The Perseids approacheth! August 12, 2004 is the date for the peak of the celebrated annual Perseid meteor shower. In actuality the shower is already upon us, it's just that the early days of the shower (which technically begins in mid to late July each year) are so mild that you may not even notice it. But in the early morning hours of Thursday, August 12, 2004, the shower will peak (most people start watching at like 1 AM or 2 AM.) Why do these things happen on predictable dates each year? And where do they come from?
Small meteoroids orbit the sun in bands, like the asteroids, except that often these bands of tiny stones generally have highly elliptical orbits. This is because they are the leavings of comets, which, when heated by proximity to the sun, grow long tails which contain gas, dust, and pebbles cast off by the comets surface. The pebbles and dust disperse somewhat but have the same trajectory as the comet, so they remain in the same orbit, whirling around the sun and trailing their parent body. Occasionally, Earth in its own nigh-circular orbit will sweep through one of these bands. When that happens, the meteoroids plunge into Earth's atmosphere and burn up in large numbers. We call such events meteor showers.
It's amazing what scientists can tell you about these storms. They can predict when the storms will happen, and when they will peak. They can tell you from what comet the pebbles and dust that make up the shower originate. (Perseids come from the comet Swift-Tuttle.) Sometimes, they can even tell you when the meteors you are viewing now left the surface of the cometary body as can be seen in this article about the upcoming 2004 Perseid Meteor Shower:
…This is a good year for Perseids, for two reasons, explains Bill Cooke of the NASA Marshall Space Flight Center. First, the Moon is new in mid-August; moonlight won't spoil the show. Second, in addition to the usual shower on August 12th, there might be an extra surge of meteors on August 11th caused by a filament of dust newly drifting across Earth's orbit.
The filament, like all the rest of the dust in the Perseid cloud, comes from Comet Swift-Tuttle. The difference is, the filament is relatively young. It boiled off the comet during the Civil War, in 1862. Other dust in the cloud is older (perhaps thousands of years old), more dispersed, and responsible for the month-long shower that peaks on August 12th. The filament will eventually disperse, too, but for now it retains some of its original ribbon-shape.
If predictions are correct, Earth will plow through the filament on Wednesday, August 11th at 2100 UT (5 p.m. EDT). This will produce a surge of mostly-faint meteors over Europe and Asia. Observers might see “as many as 200 meteors per hour,” says Cooke, who recommends getting away from city lights to watch the flurry…
…Later that night, observers in North America can see the “traditional Perseid peak” caused by the older dust from Swift-Tuttle. “Expect 40 to 60 meteors per hour, some of them bright,” says Cooke…
[Emphasis mine.]
The Perseids are so named because the meteors all appear to radiate from a central point in the constellation of Perseus. Obviously the constellation of Perseus has nothing to do with the shower, but if you look at Perseus during the shower you are looking through the forwardmost point of Earth's atmosphere with respect to the motion of the planet and the band of the perseid meteoroids.
To date I have only seen ONE Perseid shower, which, if my calculations are correct, would have been in the late 1970's. I was on a summer-camp sleepover that night and myself and several other young boys witnessed what I would call a spectacular display of meteors of all different colors. I was so impressed by the event that I tried to watch them again and again in the following years, but never with success. A summer night is easier to endure but it is a sad truth that the atmosphere is more active in the summer, and thus the Perseids tend to be the most likely to be obscured by clouds. Thus it has never failed since the 70's that every year I remember to go watch the Perseids, a frigging cloudbank rolls in and spoils the show.
But hope (and foolish optimism) spring eternal, so this year I will try again to watch the Perseids. I'll post about that when it happens.
In my adult life, the best meteor shower I viewed was the Leonid shower of 2001. Leonids appear to radiate from the constellation Leo, come from the comet Tempel-Tuttle, and they generally peak in the wee hours of November 18. November 18, 2001 was frickin' cold, but as it was a winter night, the sky was sharp and clear.
