For years, researchers have known that the solar system is bounded by a vast bubble of magnetism. Called the "heliosphere," it springs from the sun and extends far beyond the orbit of Pluto, providing a first line of defense against cosmic rays and interstellar clouds that try to enter our local space. Although the heliosphere is huge and literally fills the sky, it emits no light and no one has actually seen it.
Although the ribbon looks bright in the IBEX map, it does not shine in any conventional sense. The ribbon is not a source of light, but rather a source of particles--energetic neutral atoms or ENAs. IBEX's sensors can detect these particles, which are produced in the outer heliosphere where the solar wind begins to slow down and mix with interstellar matter from outside the solar system.
"IBEX is now making a next all-sky map, and we're eager to see if the ribbon is changing," says McComas. "Watching the ribbon evolve--if it is evolving--could yield more clues."