September 6, 2013
IBEX Data Suggests Interstellar Winds Have Changed Direction
redOrbit Staff & Wire Reports - Your Universe Online
Data obtained through NASA's Interstellar Boundary Explorer (IBEX) project has revealed that neutral interstellar atoms are flowing into the solar system from a different direction than previously observed.
That information has led scientists affiliated with the mission to believe that those particles, which flow past the Earth as the solar system passes through the surrounding interstellar cloud at speeds of 23 kilometers per second (50,000 miles per hour), have most likely changed direction over the past four decades.
The finding, which is detailed in the latest edition of the journal Science, helps officials at the US space agency map our location in the Milky Way, and is also essential for understanding our place in the cosmos in the past, present and future.
Furthermore, experts can use the data to obtain deeper insight into the dynamic nature of the interstellar winds, which in turn has major implications on the size, structure and nature of the sun’s heliosphere (a gigantic bubble which surrounds our solar system and shields the planets from potentially dangerous galactic radiation).
“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,” co-author Eberhard Möbius, principal scientist for the IBEX mission at UNH, explained in a statement. “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.”
“We concluded it's highly likely that the direction of the interstellar wind has changed over the past 40 years. It's also highly unlikely that the direction of the interstellar helium wind has remained constant,” added Dr. Priscilla Frisch, lead author of the study and a senior scientist in the Department of Astronomy and Astrophysics at the University of Chicago. “We think the change in wind direction could be explained by turbulence in the interstellar cloud around the Sun.”
Data were obtained from IBEX and 10 other spacecraft over the course of 40 years, the researchers explained. Three different methods were used to gather measurements of the neutral interstellar helium wind direction.
IBEX and Ulysses provided direct in situ measurements, while earlier measurements used fluorescence of solar extreme ultraviolet radiation of the helium atoms near the Sun and a third set included an analysis of helium flow direction from neutral particles in the solar system that become ionized near the Sun and join the solar wind.
“This result is really stunning,” said Dr. Dave McComas, IBEX principal investigator, assistant vice president of the Space Science and Engineering Division at Southwest Research Institute, and one of the paper’s authors. “Previously we thought the very local interstellar medium was very constant, but these results show just how dynamic the solar system’s interaction is.”
“Prior to this study, we were struggling to understand why our current measurements from IBEX differed from those of the past,” added co-author Nathan Schwadron, lead scientist for the IBEX Science Operations Center at UNH. “We are finally able to resolve why these fundamental measurements have been changing with time: we are moving through a changing interstellar medium.”