What caused gravitational waves detected by LIGO? I understand that in recent discovery gravitational waves have been detected. But knowing space time is not static it probably changes constantly in many places in the universe due to changes in distribution of massive bodies. For example, could the detected wave just be a slight oscillation in Gravity due to Jupiter fly by, or moon, or something similar?
It couldn't be Jupiter or the moon because 


The frequency of the detected waves is too fast. The detector found something that rotated several hundred times a second, and then stopped.
The amplitude is too big. Even though Jupiter is close, the gravitational waves it produces in its orbit are extraordinarily weak. Far too weak for us to detect them (good thing too, because if it was producing powerful gravitational radiation, it would start to spiral into the sun)


We know one thing that can produce a chirp of this frequency and amplitude, and that is a black hole merger. In the last few moments before merging, these two black holes converted about three solar masses into gravitational radiation: That is a colossal amount of energy. About $$500,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000$$Joules.  That is why for one moment it was the "brightest"  point in the gravitational sky

(Note. standard form is for wimps)