Editorial: 鈥�Space exploration for the history books鈥�
With all the excitement surrounding Curiosity鈥檚 first full chemical analysis of Martian soil this week, it鈥檚 easy to forget about another, much more distant robotic explorer. Voyager 1 could soon leave our solar system and cross over into interstellar space, the first time any human-made object has left the cosy confines of our planetary neighbourhood.
Yesterday, NASA announced that on its way out, Voyager 1 鈥� which has been travelling through our solar system since 1977 鈥� has encountered a new region of the solar system. It has been dubbed a 鈥渕agnetic highway鈥�.
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The solar wind blows charged particles from the sun鈥檚 upper atmosphere around the solar system, creating an enormous 鈥渂ubble鈥� known as the heliosphere. Charged particles travel along magnetic field lines, and the magnetic highway is thought to be the result of the sun鈥檚 magnetic field connecting up with field lines in the clouds of gas and dust of interstellar space.
The highway allows particles with low energy from the heliosphere to jet into interstellar space at high speed and high energy particles from the outside to rush in, an interaction that has been observed around other stars by the Hubble Space Telescope.
Cosmic-ray clue
The magnetic highway was identified when Voyager encountered intense cosmic radiation. The obvious interpretation would be that this happened because Voyager had finally reached interstellar space, yet its instruments did not detect any change in the direction of the magnetic field, which we would expect to see when leaving the heliosphere. This led researchers to conclude that Voyager was in a hitherto unknown region representing a bridge between the solar system and interstellar space.
Cosmic rays routinely enter the heliosphere, but we are shielded from their potentially damaging effects by the Earth鈥檚 magnetic field. 鈥淭he magnetic highway gives us an insight into how the cosmic rays get in,鈥� says Timothy Horbury of Imperial College London.
鈥淓verything we鈥檝e seen [from Voyager] is not what we expected to see,鈥� Horbury says. 鈥淧eople have been working on this for a long time. Just about every expectation we鈥檝e had has been confounded so far.鈥�
Voyager reached the termination shock 鈥� the region of the outer solar system where the solar wind starts to slow 鈥� in 2003, but it may be several months to a couple of years before the craft fully escapes the solar system. NASA scientists now say .
