BlackGEM telescopes begin search for sources of gravitational waves

Three Belgian-Dutch telescopes have started operating at ESO’s La Silla Observatory in Chile. This so-called BlackGEM network will scan the southern skies for cosmic events that produce gravitational waves, such as neutron star and black hole mergers. Leiden astronomer Rudolf le Poole is a systems engineer for the BlackGEM network. Certain cataclysmic events in the Universe, such as the collision of black holes or neutron stars, create gravitational waves, ripples in the fabric of time and space. Observatories such as the Laser Interferometer Gravitational Wave Observatory (LIGO) and the Virgo Interferometer are designed to detect these waves. But they can’t locate its source very precisely or see the fleeting light that results from collisions between neutron stars and black holes. BlackGEM is dedicated to rapidly scanning large areas of the sky to accurately track sources of gravitational waves using visible light.

“With BlackGEM, our goal is to intensify the study of cosmic events with gravitational waves and visible light,” says Paul Groot of Radboud University in the Netherlands, the project’s principal investigator. “The combination of the two tells us much more about these events than either one.”

Precise locations

By detecting gravitational waves and their visible counterparts, astronomers can confirm the nature of gravitational wave sources and determine their precise locations. The use of visible light also allows for detailed observations of the processes that occur in these mergers, such as the formation of heavy elements such as gold and platinum.

However, to date, only a visible counterpart to a gravitational wave source has been detected. Furthermore, even the most advanced gravitational wave detectors, such as LIGO or Virgo, cannot accurately identify their sources; at best, they can narrow a source’s location to an area of ​​about 400 full moons in the sky. BlackGEM will effectively scan these large regions at a resolution high enough to consistently locate the sources of gravitational waves using visible light.


BlackGEM’s three constituent telescopes were built by a consortium of universities: Radboud University, the Dutch School for Research in Astronomy, and KU Leuven in Belgium. The telescopes are each 65 centimeters in diameter and can study different areas of the sky simultaneously. the collaboration ultimately aims to expand the network to 15 telescopes, further improving its scanning coverage. BlackGEM is hosted at ESO’s La Silla Observatory in Chile, making it the first network of its kind in the southern hemisphere.

“Despite the modest 25-inch primary mirror, we got to some projects with much larger mirrors because we took full advantage of the excellent viewing conditions at La Silla,” says Groot. Once BlackGEM has precisely identified a source of gravitational waves, larger telescopes such as ESO’s Very Large Telescope or ESO’s future Extremely Large Telescope can make detailed follow-up observations, which will help shed light on some of the events. most extreme in the cosmos. .

Southern sky

In addition to its search for the optical counterparts of gravitational waves, BlackGEM will also conduct surveys of the southern sky. Its operations are fully automated, meaning the network can quickly find and observe “transient” astronomical events, which appear suddenly and disappear quickly. This will give astronomers deeper insight into short-lived astronomical phenomena such as supernovae, the huge explosions that mark the end of a massive star’s life.

“Thanks to BlackGEM, La Silla now has the potential to become a major contributor to transient research,” says Ivo Saviane, Site Manager at ESO’s La Silla Observatory. “We look forward to seeing many outstanding results from this project, which will broaden the reach of the site to both the scientific community and the general public.” Consortium

The BlackGEM consortium includes: NOVA (Netherlands Research School of Astronomy, the Dutch national alliance in astronomy between the University of Amsterdam, the University of Groningen, Leiden University and Radboud University); Radboud University, The Netherlands; KU Leuven, Belgium; the Weizmann Institute, the Hebrew University of Jerusalem, and Tel Aviv University, Israel; the University of Manchester and the Armagh Observatory and Planetarium, UK; Texas Tech University, University of California at Davis and Las Cumbres Observatory, USA; the University of Potsdam, Germany; Danish Technical University, Denmark; the University of Barcelona, ​​Spain; and the University of Valparaíso, Chile.