Added 1 new A* page:Those intrepid 33-year-old Voyager spacecraft have been making some startling discoveries way out on the edge of our Solar System, as they continue to wing their way out toward intergalactic space.|
First, fluctuating readings picked up by Voyager 1--the further out of the two--since 2007, and Voyager 2 since 2008, are now thought to indicate that the Sun's magnetic field gets "frothy" out near the furthest reaches of the solar wind, with lines of magnetic force criss-crossing, reconnecting (apparently magnetic field "reconnection" is also what causes solar flares in the Sun's atmosphere), and forming "bubbles" up to 100 million miles wide (which makes such "bubbles" larger than the distance from the Earth to the Sun, which is about 93 million miles, or 150 million kilometers), some filled with trapped cosmic rays and electrons.
This "foam" or "froth" idea--the readings from the probes don't appear to be absolutely definitive on the theory thus far--stands in significant contrast to the previously prevailing notion of the boundaries of the Sun's magnetic field, which was thought to spiral out gracefully in nice big arcs that eventually curved back to the Sun. Here's NASA's visual comparison of the two competing views--the red and blue lines represent the Sun's magnetic field, the blue areas represent the heliosphere--the bubble "blown" out of the galactic medium by the Sun's solar wind, the inner, greenish blue area ending with the "termination shock," where the solar wind collides with the interstellar wind and loses its supersonic speed--and the orange vapor surrounding it represents the interstellar wind:
concept image by NASA (source)
The shape of the outer magnetic field could have significant effects on life on Earth: a magnetic "froth" around the Solar System might be helping to keep out high-powered cosmic rays, which would otherwise be shooting their super-charged particles through our fragile bodies much more frequently than they do now. Or, the bubbles could form gaps that allow more cosmic rays through--scientists aren't sure yet.
The Voyager craft are the first ever to reach this very edge of the Solar System, so this is the first time direct data of the magnetic field that far out has been gathered--so it isn't surprising that the rule books may have to be re-written a bit.
Here is NASA's video about it:
I thought the part about the path cosmic rays take to get to the inner Solar System was interesting; I hadn't realized that they come in along magnetic field lines! I had thought they just zinged straight through on the strength of their own momentum or something.
NASA followed up that first Voyager article with another one less than a week later, about how the probes are helping recalculate the distance to interstellar space: since December 2010, Voyager 1's instruments have shown that the solar wind around it has slowed to a standstill, "marking a thick, previously unpredicted 'transition zone' at the edge of our solar system"; this boundary is now thought to be "between 10 and 14 billion miles (16 to 23 billion kilometers) from the sun, with a best estimate of approximately 11 billion miles (18 billion kilometers)."
That 11 billion miles figure is about where Voyager 1 is now, so in theory it could cross into interstellar space--where the solar wind and magnetic field from the Sun drops away entirely, leaving the probe to move through the galaxy's thin interstellar medium--at any time now. "Voyager 1 speeds outward a billion miles every three years," so it can't be much longer now--or so prevailing theories suggest. There's also the question of whether the probes will find a "bow shock" around the solar system, ie a compression of the interstellar wind as it collides with the solar wind; such bow shocks definitely exist, and have been observed around other stars, such as this half-light-year-long (~5 trillion kilometer) one that has formed between the star L.L. Orionis and the surrounding Orion Nebula:
image by NASA (source)