[Mike Darancette]

The trick, according to a recent paper, may be to use pulsars as a form of interplanetary – and possibly even interstellar – GPS.

Aren't pulsars a bit far away to be much good for interplanetary GPS?

[MHGinTN]

Not at all. Think of riding inside of a sphere. The surface of the sphere has four or more points where the radiation for pulsars strikes the sphere. As you move in the solar system the points on the surface where the radiation hits, change, giving you a means to calculate your location in the solar system in relation to where you want to end up, with the pattern at the objective location mapped for the sphere surface if you were there.