Galaxy positioning system

Oh my - seems like only a year or so ago that I was posting about pulsars being proposed as a sort of GPS system for spaceships in the solar system or beyond - but it was 2012!

Last week, in Nature, it was reported that they can indeed be used that way:

From its perch aboard the International Space Station, a NASA experiment has shown how future missions might navigate their way through deep space. Spacecraft could triangulate their location, in a sort of celestial Global Positioning System (GPS), using clockwork-like signals from distant dead stars.

Last November, the Neutron Star Interior Composition Explorer (NICER) spent a day and a half looking at a handful of pulsars — rapidly spinning stellar remnants that give off beams of powerful radiation as they rotate. By measuring tiny changes in the arrival time of the pulses, NICER could pinpoint its location to within 5 kilometres.

It is the first demonstration in space of the long-sought technology known as pulsar navigation. One day, the method could help spacecraft steer themselves without regular instructions from Earth.....The team plans to repeat the experiment in the coming months, hoping to reduce the margin of error to one kilometre or less.