NASA Spots Solar System's 'Tail'

If you were to look on our solar system from afar, it wouldn't look like a bunch of stationary spheres, but like a comet, streaking across the sky with a tail trailing behind it. Scientists had always assumed this, but now NASA has for the first time gotten a look at that tail, it announced today. NASA's IBEX probe has documented trails of fast- and slow-moving particles trailing behind our solar system, in a kind of four-leaf clover shape, with the slow particles forming two leaves, with faster-moving ones to either side.

"Many models have suggested the heliotail might be like this or like that, but we’ve had no observations," the lead author of a paper based on the findings explains. "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." Past probes have had difficulty roaming to areas that could observe the tail, but IBEX's neutral particle imaging technology allowed it to see the tail from the comfort of Earth's atmosphere. (More solar system stories.)