NASA Video Reveals "Weird Goings-On" in Tail of Elusive Comet McNaught

"It's been really exciting to have proved something I was taught in a classroom to be (slightly) wrong!"

Comet McNaught has been a bright, beautiful mystery since 2007, when a group of stupefied researchers at the Naval Research Laboratory in Washington, D.C., captured it in a satellite image. The earthlings that first spotted the comet were struck by its brightness and its strange configuration. Not only was it so luminous that it was visible during the daytime from some parts of the Earth, but it also sported several long, peacock-feather-like tails.

These tails are thought to hold important clues to how planets and moons were formed billions of years ago, but for years, they didn’t have all the tools to probe this question further. But that changed this week, when a Ph.D. student in London unraveled the mystery of Comet McNaught.

Astrophysicist Karl Battams at the Naval Research Laboratory called it “one of the most beautiful comets we’ve seen for decades.” For all its beauty, however, Comet McNaught had strange patterns in its dust tail, detailed in the video above.

Comet McNaught in 2006 

Wikimedia Commons 

Usually, comet tails — called striae — can stretch as far as 100 million miles behind the comet’s “nucleus,” the clump of ice or rock that makes up its solid core. Comets actually have two tails: one composed of ions (charged atoms) that are manipulated by the magnetic fields of the solar wind, and a “dust” tail that consists of tiny bits of matter gleaned from the comet’s nucleus. The McNaught comet’s dust tails are famous among astronomers because they feature a strange pattern of “disruption” — what otherwise should be clean lines are actually littered with small trenches, similar to what you might see in a sand dune in the desert.

These disruptions puzzled Oliver Price, a Ph.D. student at University College London’s Mullard Space Science Laboratory, when he first noticed them because, by all accounts, these dust particles should be too heavy to get bumped into strange formations by the solar wind. Nevertheless, they are disrupted. Price’s work has essentially added an important caveat to this idea:

“This result (and others) has shown that actually the solar wind can play an important role in the morphology of the dust tail as well,” he tells Inverse. “So, it’s been really exciting to have proved something I was taught in a classroom to be (slightly) wrong!”

Price called them “strange goings-on” when he first noticed them in images gleaned from NASA’s STEREO and SOHO spacecraft. He was able to stich together these images, amongst others, to create a three dimensional map that simulates how each dust particle moves from the comet’s nucleus into formation in the tail.

Perhaps most importantly, this simulation illuminated the source of these strange ripples. As the comet speeds through space, dust falls from the head of the comet into the tail. As this happens, the comet moves in and out of a sheet of magnetic activity called the heliospheric current sheet. At this juncture, the solar wind’s magnetic orientation actually changes directions, affecting how the dust particles settle in the comet’s tail. You can see it happen around 1:23 in the video, when dust particles enter the sheet and become slightly displaced, causing interruptions in the otherwise straight lines.

“It shows that magnetic interactions caused by the sun can have an important role in the behaviour of large dust clouds,” he says. This, he adds, may help us uncover what forces may have shaped the moons, planets, and comets we see today. This force was at work millions of years ago when the universe itself was just a giant dust cloud.

“When the solar system was forming, it was basically one massive dust cloud, so it means we have something else to think about when we consider how the solar system formed,” he concludes.

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