Magnetic Bubbles at the Edge of the Solar System

Magnetic bubbles at the edge of the solar system are aboout 100 million miles wide–similar to the distance between Earth and the Sun. Credit: NASA

Observations from NASA’s Voyager spacecraft, humanity’s farthest deep space sentinels, suggest the edge of our solar system may not be smooth, but filled with a turbulent sea of magnetic bubbles. Studying the nature of the Solar System is important for astrobiologists who trying to determine the conditions necessary for habitable planets, like Earth, to form.

While using a new computer model to analyze Voyager data, scientists found the Sun’s distant magnetic field is made up of bubbles approximately 100 million miles wide. The bubbles are created when magnetic field lines reorganize. The new model suggests the field lines are broken up into self-contained structures disconnected from the solar magnetic field. The findings are described in the June 9 edition of the Astrophysical Journal.

Like Earth, our sun has a magnetic field with a north pole and a south pole. The field lines are stretched outward by the solar wind or a stream of charged particles emanating from the star that interacts with material expelled from others in our corner of the Milky Way galaxy.

Old and new views of the heliosheath. Red and blue spirals are the gracefully curving magnetic field lines of orthodox models. New data from Voyager add a magnetic froth (inset) to the mix. Credit: NASA

The Voyager spacecraft, nearly 10 billion miles away from Earth, are traveling in a boundary region. In that area, the solar wind and magnetic field are affected by material expelled from other stars in our corner of the Milky Way galaxy.

"The Sun’s magnetic field extends all the way to the edge of the Solar System," said astronomer Merav Opher of Boston University. "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, the folds of the skirt bunch up."

Understanding the structure of the Sun’s magnetic field will allow scientists to explain how galactic cosmic rays enter our solar system and help define how the star interacts with the rest of the galaxy.

So far, much of the evidence for the existence of the bubbles originates from an instrument aboard the spacecraft that measures energetic particles. Investigators are studying more information and hoping to find signatures of the bubbles in the Voyager magnetic field data.

"We are still trying to wrap our minds around the implications of the findings," said University of Maryland physicist Jim Drake, one of Opher’s colleagues.