Physicists look to a new telescope to understand neutron stars and matter at the extremes

Abstract

Astronomers ostensibly know plenty about neutron stars: the hot, collapsed remnants of massive stars that have exploded as supernovae. These objects can spin up to hundreds of times a second, generate intense magnetic fields, and send out jets of radiation that sweep the sky like beams from a lighthouse. When two neutron stars collide, the ripples in space-time can be detected by gravitational wave observatories on Earth. Packing more than the mass of the Sun into a ball about 20–25 kilometers across, neutron stars pack in matter at the highest possible density before collapse. “They really are the last gasp of matter, before the event horizon and the nothingness of the black hole,” says physicist Zaven Arzoumanian at the NASA Goddard Space Flight Center in Baltimore, MD. The powerful, spinning magnetic fields of pulsars accelerate charged particles that collide with the surface at hotspots, generating the X-rays that stream out into space. Thanks to NASA’s Neutron star Interior Composition Explorer, Pulsar J0030+0451, visualized here based on data collected, has the most precise measurements of a pulsar’s mass and size. Newly elucidated hotspot shape and location data have challenged conventional views. Image credit: NASA’s Goddard Space Flight Center. And yet, what’s deep inside a neutron star remains an open question. “Understanding what happens to matter at such high densities has long been a puzzle,” says Arzoumanian. Now a small, boxy X-ray telescope mounted on the International Space Station is spilling the inner secrets of these stars. Called the Neutron Star Interior Composition Explorer, or NICER, it can measure the size and mass of neutron stars, revealing their true density. Arzoumanian presented NICER data at the April 2020 meeting of the American Physical Society, which was held online. The early results are promising, showing that the instrument has the potential to capture …