Thanks toXMM-Newton space telescope, from ESA, a team of scientists has discovered thata curious dead star has one of the strongest magnetic fields in the universe, even though all indications seemed to indicate that his magnetism was unusually weak. The object, known as SGC 0418 + 5729 (or SGR 0418 for short), is amagnetar, that is, a type of neutron star.
A neutron star is the dead core of a massive star that ended up collapsing on itself after exhausting all its fuel and exploding as a supernova. These are extraordinarily dense objects, accumulatinga mass greater than that of our Sunin a sphere barely 20 kilometers in diameter, that is, the size of a medium-sized city.
A small percentage of neutron stars transform into magnetars, objects with a strong magnetic field. For reference, they can have magnetism billions or billions of times stronger than that generated by MRI machines in hospitals. These magnetic fields causemagnetars sporadically emit powerful bursts of high-energy radiation.
SGR 0418 is located in our galaxy, about 6,500 light years from Earth. It was first detected in June 2009 by the Fermi (NASA) and Koronas-Photon (Roscosmos) space telescopes, when it suddenly lit up in the X-ray and gamma-ray bands. Since then, it has been studied with an entire fleet of observatories, including ESA’s XMM-Newton space telescope.
“Until recently, everything seemed to indicate that this magnetar had one of the weakest magnetic fields ever recorded, barely 6 x 1012 Gauss, about 100 times less intense than that of a typical magnetar,” explains Andrea Tiengo, from the University Institute of Superior Studies of Pavia, Italy, lead author of the paper presenting these results in Nature. “Understanding these results was quite a challenge. We suspected that SGR 0418 concealed a much more intense magnetic field, beyond the reach of standard analysis techniques.”
Andrea Tiengo’s team developed uA new technique capable of analyzing this magnetic field with an unprecedented level of detail, based on the study of variations in the magnetar’s X-ray spectrum over an extremely short time scale. This technique has revealed that SGR 0418 is a true magnetic monster, endowed with a very strong and twisted magnetic field, which reaches 1015 Gauss in certain regions of its surface.
“The spectral data collected by XMM-Newton, combined with a new analysis technique, have allowed us to carry out the first detailed study of the magnetic field of a magnetar, confirming that it is one of the most intense in the known universe”, adds Norbert Schartel, XMM-Newton Project Scientist for ESA. “We now have a new tool that will allow us to study the magnetic fields of other magnetars and refine our models of these exotic objects.”
