[jmyeet]

One of the first gravitational wave detections by LIGO was I think the merger of two black holes or maybe a black hole and a neutron star. It was over a billion light years away I think but was so energetic that it conveted approximately 5 Solar masses into energy in about one second. That's ~10^48 Joules. In 1 second that is ~10^48 Watts.

For comparison, the Milky Way has an estimate of 5x10^36 Watts so we're talking about the energy output, very briefly, of roughly a trillion Milky Way galaxies.

The other that gets me is amgnetars. These are neutron stars with an insane magnetic field. The strongest detected exceeds 1 billion Tesla, making is 30 trillion times stronger than Earth's magnetic field. Get too close and it would flatten atoms and ultimately break molecular bonds and rip electrons out of your body. Google seems to think that happens at ~1000km, which is pretty close to get to a neutron star but still, that's a magnetic field.

These things are quite rare and quite unstable. If you think about it, they must have a lot of protons to generate a field so strong, which means that the gravity is overcoming the strong nuclear force but also the electric repulsion.

[pdonis]

> If you think about it, they must have a lot of protons to generate a field so strong

Not necessarily. Neutrons have a magnetic moment. As I understand it, there is a magnetohydrodynamic model of how a magnetar's field gets generated, which would require protons, but it's not the only model and we don't have enough data to be able to rule out other models.

[robocat]

Aside: Carbon-13 has one more neutron than Carbon-12, so the unpaired neutron gives it a magnetic moment which is what is used for C13 Nuclear Magnetic Resonance (NMR) spectroscopy.

https://en.wikipedia.org/wiki/Carbon-13_nuclear_magnetic_res...

[taneq]

> Neutrons have a magnetic moment.

Wait, what? Huh, I have some reading to do. Thanks! :D

I thought neutron stars generally had a shell or crust of iron, which generates a magnetic field (as metals do) if the neutron star is spinning.

[pdonis]

> I thought neutron stars generally had a shell or crust of iron, which generates a magnetic field (as metals do) if the neutron star is spinning.

They do, but the neutrons themselves also have magnetic properties. (The simplest heuristic way to think of it is that neutrons are made of three quarks, and the magnetic moment is due to the quarks moving around inside the neutron. But that's a highly heuristic picture and leaves out a lot of complications.)