Reports of Nasa's Voyager 1 space probe finally leaving the solar system have turned out to be somewhat premature according to scientists.
The spacecraft launched in 1977 to study Jupiter and Saturn, had drifted into a hitherto unknown region between the outermost reaches of the solar system and interstellar space.
The region abounded with cosmic rays beyond the solar system even as charged particles from the sun were virtually absent providing a rather unusual and unexpected thoroughfare for the spacecraft.
Scientists had earlier thought that Voyager had indeed finally reached interstellar space on 25 August, 2012, becoming the first man-made object to exit the solar system.
The physical space in a galaxy not occupied by stars or their planetary systems is called interstellar space.
However, a key measurement invalidated the theory. Given the fact that the magnetic field in which Voyager 1 traveled was still aligned like the Sun's, if the probe were truly in interstellar space, scientists expected the direction of the magnetic field to be different.
According to Voyager scientist Leonard Burlaga, with NASA's Goddard Space Fight Center in Greenbelt, Maryland, one could never exclude a peculiar coincidence, but there was very strong evidence that craft was still in the heliosheath - the bubble of plasma from the sun surrounding the system.
Another measurement that threw up a second odd reading showed that the cosmic ray particles around Voyager 1 were not distributed evenly like scientists expected them to in interstellar space. Rather, the particles, which originate from distant supernova explosions, were oriented in particular directions.
Scientists therefore concluded that the probe had drifted into some kind of magnetic boundary zone, where particles from within and external to the solar system could easily trade places, but where the sun still exerted influence.
According to scientists the probe remains in a transition area which that had been dubbed the 'magnetic highway' and that it could still be some time before it broke out.
Chief scientist Ed Stone of the Nasa Jet Propulsion Laboratory, which manages the mission said it could actually be anytime or it could be several more years.
Meanwhile, Voyager 1 continues to cruise some 11.5 billion miles from the sun even as scientists look for any signs of departure.
Given the time it would take to process the data, Burlaga said there would be a lag between when Voyager 1 finally sailed into interstellar space and when the team could confirm the act.
Also the possibility of surprises beyond the solar system could not be discounted.
Burlaga said, crossing might not be instantaneous, it might be a complicated thing.