The weird form of our heliosphere, discovered some years ago and appearing to be shaped like a croissant, can be explained by the unstable heliospheric jets, according to a study published in the Astrophysical Journal.
A group of astrophysicists from the US, Russia and Greece, led by Merav Ofer from Boston University developed a new Solar-wind with Hydrogen Ion Exchange and Large-scale Dynamics (SHIELD) model, based on theoretical studies and data, collected by several space probes.
So far, the probes that have managed to reach the borders of the solar system include two Voyages, two Pioneers and New Horizons. Only Voyager 1 and Voyager 2 have crossed the border of the heliosphere and are currently moving through interstellar space.
The model was said to be one of the most compelling computer simulations of the heliosphere. It showed that the new unusual hypothetical shape of the heliosphere can be explained by its unstable borders. Generally, they are formed by heliospheric jets, flows of ionised matter, emitted as an extended beam along solar poles.
These particular jets act irregularly as they are discarded and distorted by the incoming flow of interstellar matter.
“Why do stars and black holes – and our own sun – eject unstable jets?” Opher said. “We see these jets projecting as irregular columns, and [astrophysicists] have been wondering for years why these shapes present instabilities.”
Scientists discovered that the main cause was the interaction of ionized matter with neutral hydrogen atoms of interstellar space flowing around the solar system. The phenomenon is well known to physicists, having been dubbed the Rayleigh-Taylor instability, and occurs when materials of different densities collide and a lighter material presses on a heavier one.