A view of a Perseid meteor from the Very Large Telescope array. Courtesy ESO.
This past week the Perseids meteor shower came to its peak. Of course, social media came alive with hints of a huge shower. People followed up by posting pictures of meteors from their observing sites. It’s an annual event, and most people had clear skies for it. We got a chance to see a few Perseids starting a week or so before the peak, but the actual night, it was cloudy at our place. Some years we get the bear, some years the bear gets us.
The bigger story about the Perseids isn’t what you got to see, although it’s pretty neat to watch these bits of space debris flash into oblivion as they enter Earth’s atmosphere. It’s really about what these things represent. And that is a whole lot of ancient solar system history.
The Ancient Source of the Perseids
The Perseids shower is made up of countless particles of dust that stream off of Comet Swift-Tuttle as it passes around the Sun every 133 years. Earth’s orbit intersects that stream beginning in late July through part of August each year. The peak coincides when we’re passing through the thickest part of the stream. That means we see more meteors that night.
Comet Swift-Tuttle originated early in the solar system’s history and is made of ices and dust that existed back when the Sun and planets were beginning to form. That means its materials pre-date the birth of the Sun. As the system formed and evolved, the planets did their dynamical dance to their current orbits, and in the process, sent chunks of ice out to the outer solar system. From there, those chunks got gravitational nudges that eventually sent them on long orbits around the Sun. Swift-Tuttle is one of those chunks.
So, when you see a Perseid meteor — or any meteor for that matter — flash across the sky, you’re watching a piece of solar system history vaporize before your eyes. Occasionally a chunk is large enough to reach the ground and become a meteorite. Anyone who finds it is holding a piece of cosmic history in their hands. Think about THAT the next time you see a meteor flare in fiery death overhead.
A finder chart for the Orionids this year. The radiant is simply the direction from which most of the Orionids appear to “radiate” from in the sky. It’s not an actual circle in the sky. Click for a bigger version.
I’m not a constant meteor shower watcher. Sure, I’ll go out for the Perseids and the Leonids, but the dozen or so other meteor showers that occur throughout the year aren’t always on my radar. They should be on mine and everybody else’s “check it out” list, if for no other reason than the cool realization that what you just saw flash through the sky as a meteor was a piece of solar system history vaporizing before your very eyes.
That’s the essence of what happens when a speck of dust or a grain of sand that used to be part of a comet or an asteroid encounters our atmosphere and does the cosmic dive of death. Pretty interesting to contemplate, isn’t it?
Meet the Orionids
There’s an upcoming meteor shower called the Orionids this week. It’s actually already happening, but the peak doesn’t occur until the late evening of the 21st into the early morning of the 22nd (so, Wednesday into Thursday). The highest number of meteors will likely be on the 22nd, so be prepared for an all-nighter if you can take the time. The storm is named Orionids because its meteors appear to radiate from the constellation Orion — which rises pretty late at night and is higher in the sky after midnight. Oh, and if you’ve ever heard of Comet Halley — well, the Orionid meteors come from the stream of particles left behind by the comet as it orbits the Sun. So, this is the week each year when Earth and Halley meet again!
If you’re going to watch this shower, the standard advice is to dress warm, bring along warm beverages, and find a place to lie or sit comfortably so that you can watch the sky for long periods of time. That’s often easier said than done, especially if you live in a place where the weather is taking a turn for the colder this time of year.
Meteor-gazing Experiences
I live in a pretty rural area, so we have reasonably dark skies most of the time. I can step outside and see the Milky Way after a few moments, and so meteors flaring high overhead really DO show up well against the starry backdrop. A few years ago we had a pretty good Perseid shower, and we could count a dozen or so each hour. Even though that shower occurs in August, the late evenings and early mornings can get pretty chilly here. So, we bundled up in our down jackets and stretched out in our recliner lawn chairs to enjoy the view. We probably saw a dozen or so meteors per hour, with what we called “clumps of meteors” occurring a few seconds apart every once in a while.
A four-hour time-lapse of the sky over Slovakia during the 1998 Leonids shower. This is the one I stayed up to watch from my driveway in Massachusetts. Courtesy of Juraj Tóth, Comenius University, Slovakia, CC BY-SA.3.0
Back when we lived in Massachusetts (in another rural area a few dozen miles outside of Boston), I decided I was going to watch the 1998 Leonids shower. That one occurs in November, and it was supposed to be a pretty good shower that year. So, I bundled up in my ski outfit, down jacket, blankets, brought hot cocoa out to drink and settled in for a good view. Let me tell you, even despite all the warm clothes, I started to get cold! At about 3 in the morning, after a few hours of watching and jumping up and down to keep warm, and repeated warming trips into the house, I settled down on the hood of my car for a final viewing session. Just as I did, it occurred to me — I could have had my car running for a short time to warm up the hood. So, I tried that, and it worked pretty well — aside from the waste of gas that running it for about 10 minutes represented.
Make Your Meteor-gazing Strategy
Everybody who chases meteor showers has their strategies for watching — because, as we all find out, meteors don’t just rain down in heavy showers. What we call “shower” is really just a sporadic trickle most of the time. So, there will be long periods of time — perhaps a few minutes or so — where nothing is happening. Occasionally you’ll get a bunch of meteors all at once. And, unless Earth is heading through a particularly thick part of a meteor trail, you don’t always see more than a few dozen per hour. So, perhaps “shower” is a misnomer, but then again, these things ARE showering from space over head, and they DO make a fine sight. As you wait for the next flash, take the time to search out other cool stuff in the sky. If you have a pair of binoculars, use them to scan your gaze along the Milky Way. Meteor showers aren’t just a way to watch as the solar system annihilates itself one dust speck at a time, they also give you a chance to explore the rest of the sky between those evanescent flashes of light that light up the sky.
