The Red Star was a planet that was attracted into the Rukbat System only a few million years before the Pern Expedition. Its orbit was almost parabolic in shape. Because of its orbit, It was conjectured by the original Pern colonists that the Red Star might eventually escape Rukbat's orbit or fall into the sun. It was noticed but ignored by the EEC team who explored Pern and declared it suitable for colonization. The colonists, upon arrival in the Rukbat system, speculated that they might see some spectacular meteor showers in about eight years time when the cometary trail crossed Pern's orbit.
The Red Star, named so because of its reddish hue, had an extremely eccentric orbit with a period of roughly 250 years, during which it would pass through the Oort Cloud located on the edge of the Pern system. As it passed through the Oort Cloud, the planet would drag material with it, including the ovoids that would later become the organism known as Thread. About eight to ten years after passing out of the Oort Cloud, the thread ovoids would be close enough to drop down to the planet. Intense heat and friction of entry into Pern's atmosphere burned off the outer casing of the thread, leaving attenuated filaments of the voracious life form to fall to the planet's surface. It took roughly fifty years for Pern to escape from the trail, in which time thread fell at regular intervals. The fifty year period was known as a Pass. The remaining 200 +/- years of the Red Star's orbit, when it was not close enough to Pern to drop Thread, was known as an Interval.
The surface of the Red Star changed depending where it was in its orbit. As it neared and passed the primary, its surface became super heated, boiling what little atmosphere there was and creating gigantic cyclones with powerful winds. As it travelled further out from Rukbat, it cooled and the surface became an alien and sterile landscape. At the beginning of the Ninth Pass, F'nor and Brown Canth attempted to travel to the Red Star to see if it was possible for dragons to travel there to eliminate the threat of Thread. They jumped during one of the heating periods and described furnace hot tornadic winds, reddish clouds pierced by massive lightning strikes, and wind driven sand that pierced skin. Later on in the same Pass, Lessa, F'lar, and Jaxom travelled to the planet to scout for places to set the great anti-matter engines. There, they saw a battered surface of fractured rock and a huge rift into which the teams of dragonriders later placed the anti-matter engines.
The End of Thread
In the Ninth Pass, the Pernese discovered AIVAS (Artificial Intelligence Voice Address System) in Landing during explorations of the Southern Continent. AIVAS was an artificial intelligence that the original settlers had had to abandon when Mt. Garben erupted, and as a result AIVAS had been covered in ash and remained undiscovered. Before leaving the Southern Continent, the settlers had given AIVAS the task of finding out how to destroy Thread, or at least prevent it from landing on Pern again. This was eventually accomplished by placing three antimatter engines into a long rift on the Red Star's surface. However, two of the three engines had to be placed in the rift in the past. Lord Jaxom of Ruatha did this with Ruth by traveling between times. The two explosions in the past caused the orbit of the Red Star to shift marginally, in turn causing what became known as "Long Intervals," times when the planet was not close enough to Pern to drop thread. With the third engine explosion, the Red Star was knocked so far out of orbit that Thread would no longer be close enough to land on Pern. Jaxom confirmed this by traveling fifty years into the future to check the orbit of the Red Star.