14 DAY TRIAL // A team of astronomers using ESA’s XMM-Newton space telescope have made a surprising discovery and detected what is believed to be the strongest magnetic field in the universe. The most surprising thing about it is that they found the field around a magnetar that was previously believed to have an unusually weak magnetic field.
Magnetars are particular types of neutron stars, the extremely dense objects that are sometimes created by the collapse of a dying star. Neutron stars are only a few kilometers in diameter, yet can weigh as much as our sun.
Magnetars are distinguished, as is obvious from the name, by their strong magnetic field, hundreds or thousands of times stronger than the one of regular neutron stars.
But magnetar SGR 0418+5729 was found to have a very mild field, despite showing all the signs, like bursts of radiation and flares, associated with regular magnetars.
Scientists suspected that the field was actually incredibly strong but hiding below the surface and undetectable with previous methods.
"This magnetar has a strong magnetic field inside it, but it is hidden beneath the surface. The only way you can detect that is to find a flaw on the surface, where the concealed magnetic field can leak out," says Silvia Zane, one of the co-authors of the study.
Magnetars are much too small for direct observations. However, the team looked at how the radiation coming from the object varied during its nine-second rotation.
"We found that at one point during the rotation, the magnetar's X-ray brightness drops sharply. That means something on or near one part of the surface is absorbing the radiation," Roberto Turolla, another author of the study, explains.
The observations have confirmed that the star has in fact a very strong magnetic field that sometimes breaks out to the surface.