Remnant systems can be identified by the warning beacons in hyperspace. The beacon's color and number of pings indicate the strength of the Remnants inside:
Yellow, 1 ping: Low
Orange, 2 pings: Medium
Red, 3 pings: High
Exploration ships entering a Remnant system should be prepared for a fight, as they use strong high-tech ships and can come in large numbers. With orange systems, it is recommended to bring at minimum a couple of cruisers.
Remnant fleets spawn from battlestations found in orange and red systems. The orange system stations are damaged and can be defeated by a moderately strong fleet (2-3 cruisers or a single capital, with escorts). The red system stations are at full strength and have a high-level officer; multiple battleships may be required to take one down.