Getting to Know a Neutron Star: How Heavy Can They Be?

This year the Ligo Interferomenter Gravitational-wave Observatory (LIGO) Scientific Collaboration announced the discovery of a potentially new type of object that fell into a black hole, of course never to be seen or heard from again! Black holes are always interesting, but in this case it is not the black hole that is in the spotlight.

Instead, it is that ill-fated infalling object that grabbed all the attention. This is because information was obtained that points to the discovery of the heaviest known neutron star.

Neutron stars should not be confused with ordinary stars we see in the sky. Stars are made of hydrogen and tend to shine in colors which our eyes can see. On the other hand, neutron stars are formed from the centers of massive stars. They are made of neutrons, and are very dark against the night sky.

These dim neutron stars are also densely-packed: so much so that a single teaspoon would weigh as much as Mt. Everest. Remarkably, a neutron star does not collapse under its own weight because the neutrons push back on each other with great supporting strength.

But every system has a breaking point. It is thought that at a mass of around 2.5 times the mass of the sun, the stresses become so high that the neutron star is destroyed.

The neutron star just discovered in this study has an estimated mass that exceeds the value for the upper mass limit. Thus, it would appear that nature does not care what we think.

What can we conclude from this discovery? Might this object the new heavyweight champion of neutron stars? If so, then are there still heavier ones that further challenge our understanding of matter? Or, might the object have been a featherweight black hole all along?

We will get to add more to further our understanding of these most enigmatic objects as LIGO continues its survey of colliding neutron stars and black holes in years to come.