Perseid meteor shower, 2015


Meteor shower! The very words conjure up a picture of flaming fireballs of fury flashing frenetically against the night sky.

Actually, the reality is quite different most of the time.

The Perseids peak on Thursday morning, Aug. 13, during the hour right before morning twilight. You might see as many as 100 streaks — most of them faint — per hour if you observe at exactly the right hour on exactly the right date under a dark rural sky and if it’s crystal clear that morning. You’ll still see plenty of meteors if you observe the morning after or the morning before, but your experience won’t be as good. More on that later. First, a bit of background.

Early peoples believed that meteors were stars that fell from the sky, perhaps dislodged by a high wind. As the great Roman poet Virgil wrote,

Oft you shall see the stars, when wind is near,

Shoot headlong from the sky, and through the night

Leave in their wake long whitening seas of flame.

Actually, that’s not a bad description of what a bright meteor looks like as it streaks across the sky.

Of course, meteors really aren’t “shooting stars.” They are pieces of dust and debris in space that enter the earth’s atmosphere. As they hit the atmosphere, they burn up, leaving a streak of light. Most of the pieces are no bigger than a grain of dust, so meteor showers are not known for their bright fireballs. Mostly you’ll see relatively faint streaks of light, lasting for a second or so.

Any moonless night is a good time to observe meteors. Even without a scheduled shower, you’ll see a few meteors an hour if you’re observing from a relatively dark rural site.

What makes meteor showers interesting is the frequency of those streaks of light.

Meteor showers are caused when Earth passes through a cloud of space debris left by a passing comet, thus increasing the amount of junk that enters the earth’s atmosphere.

Still, most of the yearly meteor showers are weak. They increase the total number of meteors by only a few an hour. The Perseids are the yearly exception with 100 streaks during the last hour before morning twilight on their peak morning.

Meteor showers are best observed on moonless nights away from cities. Both the moon and the glow from city lights wash out these faint steaks of light. Luckily, this year the Perseids peak on a moonless night.

Showers are best observed after midnight as our side of the planet turns into the direction Earth’s orbit around the sun. When that happens, meteors don’t have to play catch up with the earth’s rotation. They are now plummeting headlong at Earth, so we see more of them.

To put it another way, Earth is plowing into the debris cloud like your car plowing through a swarm of bugs. The “after midnight” effect is like bugs hitting your windshield, as my good buddy and observing partner Biff Smooter likes to point out. You only get bugs on your front windshield, the direction that the car is moving.

Observing before midnight is like looking out your back windshield. You won’t see as many meteors that way. Just as bugs have a hard time catching up to the speed of your car, meteors have a hard time catching up to the speed of the Earth.

Showers like the Perseids get their name from the constellation from which they seem to originate. However, that doesn’t mean you have to look in the direction of Perseus to see them. They will appear all over the sky. Your best bet is to look in the direction away from the glow of city lights. If you are observing from north of Columbus, for example, you should look to the south.

Meteor observing requires very little equipment. I’d suggest a lawn chair and a blanket. It often gets fairly cold at 3 a.m., especially if you’ve been sitting unmoving in a lawn chair for three hours. Also, take along a gallon of bug repellent. The mosquitoes are as big as buffaloes this year.

As many as a trillion pieces of space junk enter the atmosphere daily. If they are bigger than a pebble, they create a beautiful, fiery streak across the sky that may change colors, or even flake off bright pieces and explode. They often leave a faint trail of ionized gas that is visible for several seconds after the meteor has disappeared. These infrequent, but memorable, meteors are called fireballs, or bolides. They are the kind of event you’ll remember for the rest of your life.

Some of the debris is man-made. More than a few years ago, a dozen members of the local astronomy club and I were lucky enough to see the second stage of a Russian rocket come burning into the atmosphere. It took several minutes for it to move slowly across half the sky and flaked bright pieces away from itself. It’s worth going observing hundreds of times just to see something like that happen once, and we didn’t need to have a meteor-shower night to make it happen.

While you are sitting there, enjoy the starry sky. The Milky Way is overhead. The sheer beauty of the night sky is reason enough to lie outdoors in silence, drinking in the universe with your eyes.
Tom BurnsStargazing

Tom Burns is director of the Perkins Observatory in Delaware.

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