Astronomers Unveil Mystery of Pulsar’s Enigmatic Behavior

An international team of scientists has unraveled the mystery behind the puzzling behavior of the pulsar J1023 (PSR J1023+0038). From time to time, it “switches” between two brightness states. It turns out that these processes are driven by material ejections.

Pulsar J1023 as imagined by an artist. Source: ESO/M. Kornmesser

A pulsar is a rapidly rotating neutron star with a strong magnetic field that emits electromagnetic radiation from its poles. These emissions sweep through space like a lighthouse beam, and astronomers observe them when they cross Earth’s line of sight. As a result, the star appears to pulse in brightness.

J1023 is part of a binary system located 4,500 light-years away from the Sun. It was first studied by astronomers in 2009. At that time, J1023 behaved like any other pulsar, regularly flashing at a constant electromagnetic frequency. However, in 2013, it suddenly started switching between two states: a high-energy mode, where it emitted X-rays, bright visible and ultraviolet light, and a low-energy mode, where it was dimmer at these frequencies and emitted more radio waves. The pulsar can remain in each state for several seconds or minutes and then switch to the other state within a few seconds.

This switching puzzled astronomers for a long time. In a study involving 12 ground-based and space telescopes, they concluded that the switching is due to a complex interaction between the pulsar wind (a stream of high-energy particles emitted by the pulsar) and the matter flowing from the companion star to the pulsar.

In the low-energy mode, the matter being consumed by the pulsar is ejected in a narrow stream perpendicular to the disk. However, over time, the material accumulates closer and closer to the pulsar, and at that point, it gets caught in the pulsar wind, causing it to heat up. As a result, the system switches to a high-energy mode, shining brightly in X-rays, ultraviolet, and visible light. Eventually, clumps of this hot material are expelled by the pulsar in a jet. The researchers liken these clumps to hot cannonballs. When the hot material in the disk becomes depleted, the system starts shining less brightly, transitioning back to the low-energy mode.

According to the researchers, while they have managed to uncover the mystery behind J1023’s peculiar behavior, they plan to continue studying it. In the future, the researchers intend to observe the pulsar using the Extremely Large Telescope, currently under construction in the Atacama Desert. Source: