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Sun’s shock wave goes missing

Spacecraft observations redraw astronomers’ ideas about the local stellar environment

The sun isn’t quite the speed demon scientists once suspected. It chugs around the galactic center at a relatively pokey 83,500 kilometers per hour — or roughly 11,000 kilometers per hour slower than expected, says a report appearing online May 10 in Science.

While that might not sound like a big deal, the sun’s slower pace clashes with theories describing the solar system’s local environment — a protective, sun-blown bubble called the heliosphere. The sun’s speed helps shape the size and boundary of this elastic bubble, along with the interstellar dust and gas clouds it moves through.

In particular, scientists thought a shock wave — called the bow shock — preceded the bubble’s journey through space. ”We’ve spent the last quarter-century assuming there was a bow shock,” says study coauthor David McComas, a space scientist at the Southwest Research Institute in San Antonio.

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