The constellation Hercules
It is a constellation well visible in our skies thanks to the presence of several stars bright enough even for our cities: in the beautiful summer evenings we find it high on the horizon, very easy to find thanks to that lighthouse which is the star Vega of Lyra, next to which this constellation extends.
The name, history and myth of Hercules
Heracles, Hercules for the Romans, is the most popular of the Greek heroes, protagonist of numerous myths, if you will, of an entire saga! The association of the constellation with the figure of the hero begins from the 5th century BC. Before him, these stars were dedicated to Gilgamesh, the central character of the Babylonian creation myth, who at the end of the 4th millennium B.C. appears to rest on one knee, with his foot on the Dragon's head.
Ploughed cites it as "the kneeling."
In Greek mythology, Heracles is an immensely brave and good hero, but also naive. Son of Alcmena, a mortal, with whom he lay under Zeus' deception. Known for his extraordinary strength, to him Eurystheus, king of Tiryns, his cousin, assigned twelve labors, inspiration, among other things, of many constellations in the sky (killing the Lion of Nemea; fighting against the Hydra of Lerna, where we find Cancer; capturing the doe Cyrenea; hunting the boar of Erimanthus; cleaning in one day the stables of Hope; exterminate the birds of the swamp of Stinfalo; tame the Bull of Crete; do the same with the carnivorous mares of Diomedes; conquer the belt of Hippolyte, queen of the Amazons; seize the oxen of the monster Gerione trimembre; steal the golden apples of the Hesperides and finally capture Cerberus, the monstrous dog guarding the entrance to the Underworld). Hercules killed Nexus, a centaur who was very interested in his wife Deianira. Nexus, dying, advised Deianira to make Hercules wear his shirt, with the promise that this would guarantee the perennial loyalty of the hero.
It was a trap: the blood of Nessus on his shirt was a poison for Hercules, who died. His father, who according to legend was Jupiter, raised him to heaven as a constellation.
Another character of Greek mythology seems to have been linked to this constellation, for a short time, and in a part of ancient Greece, Atlas, kneeling in the canonical pose that sees him holding the world.
And again, Tamiri was seen there, kneeling in an act of supplication, after being blinded by the Muses.
Also the myth of Orpheus seems to be linked to this group of stars, and in particular, we cite Ission, represented here, with his arms tied, however, in the representations that have come to us, punished because he had tried to rape Hera.
Going back to Atlas, according to some studies of the history that was associated with these stars, there was a real choice between these and Heracles. The fact that is represented a human figure in triumphant attitude over the constellation representing the Dragon, doesn't contrast with the story reported in the myth: it was in fact Atlas, and not the hero, in the most known version, to perform the action that determined the success of the eleventh effort, to fight against Ladon, placed to guard the Hesperides' knobs.
As I've already done in similar situations of constellations with many stars nearby, also in this case I organized the 10 nearest stars in a table where next to the name, distance and spectral class, I added a link, which always characterizes the articles of this category. You already know that this is the link that opens an image made with Celestia, in which the objective is the Sun, as you could observe while traveling close to the star in question: we can do it thanks to our virtual spaceship, through which I can go to visit my (unlikely) astronomer friends scattered in the universe. Maybe in a few millennia our descendants will be able to go in person and finally they will be able to verify what is reported in these pages... And then they will say: Pierluigi was right!
Our Sun, starting from a magnitude almost equal to 4 (if seen by my friends Seicentosessantuniani) to go down to the limit of visibility to the naked eye (for my friends Chiercoli, always very doubtful), is located in an area of the sky where the brilliant Sirius is always present, accompanied in some cases by the star Vega, thanks to the fact that these two stars are also close to the Sun and for a game of three-dimensional perspective can appear close if observed at the right angle.
In particular with my friends Novantanovercolini (also called Biercoli), we can see in the same area of the sky a mixture of known stars (Vega, Altair, Sirius and some stars of the Poppa della Nave), which are scattered here and there in our sky: also this time we find them all very close to the Sun, thanks to a complex perspective game in 3 dimensions, real, that only thanks to Celestia we can appreciate.
The constellation of Hercules presents as many as 16 very big stars (over 45 times our Sun, of which 7 times over about 100 times): our comparison diagram this time is really chaotic for the presence of many red giant stars, accompanied by some K class stars and a blue giant. On all of them stands a red supergiant (no less than the α1 Her, Ras-Algethi) with a diameter of 419 times our poor yellow dwarf: we can see it at the top left, submerged by other smaller sisters and we can barely see its edge. Just think that the writing α1 Her 419x is placed more or less in the centre of a circle representing its extension: can you see it and imagine it outside the diagram?
