  Relativistic jets are observed throughout the Universe, strongly impacting
their surrounding environments on all physical scales, from Galactic binary
systems to galaxies and galaxy clusters. An important avenue to understand the
formation of these jets is by characterising the systems and circumstances from
which they are launched. Whenever a black hole or neutron star accretes matter,
it appears to inevitably result in the launching of a jet, the only exception
being the most common type of accreting neutron stars: those with strong ($B
\geq 10^{12}$ G) magnetic fields. This exception has created the paradigm that
strong magnetic fields inhibit the formation of jets. Here, we report the
discovery of a jet launched by a strongly-magnetised neutron star that is
accreting above the Eddington limit, disproving this long-standing paradigm.
The radio luminosity of the jet is two orders of magnitude fainter than seen in
other neutron stars, implying an important role for the neutron star's
properties in regulating jet power. This jet detection necessitates fundamental
revision of current neutron star jet models and opens up new tests of jet
theory for all accreting systems. It also shows that the strong magnetic fields
of ultra-luminous X-ray pulsars do not prevent such sources from launching
jets.
