(1) This bubble is the heliosphere shaped like a long wind sock as it moves with the Sun through interstellar space.

(2) As the heliosphere plows through interstellar space a bow shock forms much as forms in front of a boulder in a stream.

(3) The heliosphere shields the solar system from 90 percent of energetic cosmic rays — high-speed charged particles that would otherwise bombard the planets and harm life.

(4) Many astronomers think that the limit of the heliosphere, known as the heliopause, is about 9 billion miles (15 billion kilometers) from the sun.

(5) Understanding more about the heliosphere and its ability to filter out galactic cosmic rays could be critical for assessing the safety of human space travel, Schwadron notes.

(6) The two spacecraft are the most distant human-made objects, out at the edge of the heliosphere -- the bubble the sun creates around the solar system.

(7) The atoms recorded by IBEX, which orbits Earth, took a year or two, depending on their energies, to reach the craft from the outer edge of the heliosphere.

(8) The termination shock surrounds the system bubble called the heliosphere.

(9) "First and foremost, this is a big surprise because we thought we know a lot about this region, the edge of the heliosphere," McComas says.

(10) "When the solar wind blows out plasma it too causes a bubble: the heliosphere," he explains.

(11) Past that is the very edge of the solar system, the heliosphere, a vast, teardrop-shaped region of space containing electrically charged particles given off by the sun.

(12) One possibility is that pressure from this external magnetic field has forced particles just inside the heliosphere to bunch together into a ribbon.