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THE sun is moving through a cloud of interstellar gas more slowly than thought. That means our star doesn’t create a shock wave equivalent to the sonic boom of supersonic flights.
Scientists suggested that such a shock wave might help shield the solar system from galactic cosmic rays – charged particles from space that can damage DNA.
Now David McComas of the Southwest Research Institute in San Antonio, Texas, and colleagues have used NASA’s IBEX spacecraft to measure neutral particles streaming into the solar system. Their speed reveals that the sun is moving at about 23 kilometres per second, too slow to create a shock wave (Science, DOI: 10.1126/science.1221054).