Meteor Showers

by Oraia Helene

Meteor showers are some of my favorite things to watch in the night sky, and are all the more fun since several of them occur on a regular schedule every year. (And one of them is always right around my birthday, which is nice, too!)

The word meteor comes from the Greek meteōros, meaning “high in the air” – this is also the root of the word “meteorology,” which is applied to the study of weather rather than the study of meteors. And, actually, until the early 19th Century – around the time of an amazing meteor storm in 1833, which I’ll come back to later – meteors were assumed by the western world to be atmospheric phenomena alone. That is to say, they were taken to be something like lightning, not the result of something extra-terrestrial burning up in the atmosphere. The study of meteors is called meteorics, though usually it is just referred to as meteor astronomy.

Although meteors are sometimes called shooting stars or falling stars, they aren’t stars, falling or otherwise. Describing what they are requires a little more terminology. A meteor is the visible streak of light caused when a solid object called a meteoroid enters the earth’s atmosphere and begins to burn up. If anything is left to reach the ground, that object is called a meteorite. So, to say it again, a chunk of interplanetary rock called a meteoroid leaves a trail called a meteor as it falls through the atmosphere, and becomes a meteorite if and when it hits the ground.

Most meteoroids are tiny, on the order of a grain of sand, and millions hit the earth’s atmosphere every day. Most are either too small to be visible to the naked eye, or they make impact during the day and are washed out by the light of the sun. But, some – usually about the size of a pebble – create the bright trails we call meteors. On any given night, there are sporadic meteors at a rate of up to fifteen per hour. You might be out stargazing, or just coming home from work, and see a “shooting star.” Others occur in showers, and it is primarily meteor showers that I want to talk about today.

For the most part, meteor showers originate with comets, which leave trails of debris behind them as they swing through our solar system in their long arcs of passage. Every time through, some of the ice on the comet vaporizes, and carries along with it some of the rocky core of the comet’s head, continually renewing the “dust trail” it leaves in its wake. The famous Halley’s Comet has left trails that give us two meteor showers: the Eta Aquarids in early May, and the Orionids in late October – roughly coinciding with Beltane and Samhain, since we pass through the comet trail in two places on opposite sides of the year.

Sometimes, though, a comet or other body can break up in a more dramatic fashion, producing larger chunks and creating new meteor showers that are then encountered every year. The Geminids in mid-December are an example of this, with its meteoroids coming from the breakup of an asteroid-like body (thought to be a dead comet) about a thousand years ago. This meteor shower was first observed around 150 years ago, so it’s a relatively new one, and it may actually be growing more intense every year.

But most of the time, we’re talking about trails of very small particles. As the earth travels around the sun, it periodically passes through these trails of debris on a fairly regular schedule, which is how we can predict the major showers, and why they all enter the atmosphere from the same direction – after all, we’re plowing into them. Because of perspective, these parallel paths all appear to converge into a single point, which is why during a meteor shower, all of the meteors appear to radiate from the same place in the sky. This point is, appropriately enough, called the radiant point, and the meteor shower is typically named after the brightest star or entire constellation that appears behind that radiant. So we have the Orionids, the Leonids, the Perseids, and so on. The meteors aren’t really coming from Orion, or Leo, or Perseus, but that’s the direction you would look to find the radiant. That doesn’t necessarily mean that you have to look for the radiant in order to see the meteors, though! During a meteor shower, the meteors can appear pretty much anywhere in the sky – it’s just that if you traced all of those trails backward, they would all appear to come from the same point.

I’ve mentioned a few of the major meteor showers already, but I want to give you a little more information on my two favorites. The Perseid meteor shower, which peaks around August 12, is one of the best-known meteor showers during the year with a peak rate of about 60 meteors per hour, or one per minute. This one is caused by the debris trail of the comet Swift-Tuttle, and has been observed for 2000 years. It can sometimes be hard to see in the hazy summer skies of August, but it’s nice and reliable, and I find it a nice (if slightly off-target) birthday present. :)

The Leonids can be even more spectacular, coming in the crisp skies of fall with a peak around November 17. This shower is produced by the dust left by comet Tempel-Tuttle, and is notorious for producing very bright meteors or even fireballs that streak across the night sky. While ordinarily the Leonids aren’t quite as active as the Perseids, every 33 years or so they produce a meteor storm, with thousands of meteors per hour. The meteor storm of 1833 was particularly stunning, with estimates of 1 to 2 hundred thousand meteors per hour over most of North America. Trying to predict exactly when and under what conditions a massive storm like that will form, is not completely nailed down yet, which is why you’ll sometimes see newspaper articles discussing the potential size of upcoming meteor showers, but always noting that predictions are just predictions, and not certainties.

One nice thing about observing meteor showers is that you don’t need any special equipment – your eyes are all you need, because you want to be able to take in as wide a field of view as possible in order to catch the movement of each new meteor. The best thing to do is find a nice, dark location with as open a view of the sky as possible. Then, depending on the weather that time of year, you may need to bring a blanket and/or a hot thermos to keep yourself warm, since you’re going to be sitting still – or, better yet, lying back in a lawn chair or on a blanket – while you watch the sky and you don’t want to worry about hypothermia. Conversely, for the summertime showers, you might need bug spray. Basically, whatever you might need to spend time outdoors at that time of year. And then you just…watch.

Meteor showers are best observed in the early morning rather than the late evening, because as we move forward through the debris field, more meteors are encountered on the side turning toward the sun (which you could see as the “forward” side of the earth) than on the side turning away from the sun. It’s sort of like how you get more bugs on your front windshield than on the rest of your car. :)

The American Meteor Society has some good information about meteor showers throughout the year, and even offers opportunities to do some “citizen science.” Their website has a link to their Visual Observing Program, in which you can help monitor the various meteor showers (especially the minor ones that don’t get as much attention) and report on how many meteors per hour you spotted. Unfortunately for my friends in the southern hemisphere, most of the meteor shower activity is much stronger in the northern hemisphere, but the American Meteor Society page on meteor showers does provide information on which ones are better below the equator.

I haven’t seen much discussion from astrologers on the significance of meteor showers, although most seem to take an interest in them as celestial phenomena to be aware of and observe. Many cultures have taken meteor showers – especially the big, spectacular meteor storms – as signs and omens of various kinds, and of course single “falling stars” may easily been interpreted as signs in the heavens, if not literal falling stars. They may also have given rise to myths and legends involving a rain of fire from the sky, or the casting down of the stars at the end of the world. Nowadays, we have the tradition of making a wish on a falling star, which is significantly gentler than interpreting it as a sign of divine wrath!

Lastly, on a little bit of a language note, it’s become something of a cliché to describe someone as having enjoyed “a meteoric rise.” Although the expression is intended to evoke the fast and brilliant – but brief – appearance of a meteor, the expression has always struck me as silly, since as we’ve seen, meteors trace the path of FALLING objects. :) I’d like to see it change to something like, “BP’s stock sure had a meteoric fall after that oil disaster in the Gulf, didn’t it?”

Wikipedia has a list of all of the annual meteor showers, though you’ll have to do a web search for the exact dates in any given year.

This article was adapted from the Astra segment of Media Astra Ac Terra Episode #22.

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