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Article in prestigious Nature Astronomy sheds light on energy generation

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

UFS law experts publish unique translation

2006-06-21

Attending the launch of the publication were from the left: Prof Boelie Wessels (senior lecturer at the UFS Faculty of Law), Prof Frederick Fourie (Rector and Vice-Chancellor of the UFS), Prof Johan Henning (Dean: UFS Faculty of Law) and Adv Jaco de Bruin (senior lecturer at the UFS Faculty of Law). Prof Wessels translated the treatise from corrupted medieval lawyer Latin into English, Prof Henning is the leading author and initiator of the publication and Adv de Bruin assisted with the proofreading and editing. Photo: Stephen Collett

UFS law experts publish unique translation of neglected source of partnership law

The Centre for Business Law at the University of the Free State (UFS) has translated a unique long neglected Roman-Dutch source of the law of partnership law from Latin into English. This source dates back to 1666.

The book, called Tractatus de Societate (A Treatise on the Law of Partnership), by Felicius and Boxelius is published as Volume 40 in the research series Mededelings van die Sentrum vir Ondernemingsreg/Transactions of the Centre for Business Law. It is the first translation of this Roman-Dutch source into English and comprises of a comprehensive discussion of the South African common law of partnerships.

“Apart from various brief provisions dealing on a peace meal and an ad hoc basis with diverse matters such as insolvency, there is no comprehensive Partnership Act in South Africa. The law of partnership in South Africa consists of South African common-law, which is mainly derived from Roman-Dutch law,” said Prof Johan Henning, Dean of the Faculty of Law at the UFS. Prof Henning is also the leading author and initiator of this comprehensive publication.

“Countries such as America, England, Ireland and The Netherlands have drafted or are in the process of establishing new modern partnership laws in line with new international guidelines, practices and commercial usages,” said Prof Henning.

“However, in South Africa the most recent policy document released by the Department of Trade and Industry explicitly excludes partnership law from its present company law reform programme and clearly regards this as an issue for another day,” said Prof Henning.

“Unless there is a political will to allocate the necessary resources to a comprehensive partnership law revision program, it is a practical reality that South Africa will not have a modern Partnership Act in the foreseeable future,” said Prof Henning.

According to Prof Henning South African courts have been using the Roman-Dutch partnership law sources as authority. “The English Partnership Act of 1890 is not binding and the English text books should therefore be approached with caution,” said Prof Henning.

“A treatise on the law of partnership that has been regarded by South African courts as an important common law authority is that of a Frenchman by the name of Pothier. This treatise was translated into English and was regarded as an authority of significance in The Netherlands towards the end of the eighteenth century,” said Prof Henning.

“Pothier’s opinions are however not valid throughout in the Roman-Dutch partnership law as it did not apply to the Dutch province of The Netherlands and it sometimes also rely on local French customs for authority,” said Prof Henning.

For this reason the Centre for Business Law at the UFS decided to focus its attention again on the significance of the comprehensive treatise of Felicius and Boxelius on the Roman-Dutch partnership law. Felicius was an Italian lawyer and Boxelius a Dutch lawyer.

This long neglected source of partnership law was published in 1666 in Gorkum in The Netherlands. "A significant amount of Roman-Dutch sources of authoritive writers trusted this treatise and referred to it,” said Prof Henning.

The translation of the treatise from corrupted medieval lawyer Latin into English was done by Prof Boelie Wessels, a very well-known expert on Roman Law and senior lecturer at the UFS Faculty of Law. Prof Wessels, who has 15 degrees, spent almost ten years translating the treatise. The proofreading and editing of the translation was done by Prof Henning and Adv Jaco de Bruin, a senior lecturer at the UFS Faculty of Law.

“We want the South African courts to use Volume 40 in the research series Mededelings van die Sentrum vir Ondernemingsreg/Transactions of the Centre for Business Law as the primary source of reference when cases where Roman-Dutch Law partnership law principles are involved, are ruled on,” said Prof Henning.

The first part of the publication comprises of selected perspectives on the historical significance of the work as well as a translation of selected passages. “The intention is to follow this up expeditiously with the publication of a very limited edition of a complete translation of the work,” said Prof Henning.

A total of 400 copies of the publication will be distributed to all courts, the Appeal Court and the Supreme Court.

Media release
Issued by: Lacea Loader
Media Representative
Tel: (051) 401-2584
Cell: 083 645 2454
E-mail: loaderl.stg@mail.uovs.ac.za
21 June 2006

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