Our solar system, home to Earth and the other seven planets, may be the equivalent of our own backyard in astronomical terms, but it's still full of surprises. The latest, according to NASA, is that the entire solar system has a humongous tail, estimated to be a cool 93 billion miles long (1,000 times further than the distance from the Earth to the Sun). Called the "heliotail," the structure is made up of solar wind, or particles originally released by the Sun, some of which travel billions of miles past all the planets and escape the magnetic field surrounding the solar system. The particles are invisible to the naked eye by the time they reach the edge of the field. Nonetheless, scientists had long suspected that our solar system had such a tail based on telescopic observations of similar tails trailing other star systems, but our heliotail had never been accurately detected — until now.
"We did not have any data prior to IBEX to tell us if a tail existed."
Credit for the reveal goes to NASA's Interstellar Boundary Explorer (IBEX) mission, an unmanned particle-detecting spacecraft launched in 2008 and which remains in orbit around the Earth. "We did not have any data prior to IBEX to tell us if a tail existed, what it looked like, or how various particles behaved within that region," noted Dave McComas, IBEX's principal investigator, in a blog post today. But after three-years-worth of observations, the mission finally compiled enough data on neutral particles streaming back into the solar system from the tail, for scientists to be able to identify it and map its structure.
IBEX's observations did not disappoint: aside from being enormous in size, the tail also appears to have an unusual "clover"-like shape, with four individual lobes of particles emanating from the outside of the solar system that twist as the solar system moves through the galaxy, thanks to the pressure of the system's magnetic field. Scientists are still working to find out just how long the tail is — 93 billion miles may be a conservative estimate, but the initial results appear in a study published today in The Astrophysical Journal. Unfortunately, the study doesn't provide any insight as to how the solar system's tale compares to the hairstyle of the 1980s.