Universe’s Most Powerful Magnet
Scientists using ESA’s XMM-Newton space telescope have discovered that a curious dead star has been hiding one of the strongest magnetic fields ever seen. That is, despite earlier suggestions of an unusually low magnetic field. The object, known as SGR 0418+5729 (or SGR 0418 for short), is a magnetar, a particular kind of neutron star. A neutron star is the dead core of a once massive star that collapsed in on itself after burning up all its fuel and exploding in a dramatic supernova event.
They are extraordinarily dense objects, packing more than the mass of our Sun into a sphere only some 20 km across — about the size of a city. A small proportion of neutron stars form and live briefly as magnetars, named for their extremely intense magnetic fields, billions to trillions of times greater than those generated in hospital MRI machines, for example. These fields cause magnetars to erupt sporadically with bursts of high-energy radiation.
SGR 0418 lies in our galaxy, about 6,500 light-years from Earth. It was first detected in June 2009 by space telescopes including NASA’s Fermi and Roscosmos’ Koronas-Photon when it suddenly lit up in X-rays and soft gamma rays. It has been studied subsequently by a fleet of observatories, including ESA’s XMM-Newton.
“Until very recently, all indications were that this magnetar had one of the weakest surface magnetic fields known; at 6 x 10^12 Gauss, it was roughly a 100 times lower than for typical magnetars,” said Andrea Tiengo of the Istituto Universitario di Studi Superiori, Pavia, Italy, and lead author of the paper published in 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.”
Magnetars spin more slowly than neutron stars, but still complete a rotation within a few seconds. The normal way of determining the magnetic field of a magnetar is to measure the rate at which the spin is declining. Three years of observations of SGR 0418 had led astronomers to infer a weak magnetic field.
The new technique developed by Dr. Tiengo and his collaborators involves searching for variations in the X-ray spectrum of the magnetar over extremely short time intervals as it rotates. This method allows astronomers to analyze the magnetic field in much more detail and has revealed SGR 0418 as a true magnetic monster.
“To explain our observations, this magnetar must have a super-strong, twisted magnetic field reaching 10^15 Gauss across small regions on the surface, spanning only a few hundred meters across,” said Dr. Tiengo.
“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.”
A simple analogy can be made with localized magnetic fields anchored in sunspots on the Sun, where a change in configuration can suddenly lead to their collapse and the production of a flare or, in the case of SGR 0418, a burst of X-rays.
“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,” adds Norbert Schartel, ESA’s XMM-Newton Project Scientist.
“We now have a new tool to probe the magnetic fields of other magnetars, which will help constrain models of these exotic objects.”
Aussie Researchers Need Telescopes
Astrophysicist Brian Schmidt says he will be forced to abandon the research that won him a Nobel prize unless Australia secures access to the latest generation of telescopes.
“The astronomy that I do and won me the Nobel prize will not be possible in Australia unless this is sorted out,” Professor Schmidt said.
Professor Schmidt’s work relied on access to international optical telescopes via a global partnership co-ordinated by the federal government, which is due to end in 2015 and has not been renewed.
The Australian National University academic said the ‘crisis’ in astronomy was typical of the situation faced by many of the country’s science and medical research sectors, who could not plan their future direction because of stop-start funding and a poorly co-ordinated approach to research.
Professor Schmidt was joined in Canberra on Monday by leaders of the country’s most respected research academies and institutions who are calling for non-partisan support for a long-term scientific research policy.
“A strategic plan means we get the biggest bang for dollars spent,” he said. “This money we spend is going to be used to grow the economic future of the nation through innovation.” Without such a policy, Australia risked losing talented researchers overseas, said Professor Schmidt.
The head of science policy at the Australian Academy of Science, Bob Williamson, said the alliance, which included members of the Australian Academy of Technological Sciences and Engineering, the Cooperative Research Centres Association, Science and Technology Australia and Universities Australia, urged politicians to commit to a 10-year prospective science policy.
Professor Williamson said non-partisan support for the policy was essential to its success. “Many of the most important research programs such as cancer and astronomy require a national commitment of at least five to 10 years,” he said. The knowledge and innovation generated through research was essential to the country’s future economic prosperity, he said.
“We have to guarantee that the future of research is seen as a strategic asset so when the minerals run out, we have our scientific and technical excellence in place.” The Greens science and research spokesman, Adam Bandt, supported the push for a national research policy, saying recent cuts to funding had shown there was not a strong consensus on the importance of science and research.
A joint statement released by Opposition Leader Tony Abbott and shadow science minister Sophie Mirabella said, if elected, the coalition would provide the long-term, stable policies that scientists and researchers needed to excel in their work. “We will cut the red tape that accompanies government research programmes, as well as providing our scientists and researchers with the certainty to plan,” it read. Source” SMH