Or Something Closer?

Now this is an intriguing image.  It looks like a distant cosmic explosion, perhaps a long-ago galaxy collision or star tearin itself to bits and sending material across light-years of space. There’s interesting structure here, including that mysterious string that seems to be flailing around the lower left-quadrant of the central light cluster.  What do you think it is?

Think about it and then check out the answer below. (Click and drag between the ( ) signs to see the answer.

(It’s the city of London, as seen at night in an image taken on orbit by one of the astronauts aboard the International Space Station. Courtesy NASA/ISS (see the Gateway to Astronaut Photography, http://earth.jsc.nasa.gov/))