Discover our other sites:

You might be looking for...

Annonse

THIS CONTENT IS BROUGHT TO YOU BY NTNU Norwegian University of Science and Technology - read more

The spiders that eat stars, and the researchers who catch them

Spiders can eat their partner. Some of the most extreme stars can as well.

The comparably tiny spider pulsar blasts its much bigger neighbouring star with so much energy that the side facing it gets twice as hot as the Sun’s surface, slowly burning the star away.

(Credit: NASA’s Goddard Space Flight Center)

Steinar Brandslet Steinar Brandslet Steinar Brandslet Journalist

Presented by: Presented by: Presented by: NTNU - Norwegian University of Science and Technology

Published 23 October 2025 - 00:01

Manuel Linares is often on the lookout for spiders and is pleased when he finds a black widow or a red-backed one. But he's not a biologist, he's a physicist.

He finds the spiders far out in space.

“These are stars that could vaporise their neighbours,” says Linares, who works at NTNU’s Department of Physics.

These binary stars are called ‘spider pulsars.’

The stars got this name because they could eat their partner, just like some spiders do.

Annonse

Gathers all spiders in one place

Linares leads a group of researchers who study and search for such spider pulsars.

In an article in The Astrophysical Journal, they present more than 100 of them in a database. This database is called SpiderCat, which is openly available to anyone interested.

Several physicists have contributed to the catalogue, most notably senior researcher Karri Koljonen.

“SpiderCat is a large database that shows all known spider pulsars in our galaxy, except for those in the globular clusters that orbit the galaxy,” Koljonen sums up.

SpiderCat

SpiderCat is a catalogue of all known spider pulsars in the Milky Way, except for those in globular clusters orbiting the Galaxy. The catalogue includes the main types of redbacks and black widows, but also candidates and unusual systems such as transitional, huntsman, and tidarren.
SpiderCat is a tool for research on pulsar development, particle acceleration, and the physics of neutron stars.
The first version of SpiderCat has over 100 systems. The catalogue brings together key information such as rotation and orbital properties as well as data from radio, optical, X-ray, and gamma-ray observations among other parameters.
Lately, researchers have found many more spider pulsars. This is thanks to NASA's Fermi-LAT and other very advanced telescopes.

“SpiderCat is like a living library of these star systems in our galaxy. It helps astronomers understand how these binary stars work and change over time,” says former student Iacob Nedreaas.

But what exactly are these greedy stars?

What is a pulsar anyway?

First, we need to figure out what a pulsar is, and the short version isn’t too tricky. They are so-called neutron stars, and these are born in a dramatic way.

“A neutron star can form when a massive star explodes,” says Linares.

These stars are tiny, perhaps with a radius of just over 10 kilometres. But at the same time, they are incomprehensibly densely packed.

If you could weigh them, one cubic metre would weigh up to a quintillion kilograms. We're talking about a number with 18 zeros.

“A pulsar is a neutron star that spins around up to several hundred times per second,” he says.

In short, a pulsar is the remains of a giant star that has exploded. It spins around quickly.

Annonse

Pulsars

If you have a swivel chair or carousel on the playground, you know that it's much easier to spin around a small child than it is to spin a large adult. It's a bit like that with stars too.
An ordinary star has a certain spin, or angular momentum, that determines its rotation speed.
After the star's core has collapsed and it has turned into a neutron star, it retains more or less the same angular momentum. But because it is now tiny, the rotational speed is much, much higher.
Pulsars can also rotate faster if they accrete mass from a companion star, which adds more rotational momentum.
Some pulsars can spin several hundred times per second. Their rapidly rotating magnetic fields generate strong electric fields, which in turn produce beams of electromagnetic radiation at the star’s poles. This radiation is emitted into space and can be detected using radio telescopes.
From our fixed observation point on Earth, this radiation is seen as pulses that arrive each time the poles point towards us.

And a spider pulsar is?

“A spider pulsar is a rapidly rotating pulsar that has a star with a small mass next to it,” says PhD candidate Marco Turchetta.

This type of pulsar thus has a less densely packed companion. But how does the pulsar eat its friend?

“The pulsar emits intense radiation and particle winds. These gradually wear away the partner. Like a spider eating its mate,” he explains.

Spider pulsars are named after different spiders in English. The two main types are:

Redbacks: These pulsars have a companion star that is less massive but much larger than the neutron star.
Black widows: Here, the second star is very light, and almost gone.

There are also several variants of spiders that researchers cannot neatly fit into the other types, such as the huntsman and tidarren types.

The information provided in SpiderCat

The new catalogue SpiderCat describes how fast the neutron stars spin, and how long it takes for the two stars in the system to orbit each other. It also provides an overview of the mass of the companion star.

The researchers have also studied how the stars look in different forms of light, such as radio waves, X-rays, visible light, and gamma-rays.

The catalogue is an aid so that researchers can study how these systems work and develop.

They can learn more about the physics behind neutron stars, understand extreme particle acceleration, and explore how matter behaves under the most intense conditions in the universe.