The time scale of brightening, as well as the particular characteristics of the colors of light seen, do not match any known astronomical phenomena.
"So far it's unlike anything previously observed," said Lawrence Berkeley National Laboratory astronomer Kyle Barbary during a press briefing Tuesday at the American Astronomical Society meeting in Long Beach, California.
[. . .]
Since the object has completely faded away from sight by now, options for getting to the bottom of the mystery are slim.
Another reminder that we know so much, yet remain staggeringly ignorant.