What are neutron stars?

October 16, 2017
Neutron star. Credit: NASA

Thrilled physicists and astronomers announced Monday the first-ever observation of the merger of two neutron stars, one of the most spectacularly violent phenomena in the Universe.

But what are they?

We asked Patrick Sutton, head of Cardiff University's gravitational physics department, who contributed to the discovery.

Q: What are ?

A: You can think of them as the collapsed, burnt-out cores of .

When large stars reach the end of their lives, their core will collapse, the outer layers of the star blown off. You're left with an extremely exotic object, this neutron star.

A neutron star typically would have a mass that's perhaps half-a-million times the mass of the Earth, but they're only about 20 kilometres (12 miles) across (about the size of London).

A handful of material from this star would weigh as much as Mount Everest.

They are very hot, perhaps a million degrees, they are highly radioactive, they have incredibly intense magnetic fields... They are arguably the most hostile environments in the Universe today.

Q: Why do neutron stars merge?

A: It's very common for stars... in the Universe to actually be formed in pairs by a given gas cloud.

If the stars are large enough, then at the end of their life they explode and they leave behind neutron star cores, and the neutron stars will continue orbiting each other.

As they orbit, they give off gravitational waves and the waves carry away energy and so the stars slowly fall closer and closer together.

As they get closer together they orbit faster and faster and the gravitational wave emission speeds up.

You get a runaway process where the two stars in the last few moments of their life, they'll be orbiting each other several hundred times per second, so moving at very close to the speed of light, and eventually they will merge.

Q: What happens then?

A: Because we don't understand exactly the mechanics of how these work on the interior, it's not certain what the final fate is.

If the stars are heavy enough, we're sure they will collapse to form a black hole and some of the remaining matter... will form what is called an accretion disk orbiting just around the black hole.

It may be that if the stars are light enough, that they will actually form a single, very heavy neutron star instead of a black hole. That may be stable and stay as a neutron star forever, or it may be unstable and eventually collapse into a black hole.

Explore further: A population of neutron stars can generate gravitational waves continuously

Related Stories

Neutron stars could be our GPS for deep space travel

June 30, 2017

NASA's Neutron Star Interior Composition Explorer, or NICER, is an X-ray telescope launched on a SpaceX Falcon 9 rocket in early June 2017. Installed on the International Space Station, by mid-July it will commence its scientific ...

New way to form close double black holes

June 27, 2017

A team of three Dutch astronomers from the University of Amsterdam and Leiden University found a new way to form two black holes that orbit each other for quite a while and then merge. Their publication with computer simulations ...

A black hole in a low mass X-ray binary

April 24, 2017

A globular cluster is a roughly spherical ensemble of stars (as many as several million) that are gravitationally bound together, and typically located in the outer regions of galaxies. Low mass X-ray binary stars (LMXBs) ...

Recommended for you

After a reset, Сuriosity is operating normally

February 23, 2019

NASA's Curiosity rover is busy making new discoveries on Mars. The rover has been climbing Mount Sharp since 2014 and recently reached a clay region that may offer new clues about the ancient Martian environment's potential ...

Study: With Twitter, race of the messenger matters

February 23, 2019

When NFL player Colin Kaepernick took a knee during the national anthem to protest police brutality and racial injustice, the ensuing debate took traditional and social media by storm. University of Kansas researchers have ...

Researchers engineer a tougher fiber

February 22, 2019

North Carolina State University researchers have developed a fiber that combines the elasticity of rubber with the strength of a metal, resulting in a tougher material that could be incorporated into soft robotics, packaging ...

A quantum magnet with a topological twist

February 22, 2019

Taking their name from an intricate Japanese basket pattern, kagome magnets are thought to have electronic properties that could be valuable for future quantum devices and applications. Theories predict that some electrons ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.