Free Astronomy Magazine November-December 2017

15 NOVEMBER-DECEMBER 2017 SPACE CHRONICLES These included ESO’s Visible and In- frared Survey Telescope for Astron- omy (VISTA) and VLT Survey Tele- scope (VST) at the Paranal Observa- tory, the Italian Rapid Eye Mount (REM) telescope at ESO’s La Silla Ob- servatory, the LCO 0.4-meter tele- scope at Las Cumbres Observatory, and the American DECam at Cerro Tololo Inter-American Observatory. observe first tational T his artist’s impression shows two tiny but very dense neutron stars at the point at which they merge and explode as a kilonova. Such a very rare event is expected to produce both gravitational waves and a short gamma- ray burst, both of which were observed on 17 August 2017 by LIGO–Virgo and Fermi/INTEGRAL respectively. Subsequent detailed observations with many ESO telescopes confirmed that this object, seen in the galaxy NGC 4993 about 130 million light-years from the Earth, is indeed a kilonova. Such objects are the main source of very heavy chemical elements, such as gold and platinum, in the Universe. [ESO/L. Calçada/M. Kornmesser]