"A pair of NASA probes wandering in deep space discovered that the outer edge of the solar system contains curious magnetic bubbles and is not smooth as previously thought, astronomers said Thursday."
The distant magnetic fields of stars are not well understood, largely because the intensity of magnetic fields drops rapidly with distance. Most of what we know about stars’ magnetic activity cycles, and the way the magnetic fields generated deep in their interiors are transported to, and through, their visible surfaces, has come from thorough study of the most nearby example: the Sun. But until recently, we could only guess at what those magnetic fields did at large distances in the outer Solar System because our ability to observe their behavior has been indirect and tentative, at best.
In the late 1970’s, a chance alignment of the giant planets presented an unprecedented opportunity to launch spacecraft from Earth on a “grand tour” of the outer Solar System. The Voyager spacecraft remain among the most successful planetary missions ever launched, sending back data which, more than 20 years after the planetary phase of the mission ended, are still being actively analyzed and debated. But the spacecraft live on, almost 35 years after launch; their on-board nuclear power plants provide electricity in deep space, far beyond the effective distance of solar panels, warming the spacecraft and keeping its instruments alive. Its cameras have long since been turned off, but other science instruments are function. These have been used to detect the heliopause, a region at large distance from the Sun where the solar wind comes into pressure balance with the “interstellar medium”, or what makes up the stuff between the stars. At that point, it can be said the environment of the Sun’s influence truly gives way to the interstellar environment of the Galaxy.
The Voyagers are still functioning and just enough funding is provided annually to continue what is termed the Interstellar Mission: “to extend the NASA exploration of the solar system beyond the neighborhood of the outer planets to the outer limits of the Sun’s sphere of influence, and possibly beyond.” It was previously thought that the magnetic field lines originating within the Sun traveled great distances out to the heliopause, entraining solar wind particles with them, and gently curving back to reconnect at the Sun. This is because of a basic physical principle: all magnetic field lines must be continuous, so they form closed loops. It turns out that it may not be so simple, and that the magnetic environment at the heliopause becomes very turbulent and “frothy”. According to the work referenced here (available online), new, self consistent, 3-D computer models show that the “termination shock" of the solar wind — where the wind slows down from supersonic to subsonic speeds relative to the Sun as it encounters increasingly thick materials from the interstellar medium, is closer to us than previously thought. It also suggests that the thickness of the boundary between Solar System and interstellar space is thinner than expected. This is consistent with the story’s representation of a “‘turbulent sea of magnetic bubbles’ [that] occurs when parts of the Sun’s distant magnetic field break up and reorganize under pressure." For an idea of what this may look like, consider recent observations of the star R Hydrae:
Astronomy news, recent research results, and pretty pictures from the media along with context, commentary, and explanations for folks who dig this sort of thing. Written by a quasi-professional astronomer affiliated with the International Dark-Sky Association in Tucson, AZ.