image: The solar journey through space is carrying us through a cluster of very low density interstellar clouds. Right now the Sun is inside of a cloud, the Local Cloud, that is so tenuous that the interstellar gas detected by Interstellar Boundary Explorer (IBEX) is as sparse as a handful of air stretched over a column that is hundreds of light years long. These clouds are identified by their motions. The Sun travels through the Local Cloud at 52,000 miles per hour. As it moves, neutral interstellar helium is swept into the Solar System and the Sun's gravity concentrates this helium into a trail of helium gas, known as the 'helium focusing cone,' that follows the Sun through space. Comparisons of the helium flow direction measured over the past forty years by spacecraft from the United States, the former Soviet Union, Europe, and Japan, indicate that the direction of this flow has changed by about six degrees over forty years. This image relates to a paper that appeared in the 6 September, 2013, issue of Science, published by AAAS. The paper, by Priscilla Frisch at University of Chicago in Chicago, IL, and colleagues was titled, "Decades-Long Changes of the Interstellar Wind Through Our Solar System." view more
Credit: [Image courtesy of NASA/Goddard/Adler/University of Chicago/Wesleyan University]