UNAM Astronomers discover startling new evidence about gamma rays

About 120 km south-west of Windhoek, an ongoing study on one of the Universe’s brightest astronomical class of objects; quasars, has yielded a mammoth breakthrough.

Quasars are luminous cosmic objects empowered by gas spiraling at high speed into an extremely large black hole. A black hole is the center of gravity that is thought to gobble up the matter spiraling down into it and ejecting a small part of it in the form of large jets of plasma.

The phenomenon about quasars was telescopically observed by the University of Namibia in collaboration with the High Energy Stereoscopic System (H.E.S.S.) group. The aim is to better understand the behavior of quasar jets.

The collaboration discovered new evidence that proves: gamma-ray emission from quasars extends thousands of light-years along plasma jets. This breakthrough was discovered by 200 scientists from 13 countries who observed a radio galaxy (a galaxy that is highly luminous when observed with a radio wavelength) nearest to earth called Centaurus A for 200 hours at unparalleled resolution.

Senior lecturer in the Department of Physics and Head of the Namibian H.E.S.S. group, Dr Michael Backes, explained that the new discovery changes the understanding of quasar jets. “Research has shown that very high energy gamma-rays emitted from quasars are not only concentrated in the region close to their central black hole but in fact extends over several thousand light-years along jets of plasma” explained Dr Backes. This means that galaxies with a highly energetic nucleus emit high-frequency radiation into the Universe.  In other words, emissions from quasars contain gamma-rays which are high energy photons that form part of electromagnetic radiation.  This radiation is defined as the energy around us and takes up many forms, such as visible light, X-rays, and radio waves.

Masters graduate in Physics Jimmy Shapopi explained that “gamma rays are actually emitted in all directions from jets.  The gamma-rays then travel a long distance, several thousand light-years away from the black hole until they reach the earth’s atmosphere”. He further adds that “Once they reach this point, we then detect their arrival using the world’s best and most sensitive gamma-ray telescope, H.E.S.S. which makes it possible to study this phenomenon in great detail” said Shapopi.

Previous studies showed that the source of gamma radiation was very small and located in the vicinity of a supermassive black hole.  However, the latest discovery shows that the extended emission indicates that particle acceleration does not take place solely in the vicinity of the black hole but also along the entire length of plasma jets. Based on these new results, scientists believe that the particles are reaccelerated by a random process of probability along the jet. The discovery suggests that many radio galaxies with extended jets accelerate charged particles to extreme energies and might emit gamma rays, possibly explaining the origins of a substantial fraction of gamma rays outside of the Milky Way Galaxy. These findings provide important new insights into cosmic gamma-ray emitters, and in particular about the role of radio galaxies as highly efficient relativistic charged accelerators.

Physics lecturer, Hambeleleni Ndiyavala-Davids, explains that this discovery has the possibility to improve our technical innovation. “This recent discovery is exciting to us as we want to figure out where and how in the universe nature manages to accelerate particles much faster than accelerators built by humans. She adds “this discovery hints to the sources of where nature manages to do that and in turn understanding how this happens and if there is a possibility for us to learn something for technical innovations” explained Ndiyavala-Davids.

Backes further revealed that UNAM forms part of a large collaboration of scientist whose small contribution result into regular findings.  This group roughly releases one finding per month and a major discovery once every second year”.

In addition to H.E.S.S., the UNAM Department of Physics is also involved in other large-scale international projects like the Cherenkov Telescope Array (CTA), the Southern African Large Telescope (SALT), the Square Kilometre Array (SKA) and the African VLBI Network (AVN), and the Africa Millimetre Telescope (AMT).

Story by: Margareth-Rose Kangootui

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