Credit: NASA’s Goddard Space Flight Center/CI Lab
Imagine taking a star with twice the mass of the Sun and crushing it down to the size of Manhattan. The result would be a neutron star—one of the densest objects found anywhere in the Universe. In fact, they exceed the density of any material found naturally on Earth by a factor of tens of trillions. Although neutron stars are remarkable astrophysical objects in their own right, their extreme densities may also allow them to function as laboratories for studying fundamental questions of nuclear physics, under conditions that could never be reproduced on Earth.
Neutron stars are so dense, that a single teaspoon of one would have a mass of about a trillion kilograms.
Because of these exotic conditions, scientists still do not understand what exactly neutron stars themselves are made from, their so-called “equation of state” (EoS). Determining this is a major goal of modern astrophysics research. A new piece of the puzzle, constraining the range of possibilities, has been discovered by a pair of scholars at the Institute for Advanced Study (IAS): Carolyn Raithel, John N. Bahcall Fellow in the School of Natural Sciences; and Elias Most, Member in the School and John A. Wheeler Fellow at
Neutron star merger and the gravity waves it produces. Credit: NASA/Goddard Space Flight Center
Ideally, astrophysicists would like to look inside these exotic objects, but they are too small and distant to be imaged with standard telescopes. Researchers instead rely on indirect properties that they can measure—such as the mass and radius of a
Doomed neutron stars whirl toward their demise in this animation. Gravitational waves (pale arcs) bleed away orbital energy, causing the stars to move closer together and merge. As the stars collide, some of the debris blasts away in particle jets moving at nearly the speed of light, producing a brief burst of gamma rays (magenta). In addition to the ultra-fast jets powering the gamma rays, the merger also generates slower-moving debris. An outflow driven by accretion onto the merger remnant emits rapidly fading ultraviolet light (violet). A dense cloud of hot debris stripped from the neutron stars just before the collision produces visible and infrared light (blue-white through red). The UV, optical, and near-infrared glow is collectively referred to as a kilonova. Later, once the remnants of the jet directed toward us had expanded into our line of sight, X-rays (blue) were detected. This animation represents phenomena observed up to nine days after GW170817. Credit: