I've had colleagues working on a pulsar navigation system to improve on star sightings. The idea is to look for the X-ray signals coming from pulsars and then

I've had colleagues working on a pulsar navigation system to improve on star sightings. The idea is to look for the X-ray signals coming from pulsars and then use the frequency of the pulse to identify the pulsar and then match that to a known map to figure out where you are. It's pretty cool and theoretically can work even for interstellar spaceflight. https://en.wikipedia.org/wiki/Pulsar-based_navigation https://en.wikipedia.org/wiki/Pulsar-based_navigation