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28 October 2019 | Story Leonie Bolleurs | Photo Anja Aucamp
Dr Brain van Soelen and Prof Pieter Meintjies
UFS scientists, Prof Pieter Meintjes and Dr Brian van Soelen, are part of the prestigious H.E.S.S. collaboration that recently published in Nature Astronomy.

Think of an object with a mass exceeding that of the Sun, squeezed into a volume of a sphere with the radius of a city like Bloemfontein. This very dense, compact object, known as a pulsar, is also a great source of energy. According to Physics Professor, Prof Pieter Meintjes, this pulsar (neutron star produced in supernova explosion) is also a key element of a recently submitted paper in Nature Astronomy.

Prof Meintjes and Dr Brian van Soelen, Senior Lecturer, both from the Department of Physics at the University of the Free State (UFS), were part of the High Energy Stereoscopic System (H.E.S.S.) collaboration of 220-plus scientists worldwide who worked on the paper Resolving the Crab pulsar wind nebula at tera-electronvolt energies, published in the prestige journal Nature Astronomy. 

According to Prof Meintjes, the fact that the paper was accepted for publication in Nature Astronomy testifies of the importance of this finding in the high-energy astrophysics community.

Powerful generators of electricity

He elaborates on the study: “The name pulsar originates from the fact that rotating neutron stars produced in supernova explosions produce beams of radiation, much like a lighthouse. Every time the beam intersects the observer’s line of sight, the observer receives a pulse of radiation.”

“As a result of this enormous mass squeezed into a small volume, these objects have the same density as that of an atomic nucleus. These objects (very dense pulsars) spin very rapidly and have enormous magnetic fields; for example, the pulsar at the centre of the Crab Nebulae spins around its axis once every 33 milliseconds (millisecond: one thousandth of a second) and possesses a magnetic field strength of the order of one tera-Gauss (tera – million x million). For comparison, the average strength of the Earth’s magnetic field is 0.5. Gauss and the magnetic field strength on the Sun ranges between 1 000 and 4 000 Gauss.”

“Because of this very super-strong rapid-spinning magnet, enormous electric fields are induced that can accelerate particles such as electrons and protons to energies in excess of one tera-electronvolt (optical light that are emitted by an ordinary lightbulb has energies of the order of one electronvolt).”

Prof Meintjes continues: “This means that these fast-rotating neutron stars are extraordinary powerful generators of electricity, which fills the surrounding cloud (supernova remnant) with super-high energy-charged particles that can produce, in turn, very high energy gamma rays through various processes such as synchrotron radiation and inverse-Compton radiation, to name a few.”

H.E.S.S. collaboration 

Above one tera-electronvolt, the gamma rays are detected by huge ground-based telescopes such as H.E.S.S., utilising the Earth’s atmosphere.

“When these high-energy gamma rays enter the atmosphere, they produce showers of super-relativistic particles that produce Cherenkov light – detected by the telescope. The technique is called the Atmospheric Cherenkov Technique (ACT).”

HESS
The High Energy Stereoscopic System. (Photo: Supplied)

“The H.E.S.S. gamma-ray collaboration is but one collaboration that has studied this source intensively over the past couple of decades or so.  Being the most powerful gamma-ray telescope facility currently operational, very careful analysis of the data managed to reveal that the gamma-ray emitting region inside the nebula is about 10 times bigger in size than the region where the x-rays are emitted within the nebula.” 

“This has solved a long-standing question as to how big the gamma-ray emitting region within these supernova remnants are, compared to the region where the x-rays, for example, originates,” says Prof Meintjes. 

Both Prof Meintjes and Dr Van Soelen are members of this prestigious H.E.S.S. collaboration. Their participation in this project, together with scientists from universities such as the University of Oxford, the University of Leicester, and the University of Bordeaux, opens up valuable research opportunities for UFS postgraduate students to enter the international stage and interact with the best scientists in the world.

They are also members of the editorial board responsible for the internal review of research papers before being submitted to more prestigious journals, for example, Nature Astronomy. Dr Van Soelen is also a coordinator of multi-wavelength follow-up observations within the H.E.S.S. collaboration. 

This is the second time that Prof Meintjes published in Nature Astronomy. Previously, he was co-author of a paper on emission from a white dwarf pulsar, showing that fast-rotating white dwarf stars could in fact mimic emission from neutron star pulsars. He developed the theoretical model reported in that paper, explaining the multi-wavelength emission from radio to X-ray energies.


News Archive

Researcher in mathematics ranks among world’s top peer reviewers
2016-10-07

Description: Abdon Peer Review Tags: Abdon Peer Review

Prof Abdon Atangana, from the UFS Institute
for Groundwater Studies.
Photo: Johan Roux

Thirty-year-old Prof Abdon Atangana has received the prestigious Sentinels of Science Award 2016. This award honours the highest achievers in peer review across the world’s journals. The elite contributors to scholarly peer review and editorial pursuits internationally are also honoured with this award. Recipients have demonstrated an outstanding, expert commitment to protecting the integrity and accuracy of published research in their field.

Prof Atangana, who ranks number one in the mathematics discipline with a merit of 324, is a professor at the Institute for Groundwater Studies at the University of the Free State (UFS).

He is editor of 17 international journals, editor-in-chief of two international journals and also reviewer of more than 200 international accredited journals. He has been lead and guest editor of some special issues. He is also editor of 19 journals of applied mathematics and mathematics and has presented and participated in more than 20 international conferences.

Prof Atangana’s research interests are methods and applications of partial and ordinary differential equations, fractional differential equations, perturbations methods, asymptotic methods, iterative methods, and groundwater modelling.

“Editors in more than 100 journals
trust my opinion to assess
whether a submitted paper
can be published or not.”

Peer review requires a respected expert in a given field

According to the professor, reviewers play a central role in scholarly publishing. “In the academic field, peer review is the process of subjecting an author’s scholarly work, research, or ideas to the scrutiny of others who are experts in the same field, before a paper describing this work is published in a journal or as a book. The peer review process helps the publisher to decide whether the work should be accepted, considered acceptable with revisions, or rejected.

“Peer review requires a respected expert in a given field, who is qualified and able to perform the review in a given timeframe. Due to the impact of my research papers in the field of mathematics and applied mathematics, and also my international recognition in the field of applied mathematics, many editors in more than 100 journals of applied mathematics trust my opinion to assess whether a submitted paper in a given journal of mathematics and applied mathematics can be published or not. Only this year I was able to review more than 100 papers from different journals of applied mathematics, applied physics, mathematics, engineering and hydrology,” he said.

A successful peer reviewer displays passion for the development of science

Key to his success as peer reviewer is his passion for the development of science, his ability to write fair reports about a given manuscript, as well as his knowledge on what has been done and what are the challenges in a given field to be able to give a report that will help the advancement of science.

Currently he is developing new mathematics tools that will be used to accurately model statistical problems as well as physical problems with many layers.

“To be the number one peer reviewer in the world in mathematics is a product of love, patience and determination to enhance science,” Prof Atangana said.

His advice to young researchers is to put their trust in God and to work hard. “Not necessarily for money but for love because the future of Africa is in the hands of young Africans,” he said.

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