One of the difficulties in astronomy is determining the age of astronomical objects. Brown dwarfs and small red dwarfs have about the same temperature in the e

One of the difficulties in astronomy is determining the age of astronomical objects. Brown dwarfs and small red dwarfs have about the same temperature in the early stages of their formation. The main difference between the two is the drop in temperature over time. A super cool brown dwarf might just be an old brown dwarf. The (arbitrary) line between planemos and brown dwarfs can be drawn via mass (e.g. no matter the temperature, if it's too small for deuterium fusion, it's not a brown dwarf) and composition (e.g. via testing for lithium), though both criteria are not perfect. A cool brown dwarf can basically just be very old.