I am starting an add-on for Celestia called Uncharted Worlds which is set in the Orion Arm in The Milky Way.
It is set from 2099 AD to 2199 AD, a time when mankind has already made travel in space possible.
The add-on is focused around a collection of stars known as "The Local Collection", a group of stars all very close to Sol.
At this moment in time I have designs for at least 100 solar systems, all of them have been planed on pad and paper. Also all textures, models and data are created and modded by myself.
Other people may wish to help with this add-on, if so please PM me and I will see what I can give you

A website is also under development for this add-on however no further details about it will be revealed until I have time to do so.
To introduce the add-on to the fans of Celestia, I have created and released the first solar system of the add-on. The link is below.. enjoy!
http://www.filefront.com/13969455/Ross-128.zip//