NASA's Voyager 1 and 2 probes have revealed that the solar system is "squashed" relative to the interstellar medium.

Voyager 2 has crossed into a region called the heliosheath, where the solar wind runs up against the interstellar medium. Voyager 2 is about 1.5 billion kilometers closer to the Sun than Voyager 1, which reached the heliosheath in late 2004. Because the two spacecraft are headed away from the Sun in different directions, scientists concluded that the bubble carved into the interstellar medium by the solar wind is not perfectly spherical.

Scientists got more information from this mission than Voyager 1 because Voyager 2's plasma science instrument is still working, and managed to capture data as the termination shock at the heliosheath "sloshed" back and forth, allowing the spacecraft to sample it several times.

It'll be a while--probably 7 to 10 years--before the Voyager spacecraft leave the solar system altogether and cross into interstellar space itself, Stone said. The researchers hope that will be before the Voyagers' radioactively powered batteries are estimated to run out of juice--sometime between 2020 and 2025, he added.

The image above is not to scale, it shows the plasma from interstellar space colliding with the heliosphere that surrounds our Sun.

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