On October 16, 2017, the the LIGO Scientific Collaboration, Virgo Collaboration, and its partners announced the first observation of gravitational-waves from a pair of inspiraling neutron stars. Electromagnetic emission from the resulting collision was also observed in multiple wavelength bands. This occured on August 17, 2017 and represents the first time a cosmic event was observed with both gravitational waves and light.
First Optical Photons from Gravitational-Wave Source. Swope and Magellan telescope optical and near-infrared images of the first optical counterpart to a gravitational-wave source, SSS17a, in its galaxy, NGC 4993. The left image is from August 17, 2017, 11 hours after the LIGO-Virgo detection of the gravitational-wave source, and contains the first optical photons from the source. The right image is from four days later, when SSS17a—the aftermath of a neutron star merger—faded significantly and its color became much redder. [Credit: 1M2H/UC Santa Cruz and Carnegie Observatories/Ryan Foley]
Full article: http://ligo.org/detections/GW170817.php