There has been no satisfactory answer from the Military Media, the people who usually deal with "official" answers to the public.
However, putting two and two together, we can surmise that the unexplained light came from the launch of a thermo-nuclear Triton Missile.
There have been encounters between the U.S Navy and Chinese warships guarding the disputed Spratley Islands where the Chinese have been constructing forward airbases. Further alarming the U.S. government have been reports of Chinese missile ships engaging in joint 'first response' nuclear exercises with the Russians in the Western Pacific.
Enough has apparently been ENOUGH! Last week the U.S. Navy sent it's latest Trident missile zooming over the Chinese and Russian fleets a thousand miles out at sea. It carried a clear warning. "Don't come a step closer, or the next one may be loaded"
This is the Brave New World in which we are living folks, where the real Global Warming is but the flick of a switch away.
Jubilate.
Ian