Are the Voyager spacecraft still doing good science? You bet, as
witness the passage of Voyager 1 through the termination shock
at the edge of interstellar space. Scientists had assumed the
craft’s crossing of this boundary, where the solar wind abruptly
slows, would confirm previous theories about anomalous,
energetic cosmic rays that were thought to be produced in the
region. But Voyager did anything but, finding the cosmic ray
count to be far lower than predicted during its passage. New
work by David McComas (Southwest Research Institute) and Nathan
Schwadron (Boston University), published recently in the
Geophysical Research Letters, offers a theory why. They base
their thinking on the shape of the shock itself, previously
thought to be circular. The duo showed that a more realistic
shape made sense. “In fact, the termination shock couldn’t be
circular because the solar system is moving through the galaxy,
which would create more of a flattened egg shape,” says
Schwadron. “A flattening of the nose of the