A new mission, called the Neutron Star Interior Composition Explorer (NICER) is in the works that would unveil the dark heart of a neutron star. NICER was selected by the NASA for study as a potential Explorer Mission of Opportunity in September this year and thus will receive $250,000 to conduct an 11-month implementation concept study.

If NASA approves its construction, the mission will be launched by summer of 2016 and attached robotically to the International Space Station.

Neutron stars are born when a massive star runs out of fuel and collapses under its own gravity, crushing the matter in its core and blasting away its outer layers in a supernova explosion that can outshine a billion suns.

"We have no way of creating neutron star interiors on Earth, so what happens to matter under such incredible pressure is a mystery - there are many theories about how it behaves,"said Dr. Zaven Arzoumanian of NASA's Goddard Space Flight Center in Greenbelt, Md. who is Deputy Principal Investigator of NICER.

"The closest we come to simulating these conditions is in particle accelerators that smash atoms together at almost the speed of light. However, these collisions are not an exact substitute - they only last a split second, and they generate temperatures that are much higher than what's inside neutron stars,"

An array of 56 telescopes from NICER will collect X-rays generated both from hotspots on a neutron star's surface and from its powerful magnetic field. A neutron star has two hotspots on opposite sides, one at each magnetic pole, the place where the star's intense magnetic field emerges from the surface. The particles trapped in the magnetic field rain down and generate X-rays when they strike the surface. As the hotspots rotate into our line of sight, they produce a pulse of light, like a lighthouse beam, giving rise to the stars' alternate name, pulsars.

Thus, if researchers know a neutron star's mass, what they only need to do is find out how big it is to get the correct Equation Of State and unlock the secret of what matter does under extreme gravity.

"The problem is that neutron stars are small, and much too far away to allow their sizes to be measured directly," says NICER Principal Investigator Dr. Keith Gendreau of NASA Goddard.

"NICER will be the first mission that has enough sensitivity and time-resolution to figure out a neutron star's size indirectly. The key is to precisely measure how much the brightness of the X-rays changes as the neutron star rotates," he added.