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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

Gender bias still rife in African Universities
2007-08-03

 

 At the lecture were, from the left: Prof. Magda Fourie (Vice-Rector: Academic Planning), Prof. Amina Mama (Chair: Gender Studies, University of Cape Town), Prof. Engela Pretorius (Vice-Dean: Humanties) and Prof. Letticia Moja (Dean: Faculty of Health Sciences).
Photo: Stephen Collett

Gender bias still rife in African Universities

Women constitute about 30% of student enrolment in African universities, and only about 6% of African professors are women. This is according to the chairperson of Gender Studies at the University of Cape Town, Prof Amina Mama.

Prof Mama was delivering a lecture on the topic “Rethinking African Universities” as part of Women’s Day celebrations at the University of the Free State (UFS) today.

She says the gender profile suggests that the majority of the women who work in African universities are not academics and researchers, but rather the providers of secretarial, cleaning, catering, student welfare and other administrative and support services.

She said that African universities continue to display profound gender bias in their students and staffing profiles and, more significantly, are deeply inequitable in their institutional and intellectual cultures. She said women find it difficult to succeed at universities as they are imbued with patriarchal values and assumptions that affect all aspects of life and learning.

She said that even though African universities have never excluded women, enrolling them presents only the first hurdle in a much longer process.

“The research evidence suggests that once women have found their way into the universities, then gender differentiations continue to arise and to affect the experience and performance of women students in numerous ways. Even within single institutions disparities manifest across the levels of the hierarchy, within and across faculties and disciplines, within and between academic and administrative roles, across generations, and vary with class and social background, marital status, parental status, and probably many more factors besides these”, she said.

She lamented the fact that there is no field of study free of gender inequalities, particularly at postgraduate levels and in the higher ranks of academics. “Although more women study the arts, social sciences and humanities, few make it to professor and their research and creative output remains less”, she said.

Prof Mama said gender gaps as far as employment of women within African universities is concerned are generally wider than in student enrolment. She said although many women are employed in junior administrative and support capacities, there continues to be gross under-representation of women among senior administrative and academic staff. She said this disparity becomes more pronounced as one moves up the ranks.

“South African universities are ahead, but they are not as radically different as their policy rhetoric might suggest. A decade and a half after the end of apartheid only three of the 23 vice-chancellors in the country are women, and women fill fewer than 30% of the senior positions (Deans, Executive Directors and Deputy Vice-Chancellors)”, she said.

She made an observation that highly qualified women accept administrative positions as opposed to academic work, thus ensuring that men continue to dominate the ranks of those defined as ‘great thinkers’ or ‘accomplished researchers’.

“Perhaps women simply make realistic career choices, opting out of academic competition with male colleagues who they can easily perceive to be systematically advantaged, not only within the institution, but also on the personal and domestic fronts, which still see most African women holding the baby, literally and figuratively”, she said

She also touched on sexual harassment and abuse which she said appears to be a commonplace on African campuses. “In contexts where sexual transactions are a pervasive feature of academic life, women who do succeed are unlikely to be perceived as having done so on the basis of merit or hard work, and may be treated with derision and disbelief”, she said.

She, however, said in spite of broader patterns of gender and class inequality in universities, public higher education remains a main route to career advancement and mobility for women in Africa.

“Women’s constrained access has therefore posed a constraint to their pursuit of more equitable and just modes of political, economic and social development, not to mention freedom from direct oppression”, she said.

Prof Mama concluded by saying, “There is a widely held agreement that there is a need to rethink our universities and to ensure that they are transformed into institutions more compatible with the democratic and social justice agendas that are now leading Africa beyond the legacies of dictatorship, conflict and economic crisis, beyond the deep social divisions and inequalities that have characterised our history”.

She said rethinking universities means asking deeper questions about gender relations within them, and taking concerted and effective action to transform these privileged bastions of higher learning so that they can fulfil their pubic mandate and promise instead of lagging behind our steadily improving laws and policies.

Media Release
Issued by: Mangaliso Radebe
Assistant Director: Media Liaison
Tel: 051 401 2828
Cell: 078 460 3320
E-mail: radebemt.stg@ufs.ac.za  
02 August 2007
 

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