Pubblicato da: rainbowman56 | 13 luglio 2011

Voyager Discovers Possible Sea of Huge, Turbulent, Magnetic Bubbles at Solar System Edge By A.J.S. Rayl

Planetary News: Space Missions (2011)

From Planetary blog

June 12, 2011


Artist’s conception of the Voyager spacecraft. Voyager 1 and Voyager 2 left Earth, in August and Sdeptember 1977 resectively, to tour our solar system. They are now at the very edge of our solar system and cruising toward interstellar space. Credit: NASA / JPL-Caltech

Nearly 34 years after leaving Earth, Voyager 1 and Voyager 2, humankind’s most distant space emissaries, are closing in on the border crossing to interstellar space, flying at 17 kilometers per second now through what seems to be a strange sea of humongous and “frothy” magnetic bubbles.

The Voyagers are in the heliosheath, the boundary region between our solar system and the rest of the Milky Way Galaxy, and have been since eachcrossed the Termination Shock in December 2004 and August 2007 respectively. But about four years ago, Voyager 1 began sending home data that indicated the spacecraft was flying through something weird, something the scientists had not anticipated.

Estimated to be about 100 million miles wide each, the bubbles in this turbulent sea actually “form a sort of membrane” in the heliosheath, astronomer Merav Opher, of Boston University, announced last Thursday at a NASA press teleconference. “This is very different from what we expected.”

It certainly gives new meaning to the phrase ‘bubble-wrapped.’

As they zoom through this sea of magnetic bubbles, the Voyagers are heading, via separate routes, through the heliosheath to the very edge of our heliosphere known as the heliopause, the last boundary before “outer space.”

Our heliosphere – the ‘yellow submarine’ in which we all live – is defined by the outward flow of photons and charged particles that make up the solar wind and the Sun’s magnetic field. The movement and rotation of the galaxy causes our heliosphere to be shaped somewhat like a submarine, or a comet with a tail, complete with a sort of blunt ‘nose.’Voyager 1 is traveling in the northern hemisphere of the heliosphere’s blunt nose and is presently about 11 billion miles (117 AU) away from Earth, escaping at a speed of about 3.6 AU per year, 35 degrees out of the ecliptic plane (to the north), in the general direction of the solar apex, or the direction of the Sun’s motion relative to nearby stars; Voyager 2 is flying through the southern hemisphere and is about 9 billion miles (95 AU) away from the home planet, escaping at a speed of about 3.3 AU per year, 48 degrees out of the ecliptic plane (to the south).

Voyagers locations in heliosphere

Voyager 1 and Voyager 2 approximate locations in heliosphere
The heliosphere is the descriptor for the space formed by the Sun’s outer atmosphere, the ionized and magnetized gas called the solar wind and its magnetic field lines. Close to the Sun up to the Termination Shock, the solar wind has a speed of 1 million miles per hour. At the Termination Shock, which the Voyagers crossed in Dec. 2004, and Aug. 2007 respectively, it slows down abruptly, feeling the influence of the interstellar medium that surrounds the heliosphere. The two Voyager spacecraft are in the nose region of the heliosheath, where the solar wind slows down further and eventually turns back towards the elongated heliotail. The heliosphere is shaped by the relative motions of the Sun and the local interstellar medium. The boundaries of the heliosphere are dynamic, shaped by the relative pressures exerted by the solar wind and the interstellar gas.
Credit: NASA / JPL-Caltech

Despite the turbulence and being in a region where the solar wind and Sun’s magnetic field lines are interacting with material expelled from others in our corner of the Milky Way galaxy, the Voyagers are blissfully unaffected. “The spacecraft are unaware of all this,” assured Edward C. Stone, Voyager project scientist, professor of cosmic ray physics at Caltech, and former director of JPL, during an interview Thursday. “From a spacecraft point of view, this is a better vacuum than anything here on Earth in a laboratory. Only our sensitive instruments will tell us when the direction and the speed of the wind has changed, and when the direction of magnetic field and its strength have changed.”

Nobody knows for sure what awaits the twin spacefarers beyond the sea of magnetic bubbles or how far they actually have left to go to get to the heliopause. What the scientists do know is that for decades various theories have speculated with some sound authority as to what we would find out there at the heliosheath and beyond, yet with every passing month and every ream of scientific data, Voyager has been giving them cause to pause and rethink what they thought they knew. “It’s been one surprise after another,” said Stone.

The gargantuan magnetic bubbles are the latest surprise.

My God, it's full of bubbles

My God, it’s full of bubbles
New data returned by the Voyager 1 and Voyager 2 spacecraft indicate that a sea of gigantic, “frothy” bubbles form when the sun’s magnetic field lines become twisted and broken at the edge of our solar system. The venerable twin spacecraft are currently navigating through this sea of bubbles, depicted here in this artist’s rendering. Credit: NASA / GSFC / CI Lab


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