Armagh is a partner in two telescope projects whose key goal is to detect the optical counterpart of colliding massive dead stars. Albert Einstein predicted that when two massive objects spiral around each other, eventually merging to become one more massive object, gravitational waves would be emitted. Scientists spent a century building detectors to measure the effect of gravitational waves from these mergers sweeping past the Earth. In 2015 the two LIGO (Laser Interferometer Gravitational-wave Observatory) instruments in the USA were able to detect the signal from two merging blackholes, followed two years later by two merging neutron stars. Because of the way these detectors work, it’s not currently possible to pin-point precisely where in the sky the event took place. If we can pinpoint the source of the gravitational waves astronomers can determine its distance; identify what elements are made in such explosions and test models of binary stars, neutron stars and black holes.

The three BlackGem telescopes on La Silla, Chile. Credit: S. Bloemen (Radboud University)/ESO

One telescope project which aims to spot the source of these cosmic explosions is BlackGem, which Armagh is a partner: it released its first images taken using these telescopes today. Currently there are three 65 cm telescopes at the European Southern Observatory (ESO) site in La Silla, Chile. Each telescope can image an area of sky 8 square degrees (the moon has a diameter of 0.5 degrees) in one exposure and the goal is ultimately to have 15 identical telescopes which can map different parts of the sky. BlackGem has similar goals as the GOTO project which Armagh is also a partner. They are very complementary, with GOTO being able to simultaneously observe a much wider area of sky than BlackGem, but with BlackGem being able to spot fainter sources than GOTO.

At night on La Silla, with the Large and Small Magellanic Clouds visible. These small galaxies are orbiting our own galaxy, the Milky Way. Credit: ESO

Gavin Ramsay, who leads the Armagh participation in both projects says: “The pandemic slowed down the completion of both BlackGem and GOTO, but with the next LIGO science run due to start at the end of this month, it is fantastic to see these first light images made using BlackGem. I haven’t been to La Silla for quite a few years, but one of my PhD students, Chris Duffy, was there at the end of last year. He wrote about it for astronotes back in November 2022. Although the main goal of both projects is related to objects which release gravitational waves, BlackGem is going to facilitate many other science projects related to accreting binaries, stellar activity and Solar System objects. We’re very much looking forward to seeing more of the data.”

A `first light’ image of a region in the Galactic Bulge (just above the center of the Milky Way) taken using BlackGEM. The dark patches are due to clouds of gas and dust. Credit: BlackGem/ Paul Groot/Paul Vreeswijk/ Steven Bloemen, Radboud U.BlackGem was built by Universities in the Netherlands and Belgium and has international partners in seven other countries, including Armagh and the University of Manchester in the UK.

ESO press release:

BlackGem website:


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