Solar System Is "Bullet Shaped"

Brian Handwerk
for National Geographic News
May 10, 2007
Our solar system flies through space in the shape of a speeding bullet, according to data from NASA's two Voyager spacecraft.

The sun and its planets are known to streak through the void of space at approximately 62,000 miles (100,000 kilometers) an hour.

The system travels within a bubble of solar wind—made of charged particles from the sun—called the heliosphere.

The edge of this bubble collides with the Milky Way galaxy's magnetic field at a distance some 200 times farther from the sun than Earth is.

A research team led by Merav Opher at Virginia's George Mason University found that, just outside the solar system, this interstellar magnetic field is inclined at a 60-degree angle relative to the plane of the Milky Way.

The solar system takes on its streamlined shape as it strikes the magnetic field at this angle, Opher explained.

(See an interactive map of the solar system.)

"The shape of the solar system, this bullet, is really shaped by what lies ahead of us—the interstellar magnetic field," Opher said.

"The [prevailing] idea is that the environment just outside our solar system is patchy and turbulent," she added.

"There are lots of stars exploding and dying outside our solar system."

Opher and colleagues made the find using radio data from the veteran Voyager spacecraft. Though they have plied the skies since the 1970s, the craft only recently reached the solar system's edge.

(Read: "Voyager Probes Send Surprises From Solar System's Edge" [September 26, 2006].)

Opher's team reports its findings in tomorrow's issue of the journal Science.

The study has added new wrinkles to evolving views of the interstellar magnetic field, said Randy Jokipii, an astrophysicist at the University of Arizona.

"[The study] does indeed give us a magnetic field which is quite a bit different than that obtained by previous measurements," Jokipii said.

"In the last few years we've seen almost an explosion in our understanding of what I'd call the … local interstellar medium and its interaction with the heliosphere," added Jokipii, who provided a perspective article to the Science research.

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