The Stars Around Tir na Nua
My personal literary taste has always hovered around the Science Fiction and Fantasy genres. I enjoy finding myself transported to a world that is clearly not 21st century Earth, and yet is believable despite its fictional genesis in the mind of an author.
So, when I come to the problem of creating a Celtic world for my fantastic stories, I need for the world to be obviously different than the one we live in and yet sufficiently well thought out as to convince most readers of its plausibility. Tir na Nua, as a background for my fiction, needs to be anchored in some kind of a believable setting for me to feel good about it.
I have imagined a somewhat complex Solar System for the world of the All Mind, the new land, Tir na Nua to which Dana’s Gaellic Colonists, the Tuatha de Dana come. As with the book of invasions from Irish Mythology these children of Dana, having burned their ships (ship), make do with what they find and what seems perfectly ideal presents challenges through time.
What sort of world should I have for a world devoted to things Celtic, a place where the Celtic spirit could continue untainted by Greece or the near East, and which would not be obliterated by Rome? A very Celtic thing, a common literary device, is the triad. So, it was easy for me to imagine that the perfect solar system for a group of Celtic people would have three suns, three moons, three planets. But how to balance this idea drawn from celtic lore and realize it with some possibility in a “realistic” world? Initially I imagined it as a simple heirarchaical system with Ember revolving around Spark which in turn circles Sol na Nua. Looking for models from life I believe I may have to amend that. Here is what I wrote as I first thought about this problem.
Original idea of how Trinary System would be laid out.
So raw from my imagination I wrote this: From the informational Tir na Nua page.
. . . from the Tir na Nua page.
Yet there are differences (from Earth). The South is warmed by the sullen glow of a brown dwarf star, Ember, that the planet of Tir na Nua cartwheels around.(probably a red dwarf, and Tir na Nua is tidally locked) Much of the weather of this world of necessity comes from that most important and close relationship.
The north draws rain from the South, but it never sees Ember’s light save painted on the world’s satellites. There is ghostly blue light that shines from blue/white dwarf, Spark, (I don’t think white dwarf will work unless it is binary with Ember, very much closer than Sol na Nua) that dances closest to Ember, but the world’s most Earth-like light comes from distant Sol na Nua, it marks the day, sharing it in the North with Bright and brightening the South as well.
Tir na Nua is a world that is marked by cataclysm. The violent genesis of the planet is painted on its moons as well. Nearest is the Wanderer, a blasted lump that hurtles around Tir na Nua, racing across the sky. The Stranger is next nearest, but it is not very reflective, making a ghostly shape in the night sky. Farthest of Tir na Nua’s moons is Bright, truest reflector of the three suns of the world.
Obviously I’d worked out names for the three suns and the three moons, had some idea of how that might fit, but hadn’t imagined how there would be three planets that would be visible to Tir na Nua, or really, just how the astro-physics of the system would work.
My initial search for some kind of trianary stellar system emediately falls upon Alpha Centauri which is the third brightest star in Earth’s sky. At first blush it is very nearly perfect. Alpha CentauriA and B are locked in a binary system which is composed of stars not too different from Sol. One is slightly brighter and the other is about half as bright as our own sun.
A third star, Alpha Centauri Proxima, stands well off from this pair. It is not visable unaided from Earth and is very far from A and B, indeed it is not certain that Proxima is actually gravitationally associated with Alpha Centauri, it may be just passing through. I do not think that Alpha Centauri A and B can provide light similar to the sun for a planet orbiting Alpha Centauri proxima, but perhaps one like it could serve. Here is the germ of an idea and Alpha Centauri only the first example.
Proxima, I think it is a brown dwarf, very dim, and I imagine Tir na Nua orbiting such a star with a very fast period with its southpole pointed directly at the star. In this way Tir na Nua has an eternally hot South sending clouds of water north to return through seas to the south in a worldwide water cycle that leads to an ever increasing icecap that occasionally causes a catastrophic pole shift and destruction of the ice-cap. The dynamic center of the planet remains oriented as before with the Southpole to the brown dwarf sun (Ember), but the crust has shifted and the ice mantle that had built up on the North is broken down and the entire surface has changed orientation so that what had been is still visible but has been cast in another position and the process begins again after much turmoil. Upon actually do a little research into it I find that Proxima is a Red Dwarf, but both are very close in size to each other, but irrespective of Centauri, I need to imagine a Proxima like star that can be my Ember for purposes of my story.
In favor of a Red Dwarf instead of a Brown Dwarf is the Red Dwarfs very stable energy production and full convection of its helium so that there is very little build up of helium leading to flaring. Brown Dwarf’s, on the other hand, are often flare stars which would be an unfortunate companion for our world, Tir na Nua, that orbits very close to it’s star. The radiation that Red Dwarfs produce is primarily infared, heat, which would work well to drive my imagined weather from the southern hemisphere up to freeze on the icecap of the North. Red Dwarfs are also very low luminosity objects which I think will fit well with my world.
So it would seem, like Proxima, Ember is a Red Dwarf star. I think its low luminosity and stable energy production will allow Tir na Nua to point its Southern Hemisphere perpetually toward its star and not have the surface so hot as to be uninhabitable. Then too, I think that the color of a Red Dwarf will be better than would be the lithium burning brown dwarf that might burn pink instead of the mottled ruddiness of Ember. We shall see.
