NASA's aging Voyager spacecraft, more than three decades outbound from Earth and approaching the outermost limits of the solar system, may be seeing signs of what scientists believe are huge magnetic bubbles churning at the interface between the sun's influence and interstellar space. The unexpected bubbles, shaped like sausages more than 100 million miles across, likely affect how high-energy cosmic rays pass into the inner solar system and may shed light on how stars interact with their galactic environments.
"It's exciting. We're learning new things almost every day," Voyager project scientist Ed Stone said.
The outward flow of charged particles making up the solar wind, along with the sun's magnetic field, define a gigantic region in space known as the heliosphere. It is shaped somewhat like a teardrop because of the sun's motion, due to the rotation of the Milky Way, combined with the effects of the sun's passage through a cloud of interstellar debris produced by ancient supernova. The tail of the teardrop stretches away in the opposite direction of travel.
The outward flow of the solar wind and the entwined magnetic field act as a shield of sorts for the inner solar system, affecting the passage of high-energy cosmic rays from deep space.
NASA's twin Voyager 1 and 2 spacecraft were launched in 1977. Voyager 1 is roughly 11 billion miles from Earth, while Voyager 2 is about 9 billion miles out. Data from the spacecraft are transmitted to Earth with 20-watt transmitters.
"So it's 20 watts coming from 11 billion miles away," Stone said. "It's really a tiny amount of power. We have to use either the largest antennas, the 70-meter antennas, or we have to combine the signals from two 34-meter antennas in order to recover the data."
The Voyagers are moving through a region known as the heliosheath and have reached a point where the outward velocity of the solar wind has dropped to near zero. Just in front of the heliosheath, which defines the outermost limit of the sun's influence, is the heliopause, the boundary between the heliosphere and the interstellar wind the sun is moving through. Just in front of the heliopause is a so-called bow shock, where the interstellar wind crashes into the heliosphere.
"This heliospheric boundary is very important in shielding the heliosphere from galactic cosmic rays that come from outside our home," said Merav Opher, an astronomer at Boston University. "What shields us is the heliopause, this last region that separates us from the rest of the galaxy."
Reply With Quote
huge magnetic bubbles
Posting Permissions
Bookmarks