Future spacecraft will likely navigate by the light of distant pulsars
The universe is expanding, and accelerating, every day. More locally, the planets in our solar system are whipping around the Sun at up to 107,082 miles-per-hour. All this can make it hard for a spacecraft to pick a reference point, which is part of why our current probes have to call home for directions so often. While we obviously want to communicate with our spacecraft as they explore the galaxy, finding a way for them to plot their own course a bit more would save time and energy. Fortunately, experiments with distant pulsars have been suggesting that they can be used as reliable sign-posts as we push further and further into space.
A pulsar is a special type of neutron star. They’re incredibly dense collections of debris made of the remnants of an exploded star with the added twist of also being highly magnetized. This magnetic polarization means that a pulsar emits x-ray energy from its north or south pole, rather than in all directions at once. Since the closest pulsar is around 280 light years away, we only see the emitted energy from a pulsar when it’s pointed in our direction, which happens on a regular schedule thanks to the pulsar’s rotation. In some cases those rotations are so fast that we get what appears to be a pulse of energy on a millisecond timescale, turning the pulsar into a handy blinking landmark that our spacecraft can use as a relatively stable reference point.
Piloting by pulsar
Right now, no probe is navigating by pulsar, but several instruments have been collecting data on them. The United States Navy has concluded a test with a satellite navigating by pulsar, and instruments on the International Space Station like the Neutron Star Interior Composition Explorer (NICER) have been collecting data both on the size of pulsars and how quickly they appear to “blink” from the perspective of our solar system. With these data, researches have come up with formulas that allow for a location in space to be identified within three miles.
As we refine our pulsar tracking abilities, researchers hope to reduce that margin of error to a half-mile. Once we can reliably triangulate an object’s location in relation to the energy from distant pulsars, spacecraft should be able to handle more navigation commands without calling back to Earth for updates. Pulsar-based navigation could also be used as a secondary navigation system for more sensitive missions, such as when humans attempt our first trip to Mars. The fact that tracking pulsars only requires a modestly-sized sensor makes this method of navigation quite practical, even if it requires enormous amounts of energy being blasted from from collapsed stars light years away to work.
Source: NASA test proves pulsars can function as a celestial GPS by Alexandra Witze, Nature