The star in question, a true stellar monster is a double star, 3.35 (according to Stellarium, but 2.79 according to Celestia) and is located 382 light years away from us: if only it were closer, it would shine brightly than a red light in our skies... But how bright would it be? Do you want us to try to bring it closer to us?
Just for fun, thanks to Celestia's great flexibility and hoping not to make mistakes, I tried to approach her gradually to see the effect she does: already at a distance of 100 light years she would shine 0, while approaching her even more (at 30 al) she would have a -2.7, becoming by far the brightest in the sky (ousting Sirius, stopped at -1.45).
But I dared even more! I even brought it closer to 4.2 to the distance, the same of α Centauri: and then it would shine in the sky of an intense red light, much more than Venus, with a magnitude equal to -6.88. Fantastic! In fact, science fiction!
In this photo, among other things, you can see a well-known night lighthouse, Vega, up there on the top left, in the constellation of Lyra: look how it would disappear compared to this red light in the sky!
Let's see now how this star monster looks immense from the distance I've always used in these cases, 10 UA: its reddish-orange light is really dazzling and the star has an apparent diameter of almost 19°. Allow me my usual digression: it's not for nothing that my Ras-Algetian friends are famous for their beautiful tan, even though their Ras-signed planet orbits several astronomical units from their star.
Coming back seriously, I said that the big stars of Hercules are 16: so I had to collect them in a table, containing their size, name (clickable, to open the photo of the star seen by 10 UA) and its spectral class.
We see therefore that the following stars, by order of magnitude, are g Her, with a diameter of 152 times, 10 Her, with 130 times and 98 Her with 124x , really all of them are monsters, but if we look well not even 2 Her, 104 Her and 61 Her are to be underestimated having a diameter that goes from 91 to 94 times the diameter of the Sun... Going down in size, in this sea of red supergiants, we find θ Her of class K1 (in whose photo we have a chromatic sensation different from the other stars) and 89 Her, of class F2, that from 10 UA shines of an intense and dazzling whitish light, presenting on the celestial vault a diameter of little less than 3°.
We cannot fail to notice at what point in the "little train of stars of Hercules" the famous Rigel stands: on a par with any 105 Her (a little star that we see of 5.3 because it is 1279 light years away from us, while Rigel appears 0.15, because it is placed at 772 al). The very famous Aldebaran , poor thing, always remains at the bottom of the list with a diameter of "just" 33 times our Sun!
Deep Sky objects
After this binge of photos, numbers and magnitudes, let's enjoy the other show of celestial objects farther away, absolutely wonderful, thanks to the photos taken by the powerful Hubble space telescope.
Let's start with the very famous and already mentioned M13, a globular cluster, already well visible even with a good pair of binoculars, but that the HST shows in all its splendor (remember that clicking the picture you can have a higher resolution)
The world-famous star cluster M13
Another globular cluster, perhaps even more beautiful, is M92 (catalogued by the astronomer Messier) that here we see in all its splendor
Star cluster M92
Finally I would like to show you a beautiful spherical planetary nebula called Abell 39: really breathtaking!
The Abell 39 Nebula
Representation over time
We have arrived to the overview of images that show the constellation of Hercules as it was represented in the past: in the Uranometria
Hercules had a very long hair and a small club. Hevelius, on the other hand, showed him much older, with little hair and a longer club.
For Stellarium instead Hercules is definitely younger and the club has become a small axe
The names of the stars
We now come to the list of the names of the stars of Hercules and their meaning. I found a lot of these names on the internet, but frankly I've never heard of them:
- Rasalgethi (α Her): Arabic name, the head of the kneeling person
- Kornephoros (β Her): name meaning the one who wears the club
- Biceps (γ Her): found on the internet
- Sarin (δ Her): unknown meaning
- Rutilicus (ζ Her): found on internet
- Sophian (η Her): found on internet
- Rukbalgethi Genubi (θ Her): the southern knee of the kneeling
- Rijl al Jathiyah (ι Her): found on internet
- Marsik (κ Her): the elbow
- Masym (λ Her): the wrist
- Marfak Al Jathih Al Aisr (μ Her): found on the internet
- Beraka (ξ Her): found on internet
- Fekhiz al Jathih al Aisr (ο Her): found on internet
- Fudail (π Her): found on the internet
- Rukbalgethi Shemali (τ Her): the northern knee of the kneeling man
- Cujam (ω Her): the club
The visibility of the constellation
This constellation is very well visible in our skies, high on our heads. At 9 p.m. it is on the northeastern horizon, ready to ascend into the sky, already by mid-March. It culminates high in the South, passing right at the zenith, for the whole month of August and finally it is on the north-western horizon between the end of November and the beginning of December.
In short, a clearly visible constellation, which in summer gives a lot of torticollis to those who observe it!