Here's a report I wrote up that morning as a series of e-mails that I sent out during the shower. You can see that as the meteor activity became more intense, the messages became shorter because I didn't want to miss anything:
11/18/04 2:00-2:30 AM -
I counted 11 meteors. Some were tiny but most burned very brightly and left trails longer than, say 10 full moons placed side by side. The meteors tended to glow reddish orange and leave a greenish trail. They all seemed to appear in what I believe to be the east. Most travelled northwest, some traveled southwest. The 11'th one, a real oddball, appeared in the southwest and traveled north across the western sky, going almost all the way across perhaps spanning 2/3rds of the visible sky. This one burned brilliant purple-red, leaving a purple-white trail, and throwing off “sparkles” as it grew and dimmed in brightness. At 2:30 I came inside to warm up and write this down. Also going to fetch my telescope… looks like Old Jove is up tonite.
11/18/04 2:45-3:15 AM -
21 meteors. Pretty consistent coloration and direction. These seemed to be more overhead than in the eastern sky. Friggin cold! Hard to type my fingers are shaking. More of these meteors were tiny but there were a few big ones. I'm noticing that if you spot one, it helps to train your eyes on that area for a few more seconds, as they seem to travel in pairs and triplets sometimes. That makes sense really–when two small pebbles frozen to the surface of a comet in close proximity to each other leave that surface within moments of each other, it makes sense that they would basically have the same trajectory and heading. So a zillion years later, when one strikes the atmosphere, its “partner” is still right on its heels. Numbers 8 and 9, 16 and 17, and 20 and 21 were like that.
They're called “The Leonids” because they (generally) appear to come from the direction of the constellation Leo. My constellation recognition skills are spotty, and I don't know where Leo is tonight, but I guess it must be in the east. I recognize Orion, Taurus, and Ursa Major (the Big Dipper) in the sky tonite.
I was right about Old Jove, btw, that bright star directly overhead looked very out of place, and when I trained the scope on it, there was big old Jupiter looking back at me. Today I could see 3 of the Jovian moons and a dark band across the face of Jove. My scope isn't good enough for me to make out details like the red spot, but I was happy with it. I also trained my scope on the fuzzy Orion Nebula in (center star in the sword of Orion). Lovely, very faint and bluish, but cool to look at. It's been perhaps 10 years since I've looked at this nebula. I counted 5 blue-white stars that appeared to be “inside” the nebula.
I consired checking out Betelgeuse (or is it Rigel?) in Orion's upper-left shoulder and also the Pleiades, but the scope was VERY cold and I decided to pass on those and watch for meteors. When I go out next I'll bring binoculars for a quick peek at the Pleiades, and Betelgeuse. (Which one is the red giant star in Orion? Rigel or Betelgeuse?) I'll probably take a quick peek at the red eye of Taurus the bull. Forget what that star is called… (Aldebaran maybe?)
Gonna go back out soon. Should probably have some hot cocoa with me. It's cold. And my neck is getting sore… note to self: next time bring a beach chair.
11/18/04 3:30-3:50 AM -
THIRTY METEORS!!! More than one a minute. A lot of these were southerly and a significant number (8 perhaps?) were very low on the southern horizon. Hope that the main event doesn't take place below the horizon!
Gotta go wake Patty. Promised to wake her at 4 AM.
11/18/04 4:00-4:15 AM -
THIRTY SIX METEORS!!! One was huge and left a glowing trail of green smoke that I could study in the binoculars for a few minutes afterward. Another even brighter one blew up halfway across the sky. It too left a green glowing smoke trail.
I wonder what is in them to make them glow green?
Several minutes later I was able to relocate the smoke trails, cooler and gray now, illuminated only by the stars and perhaps light sources on the ground. Patty hasn't come down from upstairs yet. She may be too tired, I think.
11/18/04 4:20-4:36 AM -
FORTY-ONE! Think I found Leo… had to wing it from memory but the meteors appear to be coming from there. Lying down in the driveway facing south for best view. Amazing how often they are coming. Couple more with lasting green glowing smoke trails.
