ESA Science & Technology - A magnetic loop on the magnetar SGR 0418+5729

This image shows an artist's impression of a magnetic loop on the magnetar SGR 0418+5729.

Magnetars are peculiar pulsars – the spinning remnants of massive stars – that are characterised by unusually intense magnetic fields. SGR 0418+5729 was an exception among magnetars, exhibiting an unusually low dipolar magnetic field – the most direct manifestation of a magnetar's average magnetic field, which can be estimated from its spin-down rate. A study based on data from ESA's XMM-Newton X-ray Observatory has revealed that, as suspected, this magnetar conceals, in its interior, a very strong magnetic field which may even exceed 10¹⁵ Gauss (G).

The strong internal magnetic field of this magnetar reveals itself in a small feature emerging from its surface, where protons absorb some of the X-rays emitted by the magnetar. The protons are confined in this region by a strong and localised magnetic field, with lines that are probably shaped like a series of adjacent arcs, resembling the appearance of loops on the surface of the Sun.