31 March 2019
An old star strains under its own weight. In a desperate attempt to survive, it burns heavier and heavier elements, fusing elements up the periodic table just to gain the energy to keep its core from collapsing. But in the end its efforts fail. Its core collapses to form a neutron star, and the outer layers of the star are blown away into an expanding sphere of gas and dust.
For most stars, the core collapse and resulting supernova is a fairly uniform process. As a result, we see the neutron star basically in the center of the expanding shell of gas. But the death of a star can be a complex process, where the effects of rotation and strong magnetic fields can be significant. As a result, the neutron star can be given a kick as it forms. When that happens, the neutron star can move away from the center of the supernova remnant.
We’ve seen this before, but recently we’ve learned just how much of a kick some neutron stars can get. Observations from the VLA have found a particular neutron star speeding away at nearly 700 miles per second. In just 10,000 years the neutron star has traveled more than 53 light years. It’s moving so quickly that eventually the star will escape the Milky Way and begin a journey through intergalactic space.
We aren’t sure just how it got its tremendous speed. You might imagine that the original supernova explosion was somehow asymmetrical, but the expanding remnant is fairly spherical. Most likely some kind of turbulence in the collapse of the core gave it a huge push, but we can’t be sure.
What we do know is that some neutron stars can be kicked so hard they leave their home galaxy. There are likely many others drifting from galaxy to galaxy.