Two circumpolar Australian constellations: Peacock and Male Hydra

The Peacock

the constellation Peacock

That it's a circumpolar constellation can be seen immediately from the figure on the side, made with Stellarium: it's attached to the constellation Octans, the one that contains inside it the South Celestial Pole and that practically represents the Lesser Bear of the southern hemisphere. The Peacock has inside it a certain number of near stars, below the threshold of 60 al (the limit distance chosen by me in these articles, because it is the one from which the Sun is no more visible to the naked eye, having the possibility to go near the star) and a small handful of quite big stars. It also presents some absolutely fantastic deep sky objects.


The name, the story, the myth


The Peacock constellation was introduced in 1603 by Johann Bayer, after having been studied by Keyser and established by Plancius between 1596- 1598.
There exists in Greek mythology, a singular association to which the European navigators of the Australian seas might have referred: Argos, besides being the mythological figure linked to the Peacock, of which we will speak, is also the name of the builder of the homonymous nava used by Jason to perform the Golden Fleece. The antecedent of the myth of Argos is an illicit love, as often happens in Greek mythology, of Zeus. After loving IO, the father of the gods, he mutates the girl into a white heifer, in order to save her from the vengeance of Hera (Juno), his wife. His wife suspected it, however: she asked Zeus for the beast as a gift, and he could not refuse her. I was then entrusted to the care of Argos, a hundred-eyed monster called Panopte, the "all-seeing". To save her, Zeus turned to Hermes (Mercury), who put Argos to sleep with the sound of his lyre, and as soon as the last of his hundred eyes closed and the guardian slipped into sleep, he beheaded him. She was regretting then revives Argo in a peacock, and places his eyes in her tail.



In the Uranometria the peacock was represented with the usual tail

the Peacock in Uranometry

and of course we find the same thing in Hevelius...

the Peacock according to Hevelius

and in Stellarium: here you can verify what I was saying before. Maybe they could have drawn the peacock in a mirror-like manner

the Peacock according to Stellarium

Before moving on to the analysis of the particular stars contained within the constellation, I leave the floor to Silvia Pascucci

Big and near stars

The Peacock has within it three stars placed at a distance of less than 20 al, plus two others a few more distant. The closest is the star SCR 1845, class M8, placed at a small distance of 12.6 al from the Sun: my friends Scriteriati say that our star (of 3rd magnitude) is in a star $campo$ poor of bright stars, where Alpha Centauri and Capella appear. In this photo taken with Celestia we have the confirmation.

The other two nearest stars in order of distance are Gliese 693 (class M3, at a distance of 19 al) and δ Pav (class G5 at a distance of 20 al): from these two stars the Sun is obviously weaker (3a and 4a ) and is in practically the same $stellar range$ already seen. My English and Deltapavi friends didn't take offense for ignoring them, in favor of my peacock friends: from their star, γ Pav, class F6 and placed at a distance of 30 al, our Sun is almost 5a , this time in a star $field that is a sort of mini-planetarium, since it contains Capella, Pollux, Big Bear stars, but also Raccoon and Sirius. My friends are proud of it and that explains their name.


The last star of the group is ι Pav, class G0 like the Sun, at a distance of 57 al and from this star the Sun is no longer visible to the naked eye, in an area of the sky where there are Sirius, Capella and the pair of Gemini, Castor and Pollux: this is the photo I took when I went to visit my friends Pavioti, who discovered our Sun only a few years ago with their cheap telescopes to say the least.

peacock star comparison diagram

In the comparison diagram between the stars of the Peacock and other more or less known stars, we find a big star (ο Pav, class M, with a diameter of 124 times that of the Sun), three stars of class K (like the poor Aldebaran, with whom I always make the comparison), ξ Pav (79 times), ω Pav (39 times) and η Pav (36x), while I added κ Pav, a star of class F5, almost as big as the most famous star of Taurus. In this picture you can see the decidedly threatening appearance of the red giant ο Pav from a distance of 10 UA, which my Opavidi friends fearlessly observe from their planet placed at a safe distance from the star.

Deep sky objects

In this constellation of the deep south celestial deep sky there are very remarkable deep sky objects: start with the globular cluster NGC 6752


the globular cluster NGC 6752

and then move on to two interacting galaxies: NGC 6872 (which they say resemble the integral sign, , but mirror) and IC 4970, respectively with a crossed and elliptical spiral.

the galaxy NGC 6872 and IC 4970, which are interacting

After two interacting galaxies, here are three of them, caught in their phase of interaction: they are IC 4687, IC 4689 and IC 4686.

the three galaxies IC 4687, IC 4689 and IC 4686.

We now move on to a spiral galaxy, the NGC 6744...

the spiral galaxy NGC 6744

Finally we see a barred spiral galaxy, the NGC 6782, really beautiful

the barred spiral galaxy NGC 6782

Star name

Let us now turn to names: here there is little to say except that only one star has received a name. It is the main star and the name is nothing but the English-speaking version of "peacock".

  • Peacock (α Pav): the peacock

The visibility of the constellation at our latitudes is null, as already said and then in this and similar cases the principle that if the mountain doesn't come to Mohammed, Mohammed goes to the mountain is valid...

It would be enough to organize a nice trip to Australia to study all the constellations that would otherwise remain unknown. It's easy, isn't it?

