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Narrator: The Interstellar Boundary Explorer, or IBEX, spacecraft
is unique in NASA's heliophysics fleet. Instead of studying the
face of the sun, IBEX looks at the very edge of the sun's reach, starting at
about 8 billion miles away. The region begins with the
termination shock, where the solar wind abruptly slows down. It
ends with the heliopause, the boundary between the solar wind and
interstellar space. Between the two is the heliosheath, a teardrop
shaped region sculpted by the pressure of the interstellar medium.
IBEX is also different because it makes its images from particles instead of light.
Some ot the atoms it detects originally came from the sun as charged particles
travelled out to the heliosheath, 'bounced' back, and gained electrons
to make them neutral. Others were neutral to begin with, and
came from interstellar space. Both kinds are called Energetic Neutral
Atoms, or ENAs for short. Over the course of 6 months
and many orbits, IBEX can paint a picture of the entire sky in
ENAs. For easier viewing, the sphere of the sky is 'unwrapped'
and projected onto an oval, much like how a map of the spherical Earth
is projected onto a rectangle. The colors correspond to
how many atoms hit the detector from a particular region. Violet represents
few atoms, and the colors move up to red, which represents many atoms.
IBEX can also tell how energetic each atom was,
and, much like filtering light to show one color, create an
all-sky map of each energy level. Viewing the sky this way can reveal
some startling things about the edge of the solar system. IBEX is
led by Dave McComas of the Southwest Research Institute in Texas.
It's first major discovery was a 'ribbon' of bounced ENAs, showing
unexpected activity at the edge of the solar system. Subsequent measurements
show that this ribbon changes over time.
IBEX has also measured ENAs from the interstellar wind, giving scientists
a clearer picture of its composition. Surprisingly,
it turns out that the local interstellar material is different from the sun, and the
wind is slower, and coming from a different direction that previously thought.
Closer to home, IBEX has used ENAs to help understand the Earth's
magnetosphere better. And has even observed the solar wind
reflecting off the moon. As IBEX
continues to scan the sun's horizon, who knows what other discoveries it will
make? Music
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