NASA says one of its spacecraft has confirmed the long-held assumption that our solar system, like a comet, has a tail.

As our solar system moves through space, it acts like any other object moving through another medium, astronomers say -- as for example a meteor plunging through the Earth's atmosphere -- and causes particles to form a stream trailing off behind it.

But the tail of our solar "bubble," called the heliosphere, has never actually been observed until now, NASA said Wednesday.

NASA says its Interstellar Boundary Explorer, or IBEX, spacecraft has mapped the boundaries of the tail of the heliosphere for the first time.

Analyzing three years of IBEX imagery, researchers mapped out a tail, dubbed the heliotail, of fast- and slow-moving particles.

There are two lobes of slower particles on the sides, faster particles above and below, with the entire structure twisted, as it experiences the pushing and pulling of magnetic fields outside the solar system.

"Many models have suggested the heliotail might be like this or like that, but we've had no observations," David McComas, principal investigator for IBEX at Southwest Research Institute in San Antonio, said. "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."

Despite the new IBEX evidence, scientists say they still do not know how long the tail is.

"The tail is our footprint on the galaxy, and it's exciting that we're starting to understand the structure of it," said Eric Christian, IBEX mission scientist at NASA's Goddard Space Flight Center in Greenbelt, Md.

"The next step is to incorporate these observations into our models and start the process of really understanding our heliosphere."