North Yorkshire - Iridium Flares
2014 Sep 16
Tuesday, Day 259
For schools, clubs and societies - space exploration and history
Pick the Closest:
Astronomy in Yorkshire:
Very Much an "Identified Flying Object"
Occasionally something in the sky will catch your eye, like a slowly moving light that gets very bright and then fades away, all in the space of about five seconds. The chances are that you have spotted one of the sixty or so "Iridium" satellites in orbit.
Iridiums are fitted with a large, flat and highly polished panel behind behind each of their three aerials. They can occasionally produce glints that nearly rival the Full Moon in brightness.
Because of the very controlled way in which way the satellites orient themselves in space, Iridium 'flares' are highly predictable. Those in the know can wait for them and can be looking in the right direction when they occur.
The table tells you which direction to look and the maximum brightness (Visual Magnitude) to expect. The more negative the figure, the brighter it will be. For comparison, the brightest stars in the Sky are magnitude -1, Venus at its most brilliant is -4 and a Full Moon is -11.
Sometimes the flare will be a little brighter or dimmer than expected because of minor deviations in the satellite's orientation.
One thing you can do is see how different the same flare appears from a location a few miles away. It might be dimmer, brighter, and it might happen a few seconds earlier or later as the satellite travels round its orbit. It takes nearly 15 seconds for a flare event to travel across Yorkshire.
Times are local UK so will show Summer Time when it is in force.
The data for these predictions are provided by Simone Corbellini, a mathematician and satellite observer who lives in Italy. His own website covers satellite observing and flares in more depth. You can get there from the left hand menu.
Copyright © Robert Christy, all rights reserved
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