A constellation almost upside down
Lyra is a constellation that accompanies us on hot summer nights, recognizable by that nocturnal beacon that is the shining Vega. In some cases it reaches almost the zenith, so the torticollis is assured, unless we lie down on the ground, perhaps on the beach, to admire the sky, dominated (where there are not too many lights) by the Milky Way. Vega is very bright (of magnitude 0) and is one of the nearest stars to the Sun (just 26 light years, just around the corner if we think of the cosmic stairs) and this has given rise to tales of inevitable aliens and science fiction stories among which I always remember with pleasure the book first, which became a film later, by the unforgettable Carl Sagan, "Contact".
To those who have wondered why the title is so strange, I answer that we will discover it together: the sky is full of wonders but also of apparent paradoxes that are discovered only by doing certain studies or considering factors and situations usually overlooked.
The name, history and myth of the Lyre
The Lira in question refers to the musical instrument, the first of its kind built by the young man Hermes (Mercury) on Mount Cyrene, stretching cow guts over a turtle shell through ram's horns. His sound was so sweet that he could calm anyone, including Apollo, from whom Hermes stole the cattle, and whose wrath was quenched precisely by receiving the instrument in return.
Its strings according to the myth were seven, like the number of the Pleiades.
It was the instrument - given by Apollo (Hermes had stolen the nerves from Apollo's sacred oxen to build it, so to make him forgive him he gave it to them) - to his son Orpheus, born from the union with his muse Calliope, with whom he accompanied his splendid singing, able to make even stones move. Apollo gave the instrument to Orpheus, after having invented the Cetra.
Orpheus then descended into the Underworld to find his bride, the nymph Eurydice, killed by the bite of a viper. Hades (Pluto for the Latins), ruler of the underworld, and Persephone, his wife, moved to pity by the music of Orpheus and his lyre, gave him back his beloved, but warned him not to turn back and look at her until they had left the Underworld. But at the very last moment, Orpheus could not resist, turned towards Eurydice, and lost her forever.
The Arabs saw an eagle with closed wings, swooping. It is no coincidence that the meaning of the name of its alpha star, Vega, means "swooping eagle", but also "swooping vulture", apparently in reference to an Indian legend.
Another legend, dating back more than 2000 years, of Japanese and Chinese tradition, sees Altair, in L'Aquila, as a shepherd and Vega as a weaver. The two fell in love neglecting their celestial duties, she, Orihime was the daughter of the Emperor of Heaven and ruler of all the gods, Tentei, he, Hikoboshi, was a herdsman. Although their marriage had been arranged by Tentei, and the two of them saw each other for the first time on their wedding day, they were seized with such ardor and passion that they disinterested in their respective tasks, Orihime stopped producing the precious fabrics for divine clothing, Hikoboshi did not take oxen to pasture as he usually did, on the banks of the Heavenly River, he completely abandoned the cattle to himself. And for this very reason they were punished, they were sent from opposite sides of the Milky Way, so that they could never meet except on the seventh night of the seventh Moon, when a bird bridge crosses the Milky Way, seen as the Ama no Gawa River, allowing the two lovers to live together for a brief moment.
Let's start the engines
Since I'm talking about Vega, let's get ahead of the times, warm up the engines of our spaceship Celestia and get to know her better. And here comes the first partial disappointment: if we set ourselves at 1 UA (which I remember to be the distance of the Earth from the Sun), Vega appears to us very bright, blue, but definitely small compared to the monsters we've met in recent episodes. Let's read together: this star has a radius of just 2.7 times our Sun and therefore the fact that it appears so bright is due to its relative proximity to the Earth.
We already know, however, that such a small distance allows our Sun to be visible by Vegas astronomers: in fact, we see that our star shines 4.2 and is located in the sky in an area full of stars in our southern sky (above all Canopus, of -0.45, the brightest in those parts) with an intrusion by the famous star Sirius (a bit weaker, by 1.5), thanks to the fact that it too is very close to both the Sun and Vega (a little more than 33 light years) and therefore, always thinking of the sky three-dimensionally, it is easy to find it in other positions of the local sky.
Back to the title
As anticipated at the beginning of the article also this small constellation has some surprises in store for us: let's go back to the basic concept of "constellation". By this term obviously we mean a grouping of stars based on the tradition of centuries of observers who had to distinguish somehow one star from the others. All this has always been based on the brightness of stars: with very rare exceptions, the brightest star in a constellation is called α, the second β and so on until ω, the twenty-fourth. Then we moved on to numbers (the famous 119 Tau is an example), acronyms, etc.. But the basic concept is brightness, the only parameter that allowed to distinguish one star from another, apart the color.
