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How Big is a Neutron Star? Smaller Than You Think

Posted by Guy Pirro 03/20/2020 12:15AM

How Big is a Neutron Star? Smaller Than You Think

Neutron stars are compact, extremely dense remnants of supernova explosions. They are about the size of a typical city with up to twice the mass of our Sun. Neutron stars are so dense and compact, that you can think of the entire star as a single atomic nucleus. How the neutron-rich, extremely dense matter behaves is unknown and it is impossible to create such conditions in any laboratory on Earth. Physicists have proposed various models, but it is unknown which, if any, of these models correctly describe neutron star matter in nature. An international research team led by members of the Max Planck Institute for Gravitational Physics in Germany has obtained new measurements of how big neutron stars are. Their results show that a typical neutron star has a radius close to 11 kilometers. They also find that neutron stars merging with black holes are in most cases likely to be swallowed whole, unless the black hole is small and/or rapidly rotating. This means that while such mergers might be observable as gravitational-wave sources, they would be invisible in the electromagnetic spectrum.


  • Basser53 [John Neumann]
  • 03/22/2020 02:10PM
Some confusion here. You quote the radius of a typical neutron star as 11 kilometers. You also say a typical neutron star is 11 kilometers across (diameter). These are two very different measurements.


Yes, Thank you -- You are absolutely correct -- Good catch.

It should read "22 kilometers across (diameter)."

It's gratifying to see that folks are actually reading these news items rather than just looking at the pretty pictures and videos.

Thanks for pointing this out.