traveling to destinations like the moon and beyond, future interstellar travelers may

one day receive similar guidance from NASA's new pulsar-based navigation system. Which

is what exactly? When a star that's roughly one and half

times the mass of the sun explodes in a supernova, its core collapses into a smaller, dense object

called a neutron star. Neutron stars spin rapidly, emitting visible light and high energy

radiation like X-rays and gamma rays. These energetic powerhouses are known as pulsars,

and so far scientists have found over 2000 in the known universe.

The radiation emitted from a pulsar's magnetic pole doesn't align with its spin axis, creating

a beam that sweeps across the dark sky like a cosmic lighthouse. When this beam crosses

our line-of-sight, it appears as a pulse. The ones that rotate the fastest are called

millisecond pulsars, and their beams whip around hundreds of times per second. Imagine

an object with a mass more than the sun, spinning several times faster than a Formula One engine!

Historically, millisecond pulsars have been exceptionally useful thanks to their incredible

precision. Since their discovery, their timely blink has helped astronomers confirm the Theory

of Relativity, detect the earliest exoplanets, and accurately measure cosmic distances.

As NASA sets its sights on distant planets, spacefaring explorers will need a way of orienting

themselves in space. Here on Earth, we use the satellite-based GPS. These satellites

carry atomic clocks that provide extremely accurate time, which gets used by your phone

or car to help calculate your position. GPS works fine if you're on Earth or close to

it, but once you go beyond its range, the signal weakens till... you're lost. You

can't just pull over and ask for directions to the nearest planet.

Since the 60s, NASA has primarily used the Deep Space Network to track missions beyond

Earth's orbit. It's made up of three ground stations located in: Australia, U.S.' California,

and Spain. They're approximately 120 degrees apart, and they beam up radio waves to a spacecraft

and log details as the signals return. Navigational data is calculated on Earth and sent back,

helping ground control keep missions on the right path.

But if that radio link with Earth is lost, a spacecraft can find itself adrift. Some

manned missions, like the Apollo program, have even carried an antiquated sextant in

case this happened, so they could fix their position against the stars, like old timey

mariners lost at sea. A better solution would be if a spacecraft

could navigate independently… no ground control required. This is where our friends

the pulsars come in. Millisecond pulsars spin with such amazing regularity that they're

among the most reliable clocks in the universe. With their predictable pulsations, they provide

high-precision timing just like GPS satellites do. Accuracy is so important because in spaceflight,

it's the difference between landing on a planet...or crashing on it. And this technique

of X-ray pulsar navigation is actually showing promise on the International Space Station.

Mounted on the station's exterior is a piece of equipment called Neutron star Interior

Composition Explorer or NICER. It packs an array of 56 X-ray telescopes into an area

the size of a washing machine. Its purpose is to study neutron stars, including the rapidly

blinking pulsars. NICER scans the sky detecting and timestamping the arrival of X-ray photons

within 100 nanoseconds of accuracy, or better. A software embedded into NICER, cleverly named

SEXTANT or Station Explorer for X-ray Timing and Navigation Technology, then analyzes that

data, comparing it with an almanac of known pulsars, looking for their unique fingerprint.

In November 2017, NASA used four different millisecond pulsar targets to successfully

demonstrate that SEXTANT could determine the position of the ISS within 5 to 16 kilometers

of its actual position. Scientists are hoping to get more than just

navigational help from NICER. NASA currently uses radio frequencies to talk to and locate

the various rovers and probes scattered across our solar system as well as manned missions

closer to home. NASA is now considering testing SEXTANT for

use on the Lunar Gateway, a mini space station meant to aid long-term missions on the lunar

surface, and eventually, Mars. Who knows, in the future, if space explorers are lost

in a sea of stars, they can use cosmic pulsars as beacons to guide themselves home.

By the way, if you scooped-up a teaspoon of a pulsar, it would weigh as much as Mount

Everest...and you would need a very strong spoon. Pulsars are pretty amazing, so if you want

to know more, like how they are leading to new insights in general relativity, check

out this video here. Let us know what else you'd like us to cover in the comments below

and make sure to subscribe to Seeker. Thanks for watching!