On February 11 2016, the LIGO Scientific Collaboration and the Virgo Collaboration announced
the observation of gravitational waves from a binary black hole merger. The transient signal
GW150914 had been recorded five months earlier by the two Advanced LIGO detectors which
had just started their first observation run, following a few years of upgrade. Parallel to the data
analysis which led to the conclusion that the observed signal was indeed of astrophysical origin,
the two collaborations invested a lot of effort to prepare the discovery announcement. In these
proceedings, we review the main aspects of the outreach strategy developed for this event and try
to quantify its impact on the various targeted audiences: the general audience, the media and the
educational community.