|
Magnetars are young neutron stars, with magnetic fields billions of
times stronger than our most powerful Earth-based magnets. The slow
decay of their magnetic fields creates an enormous amount of stress in
their hard outer crust until it eventually fractures. This twists the
magnetic field and releases large amounts of energetic X-rays and
gamma rays as it unwinds. After a decade of silence, the magnetar XTE
J1810-197 suddenly burst back to life in late 2018.
In an article in The Conversation,
Marcus Lower and colleagues describe how
observations with Murriyang, the Parkes radiotelescope, revealed that the normally linearly
polarised radio waves were being converted into circularly polarised waves.
This "linear-to-circular conversion" had long been predicted to occur
when radio waves travel through the super-heated soup of particles
that resides in neutron star magnetic fields.
However, theoretical predictions for how the effect should change
with observing frequency do not yet match the observations all that well.
This is motivating researchers to devise more complex ideas of how radio waves escape from their magnetic fields.
(Image credit: Carl Knox, OzGrav/Swinburne University of Technology; The Conversation)
|
