The tail is invisible to the naked eye but appears on all-sky cameras during every new moon, which Earth wears like a scarf once a month.
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00:00When a comet soars across the sky, twin trails of gas and dust streak behind it.
00:05Now, a new study suggests that the moon may have a similar tail,
00:08but it's only visible once a month when Earth passes directly through it.
00:17In the 1990s, astronomers noticed that the moon has a tail.
00:21It isn't visible to the naked eye, but using a special telescope,
00:24they were able to see the faint orange glow of sodium streaking off of the moon.
00:28This sodium tail comes from lunar soil that gets blasted into space when asteroids hit the moon,
00:34and it's only visible from Earth once a month during a new moon
00:37when the moon sits between Earth and the sun.
00:40When these three bodies are aligned, photons from the sun push that airborne
00:43sodium hundreds of thousands of miles away from the moon.
00:46Earth's gravity then pinches that sodium tail into a long beam that
00:50wraps around our planet and shoots out the other side.
00:53That beam is about 50 times too dim for humans to see with the naked eye,
00:57but when astronomers look at it with the right telescopes,
01:00they see a fuzzy orange spot about five times wider than the full moon.
01:04After a few days, it vanishes.
01:07That fuzzy sodium spot always appears at the same time each month,
01:11but strangely, its brightness is constantly changing.
01:14In a new study published this month in the journal JGR Planets,
01:18astronomers tried to figure out why.
01:20After looking at 14 years worth of lunar photos,
01:22they figured out that the spot tends to appear brighter
01:25when more random meteors are sighted over Earth.
01:28What's the connection?
01:30More meteors over Earth means more asteroids slamming into the surface of the moon,
01:34which doesn't have an atmosphere to protect it like our planet does.
01:38According to the researchers,
01:39these random meteors tend to be larger, faster, and more powerful
01:43than the broken up rocks that are parts of the annual meteor showers
01:47that we see like the Leonods in November.
01:50Bigger meteors mean bigger impacts on the moon,
01:52which means a bigger cloud of sodium flying into space and eventually passing over Earth.
01:57And so, scientists on Earth see a brighter spot when our planet
02:02focuses that cloud into a beam that passes around our planet.
02:06The moon's tail and the beam it creates are both harmless to our planet,
02:09which has a strong atmosphere to protect it from those pesky particles.
02:13So the next time a new moon rises,
02:16take a minute to thank our friend in the sky
02:17for sprinkling us with a little cosmic pixie dust.
02:22Transcribed by ESO. Translated by —