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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

Workplace discrimination and unfair practices explored in new book
2017-09-13

 Description: Denine read more Tags: Denine Smit, Labour law, employee relations, bullying, vulnerability, research, Damain Viviers 

Dr Denine Smit
Photo: Supplied

Two law scholars, Dr Denine Smit and Dr Damian Viviers, from the Faculty of Law at the University of the Free State (UFS) recently launched a book titled Vulnerable Employees, which was inspired by their interest in researching, creating awareness and providing a legal exposition in relation to employees who are vulnerable and experience prejudice and dignity violations in the workplace. These include workplace bullying, appearance-based discrimination, those who are gender fluid or have mental-health conditions.
“Dr Viviers, who is also a former student of mine, and I, have been working together for years and share a common understanding in relation to our various topics of interest. We often share the same train of thought. This is how we came to work together to produce this book,” said Dr Smit.


Research focused on employee challenges in the workplace

The book expands on the field of knowledge regarding certain categories of employees who, as a consequence of various mutable, immutable and semi-immutable characteristics, as well as behavioural experiences, are rendered vulnerable in their employment relationships. The book draws on various social, psychological and other empirical considerations, as well as comparative legal research from foreign and international law, in order to expand on the legal position under the South African legal framework governing these conditions. While the book first and foremost constitutes a compendium of research to be used for this purpose, it also serves as a practical guide for all legal practitioners, human resources managers, other labour stakeholders and the judiciary.

Book draws strength in other academic fields
Vulnerable Employees was launched on 28 July 2017 at the UFS library, to an audience of academics and students, with a panel discussion made up of the authors and two other panellists. One of the panellists was Dr Katinka Botha, a leading psychiatrist in the Free State who has a wealth of experience in this field. “Her selection as a panellist was motivated by the various significant inter-disciplinary considerations and intersections between psychology, psychiatry and law, contained in the book,” said Dr Smit. 
“Dr Botha’s expertise was invaluable in shedding light on mental-health considerations during the panel discussion.” 
Mr Lesley Mokgoro, the other panellist, is a leading labour law practitioner, as well as director and head of the Dispute Resolution Practice Group at Phatshoane Henney Attorneys. “His years of experience working with all role players in the employment domain, as well as his extensive legal knowledge and expertise, made him uniquely qualified to serve on the panel and deliver an opinion of the practical and academic value of the book,” said Dr Smit.


Workplace policies key to securing employee rights

There are a number of growing trends in the workplace that could shape the practice of labour law or workplace policies. Dr Smit said the need for employers to regulate workplace culture, particularly in relation to bullying, harassment and unfair discrimination, in line with the South African legal framework, was a fundamental need in all workplaces. Effective workplace policies may be used to clearly outline the relevant “dos and don’ts” to employees, as well as the procedures and processes that may be followed in order to address such conduct. Workplace policies serve to advance legal certainty and efficiency, since the rights and obligations of all role players are clearly demarcated, or should be, in terms of a well-drafted and considered policy. 
The book is one of several publications produced by Dr Smit in collaboration with Dr Viviers on the topic of workplace discrimination and the law. The two scholars are working on another book to be published at the end of 2017.

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