NASA has launched a satellite that will study in unprecedented detail the distant regions where the outermost reaches of our solar system collide with the cold expanse of interstellar space.
The Interstellar Boundary Explorer, or IBEX, satellite was launched on Sunday from an L-1011 carrier aircraft flying from Kwajalein Atoll, which is part of the Marshall Islands in the mid-Pacific Ocean.
Orbital Sciences' air-launched Pegasus rocket sent the IBEX satellite into its initial 125-mile-high (200-kilometer-high) orbit. Eventually, the spacecraft will settle into a highly elliptical orbit (200,000 by 4,400 miles, or 320,000 by 7,000 kilometers) for its two-year scientific mission.
Interstellar space often is thought of as a vacuum, but it actually contains traces of gas and dust. The solar wind, a stream of electrically conducting gas continuously moving outward from the sun at 1 million mph (1.6 million kilometers per hour), blows against this interstellar material and pushes out a large protective bubble around the solar system. This bubble is called the heliosphere.
As the solar wind reaches far beyond the planets to the solar system's outer limits, it encounters the edge of the heliosphere and collides with interstellar space. A shock wave is present at this boundary.
"These boundaries really protect us from the fairly harsh galactic environment," Boston University astronomer Nathan Schwadron, who heads science operations for the IBEX mission, said during a pre-launch conference call with reporters.
NASA said IBEX will map the boundary region, which is important because it shields the solar system from dangerous galactic cosmic rays. IBEX is designed to detect atoms that are heated and thrown off from the boundary.
"Every six months, we will make global sky maps of where these atoms come from and how fast they are traveling. From this information, we will be able to discover what the edge of our bubble looks like and learn about the properties of the interstellar cloud that lies beyond the bubble," physicist Herb Funsten of the U.S. Department of Energy's Los Alamos National Laboratory, who is part of the mission, said in a statement.
NASA's two unmanned Voyager probes were the first to begin to explore this region, which begins about three times farther from the sun than Pluto's orbit. Voyager 1 passed the inner boundary in 2004, and Voyager 2 crossed over last year.
"The heliosphere's boundary region is enormous, and the Voyager crossings of the termination shock, while historic, only sampled two tiny areas 10 billion miles [16 billion kilometers] apart," NASA scientist Eric Christian said.
