Tip:
Highlight text to annotate it
X
[ music ]
A Big Surprise from the Edge of the Solar System.
Presented by Science at NASA.
NASA's Voyager probes are truly going where no one has gone
before. Gliding silently toward the stars, 9 billion miles from
Earth, they are beaming back news from the most distant, unexplored
reaches of the solar system.
Mission scientists say the probes have just sent back some very big
news indeed.
It's bubbly out there!
"The Voyager probes have entered a strange realm of frothy magnetic
bubbles," says Merav Opher of Boston University.
"This is very surprising."
The bubbles are large, about 100 million miles wide, so it takes the
speedy probes a whole year just to cross a few of them.
Voyager 1 entered the "foam-zone" in 2007, and Voyager 2 followed
about a year later.
At first researchers didn't understand what the Voyagers were sensing
- but now they have a good idea.
"The sun's magnetic field extends all the way to the edge of the
solar system," explains Opher.
"Because the sun spins, its magnetic field becomes twisted and
wrinkled, a bit like a ballerina's skirt. Far, far away from the
sun, where the Voyagers are now, the folds of the skirt bunch up."
When a magnetic field gets severely folded like this, interesting
things can happen.
Lines of magnetic force criss-cross, and reconnect.
The crowded folds of the skirt reorganize themselves, sometimes
explosively, into foamy magnetic bubbles.
"We never expected to find such a foam at the edge of the solar
system, but there it is!"
says Opher’s colleague astronomer Jim Drake of the
University of Maryland.
Drake says they are still trying to wrap their minds around the
implications of the finding. One consequence has to do with cosmic rays.
Cosmic rays are subatomic particles accelerated to nearly light speed by
distant black holes and supernova explosions. When these microscopic
cannonballs try to enter the solar system, they have to fight through
the sun's magnetic field to reach the inner planets.
"The magnetic bubbles turn out to be our first line of defense
against cosmic rays," points out Opher.
"We haven't figured out yet if this is a good thing or not."
On one hand, the bubbles would seem to be a very porous shield,
allowing many cosmic rays through the gaps. On the other hand, cosmic
rays could get trapped inside the bubbles, which would make them a
very good shield indeed.
"We’ll probably discover which is correct as the Voyagers proceed
deeper into the froth," says Opher.
"This is just the beginning, and I predict more surprises ahead."
For more information about places no one has ever been before, please
visit science.nasa.gov.