The Moon Has an "Extended Sodium Tail"

The tail is extremely diffuse so it won't make it through Earth's atmosphere and is not visible to the naked eye.
Loukia Papadopoulos

New research is revealing that the moon still has some more tricks up its sleeve. Around the time of the new moon, the moon actually exhibits an extended sodium tail.

"The lunar surface is constantly bombarded by the solar wind, photons, and meteoroids, which can liberate Na (sodium) atoms from the regolith. These atoms are subsequently accelerated by solar photon pressure to form a long comet‐like tail opposite the sun," wrote the researchers that spotted this phenomenon in their study.

"Near new moon, these atoms encounter the Earth's gravity and are “focused” into a beam of enhanced density. This beam appears as the ∼3° diameter Sodium Moon Spot (SMS)."

What does this mean for the Earth? Nothing much it turns out. It is just a cool thing to know even if it can not be seen by the naked eye.

“Does this have a practical application? Probably not,” Jeffrey Baumgardner, the study’s lead author and a senior research scientist at Boston University’s Center for Space Physics, told The New York Times.

“It makes the moon sort of look like a comet,” he added. “It has a stream of stuff coming off it.”

So how did the researchers actually spot this nearly invisible tail? Boston University has several all-sky-imaging cameras around the globe that were designed to spot auroras. However, they are now used to see sodium in Earth’s atmosphere in particular when meteors burn up before reaching Earth's surface.

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The cameras first spotted the moon's sodium tail back in November 1998 at the McDonald Observatory in Fort Davis, Texas. It took additional research, including models that simulated where the sodium spot could be coming from, for the scientists to conclude that it was indeed a moon tail.

Luckily, the researchers assure us that the tail is extremely diffuse which means it won't be sending any sodium dust particles our way. The study was published in the journal Advanced Earth and Space Science.

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