Following the first detection of Gravitational Waves by the LIGO Collaboration in 2016, the key researchers behind the project were awarded the Nobel Prize for Physics in October 2017. Despite what one may think, this was the very successful and well-recognized end of a long (scientific) journey. It was, indeed, only the beginning of the new era of Multi-Messenger Astronomy.
Astronomy, as everyone knows, uses visual light, ever since Galileo first used a telescope to point it at the stars some 400 years ago. During the last century, other forms (scientifically: wavelengths) of light like gamma rays, X-rays, Ultraviolet and Infrared radiation, as well as microwaves or, more generally, radio waves, have also been used to study the Universe. Radio telescopes are particularly en vogue in Africa as mankind‘s largest astronomical endeavour is being built on the African continent: the Square Kilometre Array, SKA. The form of light being used for astronomical observations most recently are very high energy gamma rays as observed by the High Energy Stereoscopic System (H.E.S.S.) in Namibia. After the first detection of those gamma rays in 1989, H.E.S.S., being a second generation telescope system, is operating in the Khomas Highlands since 2003 and has been awarded several scientific merits since.
Now that Scientists can regularly detect and pinpoint the origin of gravitational waves, which are vastly distinct from any form of light, the era of not just multi-wavelength, but even multi-messenger astronomy has truly begun. The two different messengers (light and gravitational waves) combined can reveal much deeper insights into the most violent phenomena in the Universe.
Exactly this happened when, on 17 August 2017, gravitational waves were detected from the collision of two ultra-dense remains of giant starts, called neutron-stars. As soon as the automatic data analysis procedures had spotted something interesting going on, a message was sent around the world to collaborating observatories to complement this gravitational wave detection with as much coverage by as many different telescopes as possible. Excitement in the international astronomy community grew even further as the Fermi-Gamma-ray Space Telescope as well as ESA’s INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) detected a short outbreak of gamma rays (a Gamma-Ray Burst) from the same direction, about 2 seconds afterwards.
In an unprecedented way, more than 70 observatories around the world followed the call for co-observations, amongst them, the H.E.S.S. telescopes. Of all telescopes that cannot see a large fraction of the sky all at once, i.e. that needed to be pointed to the position determined by LIGO, the H.E.S.S. telescopes were the first to observe in the direction of the event.
This enormous international effort, along with the rich set of information about merging neutron-stars and their connection to gamma-ray bursts, as well as this multi-messenger observation truly being the first of its kind, made the UK Institute of Physics (IOP) journal Physics World award the international team of scientists the “Physics World 2017 Breakthrough of the Year” award on 11 December 2017. On 21 December, the multi-disciplinary and, arguably, most-renowned scientific journal in the world, Science also named the very same observation “2017 Breakthrough of the Year”.
These awards also particularly emphasise the collaborative nature of “big science” these days. “The explosion was easily the most studied event in the history of astronomy, with 3674 researchers from 953 institutions collaborating on a single paper summarizing the merger and its aftermath”, states Science, whereas Physics World is even more explicit in saying that the award was deliberately “given to thousands of scientists working in nearly 50 collaborations worldwide.” Further, they believe that this observation “is a shining example of how our knowledge of the universe can move forwards when people from all over the world join together with a common scientific cause.”
In this big international effort, Namibia was represented by 4 staff members of the Department of Physics at UNAM joined by Namibian PhD students at Humboldt University Berlin (Germany) and North-West University (SA).
The High Energy Stereoscopic System (H.E.S.S.) is a system of four 12 metre and one 28 metre diameter telescopes, situated in the Khomas Highlands about 120 km south-west of Windhoek. The telescopes are operated by an international collaboration of more than 250 researchers from 13 countries. The University of Namibia (UNAM) is a member of the H.E.S.S. collaboration since its inception. Currently, there are 3 Namibian PhD and 2 MSc students conducting their research in the context of H.E.S.S and gamma-ray astronomy in the Department of Physics at UNAM. Out of the more than 3,600 authors from 953 institutes of the honoured observation, 5 are based in Namibia at UNAM.