Powerful Relativistic ‘Blades’ Can Divide Entire Stars in Half Using Outflows of Plasma Shaped by Extremely Strong Magnetic Fields

A new study suggests that highly magnetized neutron stars can form 'blades' of plasma, cutting the star in half.

Magnetars and Gamma-Ray Burst

Magnetars are some of the most threatening celestial objects in the universe, which contain some of the most intense magnetic fields ever measured. Like the Sun, these hyper-dense balls of matter are smaller than the stars but shine many times brighter.

These highly magnetized neutron stars are considered sources of classical gamma-ray bursts (GRBs). GRBs are some of the most powerful explosions in the sky, but they happen so far away that we can only see them as a brief but intense blip of excess gamma-ray radiation.

Only a few objects can generate the energies needed to power a GRB, and most astrophysicists assume that either black holes or magnetars are involved. Magnets are believed to meet this extreme energy requirement with large enough surface magnetic fields and short spin-down times. This likely happens when they are engaged in something violent, such as the ripping apart of a star. However, experts still struggle to explain why some GRBs fade away very slowly.

Star Bisecting Blades

In a recent study, Marcus DuPint and Andrew Macfadyen from the Center for Cosmology and Particle Physics at New York University suggest that stars could be sliced in half by ultra-powerful outflows of plasma shaped by powerful magnetic fields. These star-splitting relativistic blades could explain some of the brightest explosions in the universe.

The scientists investigated the possibility that lingering GRBs may occur upon the death of some massive stars. As the core of the star collapses, it forms a neutron star made of ultra-dense neutrons surrounded by heavy layers of hydrogen and helium. That neutron star can acquire an extremely strong magnetic field through rapid compression and rotation. This turns the neutron star into a magnetar, which hosts the most powerful magnetic fields in the universe.

Various challenges surround the newborn magnetar. Its gravitational pull draws the remaining atmosphere of the parent star onto it, but the intense radiation and magnetic fields strike that plasma around in excitement. In a previous study, scientists concluded that in the maelstrom, a jet forms along the spin axis of the magnetar, which punches its way through the dying star.

The authors of the new study suggest that the magnetic fields of the magnetar can also release intense bursts of radiation along its equator. These radiation beams are shaped by the extreme centrifugal forces of the rotating star, forming a blade that moves outward through the star at nearly the speed of light while carrying more energy than a supernova explosion.

It was also found that the relativistic blade can perfectly split the star in half on its way out. Then, it travels for a distance well over several times the radius of the original star before finally losing steam. This could explain the existence of longer-lasting GRBs.

In the future, the researchers plan to investigate how the blade evolves with time and how the ensuing death of a star unfolds. The findings from this research can help them identify key signatures of this type of explosion and determine if the previously observed GRBs can be explained with this model.