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)
The signal found was quasi-periodic, with a rapidly increasing frequency - characteristic of a merging binary system (a so-called "chirp").
The characteristic frequency of the GWs of a "binary" system are at twice the orbital period. So the frequency "emitted" by the Jupiter-Sun system would be wayyyy to low to be detected by LIGO, which is sensitive down to around 10 Hz (ie orbital periods of 0.2 s or shorter).
These sorts of periods are only found in binaries involving stellar-sized black holes and neutron stars just before they merge.
The interesting thing about the power produced by a binary is that it goes as mass to the power of 5. Another point is that we detect the wave amplitude, which only falls as the inverse distance to the source.
Thus LIGO is most likely to see the merger of the rarest, most massive black hole systems at very large distances.