A planetary ring for Thalassa

We left our old worlds, each of us. This is it. We can't go any farther. This is The Edge.
Post Reply
Stone Giant
Posts: 627
Joined: Fri May 23, 2008 8:40 am
Gender: male
Location: Fano, Italy

A planetary ring for Thalassa

Post by LoZompatore »

In the following I try to figure out a realistic planetary ring around Thalassa, as suggested by Jackob_Pawlowicz in his post about religion.

I found a scientific article which does most of the calculations about a realistic planetary ring orbiting around the Earth, including its dimensions and the temperature decrease along the tropical belt of the winter emisphere due to shading induced by the ring itself (for those of you who are interested, the link to the article is here: http://www.star-tech-inc.com/papers/ear ... _rings.pdf). I just applied those calculations to Thalassa, in order to figure out some features for it.

A schematic piture (elaborated from the article) of the ring and its structure is shown below:


In short, the ring system is extended between about 2600 kilometres (about 1625 miles) and 4300 kilometres (about 2690 miles) above Thalassa'equator, it is about 800 m (half a mile) thick and it is made of dust grains. It is kept in place by two small moonlets (some miles across) which orbits on its borders and acts as shepherd moons. As you can see from the picture above, the ring casts a shadow on the winter emisphere inducing a decrease of 2-3°C (3.6 - 5.4 °F) in the average temperature of the tropical belt (the latitudes between 10°-30°) located in this emisphere. The other latitudes in this emisphere will see an average temperature decrease of 1°C (1.8 °F).
The inner and outer moonlets could be as small as the ring thickness (half a mile) in order to keep the system stable (on a time scale of many millions of years), but I increased their diametres to 8 km (5 miles) and 24 km (15 miles) respectively, just to make them visible from Thalassa's surface and have them larger than mere floating rocks.
A likely view of the ring as seen from Thalassa's surface would be simlar to this:


Due to the fact that the moonlets are far nearer to Thalassa than the main moon (Nara), the moonlets would appear as small globes circling the sky every few hours. Let's say that the two moons are made of different materials and the inner one is brighter than the outer one, just to help distyinguish between them. It is likely that both moonlets could have irregular shape due to their small dimensions, but by now let's say that they are spherical just to keep things simple. ;)
Notice that even if the two moonlets are actually much smaller than the main moon, they will appear comparable to Nara due to their proximity to Thalassa, so they would appear as bright disks in the sky, immersed in the haze coming from the nearby ring dust particles. Assuming some 2000 miles for Nara's diameter (slightly smaller than Earth's Moon) and calculating the distance from Thalassa's equator in order to have for Nara a revolution period of 28 days it is possible to compare the relative dimensions of the three moons as seen from Thalassa's surface:


To keep things simple, the inner moonlet orbit is such that it will circle Thalassa in just 2.4 hours (so to make exactly 10 orbits every 24 hours), while the outer moonlet will circle the planet in exactly 3 hours (8 orbits in 24 hours). The whole ring included between the moonlets will circle the planet with intermediate periods. Though the spinning of the dust itself would not be discernible, the moonlets will be visible and they would move pretty fast in Thalassa's sky.

Due to the fact that both moonlets are quite close to the planet, they will not be visble worldwide. The inner moonlet will be visible only from the equator until the lower temperate region (41° latitude), while the outer moonlet (and the whole ring, including its shadow) will not be visible above 50° latitude on both emispheres (see the picture below):


These moons could be used to mark the passage of time around the day. Notice that the two moon align themselves every 12 hours (corresponding to 5 evolutions of the inner moon and 4 revolutions of the outer moon), so it is possible to precisely divide the day in two equal parts.

An interesting phenomenon visible only in regions close to Thalassa's equator would be the eclipse of the external moonlet by the internal one, also happening every 12 hours. Notice that - along the equator - the ring is actually seen as a narrow hazy belt which divides the sky in two. The eclipse of the two moonlets would not last long, due to the relative high speed of both bodies, but it would create a sort of "eye in the sky" phenomenon. I wonder if it could have some magical/mystical consequence on Thalassa's surface.
Could we say that the fact that the center of the Edge is placed exactly along the Equator has something to do with this odd eclipse phenomenon?

If you like the idea of the ring/moonlets, would you like also to give some names to them? Would they be included in any cosmogony/cosmology for Thalassa?


User avatar
Posts: 37
Joined: Fri Jun 27, 2008 8:41 pm
Gender: male
Location: Copenhagen, Kingdom of Denmark or Darokin City, Rep. of Darokin

Re: A planetary ring for Thalassa

Post by Jakob_Pawlowicz »

The rings could be what is left of the Moonstrike, held at bay by the will of the deities (or the normal laws of gravity, but the will of the deities sounds sooo much cooler :mrgreen: )
I like it. Then we would have two children of Naryan and Nara, each able to travel both the sky of night and day...... ooh I must go write some more. :)
"Orcs do maintain the best dungeons.....!"

Post Reply

Return to “The Edge”