Ed Stone on sun’s ‘bubble’ in interstellar medium
Evidence from the Voyager spacecraft reveals that the shape of our solar system is ‘squashed.’
EarthSky spoke to Ed Stone, Chief Scientist of the Voyager Mission, at the December 2007 meeting of the American Geophysical Union in San Francisco. Stone described the solar system, saying that our sun streams charged particles, known as the solar wind, in all directions from its center. The interstellar medium, gas and dust between stars, surrounds the solar wind, defining the shape of our solar system.
Ed Stone: The sun creates a bubble around itself. And there’s something outside, pushing in on the southern hemisphere of that bubble, pushing it closer to the sun from the south than the bubble is in the north. We believe it is the magnetic field, which is in interstellar space. It’s angled, tilted in such a way that it’s pressing harder in the southern hemisphere of this bubble than on the northern hemisphere of the bubble.
Stone bases his claim of a ‘squashed’ solar sytem on the distance each of the two Voyager spacecraft had to travel in order to reach the boundary of the bubble around our solar system. He said that in August of 2007, Voyager 2 reached the edge about a billion miles closer to the sun than Voyager 1 did in 2004. So we know that the bubble is lopsided.
EarthSky asked Stone why he studies the edges of our solar system.
Ed Stone: We would like to get to interstellar space, to find out what’s outside, to look at material that’s come from other stars. Inside our bubble, everything comes from the sun. We’d also like to understand how stars like our sun interact with the material that’s outside. Sometimes, as the material outside changes, which it will on timescales of hundreds of thousands to millions of years, the size of our bubble will change. And the bubble provides a shield against the galactic cosmic rays which are outside.
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