December 2, 2023


The European Southern Observatory’s (ESO) new BlackGEM telescope array at the La Silla Observatory in Chile has officially begun scanning the southern sky for sources of gravitational waves.

Gravitational waves are ripples in space-time caused by violent, energetic space phenomena, such as black hole or neutron star collisions, or massive stars exploding as supernovae at the end of their lives.

Existing observatories, such as the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo Interferometer, are specifically designed to detect the ripples caused by gravitational waves. Interferometers combine two or more light sources to create interference patterns that can be measured and analyzed. However, LIGO and Virgo were unable to determine the exact source of the gravitational waves, nor could they see the light from colliding neutron stars or black holes.

That’s the BlackGEM difference. It can detect gravitational waves and visible light from these events and use this information to pinpoint the precise location of the wave’s source. Using visible light also means that BlackGEM can obtain detailed observations of processes, such as the formation of heavy elements such as gold and platinum, from these interstellar collisions.

“With BlackGEM, we aim to expand the study of cosmic events with gravitational waves and visible light,” said Paul Groot of Radboud University in the Netherlands and lead researcher on the project. “The combination of the two tells us more about these events than just one or the other.”

The BlackGEM array consists of three telescopes built by Radboud University, the Netherlands Astronomical Institute and the University of Leuven in Belgium. Each telescope is 25.6 inches (65 centimeters) in diameter and can scan different parts of the sky simultaneously. There are plans to expand the array to 15 telescopes.

The BlackGEM telescope inside its dome.  The BlackGEM array consists of three 65 cm telescopes located at ESO's La Silla Observatory.
One of the 25.6″/65 cm diameter BlackGEM telescopes inside the dome

Luis Calcada/ESO

They may be relatively small, but because of their location, these telescopes can see a lot. They are located on the outskirts of Chile’s Atacama Desert at an altitude of 2.4 kilometers (1.5 miles).

“Despite only having a 65-centimeter (26-inch) primary mirror, we delved into projects that used larger mirrors because we took advantage of the excellent observing conditions at La Silla,” Groot said.

Once BlackGEM identifies the source of the gravitational waves, the information is sent to larger telescopes, such as ESO’s Very Large Telescope, also in the Atacama Desert, which allow for more detailed follow-up observations.

In addition to searching for sources of gravitational waves, BlackGEM will also keep an eye on short-lived astronomical events such as supernovae.

“Thanks to BlackGEM, La Silla now has the potential to become a major contributor to transient studies,” said Ivo Saviane, site manager at the La Silla Observatory. “We look forward to seeing the many outstanding results contributed by this project, which will expand the reach of the site to the scientific community and the general public.”

The following video, produced by ESO, shows footage from the BlackGEM Array at the La Silla Observatory in Chile’s Atacama Desert.

BlackGEM Array at ESO’s La Silla Observatory

source: European Southern Observatory