Neutron stars are one of the weirdest things out there. When massive enough stars die, their outer layers explode away as supernovae while their leftover cores collapse down. The cores are massive, and without the pressure from ongoing nuclear reactions pushing outward, gravity is able to crush them so tightly that protons and electrons can’t exist separately, and the entire thing collapses into just neutrons. Depending on the exact circumstances of both the initial collapse and the surrounding environment, the resulting dead star may be rapidly spinning like a pulsar. It may have a powerful magnetic field and be called a magnetar, and it may be both.
And it may, sometimes, emit millisecond-long flashes of radio emission, giving off a fast radio burst (FRB).
And a neutron star that repeatedly gives off fast radio bursts has been found with a companion that gives off constant, faint, radio emissions.
And this is the second neutron star like this we’ve found.
And in astronomy, two of a thing count as a trend, so it appears that fast radio bursting neutron stars may come with companions that softly emit radio all the time.
Fast radio bursts are a fairly new discovery, and we don’t know much about them yet. Being able to precisely locate them on the sky and then figure out their environments is going to be key to advancing our understanding. Environments can alter how we see things, and in this case, they can also alter where we see things to be.
In general, when a radio pulse travels through the universe, different colors of light can travel through material at different speeds. In a vacuum, light moves at the speed of light, but when going through clouds of electrons, higher frequency light travels faster than lower frequency light. This spreads out as a pulse, and if we know the density of electrons between us and a distant object, the amount that we see the light dispersed can tell us where the radio pulse originated.
With this object, we can see it is located in a galaxy only a few billion light-years away, but the normal dispersion technique indicates it is 8-9.5 billion light-years away. According to team researcher Kshitij Aggarwal: This means that there is a lot of material near the FRB that would confuse any attempt to use it to measure the gas between galaxies. If that’s the case with others, then we can’t count on using FRBs as cosmic yardsticks.
Essentially, the material around the source is faking us out and leading us to believe the object is simply farther away. And now when we find object three, we have to hope we can also see where it is through some other means. But first, we have to find object three.
This work is published in Nature Astronomy with first author C-H Niu.
NRAO press release
“A repeating fast radio burst associated with a persistent radio source,” C.-H. Niu et al., 2022 June 8, Nature