The Prolmar sector is a region of space many light years from the home worlds of the Twelve Colonies. The sector has been mapped to some degree, as sufficient data is available to calculate an FTL jump to its location. Yet Prolmar appears to be a remote region of space that has only rarely been visited by Colonial ships. It is said to be located "well beyond the Red Line" - requiring complex calculations to accurately triangulate the jump end-point, possibly even several jumps to reach the destination.
After the Cylon holocaust, Commander Adama chooses Prolmar as the general direction to take humanity's survivors following their escape from the Cylons. Lieutenant Gaeta is assigned the sole responsibility of plotting the jump (though no one has ever plotted one this far away before). The jump is successful, but the Cylon armada soon follows, stalking the Fleet relentlessly through Prolmar. They attack every 33 minutes for 5 days, until the civilian ship they use to track the Fleet is destroyed by Galactica's Vipers (TRS: "33").
It is unknown whether the Fleet is still inside the Prolmar sector (as of "Daybreak, Part II"), but it appears very unlikely considering the distance traveled since "33".