A neutron star is formed following the violence of a supernova, with the caveat that the original star’s mass was between eight and 30 times the mass of Sol (Earth’s star). The supernova, in which a massive star blows off its gaseous outer shell, occurs when the star has exhausted its nuclear fuel and has converted most of its core to iron. Iron will not support fission or fusion without the addition more energy, and the core will explode when the core reaches about 1.4 solar masses.
The tell-tale signs of a neutron star’s formation
The most obvious sign will of course be visual; a supernova will be detected in astronomical photographs or visually by observing the skies. Having blown off their outer layers (their atmosphere, essentially) in cosmic blasts, supernovae are hard to miss.
A super-massive star that blows itself apart after the exhaustion of the fuels that can support fusion “cools off very quickly … by neutrino emission,” and scientists build detectors in very deep chambers in the Earth, filled with water, to find evidence of such emissions. This process requires extreme patience and yields low numbers of neutrons, no matter what the event, so finding significantly large numbers of neutrons seems to indicate that a supernova has occurred, producing a neutron star.
Other indications from neutron stars
Neutron stars have been found to be about 10 kilometers in diameter. At this very reduced size, their angular momentum is very small compared with that operating within the larger original star. Therefore, “[n]eutron stars rotate very rapidly, up to 600 times per second.”
Despite their tiny physical size, neutron stars display the strongest magnetic fields of any object in the known universe. “[E]ven the feeblest neutron star magnetic fields are a hundred million times Earth's.”
A neutron star that has a companion star may pull material away from that companion and form an accretion disk around itself, periodically obscuring signals from the neutron star. It appears one of these (J1023) was discovered by the Green Bank Telescope in West Virginia in 2007. “The 2007 GBT observations showed that the object is a millisecond pulsar, spinning 592 times per second.” The radio waves from pulsars may be observed “pulsing” like the light from a terrestrial lighthouse, which is how the phenomenon got its name.
Measuring stellar phenomena
Scientists use computers to simplify the magnificent complications of cosmic mathematics, orbital movement through gravity fields, and the complexity of how stars evolve when their fuel is running low. They still require ever more precise observations of stars in nature in order to hone their data and acquire more accurate calculations. Space telescopes have become very important tools for gathering needed data, along with the continuing utility of ground-based radiotelescopes.
All of it is expensive, but all of it leads to better theories concerning how the universe works and in what ways it will evolve in the future. This will greatly assist those explorers who journey into space for exploration and, someday, perhaps for colonization.