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Ragnar is a gas giant located on the outer edge of the Helios Gamma/Delta system, and site of the Ragnar Anchorage munitions station. After the Fall of the Twelve Colonies, Commander Adama, assuming command of the Colonial Fleet after Admiral Nagala's death, orders all ships to Ragnar; President Laura Roslin's fleet is the only known assemblage of ships to make this rendezvous.
Ragnar is wracked by violent storms. Ragnar Anchorage appears to be located in an area of relative calm within the storms. The storms themselves create a high level of electromagnetic discharges, which interfere with a range of systems, including a ship's ability to plot FTL jumps. While this effectively hides the Anchorage station from enemy scans, it also means that a ship must cross the "EM threshold" above the main bulk of the storms before attempting a jump. This problem requires Commander Adama to place Galactica directly between the planet and an opposing force of Cylon basestars to provide the necessary protection for the civilian Fleet to jump away from Colonial space.
Another side effect of the storm is the emission of a form of radiation that adversely affected the Cylons' silica pathways, a technology integrated into humanoid Cylons. When Leoben Conoy appears to fall sick while trapped on the station with Adama, it gives the commander his first clue that Conoy is a Cylon construct (TRS: Miniseries).