Free Astronomy Magazine November-December 2017

14 NOVEMBER-DECEMBER 2017 SPACE CHRONICLES Observatory (LIGO) in the United States, working with the Virgo In- terferometer in Italy, detected grav- itational waves passing the Earth. This event, the fifth ever detected, was named GW170817. About two seconds later, two space observato- ries, NASA’s Fermi Gamma-ray Space Telescope and ESA’s INTErnational Gamma Ray Astrophysics Labora- tory (INTEGRAL), detected a short gamma-ray burst from the same area of the sky. The LIGO–Virgo ob- servatory network positioned the source within a large region of the southern sky, the size of several hun- dred full Moons and containing mil- lions of stars. As night fell in Chile many telescopes peered at this patch of sky, searching for new sources. by ESO ESO telescopes light from grav wave source i F or the first time ever, astrono- mers have observed both grav- itational waves and light (elec- tromagnetic radiation) from the same event, thanks to a global col- laborative effort and the quick reac- tions of both ESO’s facilities and others around the world. On 17 August 2017 the NSF's Laser Interferometer Gravitational-Wave