The Red Star is a wandering planet that brings Thread from the Oort cloud to Pern. It is barren of any life, and its red coloring comes from the dust and gases that make up its atmosphere. The Red Star 'visits' the Oort cloud once in each orbit, barely brushing or entering the edge of it, where it gets the Thread spores. It takes the Red Star about two hundred Turns, or years, to finish each orbit.The Red Star meets and crosses Pern's path once in each orbit, showing the deadly thread into the planet's atmosphere.
The Oort Cloud
An Oort cloud surrounds the perimeter of the Rukbat system. It is composed of smaller particles than expected of such a body, as Oort clouds are usually nebulous collections of stone and ice chunks.
Thread is that icky, dangerous, string-like organism that's spun off of the Red Star (during the 50 years that it passes close enough to Pern to send us its bugs), and which falls through Pern's atmosphere, seeking to burrow into the ground. It devours any organic thing it touches, and will burrow into the ground and destroy many acres of forest, grasslands, and crops. It drowns in water, can freeze to death, and can be burned by fire or acid. Pern's primary defense against Thread is dragons, who rise to meet the Threadfalls and char the thread with their flaming breath.
The Star Stones are a group of stones that when looking through the Eye Rock properly, frames the Red Star when a pass is imminent.
Distance Viewers are one of the primary tools of Starcraft. They are used to view the skies and make observations unaided eyes can't normally see. It was the discovery of a Distance Viewer that marked the beginning of Starcraft.There are three types of DVs: Reflecting, Refracting, and Composite. Hand-held DVs, which are issued to each member of Starcraft, are of the Refracting kind. The large Observatory Distance Viewer is a Composite 'viewer. The difference between the three types is the method of magnification. Refracting DVs REFRACT light through clear lenses, and reflecting DVs REFLECT light with mirrors; composite use both mirrors and lenses.The workings of a DV are taught in an Optics Class, which all apprentices are required to attend.
Pern has two moons, Belior and Timor. It is commonly believed that Belior, the closer of the two, is also the larger, but with the discovery of distance viewers, it was made known that the larger was actually Timor; about the same size as Luna.
The Dawn Sisters
The Dawn Sisters, also known as the Day Sisters, are a trio of 'stars' seen at dawn and dusk. Though they can be seen from just about everywhere on Pern, they are clearest on the Southern Continent. The Dawn Sisters were originally the three ships that brought the colonists to Pern, but were gutted of anything useful on land.
Pernese constellations are much like Terran consts in the way that they are both patterns, or pictures, made up of stars. Most of Pernese consts were named, or founded because of a strong memory, resemblance, or drunkenness.(The Gather Circle is a group of five stars that two drunken people though resembled themselves at a Gather...)
Take a look at the constellations.