My wife has elected to sleep in. *sigh* Ah well…
11/18/04 4:40-4:54 AM -
FIFTY FIVE METEORS! It's really picking up. I definitely found Leo, he's almost overhead and the meteors radiate out in all directions from him. Total meteors I've spotted so far: 194. Freezing out there… I am c-c-cold! Going back out. 5 AM is supposed to be peak. It's 4:56 now.
11/18/04 5:00-5:17 AM -
SEVENTY FIVE! Including one that fishtailed back and forth as it burned up! Wacky!
11/18/04 5:20-5:35 AM -
ONE HUNDRED AND TEN!!!!!!!!!!!!!!
11/18/04 5:38-5:50 AM -
Fifty two. Sky getting very blue. Hard to see the dim ones. Feels like it's letting up some anyway.
I've seen 4 satellites tonite. The last one caught my eye because it was tumbling and catching the sunlight at irregular intervals, causing it to flash as it reflected sunlight at me. As I watched it through my binoculars a big bright meteor went right through my field of vision in the binocs… COOL! Bright green trail behind it.
These seem to be much more consistently colored than the Perseid shower I saw on a summer camp sleepover when I was a kid.
BTW I did check out the eye of Taurus and the red star in Orion through binoculars. Very ruddy those. Took a peek at the Pleiades… lovely, like diamonds they are. Took a last look at Jupiter too. Through the binocs I could only see 2 moons and couldn't make out the dark band. Think the constellation he is in right now is Gemini. Also, there seems to be a star out of place in Taurus. Wondering if it is saturn… looks a little odd to me, I'll have to doublecheck that later.
It's 5:56 now. Going back out for my last 15 minute stretch. I think it will be too bright after that.
11/18/04 5:56-6:10 AM -
Twelve. Sky is too bright, can't even see Leo anymore (Leo is a pretty dim constellation anyway, as constellations go.)
Jupiter is still bright and beautiful, and above it I can still see two bright stars. Pretty sure those are Castor and Pollux, the heads of the Gemini twins.
Can see Orion's belt low on the horizon. Where Taurus was I can see nothing, but the out-of-place star is still there and quite brilliant. It doesn't appear to be twinkling and I'm becoming convinced it is a planet. I remember seeing Mars a lot last month, and this looks too creamy-colored to be Mars, and it's not bright enough to be Venus. I think it is Saturn–it's the right brightness and color. Too many trees in the way to doublecheck with my telescope. I'll have to find an online planetarium somewhere and see what's up this morning (celestially speaking).
The wind has been picking up since about 5:00 AM and it's gotten steadily colder. Anyway, seeing as how the show appears to be over, I've gathered up my now ice-cold cocoa, my popcorn bag, and the pillow I was resting my head on during those stretches when I laid down. (I put the pillow inside of a plastic trashbag to keep it clean.)
Total count was 443 meteors over a period of 4 hours 10 minutes (about 1.7 per minute). Having gone in and out of the house during that time, I wasn't observing for a total of 65 minutes (during which time I was writing up notes, trying to wake Patty, brewing cocoa and popcorn, and so forth) which means I observed 443 meteors in 3 hours 5 minutes really, giving a rate of about 2.4 meteors per minute. So if I had been observing the whole time, it's reasonable to expect I would have seen about 600 meteors between 2 AM and 6:10 AM. Sounds like a heavy storm.
Think I'm gonna try to graph out the meteor activity over time.
11/18/04 7:52 AM -
Here's a graph of the activity showing a definite peak at about 5:27 AM.
I was reminded of meteor-watching by a recent comment from my old buddy Tom.
In closing I'd like to recommend that people interested in watching meteor showers and storms check out Gary W. Kronk's Meteor Observing Calendar. This site will tell you about meteor showers during any month, including several less well-known showers. Furthermore Gary includes detailed informations about where and when to observe each shower, what the showers tend to look like, which ones are “hot” this year, as well as interesting historical details about each shower (here are his histories of the Perseids and the Leonids for example.)