For the first time astronomers have observed our solar system's tail using NASA's Interstellar Boundary Explorer, or IBEX.
Our sun releases a stream of charged particles, called solar wind, that forms a bubble around our solar system known as the heliosphere. IBEX mapped the boundaries of the tail of this solar bubble, called the heliotail.
The tail is made up of fast- and slow-moving particles, which scientists determined by stitching together three years of images beamed back by IBEX.
The finding was detailed in a paper published on Wednesday, July 10, in The Astrophysics Journal.
"Many models have suggested the heliotail might be like this or like that, but we’ve had no observations," principal investigator David McComas said in a statement. "We always drew pictures where the tail of the heliosphere just disappears off the page, since we couldn’t even speculate about what it really looked like."
Looking straight down at the tail, it appears to be in the shape of a four-leaf clover. Slow-moving particles make up the the two side leaves, while fast-moving particles make up the top and bottom leaves. The whole shape is slightly twisted, suggesting it's being influenced by the magnetic field from another galaxy as the tail moves away from the sun's magnetic field.
"This shape makes sense, given the fact that the sun has been sending out mostly fast solar wind near its poles, and slower wind near its equator for the last few years — a common pattern in the most recent phase of the sun’s 11-year activity cycle," NASA explains.
Astronomers have long-believed that our solar system, like a comet, has a tail that trails behind it. The particles in the tail don't shine so it's hard to spot them using conventional telescopes.
IBEX uses a technique called energetic neutral atom imaging. The instrument collects neutral atoms created by collisions at the boundary of the heliosphere. The resulting neutral atoms can take several years to hit IBEX. Because the particles move in a straight line, however, they can provide clues about the original charged particles. Scientists can map out the particles to create a picture of what's happening in far-off regions.