Fun With Satellites: Iridium Flares
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Ever been outside in the evening, lying back, looking up at the night sky, when suddenly your eyes catch a tiny white object floating effortlessly across the great dome above you? I'm not talking about those moving "stars" with red and green flashing lights; those would be planes. I'm not talking about bright lights that hover over great cities and suck people up into their deadly death rays of doom; those would be the results of heightened imaginations. I'm talking about man-made satellites and how to spot them yourself.
Satellites are merely objects that revolve around a planet. One well-known satellite that might be categorized by astronomers as "stinking big" is, of course, the Moon. But the tiny lights you see in the evening hours after sunset and the wee hours of the morning before sunrise are man-made satellites that typically vary from table- to house-sized.
Since they don't have their own light source, to be seen they must reflect light. But what light? The sun's of course. That explains why the time to see them is in the hours after sunset or before sunrise. It is then that we are in darkness but they are still high enough to catch a glimpse of the sun's light and throw it our way.
But you need not be limited to a seemingly random display of the cheesy little corporate satellites. If you know when and where to look you can see the big guys, like the Hubble Space Telescope (HST), the Shuttle, the International Space Station (ISS) or, the most challenging and fun, the iridium flares.
Iridium flares is the common term for the spectacular burst of light given off by a species of communication satellite called Iridium. They have geometric shapes and mirrored sides which means that if you catch them at the just the right moment, as they spin around and around, they can mirror the sun's light right back at you and for a few seconds be the brightest object in the sky.
But how can a layperson find out when a flare is, or when the other big guys are scheduled to fly over? It's easier than you think.
There is a website called Heavens Above which provides a wealth of easily understood information regarding all these heavenly events --- and much, much more.
Knowing your exact location via one of those hand-held Global Positioning Systems is preferred, but just entering your city will provide enough information so you can see most everything with uncanny precision. Heavens Above provides you with a local sky map so you can see how and exactly when these man-made moons will travel across the sky, accurate to the second.
And to make sure your clock is in sync with the world's atomic clocks, they give you the exact time to set your watch by.
Heavens Above also provides you with personalized all-sky charts, locations of all the planets and constellations, and even the histories behind the constellations.
As to those iridium flares. If your clock is in sync, and you know your exact location, you can go out into your front yard, look up at the right part of the sky at the right moment and before your very eyes you can see a seconds-long burst of brightness. Predicting heavenly events impresses the neighbor kids to no end, believe me.
Heavens Above is at http://www.heavens-above.com. Have fun!
Mark Ritter can be reached here.
Photo courtesy Paolo Bussoula (whose website is in Italian).
Posted by Administrator at 2002.01. 5 03:19 PM | Comments (0)
