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The Sciences

Space Probe Launched to Study the Surprising Drop in Solar Wind

80beatsBy Eliza StricklandOctober 20, 2008 1:45 PM
IBEX launch

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On Sunday, a small space probe with a big mission took off from Earth in a flawless launch, setting off on a two-year assignment to map the edge of our solar system. The Interstellar Boundary Explorer soared into space aboard an Orbital Space Sciences Pegasus rocket that fired as planned at 12:48 p.m. CDT, moments after dropping from the belly of a modified airliner that flew across the South Pacific near Kwajalein Atoll [San Antonio Express-News].

The $169 million NASA probe will settle into a long, elliptical orbit around Earth that takes it beyond the interference of our planet’s magnetosphere, and almost as far as the moon. From there the IBEX will record the impacts of particles that are formed at the edge of our solar system’s protected space, a region known as the heliosphere. The solar wind, a stream of charged particles spewing from the sun at 1 million miles per hour, carves out a protective bubble around the solar system. This bubble … shields against most dangerous cosmic radiation that would otherwise interfere with human spaceflight [AP]. At the edge of the heliosphere, the solar wind slows down as it slams into interstellar space; IBEX will observe the particles created in this “termination shock” to chart the solar system’s perimeter.

Researchers got reports back from the termination shock when the two Voyager probes crossed that boundary in 2004 and 2007 respectively, almost three decades after their launches from Earth. The Voyagers send back the intriguing information that the termination shock isn’t a fixed point, but seems to fluctuate due to gusts in the solar wind. Lead IBEX scientist David McComas says the new probe should put the Voyager findings into context. “It’s like having two excellent weather stations that provide detailed reports of the weather in their areas, but not having the satellite data that tell you how the weather fronts are changing,” he says. “For this global view we need IBEX” [Physics World]. Researchers will spend the next few weeks checking the IBEX’s systems and making sure it settles into orbit properly; the first scientific data will come back in about a month.

One of the IBEX’s goals is to try to explain the recent finding that the solar wind has dropped to its lowest level in 50 years, which could be causing the heliosphere to shrink slightly, and could allow more interstellar radiation to penetrate our solar system. “Why the sun would be putting less flux out, no one knows,” [said] David McComas. “We don’t believe we’re in imminent danger, but we’ve only measured the solar wind for about 50 years.” In the past decade, the wind’s intensity has waned by about 25 percent. The variation could be part of a natural cycle, McComas said [Bloomberg].

Image: NASA/GSFC

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