The Rosharan system is comprised of a series of enormous gas giants which crowd the outer reaches of the system. However, nobody has been able to observe them directly, as their manifestations in Shadesmar is minor.
There are three worlds in the habitable zone, all of which are inhabited to one extent or another. There is Ashyn, the burning world, which suffered a cataclysm long ago. People there live in very small pockets of survivability, including the famous floating cities.
The middle world, Roshar, is the showpiece of the system. Roshar is home to a diverse and unique ecology containing dramatic megafauna and fascinating symbiotic relationships between creatures (both humanoid and not) and Splinters of Investiture.
Is there more significance to the 10 other planets around the Rosharan star system and them being gaseous? We know that Roshar's moons have unnatural orbits; so there seems to be some astronomical manipulation in the system.
Yes there is significance of 16 in cosmere and 10 in Rosharan system.
The outer 10 gas giants in the Rosharan system suggest a tie to the number 10 that predates the arrival of the current Shards. Is the prominent numerology we see around the cosmere an inherent property of the planets, rather than the Shards who invest them?
Would Ashyn/Braize share the 10-centric numerology of Roshar?
Yes 10-centric is for the entire Rosharan planetary system ... wait Braize is 9-centric.
Q: How advanced is astronomy on Roshar?
A: Depends on the region. Some people ... the astronomy's getting moderately well.
Q: Surely they've seen Ashyn and Braize in the sky, and I'm wondering how long it will be before they start detecting signs of civilization on Ashyn.
A: That would depend on a couple of things, such as, the easiest way to detect civilization is with radio waves ... so you need some good telescopes. I don't think that would be, even if they spotted it, as revolutionary as you might think it would be, because we thought there were people on all of our planets for most of the history of mankind, and it didn't really affect how we viewed cosmology. I think if you went to Roshar and asked them, they'd be like "Yeah, totally, people live on those planets. Obviously." Just like if you went back and said "Do people live on the moon?" in the 1700s, people would be like, "Yeah probably, seems like they must."