Satellites
The International Space Station is not the only Earth-orbiting satellite that can be seen with the naked eye. On average, you will be able to see another satellite every five to ten minutes or so. However, most of them are much fainter than ISS.
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Once I counted 23 satellites in just 40 minutes! They are visible if you look harder.
Orbiting IRIDIUM satellites are also easily viewed, in the form of what are called "Iridium Flares", which give the appearance of a suddenly and briefly visible (only lasting a few seconds) bright star as the relatively narrow beam of sunlight reflected from one of an Iridium satellites solar panels passes over the observers location. With 66 Iridium satellites encircling the earth in a precisely spaced "net" of coverage, the chances of a Flare at almost any location at some point in time on most days is very good. Perhaps Mr. Meijers and the rest of the Twisst team that created this wonderfully handy service will someday create another one to send us twits for these also! A big thanks to the Twisst Team for a job well done!