Surprises At The Edge Of The Solar System

Voyager I has discovered several:

In three studies published Thursday in the journal Science, Voyager researchers provided the most detailed view yet of a mysterious region more than 11 billion miles from Earth, where the sun’s ferocious solar winds slow to a whisper and pieces of atoms blasted across the galaxy by ancient supernovae drift into the solar system. The area, which has been dubbed the “magnetic highway,” is a newly discovered area of the heliosphere, the vast bubble of magnetism that surrounds the planets and is inflated by gusting solar winds. Like Earth’s magnetosphere, which shields us from radioactive solar winds, the heliosphere shields the solar system from many of the cosmic rays that fill interstellar space. …

Toward the end of July 2012, Voyager 1‘s instruments reported that solar winds had suddenly dropped by half, while the strength of the magnetic field almost doubled, according to the studies. Those values then switched back and forth five times before they became fixed on Aug. 25. Since then, solar winds have all but disappeared, but the direction of the magnetic field has barely budged. “The jumps indicate multiple crossings of a boundary unlike anything observed previously,” a team of Voyager scientists wrote in one of the studies.

Adam Mann adds, “No one is entirely sure what’s going on”:

“It’s a huge surprise,” said astronomer Merav Opher of Boston University, who was not involved in the work. While the new observations are fascinating, they are likely something that theorists will debate about for some time, she added. “In some sense we have touched the intergalactic medium,” Opher said, “but we’re still inside the sun’s house.”

Extending this analogy, it’s almost as if Voyager thought it was going outside but instead found itself standing in the foyer of the sun’s home with an open door that allows wind to blow in from the galaxy. Not only were scientists not expecting this foyer to exist, they have no idea how long the probe will stay inside of it. Stone speculated that the probe could travel some months or years before it reaches interstellar space.

“But it could happen any day,” he added. “We don’t have a model to tell us that.” Even then, Stone said, Voyager would not have really left the solar system but merely the region where the solar wind dominates.

Alex Knapp notes that the Voyager crafts still have years of life in them:

It’s not clear yet when Voyager 1 will leave the solar system – scientists won’t know for sure until it actually gets there. That could be anywhere from a few months to a few years away. It’s sister craft,Voyager 2, is also expected to enter interstellar space, but that will be some time later. Both probes have enough power to last to 2020, so we should learn quite a bit about interstellar space before they fall silent.

Mataconis’s take:

In terms of pure science, we’ve arguably gotten more from these two small unmanned craft than we have from the manned space program itself. That’s not too shabby.