If you could see the bubbles contained in the invisible magnetic field, scientists say they would look like giant sausages, approximately 160 million kilometers across.

    Detected by an instrument on board the Voyager space probes that measures energetic particles, scientists say the bubbles are formed when the so-called solar wind, a stream of charged particles from the Sun, trails outward to the edge of the solar system and twists as a result of the Sun’s rotation, interacting with material from stars on the other side of the divide.

    Using a new computer model to analyze the data, astronomers say the solar magnetic field is broken up at the boundary with intergalactic space into the turbulent, bubble-like structures.

    Astronomer James Drake of the University of Maryland likened the foamy bubbles to water coming out of the jets of a Jacuzzi tub.

    “Those jets are very bubbly," said Drake. "Well, this thing is very bubbly.  Like the most bubbly parts of your Jacuzzi.  So, it’s very bubbly indeed as far as we can tell.”

    But experts say the Sun’s magnetic field is very weak at the edge of the solar system and the bubbles are not so turbulent as to disrupt the Voyager spacecrafts which entered the final layer of the solar system, called the heliosphere, in 2007 and 2008.

    Launched in 1977, the 33-year-old space probes are now more than 14 billion kilometers from home, traveling a distance of approximately 450 million kilometers per year at different locations inside the heliosheath, the outer ring of the immense magnetic bubble in the solar system created by the Sun’s magnetic field.

    NASA scientists say the twin space probes, the most distant observatories operated by the space agency, are good for at least another five years.

    Boston University astronomer Merav Opher says scientists are now trying to figure out what’s on the other side of the heliopause, the boundary between our solar system and intergalactic space.

    “This is a complete new area," said Opher. "We have never been near the heliopause before.  And now it will be complicated because you have an interspace full of your bubbles and you are going towards the other side.  So how this interface will be we don’t really know.”

    The article describing the discovery of magnetic space bubbles by the Viking spacecrafts is published this week in the Astrophysical Journal.