium we see that it is in an area of the sky poor of bright stars, but surrounded by sacred monsters, represented by Orion, the Greater Dog and the Lesser Dog and Gemini. Once you understand where it is (practically next to Orion), you don't forget it anymore, but unfortunately it doesn't have particularly flashy stars. We will discover later on that, even if it is quite big as a constellation, it doesn't have any star named with an Arabic, Greek or Latin name, apart from three names that I found on the internet, that I had never heard before and that I will talk about later: all its stars have at least a magnitude equal to 4 and therefore they are already invisible in the bright city skies.


Unicorn representations

The constellation Unicorn was created in the 17th century and therefore, compared to other constellations, is more modern, so much so that we do not find a representation of it in Bayer's Uranometry, prior to the creation of the Unicorn itself.
Hevelius, on the other hand, represents it upside down as usual, but we have no problem turning it over.

Finally the very modern version given by Stellarium

In both cases there is nothing to add: the mythical animal is correctly represented as a horse with a long horn on its forehead: the more difficult it is to see the drawing of the constellation. Maybe also this time H.A.Rey has seen us right, as long as we can see (always with a good dose of imagination) a unicorn with the neck turned towards us.

Few big stars


Well, as usual I joked... but now let's go back seriously to see if and how many big stars there are in this poor constellation: from the diagram beside we see that above 40 times the Sun's ray there is a train of stars of various spectral class: 13 and γ Mon (we read monocerotis) with 57x, ζ Little smaller Mon with 51x, 17 Mon (of spectral class G like the Sun, but 47 times big) and 28 Mon with 45x, which however is bigger than the famous Aldebaran. But in addition to these stars, there is a particularly mysterious one, since it has had a rather unique and anomalous behavior over the years, exploding like a nova, but re-exploding other times. Mystery? Let's hope Jakob doesn't find out...


A mysterious celestial body

I'm talking about the variable star V838 Mon, until then an anonymous fifteenth star, exploded in February 2002 as a nova (and therefore immediately called Nova Monocerotis 2002), reaching 7: after a while the brightness started to weaken, as it happens in these catastrophic cosmic events. But the strange thing is that a month later it re-exploded, emitting this time in the infrared, and then it re-blown again. But that's not enough: in April there was a third explosion, once again emitting in the infrared, which was followed by the usual fading and it all ended there, with the return of the star to its initial brightness.
This absolutely unusual behavior has given a lot to think about Astronomers, from some of which almost science fiction hypotheses have been put forward.

Among other things, its diameter was measured using interferometric methods and was found to be more than 1500 times that of the Sun, so the diagram of what our Solar System would look like with this supergiant, spectral class L, instead of the Sun, is immediately taken. This star has been the object of continuous monitoring by NASA scientists through the magnificent Hubble Space Telescope: the photos showed that over the years a so-called light echo, emitted by the star at the time of the explosion, hit clouds of surrounding interstellar matter that thus began to reflect this light, producing a sort of luminous ring that expands over time. Bringing together these photos as a sort of time-lapse covering a few years, NASA scientists have produced this film so beautiful that it leaves one speechless:

click to see the movie of the evolution of V838 Mon in high resolution

There would be a lot to talk about about this celestial body, especially for the various particularly complex models that could explain the mysterious behavior: for now I don't want to go too far from the trace of the article.

Nebulae and galaxies in the Unicorn


Let's go now to see some wonderful images (very big!) of DSO objects present inside this constellation that, started quietly with a few bright stars, then exploded (it's worth saying!) gaining a good score!
Could a beautiful open heap be missing? Absolutely not! In this case it's M50.

Famous instead is the object we see now, the Rosette Nebula...

Now let's move on to the Christmas Tree Cluster, whose name seems to be right.

The tip of the Christmas tree, upside down, is the so called Cone Nebula, which we see here in super-detailed

The names of the Unicorn stars


I was saying before that this constellation has never received official names assigned to its stars. I found three names on the internet here and there, and I'm quoting them here for the record.

  • GlossyMon): from Latin, with obvious meaning, even if not really real, given the poor brightness of the star.
  • CerastesMon): from Latin, horned, term associated with the fearsome and supple snake called the Horned Viper
  • TempestrisMon): from Latin, but difficult to interpret, given the meaning of storm

The Unicorn in the sky


The Unicorn appears on the eastern horizon in mid-December, at 9 p.m., and then it will be visible for the next six months: it will be on the western horizon in mid-May. Instead, at the end of February, the constellation culminates in the sky at one on the horizon of more than 40 degrees. However, the suggestion remains valid to search for it in the sky starting from the much more famous and visible Orion, right next to it and preceding it at all times.



Audio Video The constellation Unicorn (Monoceros-Mon)
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