While taking pictures for a night sky timelapse video, astrophotogrpaher Babak Tafreshi got a surprise in his field of view: a tumbling satellite! He made a special video to highlight it:
Pretty neat. A lot of people aren't even aware that satellites are visible at night at all, but really on any given night dozens of satellites can be visible passing through the sky; in fact the space station is so bright it's actually now the third brightest object in the sky, surpassing even Venus.
The satellites come in a lot of flavors: communications, military, scientific, even old rocket boosters abandoned in orbit after their job was done. Sometimes those satellites have to maintain a specific attitude, or angle, as they orbit the Earth, but not all of them do (especially those boosters). These can tumble end over end, and so their brightness changes as we look at them. They shine by reflecting sunlight, so when we see a long booster end-on it's fainter than when we see it from the side. As they tumble, then, they brighten and fade.
That's what Babak caught here. I don't know what satellite he's seeing, but clearly from its behavior it's tumbling as it orbits [UPDATE: Babak told me that it's been identified as a Cosmos 2364, a defunct navigation satellite, and it's most likely rotating, not tumbling, and the change in brightness is due to how sunlight is reflecting off its solar panels]. I've seen this myself many, many times and it's fascinating to watch. In this time lapse it's sped way up, of course, so it's more stately when you see one by eye.
If you want to see satellites yourself, then I always suggest Heavens Above, which is my go-to site to find out what's up. Just enter your latitude and longitude (you can get them from Google Maps, for example) and off you go! They're also easy to photograph, too (check the Related Posts below for more). It's fun, and actually pretty cool: you can get pictures of things screaming around the Earth at tens of thousands of kilometers per hour! And all you need is an inexpensive camera and a tripod.
And you don't even need that to enjoy them. Just go outside at the right time, face the right direction, and look up. That's all it takes.