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Bell Tone

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Music

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Narrator: The Interstellar Boundary Explorer, or IBEX, spacecraft

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is unique in NASA's heliophysics fleet. Instead of studying the

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face of the sun, IBEX looks at the very edge of the sun's reach, starting at

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about 8 billion miles away. The region begins with the

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termination shock, where the solar wind abruptly slows down. It

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ends with the heliopause, the boundary between the solar wind and

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interstellar space. Between the two is the heliosheath, a teardrop

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shaped region sculpted by the pressure of the interstellar medium.

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IBEX is also different because it makes its images from particles instead of light.

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Some ot the atoms it detects originally came from the sun as charged particles

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travelled out to the heliosheath, 'bounced' back, and gained electrons

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to make them neutral. Others were neutral to begin with, and

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came from interstellar space. Both kinds are called Energetic Neutral

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Atoms, or ENAs for short. Over the course of 6 months

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and many orbits, IBEX can paint a picture of the entire sky in

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ENAs. For easier viewing, the sphere of the sky is 'unwrapped'

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and projected onto an oval, much like how a map of the spherical Earth

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is projected onto a rectangle. The colors correspond to

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how many atoms hit the detector from a particular region. Violet represents

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few atoms, and the colors move up to red, which represents many atoms.

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IBEX can also tell how energetic each atom was,

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and, much like filtering light to show one color, create an

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all-sky map of each energy level. Viewing the sky this way can reveal

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some startling things about the edge of the solar system. IBEX is

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led by Dave McComas of the Southwest Research Institute in Texas.

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It's first major discovery was a 'ribbon' of bounced ENAs, showing

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unexpected activity at the edge of the solar system. Subsequent measurements

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show that this ribbon changes over time.

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IBEX has also measured ENAs from the interstellar wind, giving scientists

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a clearer picture of its composition. Surprisingly,

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it turns out that the local interstellar material is different from the sun, and the

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wind is slower, and coming from a different direction that previously thought.

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Closer to home, IBEX has used ENAs to help understand the Earth's

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magnetosphere better. And has even observed the solar wind

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reflecting off the moon. As IBEX

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continues to scan the sun's horizon, who knows what other discoveries it will

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make? Music