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The other night, while driving home, I saw the constellation Orion looming large over the horizon. This leaning ancient warrior was fighting off Taurus the Bull as he does every winter from here in the Northern Hemisphere. The return of this particular set of stars to my home commute can only mean 2 things, 1) I stayed on campus far too late (which wasn’t the case) or 2) it’s almost the end of the semester (which was the case). For me, the end of the semester marks several coincident things that I need to pay attention to. The first is final’s week (next Monday through Friday), the second is my Birthday (Wednesday) and the third is the Geminids meteor shower ( now through about December 17, peaking December 13-14. (see here for free chart creation tools – you don’t really need though, these meteors shower the entire sky with their light. Just go outside anytime after dark and look up for a few minutes)

While having my birthday and finals align themselves has been a fairly constant source of annoyance, having my Birthday and a meteor shower align is kind of cool. (Of course, that whole “finals week” thing makes it often hard to actually enjoy them, but what’s life without dichotomy?)

The Geminids are consistently one of the more active meteor showers. This may be due to the 1.5 year period of the parent object, 3200 Phaethon. This strange object refreshes the meteor stream every other year, keeping the source of the storm fresh. This year — TODAY, Dec 10 — this object actually passes within 47 lunar distances of Earth, making for a particularly fresh storm.

Most meteor showers come from comets, but Phaethon looks a lot like an asteroid. We think we have some understanding of the mystery involved. It’s thought Phaethon is a former comet ran out of surface volatiles – the pockets of material that can turn into gas and produce a tail. It has also built up a thick crust of interplanetary dust grains – bits and pieces of left over stuff from the solar system’s creation, knocked off of asteroids, planets and other objects during collisions, or spewed into space by particularly spectacular volcanoes. This combination means that Pantheon is in many ways the equivalent of a snowball rolled around in dirt until it looks like a mud ball. As that mud ball rolls around the sun, it leaves behind a trail of dirt, ice, and other stuff that is aligned just right for the Earth to smack into them once a year.

Meteor showers are really nothing more than the Earth smacking through a column of dust and ice left behind by some comet or comet like object. When these objects hit our atmosphere, like bugs hitting a windshield, they give off tremendous amounts off light as they burn up in the atmosphere. A lot of scientists encourage people to go out and report their observations (although I have to admit I can’t find anywhere to report this shower online – anyone know anywhere?) so that we can get better measurements of the paths of the parent object. As the Earth passes through this years tail and the tail from 1.5 years again and from 3 years ago, etc, etc, we get separate peaks in the number of meteors we see each hour. It takes a whole globe of people looking up to measure where our atmosphere is hitting how many objects per hour. Imagine driving down the road with a clean wind shield and crossing a stream of gnats. You can measure the distribution of the gnat stream by counting how many dead gnats you end up with on different parts of your wind shield.

In general, just like the gnats won’t harm your windshield, the its and pieces of comet-like-thing that cause the meteor shower won’t harm the Earth. That said, there is a probability that someday in the future we will cross the comet instead of the comet’s stream. There is no concern for anytime in the next several 1000 years for any of the known objects, but …. there is a neat possible history of a possible past collision between the Earth and a fragment of Comet Enke (the parent of the Taurid Meteor Shower) that may (may may may – the data is week) have aided in the end of the bronze era.

So, you’re safe today. 3200 Phaethon is a little bit close (and landed on the Potentially Hazardous Asteroid List (scroll down)) but no possible harm will actually come. Instead, go out, look up, and catch yourself a look at a falling star falling comet dust.