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Interstellar winds buffeting our solar system have shifted direction, study finds

According to a news release from the University of New Hampshire, researchers have found that the interstellar winds buffeting our solar system have shifted direction over the last 40 years.

The discovery, which was made using NASA’s Interstellar Boundary Explorer (IBEX) mission and several other spacecraft, assists scientists with their effort to chart our location within the Milky Way galaxy and is critical for comprehending our place in the cosmos.

The finding also helps scientists better their understanding of the dynamic nature of the interstellar winds, which has significant meaning for the size, structure and nature of our Sun’s heliosphere.

“It was very surprising to find that changes in the interstellar flow show up on such short time scales because interstellar clouds are astronomically large,” notes co-author Eberhard Möbius, University of New Hampshire principal scientist for the IBEX mission. “However, this finding may teach us about the dynamics at the edges of these clouds—while clouds in the sky may drift along slowly, the edges often are quite fuzzy and dynamic. What we see could be the expression of such behavior.”

The data from the IBEX spacecraft reveal that neutral interstellar atoms are moving into the solar system from a different direction than previously detected. These atoms move past our planet as the interstellar cloud encircling the solar system passes the Sun at 23 kilometers per second.

According to the researchers, the most recent IBEX measurements of the interstellar wind direction varied from those obtained by the Ulysses spacecraft in the 1990s. That variation convinced the IBEX scientists to compare and contrast the IBEX measurements to data obtained by 11 spacecraft between 1972 and 2011. The scientists hoped to collect as much evidence from as many sources as possible to identify whether the latest instruments just offered more accurate results, or whether the wind direction itself altered over the years.

According to NASA, the diverse set of observations depended on three different techniques to measure the incoming interstellar wind. IBEX and Ulysses directly measured neutral helium atoms as they moved through the inner solar system. IBEX’s measurements are taken in close proximity to Earth, while Ulysses’ measurements stretch out to the orbit of Jupiter.

The third method to measure the helium wind depends on the reality that after this interplay with the Sun’s radiation, a small number of neutral helium atoms gain an electron, and thus become charged. NASA’s STEREO and ACE are designed to examine charged particle and can determine the longitudinal direction of the particle wind.

According to NASA, the measurements from these varied sources reveal that the direction of the interstellar wind has altered some 4 to 9 degrees over the last 40 years.

“Prior to this study, we were struggling to understand why our current measurements from IBEX differed from those of the past,” adds co-author Nathan Schwadron, lead scientist for the IBEX Science Operations Center at the University of New Hampshire. “We are finally able to resolve why these fundamental measurements have been changing with time: we are moving through a changing interstellar medium.”

The results are described in greater detail in the journal Science.