Our Solar System Has a Tail

Not like the tail monkeys use to scale trees. This one, called the heliotail, consists of solar wind, or particles released by the sun, and is estimated to be 93 billion miles long.

As an object moving through another substance, the system’s particles form a stream trailing behind, according to a newly published report from NASA. always assumed the tail existed, but it has never been observed until now after three years of observations. “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,” David McComas, lead author on the paper, said in a press release.

NASA’s Interstellar Boundary Explorer, or IBEX, mapped the boundaries of the tail of the heliosphere using a particle-detecting spacecraft, launched in 2008, that orbits around the Earth. Other telescopes have seen tails around several stars but couldn’t detect one around our star, in part because the particles within the tail and heliosphere don’t shine.

In a technique called energetic neutral atom imaging, IBEX measures neutral particles created by collisions at the heliosphere’s boundaries. The process assumes that paths of neutral particles aren’t affected by magnetic fields within the heliosphere. I’ll try to explain it simply. The atoms travel for years and years before IBEX detects them. The solar wind comes from sun streams and moves past our planets, eventually circling back along the tail due to pressure from interstellar material. The particles then join a bunch of other particles moving inside something called the heliopause.

Still with me? OK, good.

Some of the particles bump into faster charged particles and exchange electrons, resulting in a slow charged particle and a fast neutral atom no longer controlled by the magnetic fields.

“By collecting these energetic neutral atoms, IBEX provides maps of the original charged particles,” said McComas, an investigator for IBEX at Southwest Research Institute. “The structures in the heliotail are invisible to our eyes, but we can use this trick to remotely image the outermost regions of our heliosphere.”

Eric Christian, IBEX mission scientist at NASA’s Goddard Space Flight Center, said that the new information will help us track our place within the galaxy. “IBEX can observe far away structures, even from Earth orbit, he said in the release. “And IBEX scans the entire sky, so it has given us our first data about what the tail of the heliosphere looks like.” Seems like a lot of jargon, but the finding is a huge step in understanding our importance in a greater outer space context. And the results are pretty — someone looking at the tail image will see something resembling a four-leaf clover. Talk about a really, really long tail.