The BlackGEM array, composed of three brand-new telescopes situated at ESO’s La Silla Observatory, has commenced its operations. Its primary objective is to scan the southern sky in search of cosmic events that generate gravitational waves, such as black hole and neutron star mergers.
Gravitational waves are produced during cataclysmic events in the universe, causing ripples in the fabric of space and time. While observatories like LIGO and Virgo are designed to detect these waves, they struggle to pinpoint their exact origin and observe the accompanying transient light resulting from neutron star and black hole collisions. BlackGEM is specifically designed to rapidly scan large portions of the sky with visible light in order to precisely locate sources of gravitational waves.
Paul Groot, the Principal Investigator of the project from Radboud University in the Netherlands, explains, “With BlackGEM, we aim to enhance the study of cosmic events by combining the detection of gravitational waves and visible light. The combination of these two sources provides us with significantly more information about these events than using just one of them.”
By detecting both gravitational waves and the visible light emitted from their sources, astronomers can confirm the nature of these events and accurately determine their precise locations. Using visible light also enables detailed observations of the processes occurring during these mergers, including the formation of heavy elements like gold and platinum.
To date, only one visible counterpart to a gravitational-wave source has been detected. Furthermore, even advanced gravitational-wave detectors like LIGO and Virgo can only narrow down the location of a source to an area roughly equivalent to 400 full moons in the sky. BlackGEM, on the other hand, can efficiently scan such large regions at a higher resolution, consistently locating gravitational-wave sources using visible light.
The three telescopes that make up BlackGEM were constructed by a consortium of universities, including Radboud University, the Netherlands Research School for Astronomy, and KU Leuven in Belgium. Each telescope has a diameter of 65 centimeters and can simultaneously investigate different sections of the sky. The collaboration ultimately plans to expand the array to include 15 telescopes, further improving its scanning coverage. BlackGEM is hosted at ESO’s La Silla Observatory in Chile, making it the first array of its kind in the southern hemisphere.
Despite the relatively modest size of the telescopes’ primary mirrors, measuring 65 centimeters in diameter, BlackGEM can delve as deeply into space as projects with much larger mirrors. This is made possible by taking full advantage of the exceptional observing conditions at La Silla, as emphasized by Groot.
Once BlackGEM accurately identifies a source of gravitational waves, larger telescopes like ESO’s Very Large Telescope or the future ESO Extremely Large Telescope can conduct detailed follow-up observations. These observations will contribute valuable insights into some of the most extreme events in the cosmos.
In addition to its search for optical counterparts to gravitational waves, BlackGEM will also conduct surveys of the southern sky. The array’s operations are fully automated, enabling it to swiftly locate and observe transient astronomical events that appear suddenly and fade rapidly. This capability will offer astronomers a deeper understanding of short-lived phenomena such as supernovae, the colossal explosions marking the end of massive stars’ lives.
Ivo Saviane, the site manager at ESO’s La Silla Observatory, expresses his excitement about BlackGEM’s potential to make significant contributions to transient research. He anticipates outstanding results from this project, which will expand the reach of the site for both the scientific community and the general public.