Voyager May Be at End of Solar System

Wednesday, November 5, 2003

(3:13 PM ET)

By Andrew Bridges

Associated Press Writer

``The inference that the solar wind's velocity basically went to zero seemed to us to be rather compelling argument we were in the vicinity of the termination shock and the boundary of the solar system.''

-- Louis Lanzerotti, of Bell Laboratories and the New Jersey Institute of Technology

Image Credit: JPL & NASA

AP
The Voyager 1 spacecraft, the most distant human-made object, has reached the end - or perhaps just the beginning of the end - of our solar system, scientists argue in two new studies.

As of Wednesday, 26 years after its launch, NASA's Voyager 1 was 8.4 billion miles from the sun. That's 90 times the distance separating the Earth from our star.

As the robotic spacecraft continues to push far beyond the reach of the nine planets, two teams of scientists disagree whether it passed into the uncharted region of space where the sun's sphere of influence begins to wane.

The sun sends out a stream of highly charged particles, called the solar wind, that carves out a vast bubble around the solar system.

Beyond the bubble's ever-shifting boundary, called the termination shock, lies a region where particles cast off by dying stars begin to hold sway.

That region, called the heliopause, marks the beginning of interstellar space and the end of our solar system. Whether Voyager 1 reached that mark or is still on approach remains unclear, with scientists providing evidence for both claims. Details appear Thursday in the journal Nature.

``Neither explanation is certain,'' writes Len Fisk, of the University of Michigan, in an editorial accompanying the two studies.

Scientists have long theorized that a shock wave exists where the hot solar wind bumps up against the thin gas of the interstellar medium. A similar shock wave precedes aircraft flying faster than the speed of sound, causing a sonic boom.
(More: Netscape Network News with CNN)
2003 © The Associated Press.

On the Net:

* VOYAGER: Celebrating 25 Years of Discovery

Voyager at 90 AU

JPL & NASA

Dan