NASA today announced that its Interstellar Boundary Explorer (IBEX) has mapped the structure of our solar system’s “tail.” The tail, called the heliotail, is shaped like a four-leaf clover, much like the tails seen around other nearby stars.

“By examining the neutral atoms, IBEX has made the first observations of the heliotail,” said David McComas, lead author of a paper on the findings published this week in the Astrophysical Journal and an IBEX principal investigator at the Southwest Research Institute. “Many models have suggested the heliotail might look like this or like that, but we have had no observations. We always drew pictures where the tail of the solar system just trailed off the page, since we couldn’t even speculate about what it really looked like.”

Finding the shape of our heliotail, researchers say, was more difficult than measuring the ones found around other stars, since the particles in the heliosphere cannot be detected using conventional measurements. The IBEX was able to detect neutral particles created by collisions at the boundary of the heliosphere and interstellar space. Such particles are not affected by the sun’s magnetic field, allowing researchers to construct a model of the heliosphere’s shape.

“Since first light in 2008, the IBEX mission team has amazed us with its discoveries at the interstellar boundary, including a previously unknown ribbon of energetic neutral particles stretching across it,” said Arik Posner, a NASA IBEX program scientist. “The new IBEX image of the heliotail fills in a previously blank area on the map. We are first-hand witnesses of rapid progress in heliophysics science.”

The exact length of the heliotail is still unknown, as it can be seen fading gradually into interstellar space. Also, the clover-shape of the tail rotates the further away it gets from the sun as it becomes more influenced by the local galactic magnetic field.