Is our solar system stable

The dense accumulation of atoms has almost disappeared within six months - researchers are puzzled

Compression at the edge of the heliosphere

San Antonio (USA) - The conditions at the outer edge of our solar system are far less stable than previously assumed. Measurements by the IBEX satellite show that a recently discovered compression of atoms has almost disappeared within six months. The accumulation is part of a band of atoms that spans the entire solar system at a hundred times the distance between the earth and the sun. The researchers have so far no explanation for the rapid change and now have to rethink their models for the interaction of the solar wind with the surrounding interstellar gas.

"It was a shock for us to discover this thin ribbon," admits David McComas of the Southwest Research Institute in San Antonio, Texas, "but what is even more shocking is that something can change there on such short time scales." The band of neutral atoms is located in a zone in which the solar wind, a stream of particles emanating from our central star, encounters the gas in interstellar space. McComas and his colleagues report in the journal "Journal of Geophysical Research - Space Physics" on the changes observed at the edge of the solar system.

Initial attempts at explanation interpreted the ribbon and the compression as atoms that left the heliosphere - a bubble in the interstellar gas dominated by the magnetic field of the sun - and were thrown back by the interstellar magnetic field. But the rapid changes now observed cannot be reconciled with this explanatory approach, according to the researchers. Complex processes in which the magnetic fields are restructured in this zone could possibly play a role.

An understanding of the processes at the edge of the solar system is important, among other things, because the heliosphere protects the inner solar system from high-energy cosmic rays. Any instabilities could, for example, endanger the health of astronauts on long space flights to the moon or Mars.