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NEWSCIENCENEWSCIENCENEWSCIENCE oe micetmeaed| | UPDATE: Knot in the Ribbon at the = While the second map, released map has changed significantly. | Edge of the Solar System "Unties" publicly with the just-published Overall, the intensity of ENAs has lhe unusual "knot" in the bright, paper, shows the large-scale dropped 10% to 15%, and the hotspot Tharrow ribbon of neutral atoms structure of the ribbon to be has diminished and spread out along | emanating in from the boundary _ generally stable within the six-month the ribbon. between our solar system and_ period, changes are also apparent. "We thought we might detect small | interstellar space appears to have The polar regions of the ribbon changes occurring gradually] "untied". Researchers believe the display lower emissions, and the throughout the Sun's Il-year-long| ribbon forms in response to knot diminishes by as much as a activity cycle, but not over just six | interactions between interstellar third and appears to "untie" as it months,” notes David McComas, | space and the heliosphere, the spreads out to both lower and higher principal investigator for the IBEX | protective bubble in which the Earth _ latitudes. mission. "These observations show | and other planets reside. "What we're seeing is the knot pull hat the interaction of the Sun with Sensitive neutral atom detectors apart as it spreads across a region of he interstellar medium is far more | aboard IBEX produce global maps of the ribbon," says Dr David J. dynamic and variable than anyone | this region every six months. McComas, IBEX principal investigator envisioned.” Analyses of the first map, released and an assistant vice president at In the past, space physicists had | last fall, suggest that the ribbon is Southwest Research Institute in San ittle notion of what to expect along | somehow ordered by the direction of Antonio, Texas. "To this day, the he boundary where the Sun's own | the local interstellar magnetic field science team can't agree on exactly magnetic bubble, the heliosphere, | outside the heliosphere, influencing what causes the knot or the ribbon, meets interstellar space. It takes | the structure of the heliosphere more but by comparing different sky maps about a year to reach the| than researchers had previously we find the surprising result that the eliosphere's edge. Finally, the ENAs | believed. The knot feature seen in region is changing over relatively ake another six months to many | the northern portion of the ribbon in short time periods. Now we have to years to complete the return trip back | the first map stood apart from the _ figure out why." o Earth. rest of the ribbon as the brightest (Source: ScienceDaily.com, 1 October With ENAs starting out from such a | feature at higher energies. 2010, http://tinyurl.com/35msrm6) wide range of distances and travelling ‘ back towards Earth at different speeds, IBEX mission scientists had expected that any highs and lows in intensity arising within the heliosheath would be hopelessly smeared out in the spacecraft's all-sky maps. So they're elated by the variations and changes seen so far by IBEX. These early results hint that the solar wind and the interstellar flow might be interacting in a thinner layer than many researchers had imagined possible. "The public might think that scientists make measurements and instantly know what's going on, but that is not how science really works," McComas observes. "We thought the outer heliosphere would be stable over time—and IBEX is showing us that it's not. This is changing the | One of the clear features visible in the IBEX maps is an apparent knot in the game completely.” ribbon. This visualisation shows a close-up of the ribbon (green and red) (Source: ScienceDaily.com, 30 September | Superimposed on the stars and constellations in the night-time sky. (Source: 2010, http://tinyurl.com/34magku) IBEX Science Team/Goddard Scientific Visualization Studio/ESA) 52 * NEXUS DECEMBER 2010 - JANUARY 2011 www.nexusmagazine.com