On October 19, NASA will launch the small Interstellar Boundary Explorer (IBEX) into orbit on a mission to map the turbulent edge of our solar system, where the solar wind slams into interstellar space. While it won’t actually travel beyond all the planets to investigate the solar system’s far reaches, the coffee table-sized spacecraft must escape the area where Earth’s magnetic field reigns, which could interfere with its measurements. The $169 million observatory is due to climb 200,000 miles (322,000 kilometers) above Earth and settle into orbit there for a mission of at least two years. For comparison, the moon orbits about 240,000 miles (385,000 km) from Earth [SPACE.com].
The edge of the solar system is currently being explored directly by the Voyager 1 and Voyager 2 spacecrafts; both Voyagers launched 31 years ago and recently passed the point where the solar wind is slowed by interactions with the interstellar plasma, a point known as the termination shock. These crafts “are making fascinating observations of the local conditions at two points beyond the termination shock that show totally unexpected results and challenge many of our notions,” said [IBEX researcher David] McComas [World Science].
One of the surprises that arose from the Voyager missions was the discovery that the termination shock is not a fixed point, but appears to be instead a flexible boundary that advances and retreats; this finding seems to have been confirmed recently by new observations of the varying strength of the solar wind. Researchers hope IBEX will add to the Voyagers’ direct observations by mapping the termination shock, and the space beyond, over its two-year mission.
IBEX works by detecting high-speed atoms that are radiating out from the interstellar boundary region, and gradually building up a map of where they came from. The findings of the IBEX will add to our understanding of how our solar system figures into the grander scheme of things, researchers say. “One of [IBEX's] prime goals is to tell us the place of the solar system in the galaxy,” said [IBEX scientist] Eric Christian…. “How the solar system moves through the galaxy is scientifically interesting and may be interesting from an evolution-of-Earth standpoint” [SPACE.com].
Image: NASA GSFC