On February 11, 2016 the National Science Foundation and the leaders of collaboration LIGO (Laser Interferometer Gravitational-Wave Observatory) announced the first direct detection of gravitational-waves. The signal discovered was labeled as GW150914 by the date of September 14, 2015, and it fits, surprisingly, very well with the waveform predicted by general relativity for the merger of two black holes. Although this discovery is not yet confirmed through independent experiments (VIRGO or Kagra), the fact that the same signal has been discovered in the two LIGO detectors (which are separate 3,002 Km.) almost simultaneously leaves very little doubt about the astrophysical origin of the detected signal. Recently, on June 1st, 2017, the LIGO team announced the third gravitational-wave detection GW170104 dated on January 4, 2017. This means that  the three detections of gravitational-waves are extremely important not only to provide a verified direct caption of the existence of gravitational waves, and consequently confirm the existence of twenty (or more) solar-mass black holes, but also because it opens a new window in astronomy and offers the possibility to explore the universe with completely new methods, and furthermore, the fact that the signal matches the predictions of general relativity provides strong evidence for the validity of general relativity in the regime strong gravity. The observation of GW170104 consolidates LIGO as a powerful observatory of  the "dark side of the Universe" and it gives us a hint about the formation of binary black hole systems. 

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Thus welcome to the next astronomy age!

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