(Shown in a Hubble Space Telescope image, the
"astrosphere" around the star L.L. Orionis approximates
the heliosphere around our solar system, and others)
Mission scientists got their first surprise six months after launch, once the spacecraft had scanned enough overlapping strips of sky to create a complete 360° map. Instead of recording a relatively even distribution all the way around, as expected, IBEX found that the counts of ENAs — and thus the strength of the interaction in the heliosheath — varied dramatically from place to place. The detectors even discovered a long, enhanced “ribbon,” accentuated by an especially intense hotspot or “knot,” arcing across the sky. (IBEX Explores Galactic Frontier, Releases First-Ever All-Sky Map)
Now scientists have finished assembling a second complete sweep around the sky, and IBEX has again delivered an unexpected result: the map has changed significantly. Overall, the intensity of ENAs has dropped 10% to 15%, and the hotspot has diminished and spread out along the ribbon. Details of these findings appear in the September 27th issue of Journal of Geophysical Research (Space Physics).
“We thought we might detect small changes occurring gradually throughout the Sun’s 11-year-long activity cycle, but not over just 6 months,” notes David McComas (Southwest Research Institute), principal investigator for the IBEX mission and the paper’s lead author. “These observations show that the interaction of the Sun with the interstellar medium is far more dynamic and variable than anyone envisioned.”
[link to www.nasa.gov]
(Visuals 1-5, previous information)
From Visual #6
The IBEX science team compares the first and second maps to reveal whether there are time variations in the Ribbon or the more distributed emissions around the ribbon. This animation fades between the first and second IBEX maps. We see that the first and second maps are relatively similar. However, there are significant time variations as well. These time variations are forcing scientists to try to understand how the heliosphere can be changing so rapidly.
[link to www.nasa.gov]
From Visual #7
One of the clear features visible in the IBEX maps is an apparent knot in the ribbon. Scientists were anxious to see how this structure would change with time. The second map showed that the knot in the ribbon somehow spread out. It is as if the knot in the ribbon was literally untangled over only 6 months! This visualization shows a close-up of the ribbon (green and red) superimposed on the stars and constellations in the nighttime sky. The animation begins by looking toward the nose of the heliosphere and then pans up and left to reveal the knot. The twisted structure superimposed on the map is an artist's conception of the tangled up ribbon. The animation then shows this structure untangling as we fade into the second map of the heliosphere.
From Visual #10
The changes in the size of our solar system’s boundaries also cause changes to the galactic cosmic rays that enter the solar system. Although these boundaries do a good job of deflecting the majority of harmful galactic radiation, some fraction of this galactic radiation always makes it into the solar system. When the boundaries shrink in size and the solar wind becomes weaker, galactic cosmic rays have a much easier time gaining access into the inner solar system. In contrast, when the solar wind becomes more powerful, the boundaries inflate and galactic cosmic rays have a harder time penetrating into the solar system. The discovery by IBEX reported here is consistent with inward falling of the boundaries surrounding the solar system. This should allow more galactic radiation to enter the solar system. This animation shows changes in the boundaries around our solar system as they deflate and inflate with time. The fast moving galactic cosmic rays are shown coming in from all directions. When the boundaries deflate, more of the cosmic rays make it into the inner solar system, increasing the radiation levels throughout the solar system.