I’m getting an early birthday present tomorrow — and by early I mean 3:27 a.m.! It seems that the path of an "Iridium flare" passes just 2.7 kilometers west of my home in Denver at that time. The prediction is that from my front yard, the flare will reach a magnitude of minus 8 for a few seconds. If my calculations are correct, this is 23 times brighter than Venus at its brightest. On top of this, it appears halfway up in the west, higher than I am ever likely to see Venus in a fully darkened sky.
Of course, there are those pesky city lights and a crescent moon in the opposite part of the sky, but while well within the city limits, I live in a secluded area. I can even remember (once) being able to see the Milky Way, so something 23 times brighter than Venus will be spectacular if there are no clouds!
I’m sorry, but you likely won’t see this flare. This is my birthday flare. (Well, OK, I’ll share it with anyone living within a few miles of me who knows when and where to look.) But you’ll have to find your own flare.
Iridium flares are a localized phenomenon, so unless you live near me, you are not likely to see the same flares that I can see. That’s because these flares don’t originate in some other part of the galaxy, or even from some other part of the solar system. If they did, they could be seen over potentially half the earth at a time.
Instead, Iridium flares are produced by sunlight bouncing off reflective panels on a number of communications satellites about 800 km (500 miles) above the earth. As the satellites move through space, the sunlight glints off at predictable angles, and you have to be at the right location on the planet to see it. But there are a large number of the satellites, so catching a flare, which can last up to 15 or maybe even 20 seconds at times, is not that rare. They look a bit like a bright meteor in slow motion. Actually this could be quite annoying if it happens to ruin an astrophoto you are taking. But they can also be a lot of fun to watch.
The satellites are called "Iridium" because there were originally planned to be 77, which is the number of protons in an Iridium atom. I’m not sure how many were actually launched, but I have heard 66. The satellite numbering goes higher, however. The one poised to give me a show is #81. At any rate, there are plenty to go around, but if you want to view a flare, you have to get a prediction.
Fortunately, there are websites and even software that can provide predictions for your specific location. If you use the Opera browser, there is even a widget that will get the calculations for you. Not surprisingly, it is called
Iridium Flare. It only works with Opera, but it is pretty neat. I haven’t used any of the other software, but the
Heavens Above website produces excellent predictions. You can register for free so it will hold your information, or you can just use it once. In any event, you must input accurate latitude and longitude information for your street address (or wherever you are observing), preferably not just for your city. You can find your latitude and longitude in many ways. One of the easiest is to go to Microsoft’s
TerraServer and enter your address, then request an available image from the selection and your latitude and longitude will be displayed in the box on the left. Sometimes the flares are so bright that you can see them in broad
daylight, so you can request daytime predictions, too.
So I’m set. I’ve got my prediction. All I have to do now is set the alarm and hope the sky is clear at 3:27 tomorrow morning. But come to think of it, that’s a pretty awful thing to do to a guy on his birthday–making him get up at such an abominable hour! Maybe I’ll just try for a daytime flare. Hmmm.
Image from Astronomy Picture of the Day of an Iridium flare on October 22, 1999. Credit: J. W. Young ( TMO, JPL, NASA) Used With Permission.
POSTSCRIPT 11 JUNE: I saw it. It wasn’t easy getting up so early, but I saw the flare. The sky was rather hazy with maybe 50 percent patchy cloud cover. Vega, the fifth brightest star in the sky, was just visible. But there, right on time and in the predicted position, was Iridium 81, traveling from North to South. In the space of maybe 6 seconds it moved only a few degrees, but went from barely visible to brighter than Venus and then faded quickly as it passed behind a cloud. It really was bright, brighter than I had ever seen Venus, but the seeing conditions were terrible. I want to see a -8 in a truly dark sky — and maybe one in daylight, too!
Wow! How on Earth did you ever figure out this was going to happen? And on your birthday? 23 times brighter than Venus???
Hey … happy birthday!
You deserve it!
Deborah
Hi, and thanks. I like to look for unusual things in the sky, rather than doing a lot of telescopic observing. I have a link on my computer to get the daily predictions of the Iridium satellites, as well as the Opera widget (although I rarely use Opera), and I occasionally check. I just happened to notice the -8 predicted for this morning. I hadn’t seen one that bright yet, so I thought I’d give it a shot. Now I’m ready for the real challenge — a daylight Iridium observation! There’s a -6.9 tomorrow night just before sunset here in Denver, so maybe I’ll try.
Happy Birthday! Very cool birthday candle.
Cool birthday present.
One time a saw a daytime flare. It was awesome.
I regularly check Heavens Above on the Dr. Sky website.
I saw the flare at exactly the second it was predicted
and in the direction exactly predicted. It was cool.
Good idea to look for a birthday flare, day or night.
….Linda
Linda, I missed my most recent chance a few days ago due to clouds, but I’ll try again! By the way, keep an eye out for “noctilucent” clouds!
LS