Voyager’s Long Run of Surprises Continues [Nature]

The two Voyager spacecraft continue logging the miles…and the important data. Even after 35 years and billions of kilometers, they reveal new information about the solar system and communicating it back to Earth using the power equivalent of a refrigerator light bulb. Most recently, scientists have had to rework their models of the heliopause—the area at the edge of the Solar System. My recent article in Nature reports on the new Voyager data and its possibilities:

In the latest twist in the story, the craft seems to be traversing an unexpected ‘dead zone’ […]

Decker’s team first reported the change last year, when it had measurements of the particles’ velocity only in the radial direction, outwards from the Sun. At the time, the team thought that the change was a sign that the craft was nearing the heliopause, where solar particles are expected to collide with powerful winds generated by supernovae that exploded some 5 million to 10 million years ago. The collision would force the solar particles to stop moving outwards and push them sideways, like a stream of water hitting a solid surface.

To test the idea, engineers commanded Voyager 1 to roll on its side seven times, so that its instruments could record particle velocities along a line perpendicular to its course. Given that sending a command to Voyager 1 now takes 17 hours, and that the spacecraft’s transmitter runs at 23 watts — about as powerful as a refrigerator light bulb — such communication is a feat in itself. The researchers were astonished to find that the particles had zero velocity in this polar direction, too — indicating that they were almost stationary rather than being buffeted by stellar winds. That cannot happen at the heliopause, says Decker.

The story is featured on the Knight Science Journalism Tracker site:

Ron Cowen: Voyager’s long goodbye ; Rather than a tumultuous region of shifting breezes, the probe seems to be in a relatively calm spot, a sort of dead zone, it says here. The researchers suspect the spacecraft, communicating over the vast gulf (Cowen writes) with a transmitter “about as powerful as a refrigerator light bulb,” is not even close to the heliopause.