Here is material from Wikipedia about the habitability of a Red Dwarf star:
Planetary habitability of red dwarf systems is subject to some debate. In spite of their great numbers and long lifespans, there are several factors which may make life difficult on planets around a red dwarf. First, planets in the habitable zone of a red dwarf would be so close to the parent star that they would likely be tidally locked. This would mean that one side would be in perpetual daylight and the other in eternal night. This could create enormous temperature variations from one side of the planet to the other. Such conditions would appear to make it difficult for forms of life similar to those on Earth to evolve. And it appears there is a great problem with the atmosphere of such tidally locked planets: the perpetual night zone would be cold enough to freeze the main gases of their atmospheres, leaving the daylight zone nude and dry. On the other hand, recent theories propose that either a thick atmosphere or planetary ocean could potentially circulate heat around such a planet, or life could survive by migration. Alternatively, a moon in orbit around a gas giant planet may be habitable. It would circumvent the tidal lock problem by becoming tidally locked to its planet. This way there would be a day/night cycle as the moon orbited its primary, and there would be distribution of heat.
In addition, red dwarfs emit most of their radiation as infrared light, while on Earth plants use energy mostly in the visible spectrum. Red dwarfs emit almost no ultraviolet light, which would be a problem, should this kind of light be required for life to exist. Variability in stellar energy output may also have negative impacts on development of life. Red dwarfs are often covered by starspots, reducing stellar output by as much as 40% for months at a time. At other times, some red dwarfs, called flare stars, can emit gigantic flares, doubling their brightness in minutes. This variability may also make it difficult for life to develop and persist near a red dwarf. Gibor Basri of the University of California, Berkeley claims a planet orbiting close to a red dwarf could keep its atmosphere even if the star flares.
Again, this seems ideal. I imagined Tir na Nua tidally locked with Ember the temperature midigated by a thick atmosphere AND seas as well as a planetary water cycle. Light for Terran Life is to be supplied by the companion binary pair that Ember is a somewhat distant tertiary body, but still gravitationally related. Still, the relation of Proxima to Alpha CentauriA and CentauriB is not near enough to allow them to effectively provide the daylight for the world of Tir na Nua. Alpha Centauri provides a model, but its stats are not quite right. It seems to me to be a matter of scale of proximity, not a case of the structure and light produced being incorrect for my imagined system. Alpha CentauriAB IS composed of Sol like stars though their variable distance of 8 to 11 au and period of 80 years doesn’t seem to work for me. Also as I believe I mentioned, Proxima stands WAY too far away. I will look for other examples that would work better.
Our own sun is a G2 main-sequence star, so ultimately we are looking to match that as closely as possible. Commonly called a yellow dwarf, it is a G-type main-sequence star (G V), or G dwarf star, it is luminosity class V of spectral type G. Other well-known examples of G-type main-sequence stars include Alpha Centauri A, Tau Ceti, and 51 Pegasi.
There is a three star system that bears a look, 16 Cygni. 16 Cygni or 16 Cyg, is a triple star system in the constellation Cygnus, about 69 light-years away from Earth. It consists of two Sun-like yellow dwarf stars, 16 Cygni A and 16 Cygni B, together with a red dwarf, 16 Cygni C. In 16 Cyg, Cygni A and C are closely associated in a tight binary system of about 860 AU and the other yellow dwarf, Cygni B is between about 877 to 15,180 AU away from AC with an orbit that might take 20 thousand to as much as a millions of years. Also interesting is that In addition B orbits between 100 and 160 degrees inclination, that is against the A–C pole such that 90 degrees would be ecliptical. Frankly, for my purposes it seems that Cygni A-C is not really close enough for A to essentially provide sunshine for Tir na Nua and B might be too far off to be considered a sun, even a small dim one for purposes of the trinary star system that includes the planet Tir na Nua.
In my earlier work, before I actually looked for examples of known star systems, I imagined a Red Dwarf like Proxima or 16 Cygni C as being the principal around which Tir na Nua rolls in a tidal locked, close orbit. I also imagined two other suns, one very blue and then one that provides what ever is likely to be most necessary for terran life to thrive. So Spark would supply a good dose of ultraviolet light for plants from a very bright point of light, perhaps star like, but hopefully normally visible in the Tir na Nuan sky. I think I assumed this star would be a white dwarf. I’ll need to look for a pair that could provide enough light despite being fairly far away from Ember and Tir na Nua. Research will need to continue.
So what have I learned? First, my ideas for Ember seem to be better served by a Red Dwarf star rather than a Brown Dwarf Star. It can still be fairly dim, but the stability of the Red Dwarf and the fact that it is still Main Sequence allows for Tir na Nua to be in a VERY close orbit and therefore tidally locked so that its South Pole faces perpetually at Embers sullen red/orange glow. I also learned that Yellow stars, like the Sun, are mainly main sequence stars, that they are often found in Binary configurations, so I believe that rather than a strictly hierarchical arrangement with Tir na Nua, orbiting Ember, which orbits, Spark, which orbits Sol na Nua Sol na Nua should rather be in a close binary association with Ember.
Spark, on the other hand, I imagined as a white dwarf but I discovered that won’t work at all. Blue-White stars are that color because of surface temperature which is largely determined by mass. A white dwarf wouldn’t be bright enough, even if it was closely binary with Ember and so it should be the farthest away only appearing small and blue, like a spark, because of its distance from the two closely associated Ember, and Sol na Nua which needs to provide the normal light for the earth type plants and animals.
Therefore, it appears that what we should have is a binary system with a primary that is a yellow dwarf star that is larger and more luminous than is Earth’s sun, and Ember, a red dwarf that has Tir na Nua gravitationally locked in a very close orbit. Spark is a third star in the trinary system, but is some distance away from the binary Ember and Sol na Nua so that it appears as a small blue sun despite being a blue-white Giant Star.
Next up I need to think about orbital attitude, (I think that is the term,) basically how the planes of the various orbits are oriented toward each other. I should also nail down how much distance I need between the various stars, their luminocity to provide proper light at the AU distance they will average and just what a day would look like with the various suns rising and setting despite fairly exotic courses in Tir na Nua’s sky.