Over the past decade, scientists have detected a puzzling phenomenon: radio pulses coming from within our Milky Way galaxy that would pulse every two hours, like a cosmic heartbeat. The long radio blasts, which lasted between 30 and 90 seconds, appeared to come from the direction of the Ursa Major constellation, where the Big Dipper is located.
I think it is interesting that when pulsars (rapidly spinning neutron stars) were first discovered, a fairly serious competing explanation (before more data was gathered) was that they could be something like interstellar lighthouses.
Now… they are not artifically constructed… but, if somebody actually was in a situation like Adama finds himself in, in the BSG revamp… they could actually serve that purpose, given that they have pretty stable, intense and specific pulse frequencies… if you could find even a few you recognized, you might at least be able to broadly traingulate and figure out where the hell you are.
Either way, neat to find out there are even more ways nature can unintentionally produce a reasonably reliable clock.