Astronomers this week revealed that one of the strongest magnetic fields ever observed has been spotted around a neutron star. The object, dubbed SGR 0418, is also a magnetar – a subset of neutron stars that have strong magnetic fields.

Neutron stars are what is left of stars that burn up their fuel and undergo supernova but do not become black holes. The super-dense objects pack more mass than some stars into spheres smaller than the size of the Earth.

SGR 0418 is located only 6,000 light years from our solar system. Until now, the object was mistakenly measured to have an extremely weak surface magnetic field.

“Until very recently, all indications were that this magnetar had one of the weakest surface magnetic fields known; at 6 trillion Gauss, it was roughly a 100 times lower than for typical magnetars,” said Andrea Tiengo, lead author of the paper on the magnetar published in the journal Nature. “Understanding these results was a challenge. However, we suspected that SGR 0418 was in fact hiding a much stronger magnetic field, out of reach of our usual analytical techniques.”

Tiengo and his colleagues developed a new technique to measure X-ray variations in more detail. The astronomers used the European Space Agency‘s XMM-Newton telescope to observe SGR 0418 and found that it has an extremely powerful magnetic field – measured at around 1 quadrillion Gauss in short spans across its surface.

“On average, the field can appear fairly weak, as earlier results have suggested,” said Tiengo. “But we are now able to probe sub-structure on the surface and see that the field is very strong locally.”

(Image courtesy ESA/ATG Medialab)