Mysterious 'ribbon' marks boundaries of solar system
The first complete maps of our solar system produced by the IBEX space satellite have revealed a bright ribbon-like structure — composed of densely packed atoms — that runs around its edges. An international team of scientists is baffled by the presence of the ribbon, which was not seen by the two previous Voyager satellite missions, and further investigation into its role may lead to exciting new evidence on how the heliosphere really operates. The findings were published in the Science journal.
NASA's Interstellar Boundary Explorer (IBEX) space satellite, launched in October 2008 on a two-year mission, is exploring and monitoring the boundary between our solar system and the Sun, particularly the interactions between the Sun and the heliosphere — the 'bubble' that encloses the solar system, protects it from harmful cosmic rays and marks the boundary of our solar system with outer space.
The IBEX satellite's mission was to create the first complete picture of what is happening at the edge of the heliosphere by imaging the energetic neutral atoms (ENAs) that surround the region. The satellite's first 'all-sky maps' of the edge of the solar system — which is more than 9 billion miles long — have revealed a bright and dense ribbon of ENAs that makes nearly a full circle around the solar system.
IBEX principal investigator David McComas of the Southwest Research Institute, Texas, US, said of the phenomenon: 'We’ve observed about a million ENAs over the 6 months that it took to make the sky map. Exactly where the galaxy's magnetic field is most wrapped around the outer boundary of the heliosphere, that’s where the ribbon runs.
'That could be an unbelievably remarkable coincidence, or it could be a fabulous clue that somehow this external magnetic field is actually imprinting on to our heliosphere through some process that we don’t yet understand. There is also some suggestion that it’s actually slightly different and maybe evolving over the six months since the first sky map.'
Scientists at the Southwest Research Institute explained the ribbon of ENAs near the edge of the heliosphere had not been predicted by models or theories. They also noted that its presence seems to show that the surrounding galactic environment is easily imprinted on the heliosphere and could be caused by interactions between the local interstellar magnetic field and the heliosphere.
The findings from the IBEX satellite were backed up by images of the interaction between the heliosphere and interstellar space from another satellite, the Cassini spacecraft, which is currently exploring the planet Saturn. The Cassini imaged its own set of maps of the heliosphere in which the ribbon appeared as a broader 'belt'.
Scientists have long speculated that solar winds formed the structure of the heliosphere, but the presence of the ribbon seems to cast doubt on this.
Scientists comparing the IBEX findings with previous models of the heliosphere concur that no existing model can explain the presence of the ribbon, which may be a permanent or temporary feature of the heliosphere. Space science may now have to change its ideas about the structure of the heliosphere and how it interacts with interstellar space.
The European scientists that participated in this study were from the University of Bern (Switzerland), the Space Research Centre of the Polish Academy of Sciences (Poland), the University of Bonn (Germany), Ruhr-Universität Bochum (Germany), Moscow State University (Russia), the Russian Academy of Sciences' Space Research Institute and the Institute for Problems in Mechanics, and the Office for Space Research and Technology (Greece).