The findings are based on data from by NASA's Interstellar Boundary Explorer, or IBEX. The Earth-orbiting spacecraft was launched in 2008.
Scientists always presumed the heliosphere had a tail, but this provides the first real data on the shape.
Chief IBEX investigator David McComas, who's with the Southwest Research Institute in San Antonio, says it's difficult to calculate the length of the heliotail. But the evaporating end of the tail could stretch 100 billion miles.
The findings were published in the Astrophysical Journal.
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