The Earth may be about to move into a million-degree cloud of interstellar gas, according to Polish and US scientists.
They suggest that the Ribbon of enhanced emissions of Energetic Neutral Atoms, discovered last year by NASA Small Explorer satellite IBEX, could be explained by the fact that we're approaching the boundary between the Local Cloud of interstellar gas and another cloud of a very hot gas called the Local Bubble.
If this hypothesis is correct, the Ribbon is simply a geometric effect, and IBEX is catching matter from a hot neighboring interstellar cloud, which the Sun might enter in a hundred years.
The team's model suggests that the boundary between the Local Cloud and the Local Bubble might be a few light years away, as was believed earlier, but within a thousand astronomical units - a thousand times closer.
This might mean that the Solar System could enter the million-degree Local Bubble cloud as early as the next century.
But don't panic.
"The Sun frequently traverses various clouds of interstellar gas during its galactic journey," says co-author Dr Andrzej Czechows from the Space Research Centre of the Polish Academy of Sciences. Such clouds are of very low density - much lower than the best vacuum obtained in Earth labs.
Once in, he says, the heliosphere will reform and may shrink a little and the level of cosmic radiation entering the magnetosphere may rise a bit - but that's all.
"Perhaps future generations will have to learn how to better harden their space hardware against stronger radiation," Grzedzielski suggests.
More information in Astrophysical Journal Letters.