NASA scientists have created a first-ever map of our solar system's "tail." The researchers only now know of the "heliotail," as they call it, thanks to recently retrieved data from the Interstellar Boundary Explorer (IBEX) spacecraft. They published a report of their findings in the latest edition of the Astrophysics Journal.
The IBEX launched into Earth orbit in 2008 and has been scanning space for particles coming toward our planet from the "heliosphere," the boundary that astronomers identify as the furthest end point of our solar system, about 8 billion miles beyond the outermost planets. It forms from outgoing solar wind from our sun blowing against the "interstellar medium," the thin clouds of particles that course throughout deep space. Where these two opposing forces meet, there emerges a bubble of inertia. This bubble is the heliosphere.
That heliosphere filters and deflects most of the interstellar particles before they have a chance to reach our planet, and for us, that's an extremely good thing. If it weren't there, the intense influxes of cosmic radiation would wear away at our ozone layer and do systematic damage to our bodies and genes.
IBEX is the first spacecraft to study the heliosphere in depth, and while it can't show us the heliosphere directly—all the region's activities take place at the atomic level and produce no visible light, so to us and to our telescopes it would all appear to be nothing but empty space—the five years that the spacecraft has spent monitoring for interstellar particles have taught us much. Case in point: We now know that the heliosphere has a heliotail.
According to NASA, the tail forms from the fan-out of the solar wind as it runs into the heliosphere. Magnetic fields from the interstellar medium act upon the outgoing solar wind particles in uneven ways and contribute to an overall erratic tail shape that somewhat resembles a four-leaf clover whose cross-section flattens out into a twisted oval. The "clover" effect is the end product of some jetties of solar wind particles receiving varying degrees of magnetic pull than others and consequently traveling faster or slower.
Scientists are actually not that surprised by this tail. They had suspected it was there, as they have detected similar tails emanating from other star systems. The IBEX data is just the final proof that they needed that our star system is tailed, too.
The jury is out, though, on how long this tail extends. Most believe that there is no exact end point per se; instead, it slowly fades out and dissipates into the rest of interstellar space.
