British scientists have found a clever way to find the mass of certain stars, even if they're alone out there in space.

Usually, when physicists, cosmologists, and mathematicians want to know the mass of a celestial object like a moon, planet or star, they use their relationship to other objects to calculate it. The gravitational pull between a planet and its moon, between two stars, or any other two celestial objects, is what determines its weight. Similarly, our "body weight" (more technically, our mass) is caused by the gravitational force between our bodies and the ground. 

That same method can't work when you're measuring an object that doesn't have a nearby neighbor. Once an object is virtually alone in space, its weight becomes unknowable. Or that was the case until now.

The mathematicians and scientists from the University of Southampton in the U.K. have announced that they can measure the mass of one celestial object - a young pulsar - even if it has no gravitational relationship with a nearby object. They published their findings on Friday, Oct. 2, in the journal Science Advances.

Pulsars are a special kind of rotating star that is born when a massive star (around four to eight times as big as our sun) explodes. That explosion causes a mess of star parts to shoot out, and the central part of the star collapses so intensely that it smashes the remaining electrons and protons together, forming a neutron star. 

Pulsars get their name from how they look through a telescope; if you watch a pulsar, you will see that it appears to pulse. That's because it shoots out beams of lights from its magnetic poles, and those lights turn round and round like a lighthouse. From a distance, it looks like a steadily pulsing light. The light is usually very predictable, but young pulsars are less reliable (no surprise, there). They sometimes experience "glitches" wherein they speed up for a bit, and then return to their original speed.

Those glitches actually reflect what's going on inside the star at its core, which is made up of superfluid that's constantly spinning and occasionally crashing into the outer edges of the star, speeding it up for a while before it returns to normal. The scientists have used advanced nuclear physics and mathematics to work backwards from the glitch to the amount of superfluid, to the mass of the pulsar. 

And that is how you find the weight of a pulsing star. Tell your friends.

Photo: Judy Schmidt | Flickr