Watch how NASA’s Neutron star Interior Composition Explorer (NICER) has expanded our understanding of pulsars, the dense, spinning corpses of exploded stars. Pulsar J0030+0451 (J0030 for short), located 1,100 light-years away in the constellation Pisces, now has the most precise and reliable measurements of both a pulsar’s mass and size to date. The shapes and locations of its hot spots challenge textbook depictions of these incredible objects.
Music: "Uncertain Ahead" and "Flowing Cityscape" (underscore). Both from Universal Production Music
Scientists have reached a new frontier in our understanding of pulsars, the dense, whirling remains of exploded stars, thanks to observations from NASA’s Neutron star Interior Composition Explorer (NICER). Data from this X-ray telescope aboard the International Space Station has produced the first precise and dependable measurements of both a pulsar’s size and its mass.
The pulsar in question, J0030+0451 (J0030 for short), is a solitary pulsar that lies 1,100 light-years away in the constellation Pisces. While measuring the pulsar's heft and proportions, NICER revealed that the shapes and locations of million-degree hot spots on the pulsar’s surface are much stranger than generally thought.
Using NICER observations from July 2017 to December 2018, two groups of scientists mapped J0030’s hot spots using independent methods and converged on nearly identical results for its mass and size. One team, led by researchers at the University of Amsterdam, determined the pulsar is around 1.3 times the Sun’s mass, 15.8 miles (25.4 kilometers) across and has two hot spots — one small and circular, the other long and crescent-shaped. A second team found J0030 is about 1.4 times the Sun’s mass, about 16.2 miles (26 kilometers) wide and has two or three oval-shaped hot spots. All spots in all models are in the pulsar’s southern hemisphere — unlike textbook images where the spots lie on opposite sides other at each magnetic poles.
One team, led by researchers at the University of Amsterdam, determined J0030 is 1.3 times the Sun’s mass, 15.8 (25.4 kilometers) across and has two spots — one small and circular and the other long and crescent-shaped. This visualization shows J0030 from its equator, 90 degrees from the spin axis.
The Amsterdam-led team determined that NICER’s line of sight onto the pulsar is 54 degrees from the spin axis, as shown in this wireframe animation. The pulsar is so dense its gravity warps nearby space-time — the “fabric” of the universe as described by Einstein’s general theory of relativity. Space-time is so distorted that light from the side of the pulsar facing away from us is “bent” and redirected into our view, shown by the warped gridlines. This makes the star look bigger than it really is.
Another team, led by a researcher at the University of Maryland, found that J0030 is 1.4 times the Sun’s mass, about 16.2 miles (26 kilometers) wide and has two or three oval hot spots. This visualization shows the three-oval model from the equator, 90 degrees from the spin axis.
The Maryland-led team calculated that NICER views J0030 58 degrees from its spin axis, as shown in this wireframe. The two teams determined slightly different viewing angles based on their independent modeling methods.
This visualization shows the spot-and-crescent and three-oval models side by side. J0030 challenges the traditional textbook image of pulsars. Scientists are still trying to understand what caused the shape and arrangement of its hot spots.