Where does the solar system end, and interstellar space begin? The boundary between the solar system and the rest of the Galaxy is called the heliopause, a bubble in interstellar space produced by the sun's wind. This is the place where the pressure of the solar wind is matched by the pressure of the surrounding space. Our two intrepid probes, Voyager 1 and Voyager 2, are somewhere in the vicinity of the heliopause, providing actual measures of local regions of the bubble. But the big picture is currently being obtained by the Interstellar Boundary Explorer, or IBEX. IBEX, launched on October 19, 2008, has been measuring emission from Energetic Neutral Atoms (ENAs) produced by the interaction between the solar wind and the interstellar medium near the heliopause. The image above is the first IBEX all sky map, showing the bubble of ENAs surrounding the sun. And this map showed a totally unexpected result: the bright band of ENA emission seen in green in the image above. As shown, this band lies perpendicular to the local Galactic magnetic field, indicating some heretofore unexpected interaction between these atoms and the Galaxy's magnetic field, but no one yet understands how this interaction works.
Published: October 19, 2009
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Page Author: Dr. Michael F. Corcoran
Last modified Sunday, 25-Oct-2009 10:10:33 EDT