Voyager at the edge of our solar system Jun 28, 2013 17:06:58 GMT 12
Post by kiwithrottlejockey on Jun 28, 2013 17:06:58 GMT 12
From the Los Angeles Times....
Voyager 1's journey to solar system's edge upends theories
The mysterious region 11 billion miles away proves to be even stranger
than previously thought, according to Voyager's latest readings.
By MONTE MORIN | 6:58PM - Thursday, June 27, 2013
Scientists report on Voyager 1's strange findings at the edge of the solar system. — Picture: Associated Press/NASA.
AS THE Voyager 1 spacecraft speeds toward interstellar space at a rate of almost a million miles a day, the NASA probe is causing scientists to jettison some long-standing theories on the nature of our solar system and life along its cold, dark edge.
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.
Scientists had long envisioned its outermost layer, the heliosheath, to be a curved, distinct boundary separating the solar system from the rest of the Milky Way. They theorized that once Voyager 1 crossed that threshold, three things would happen: The sun's solar winds would become still; galactic cosmic rays would bombard Voyager from every angle; and the direction of the dominant magnetic field would change significantly because it would be coming from interstellar space, not the sun.
All of those predictions have been turned on their head by Voyager's latest instrument readings.
Although Voyager 1 is equipped with video cameras, they were shut off more than 20 years ago to save power and memory. Instead the craft observes its environment with a fragile, lattice-work antenna that measures magnetic fields as well as a cosmic ray detector and a plasma detector. (Befitting a space probe launched in 1977, the data are stored on an eight-track tape recorder.)
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 August 25th. 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. They labeled the new area the heliosheath depletion region.
Stranger yet, Voyager 1 detected an increase in galactic cosmic rays — but found that at times they were moving in parallel instead of traveling randomly.
"This was conceptually unthinkable for cosmic rays," said Stamatios Krimigis, a solar physicist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., and leader of another one of the studies. "There is no cosmic ray physicist I know who ever expected that they would not all be coming equally from all directions."
The confusion hasn't ended there.
One Voyager project scientist reported in March that the spacecraft had entered interstellar space after more than 35 years of travel. The paper by Bill Webber, a professor emeritus of astronomy at New Mexico State University, triggered a media furor in the process.
Scientists including Krimigis and Edward Stone, a Voyager project scientist at Caltech, contended that the probe had not left the solar system. Voyager 1 remained within the sun's zone of magnetic influence, and therefore within the heliosphere, they said.
"We're not free yet," Krimigis said. "This is a new region that we didn't know existed. We have no road map, and we're waiting to see what's going to happen next."
Theorists are struggling to explain the data. Some say the unexpected increase in magnetic strength is the result of spiraling magnetic fields being compressed against the interstellar medium. Others say this is impossible since there is no solar wind to push them against that boundary, and that there must be another explanation.
Len Fisk, a professor of space science at the University of Michigan, described the studies' findings as "a complete surprise." He said Voyager 1's travels were proving to be both puzzling and exciting.
"It's causing a fundamental reconsideration of how the heliosheath interacts with the local interstellar medium," said Fisk, who was not involved in the new analysis.
One of the possible explanations for Voyager's peculiar magnetic readings is that the sun's magnetic fields have combined with the interstellar magnetic field in places — a process called magnetic reconnection.
Such reconnection has been observed between the magnetic fields of the sun and Earth, said Stone, a former director of the Jet Propulsion Laboratory in La Cañada Flintridge. "Maybe that's what's happening here, but we really don't know," he said.
Adding still more mystery is the fact that Voyager 2 has yet to experience anything like its twin. Both spacecraft are headed toward the forward edge of the heliosphere, but are more than 9 billion miles apart.
Although Voyager 1 was launched 16 days after Voyager 2, it followed a more direct route toward the edge of the solar system. Since 1998, when it overtook Pioneer 10, it has been the farthest man-made object from Earth.
Voyager scientists say they're in no position to predict when the probe may finally exit the solar system. It could be months, or it could be years.
"I wouldn't dare to make an estimate," Krimigis said. "Voyager will probably prove us wrong, again."
Related news stories & links:
• Interactive Graphic: Voyagers are traveling near the edge of the solar system
• Graphic: The travels of the two Voyager spacecraft
• Scientists debate whether Voyager 1 has left the solar system
• Voyager 1 and a poignant farewell to a scientist