As science and technology progress, parameters of evaluation, of classification of stars that were unimaginable until now, appear: among them we have for example the surface temperature, the spectral class, the size. My reasoning is based on the latter data, as it was obviously clear from the very first episodes: I certainly do not intend to create a revolution in the way we look at constellations, but I just want to emphasize an aspect that has never been sufficiently considered. The stars have a dimension of their own that is certainly fun as well as instructive to bring up and maybe look with a different eye at the stars, up there in the sky.
In the constellation of the Lira, if we base ourselves on the dimension of the stars we can notice some curious peculiarities: Vega is wonderful, every time I observe it together with the other stars I remain amazed by so much beauty of the nature. But if we analyze the dozen stars of Lyra from the point of view of size we discover that the α Lyr is even the smallest, with that value of 2.7 solar rays that we have seen previously. The Sheliak star, β Lyr is 31 times the size of the Sun, Sulaphat 15 times, δ2 Lyr is even 250 times our Sun.
But instead of other numbers, let's look at this diagram of comparison between the sizes of the stars: it is always the same that I modify each time, always leaving little of what I saw before. Remember the Swan with its 11 monsters? I certainly couldn't take them with me every time and even now, just to show how big the stars of the Lyre are, I had to do some cleaning! Let's analyze the diagram: do you find Vega on the left? Good! Continuing to the right I put the other stars, jumping δ2 that I had to move up because too big, passing through θ Lyr (59x), λ Lyr (88x) and folding upwards with the variable R Lyr (170x). It really seems that the constellation is upside down! Here the star θ, which is the eighth in the ranking as luminosity, is almost twice Aldebaran, as well as λ Lyr (you do the count in which order it is in the constellation) is much bigger than Rigel, the beautiful star of the beautiful Orion. I find that all this is very but very fascinating as well as unexpected: as I write these articles I discover things that I didn't even imagine.
A dive into art
A slightly more earthly comparison came to mind: how many of you, including myself, who are not experts in art, could say with certainty how big is the Mona Lisa's painting? And the Lady with the ermine? Guernica? The Howl of Munch? I have quoted absolutely at random four masterpieces, that maybe we see as reproductions all the same, climbed, in a gallery of images on our PC. Of Guernica I know it's big, but I still remember the amazement when I heard that the canvas of the Mona Lisa is 77x53cm or better 53×77 as we are used to the size of our monitors or images on PCs (horizontal x vertical): the horizontal dimension is 20 inches, smaller than the diagonal of my 22″ monitor... One sees it in a picture and imagines something else... Munch's Scream is a bit bigger (73×91), the Lady with the ermine is smaller than the Mona Lisa (40×55): and to think that in Rome for a long time she appeared on wall posters and on public transport and (if one doesn't know her for having seen her with one's own eyes) it was not possible to evaluate her exact dimensions. Guernica ? An oil on canvas 782×350 cm, huge. So here is the point: studying the paintings on books, seeing them in reproductions, one probably can't account for the dimensions. And here, of course, I'm not arguing about the beauty of art masterpieces, but about their physical size.
Going back to the stars, maybe it would be the case to create the "Committee for the revaluation of forgotten or perhaps never known stars", as well as the "Commission for the devaluation of only bright stars": I'm obviously joking because the basis of my ramblings is the physical dimension. Anything else would happen by bringing into question the intrinsic brightness of the individual stars, another parameter that, thanks to the "apparent" puts the stars in line once again, making some of them stand out and sinking others. As I said since the first episode, I had to make some choices in talking about the constellations and one was to consider first of all the dimension, completely neglecting the apparent, the spectral class (if not for the color of the stars in the diagrams) and many other characteristics that would have led to the writing of a book for each constellation.
The names of the stars
Here is the meaning of the stars of the constellation Lyra.
- Vega (α Lyr): from Arabic, the attacking eagle
- Sheliak (β Lyr): from Arabic, the harp
- Sulafat (γ Lyr): from Arabic, the tortoise
- Aladfar (η Lyr): from Arabic, the eagle's claws
- Al Athfar (μ Lyr): from Arabic, the eagle's claws
The name of the star Sulafat comes from the fact that in ancient times the sound box of a lyre was made with a tortoise shell, while the claws are a bit too high, for example, compared to the representation of the Uranometria: maybe everything would be all right if the eagle and the lyre were drawn upside down...
The famous M57
We cannot talk about the constellation Lyra without mentioning the very famous ring nebula, the famous M57, here photographed by the Hubble Space Telescope. It is located more or less halfway between Sheliak and Sulafat and requires an important aperture telescope to be able to photograph it: with amateur apertures you can already see a disk, but without many details, admitted to make the observation in areas without lights around.
Where and when to observe?
The constellation Lyre is typically visible in summer and autumn: at 9 p.m., a convenient time, it is visible in the months from May (when it will be seen low on the horizon in the NE) until around Christmas (when it will be setting in the NW this time). The peak, with the Lira in the South, is at the beginning of September, when at that time and at our latitudes it will be almost exactly at the zenith, above our heads!