The Male Hydra

the constellation of Male Hydra

Also this constellation is bordering Octans, so also in this case we are dealing with a zone of sky absolutely invisible at our latitudes. Looking at the photo of the constellation made with Stellarium, you can be perplexed in trying to understand the shape of the object obtained by joining stars, in this case not too weak (3a ) : an important factor is that the constellation is located between two white balls that we know are the LMC (Large Magellanic Cloud) on the left and the SMC (Small Magellanic Cloud) on the right, respectively in Dorado and Tucano. So, having the possibility to observe the southern sky live, once the two clouds have been spotted, the Male Hydra is exactly in the middle of the two... if one knew what a male hydra is...

It's soon said! In simple terms it is a sea serpent, Hydrus in Latin, so, as in the case of Hydra or Eridanus or the Dragon or the Snake, it is easy to find our good sea serpent in a sequence of stars (otherwise chaotic) .

The closest of the two, β Hyi, is of class G2 exactly like our yellow dwarf, with a diameter equal to 1.8 times that of the Sun, all at a distance of only 24 al from us. What better occasion to visit my friends Betàidri ? They live on a planet rich in water, air, clouds, smog, pollution, which they call Betàterra... The whole world is a country, isn't it?

In their nights, the Sun, which they call Betàsole (be careful to always accent the "a", otherwise they get offended) is a star of 4a in a zone of sky where there are stars very well known to us, the Betàpolar, Betàalfa Betàcentauri (I forgot that their tongues do not twist as to us in pronouncing these names, since they are without them) and other stars of the Betàorsa Betàmaggiore as well as Betàminore. Up there on the top left appears, in this purely boreal sky, the well known Betàsirius, the Betàalpha star of the Betàcane Betàminore. Who knows where is Betàbetelgeuse. Amazing.

The second nearby star is GJ 3021, class G8, placed at 57 al from our Sun: my friends Giottoni, skilled both in painting and music, sent me this picture, in which you can see the Sun in a zone of sky where, together with the stars just mentioned (but called in a different way) appear other known stars such as Giottopolluce, Giottocapella, Giottovega and Giottoaltair, this time pronounceable without strange accentuations. Can you guess what they call our yellow dwarf?

The name, the story, the myth


The constellation Hydrus, male Hydra, was one of the constellations formed by Petrus Plancius, starting from the drawing up of the maps of the three Dutch navigators Pieter Dirkszoon Keyser (also known as Petrus Theodorus, Plancius' pupil cartographer who personally commissioned him to map the southern sky) and the brothers Cornelius and Frederik de Houtman, who between 1595 and 1603 embarked on two expeditions, reaching the East Indies. Vechter Willemsz also helped with the mapping. It is said that Keyser observed from the crow's nest with an instrument entrusted to him by Plancius. Keyser died during the return voyage (1596), and it was de Houtman who delivered the work to Plancius. The cartographer developed and published a new celestial catalogue in which 135 stars appeared, divided into twelve new Australian constellations, including the Hydrus. The cartographer Jodocus Hondius inserted in the globe studied by him the new constellations, it was 1598. Two years later, in 1600, the astronomer Willem Blaeu, Tycho Brahe's assistant, brought back in his globe the twelve constellations. But thanks to the adoption of Johann Bayer in 1603, in his "Uranometria", the final consecration took place. It is not surprising if this group of stars lacks the mythological link, as is the case of the female Hydra. Bayer wanted to consider it as a complement of the ancient constellation of the female Hydra, the southern part of the long constellation. Or the cartographer would have taken advantage of the proximity of this group of stars to the constellation Eridanus, dedicated to the river, placing in its proximity an animal familiar to that context.

Its inscription inside the catalogue and on the previous globe of 1598, was under the double wording (Dutch/Latin) of Whaterslange/Hydrus, both with the meaning of "water snake". From some studies it would seem that the constellation was also called Hydrus Polaris, since it included the nearest star to the celestial south pole (today a star merged with the constellation of Octant, lambda star).

Two medium-large stars

Male Hydra star comparison with other notes

From the comparison diagram between the stars of the Male Hydra and other known and other decidedly enormous stars, two class M stars appear, π1 Hyi and γ Hyi, having a radius respectively 74 and 68 times that of the Sun: accustomed to three-digit values, these monsters look like normal stars. On the contrary, the 74x of π1 Hyi allow this star to be even bigger than the mythical Rigel and my Morenidri friends are really proud of this, so much so that this star (from them of 0.28) they call it "Rigel χ6".

π1 Hyi view from 10 UA

At first I didn't understand either, but then, if you read it better, you can see that the name reads "Rigel who you are". Reflecting better, their sun, dazzling even from 10 UA, irradiates their planetary system with its reddish light and with radiations entering their 4 brains, creating tangible consequences: think that their race is called Quadcore.

Other news

Among the deep sky objects present in this constellation, we see first of all NGC 1511, a barred spiral galaxy visible almost of shear

the spiral galaxy NGC 1511

then we move on to the globular cluster NGC 1466.

the globular cluster NGC 1466

and finally we see the irregular galaxy NGC 1473

the irregular galaxy NGC 1473

As always, we can see how the Male Hydra was represented by Hevelius

the Male Hydra according to Hevelius

and how it is depicted more modernly by Stellarium

the Male Hydra according to Stellarium

I conclude the analysis of this little known constellation, saying that none of its stars has been baptized neither by the ancients nor modernly (don't let the nice Betàidri know it...) : I repeat that being austral circumpolar it is never visible at our latitudes.



Audio Video Two circumpolar Australian constellations: Peacock and Male Hydra
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