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(music)

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(music)

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Like a comet, our solar system has a tail.

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It has never actually been observed. Until now. NASA's 

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Interstellar Boundary Explorer, or IBEX recently mapped the boundaries

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of the solar system's tail, called the heliotail. By combining

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observations from the first three years of IBEX imagery, scientists have mapped

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out a tail that shows a combination of fast and slow moving 

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particles. IBEX can map such regions because it uses a technique called energetic

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neutral atom imaging. An energetic charged particle 

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in the outer heliosphere hits a hydrogen atom, stealing its electron

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and becoming neutral. It then travels straight, though some of them come back

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toward the inner heliosphere. They're they collide with IBEX, and are 

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detected. By plotting out such neutral atoms and where they came from, 

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IBEX has recently been able to describe the tail streaming behind the solar

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system. The tail is composed of solar wind plasma and magnetic 

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field. The solar wind streams out from the sun in all directions, out

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past the farthest planets. It eventually slows down, 

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bending back along the tail, due to pressure from the interstellar gas and magnetic

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field. Based on the map of the heliotail, if we could look straight 

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down the tail, we would see a shape a little like a four-leaf clover. 

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The two side leaves are filled with slow moving particles, and the 

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upper and lower leaves with fast ones. This is in line with how 

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the sun releases fast solar wind near its poles, and slower wind 

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near its equator. The four-leaf clover does not align perfectly with 

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the solar system. The entire shape is rotated slightly. 

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This indicates that as it moves farther away from the sun's magnetic influence 

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the charge particles have begun to be pulled into a new orientation,

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aligning with the magentic field of the local galaxy.

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Scientists still do not know how long the tail is, but think that it 

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eventually fades away and becomes indistinguishable from the rest of 

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interstellar space. Together, data from instruments in space 

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and analysis at labs on the ground will continue to improve our understanding 

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of the comet-like tails streaming out behind us.

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(beeping)

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(beeping)

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(beeping)

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