Joining the search for the sources of gravitational waves

BlackGEM is a wide-field array of optical telescopes to be located at ESO’s La Silla Observatory in Chile’s Atacama desert. It will initially comprise 3 telescopes, each 0.65 metre in diameter, and the aim is to eventually expand the array to 15 telescopes. The telescopes can look at different parts of the sky, thus covering a very large area. The array is largely robotic and remotely controlled from Radboud University, the Netherlands. It was jointly developed by Radboud University, the Netherlands Research School for Astronomy (NOVA), and the KU Leuven, Belgium.

BlackGEM’s scientific goals are to detect and characterise optical counterparts to gravitational wave detections. To enable this, it will conduct an all-sky survey of the southern sky, perform a bi-weekly scan of the southern sky, and characterise intra-night transients, new stars that appear or disappear within a single night.

Events that produce detectable gravitational waves are expected to occur within approximately 650 million light-years of Earth. Many will therefore be located in or near resolved galaxies and will be faint. It is essential for BlackGEM to have high spatial resolution in order to resolve and accurately locate these sources against the background of the night-sky, making La Silla — with its excellent weather and thin atmosphere — an ideal observing site.

Science with BlackGEM

BlackGEM is joining the search for some of the most powerful and dramatic events in the Universe: merging neutron stars and black holes. Such exotic events cause ripples in the fabric of spacetime known as gravitational waves, and BlackGEM will work in conjunction with the new generation of gravitational wave detectors such as LIGO and Virgo to follow up these events in visible light. BlackGEM will pinpoint the sources responsible for gravitational waves so that bigger telescopes — such as ESO’s Very Large Telescope (VLT) — can carry out detailed follow-up observations, providing astronomers with insight into some of the most extreme events in the cosmos.

The BlackGEM array can also function as a highly capable survey telescope and a portion of its time will be spent surveying the southern skies (30 000 square degrees in six optical filters). Detailed surveys provide astronomers with statistical information about objects in the sky, enabling, for example, studies of galactic evolution from the early Universe to today. During this survey, BlackGEM will also study fast (less than one day) transient sources. Transients are astronomical events that only last for a certain amount of time; usually these are deep sky events such as supernovae, gamma-ray bursts, transits, and tidal disruption events.

More about BlackGEM


Name: BlackGEM
Site: La Silla
Altitude: 2375 m
Enclosure: 4.5 m clamshell dome per telescope
Type: Optical survey telescope
Optical design: Modified Dall-Kirkham (Wynn-Harper)
Diameter. Primary M1: 3 x 0.65 m
Material. Primary M1: Fused silica
Diameter. Secondary M2: 0.26 m, tip-tilt controlled
Material. Secondary M2: Fused silica
Mount: Equatorial
First Light date: 2023
Active Optics: Yes, M2 tip-ilt controlled
Camera: 110 Megapixels per telescope (a single 10500x10500 pixel CCD detector)
Filters: Sloan u,g,r,i,z + q (440–720nm)
Images taken with BlackGEM: Link
Images of BlackGEM: Link
Videos of BlackGEM: Link
Press Releases with BlackGEM: Link