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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 awards honorary doctorates during its centenary week

2004-10-07

The University of the Free State (UFS) will award 12 honorary doctorates on Thursday 14 October 2004 to a diverse group of outstanding South Africans and international experts.

This will be the last in a group of 18 honorary doctorates that the UFS will be awarding in its centenary year.

The awards comprise of a number of well-known language experts and writers, experts in higher education, first-time awards in community service and development studies, as well as music.

“This reflects quality and also diversity, a spectrum of convictions as well as the recognition of persons who played a major role in changing society in the last couple of decades, “ says Prof Frederick Fourie, Rector and Vice-Chancellor of the UFS.

The awards can be grouped in the following categories:

Language and literature:

Mr Karel Schoeman (D Litt (hc)) – well-known Afrikaans author and former student of the UFS. Some of the awards he has received include the Hertzog prize for prose (1970, 1986 and 1995), the CNA prize (1972 and 1994), the Old Mutual prize (1985 and 1991), the SABC prize for best television drama in 1990, the M Net book prize in 1997 and the State President award (former President Nelson Mandela: Order for Excellent Service – silver) in 1999. It is an honor for the UFS to have this gifted and creative person among its former students. This conferment is a fitting recognition of his status as leading South African writer.

Ms Antjie Krog (D Litt (hc)) – well-known South African poet and former student of the UFS. Her popularity as poet is evident in her piercing honesty and unequalled power of expression. Some of the awards she has received include the Eugéne Marais prize in 1973, the Rapport prize in 1987, the Hertzog prize in 1990 and the RAU prize in 2000. Her writing has been translated into seven languages. She has also received numerous honors for her involvement in and journalistic documentation of the Truth and Reconciliation Commission’s (TRC) proceedings. It is therefore an exceptional privilege for her alma mater to honor her with an honorary doctorate.

Prof Jaap Steyn (D Litt (et phil) (hc)) – recently, Prof Steyn again distinguished himself as biographer whose thorough research is apparent in the published biographies of illustrious writers such as NP van Wyk Louw and MER. The numerous awards, among which the Stals prize from the South African Academy of Science and Art for the Van Wyk publication, are a matter of record. He conducted the research for this great prize-winning work as honorary professor at the UFS.

Prof Jakes Gerwel (D Phil (hc)) – Chancellor of the University of Rhodes and Director of Naspers, Old Mutual, Gold Fields and Brimstone. His doctoral thesis was published in The Netherlands under the title Literatuur en apartheid. Konsepsies van “gekleurdes” in die Afrikaanse roman tot 1948 (1983). He received an honorary doctorate from Clark College ( Atlanta), the City University of New York and Missouri in the USA, the University of the Western Cape, the University of Cape Town, the University of Natal, Rhodes University, the University of Stellenbosch and the University of the Witwatersrand. He is also outstanding professor in the Humanities at the University of the Western Cape, honorary professor in the Humanities at the University of Pretoria, and was the chairman of the Human Sciences Research Council (HSRC).

Development Studies:

Dr Frederick van Zyl Slabbert (D Phil (hc)) – for his academic achievements, his endeavors for bringing about a peaceful transition in South Africa and his demonstration of the social investment role of the corporate sector. Dr Van Zyl Slabbert has received honorary degrees from the University of Natal and the Simon Fraser University in Canada. He has published seven books and various academic articles.

Community Service:

Prof Robert G Bringle (D Phil (hc)) – from the Indiana University-Purdue University Indianapolis (IUPUI) in the USA. He is currently Chancellor’s Professor of Psychology and Philanthropic Studies at the IUPUI and also Director of the IUPUI’s Centre for Service Learning. He is honored for his exceptional contribution to several of the UFS’s community service projects as well as his role in the advancement of a multi- and inter-disciplinary approach to academic development and the integration of service learning within the faculties of the UFS. He has also made a valuable contribution to the conceptual framework of the UFS’s unique community service policy and more recently to the advancement of a research culture regarding community service.

Higher education:

Dr Khotso Mokhele (D Phil (hc)), President of the National Research Foundation (NRF) is honored for his contribution to the South African higher education sector. He has also made a substantial contribution to the development of the research capacity of universities and technikons in South Africa. Dr Mokhele was born in Bloemfontein and matriculated at the Moroka High School in Thaba Nchu.

Prof Saleem Badat (D Phil (hc)), the Chief Executive Officer of the Council on Higher Education (CHE). Prof Badat has devoted himself to transforming and building South African higher education, and has constantly challenged the higher education sector to retain the moral basis of higher education and tackle its challenges with intellectual honesty, ingenuity, creativity and courage. He is honored for his intellectual leadership in the development of a equitable, just and quality higher education system in South Africa.

Law:

Prof HA (Boelie) Wessels (D Legum (hc)) – for his contribution to the fields of Roman Law, Legal History at the UFS. He is currently a part-time lecturer at the UFS’s Faculty of Law.

Medicine:

Prof CJC Nel (D Phil (hc) Posthumous) – for the way in which he strived for the advancement of excellent medical education in the country. Prof Nel also did pioneering work in the field of transformation in higher education. Under his guidance the School of Medicine at the UFS became one of the first medical schools to adopt a parallel-medium system of instruction.

Music:

Prof Leo Quayle (D Mus (hc)) – for the significant contributions he has made to the development of music – not only in Bloemfontein, but also on national level and abroad. His initiative, enthusiasm and dedication contributed to the eventual founding of the Free State Musicon, as well as the first symphony orchestra and the first string quartet in Bloemfontein. Prof Quayle is a former head of the Department of Music at the UFS.

Prof Jack de Wet (D Mus (hc)) – well-known for his exceptional contribution to violin tuition in South Africa. As pedagogue of international stature, he still moulds violinists who compete at national and international level. At an advanced stage of his career, he still actively conveys his knowledge, experience and distinctive insight in his field of speciality to yet another new generation of young violin teachers. Today the symphony orchestras in Bloemfontein and Port Elizabeth also stand on the foundations laid by him.

Media release
Issued by: Lacea Loader
Media Representative
Tel: (051) 401-2584
Cell: 083 645 2454
E-mail: loaderl.stg@mail.uovs.ac.za
7 October 2004

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