Coronal loops on the Sun imaged in extreme ultraviolet light by NASA's SDO mission

“NICER tracked how three bright, X-ray-emitting hot spots slowly wandered across the object’s surface while also decreasing in size, providing the best look yet at this phenomenon,” said George Younes, a researcher at George Washington University in Washington and NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

“The largest spot eventually coalesced with a smaller one, which is something we haven’t seen before.”

This unique set of observations, described in a paper led by Younes and published Jan. 13 in The Astrophysical Journal Letters, will help guide scientists to a more complete understanding of the interplay between the crust and magnetic field of these extreme objects.

A magnetar is a type of isolated neutron star, the crushed core left behind when a massive star explodes.

Compressing more mass than the Sun’s into a ball about 12 miles (20 kilometers) across, a neutron star is made of matter so dense that a teaspoonful would weigh as much as a mountain on Earth.