August 15, 2013
Nearby Magnetar Has One Of Universe’s Strongest Magnetic Fields
redOrbit Staff & Wire Reports - Your Universe Online
An odd type of neutron star located approximately 6,500 light years from Earth has one of the strongest magnetic fields in the universe – despite previous suggestions it possessed an unusually low magnetic field.
Using the European Space Agency’s (ESA) XMM-Newton space telescope, a team of astronomers studied the object, a magnetar known as SGR 0418+5729 (SGR 0418). This dense and compact object, which is the dead core of a once massive star that had blasted away its outer layers when it exploded in a supernova, was first discovered in June 2009 by NASA and Roscosmos space telescopes.
“Until very recently, all indications were that this magnetar had one of the weakest surface magnetic fields known,” explained Dr. Andrea Tiengo of the Istituto Universitario di Studi Superiori. “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.”
Despite spinning more slowly than neutron stars, magnetars still complete a rotation in a matter of seconds. Usually, researchers determine the strength of a magnetar’s magnetic field by measuring the rate at which its spin is declining. After observing SGR 0418 for three years, astronomers came to the conclusion it had a weak magnetic field.
However, Dr. Tiengo and his colleagues developed a new technique that involved searching for variations in the X-ray spectrum of the magnetar over extremely short time intervals as it rotates. Using this method, they were able to study SGR 0418’s magnetic field in greater detail and discovered it had far stronger magnetic field than previously believed. Their findings appear in the journal Nature.
“To explain our observations, this magnetar must have a super-strong, twisted magnetic field reaching 1015 Gauss across small regions on the surface, spanning only a few hundred meters across,” Dr. Tiengo said. “On average, the field can appear fairly weak, as earlier results have suggested. But we are now able to probe sub-structure on the surface and see that the field is very strong locally.”
“The spectral data provided by XMM-Newton, combined with a new way of analyzing the data, allowed us to finally make the first detailed measurements of the magnetic field of a magnetar, confirming it as one of the largest values ever measured in the Universe,” added ESA XMM-Newton Project Scientist Norbert Schartel. “We now have a new tool to probe the magnetic fields of other magnetars, which will help constrain models of these exotic objects.”
According to researchers from University College London’s Mullard Space Science Laboratory (MSSL), who were involved in the research, only the large scale magnetic field of these neutron stars had been measured. This study marks the first time astronomers have been able to detect a strong, localized surface magnetic field on a magnetar.
Magnetars were discovered when astronomers witnessed their unusual behavior, including sudden radiation outburst and occasional giant flares, in X-ray wavelengths, MSSL explained. Those unusual features were caused by the evolution, dissipation and decay of their magnetic fields, which have the potential of being thousands of times more intense than radio pulsars and other types of neutron stars.