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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

The state of HIV/AIDS at the UFS
2010-05-11

“The University of the Free State (UFS) remains concerned about the threat of HIV/AIDS and will not become complacent in its efforts to combat HIV/AIDS by preventing new infections”, states Ms Estelle Heideman, Manager of the Kovsies HIV/AIDS Centre at the UFS.

She was responding to the results of a study that was done at Higher Education Institutions (HEIs) in 2008. The survey was initiated by Higher Education AIDS (HEAIDS) to establish the knowledge, attitudes, behaviours and practices (KABP) related to HIV and AIDS and to measure the HIV prevalence levels among staff and students. The primary aim of this research was to develop estimates for the sector.

The study populations consisted of students and employees from 21 HEIs in South Africa where contact teaching occurs. For the purpose of the cross-sectional study an ‘anonymous HIV survey with informed consent’ was used. The study comprised an HIV prevalence study, KABP survey, a qualitative study, and a risk assessment.

Each HEI was stratified by campus and faculty, whereupon clusters of students and staff were randomly selected. Self-administered questionnaires were used to obtain demographic, socio-economic and behavioural data. The HIV status of participants was determined by laboratory testing of dry blood spots obtained by finger pricks. The qualitative study consisted of focus group discussions and key informant interviews at each HEI.

Ethical approval was provided by the UFS Ethics Committee. Participation in all research was voluntary and written informed consent was obtained from all participants. Fieldwork for the study was conducted between September 2008 and February 2009.

A total of 1 004 people participated at the UFS, including the Main and the Qwaqwa campuses, comprising 659 students, 85 academic staff and 256 administration/service staff. The overall response rate was 75,6%.

The main findings of the study were:

HIV prevalence among students was 3,5%, 0% among academics, 1,3% among administrative staff, and 12,4% among service staff. “This might not be a true reflection of the actual prevalence of HIV at the UFS, as the sample was relatively small,” said Heideman. However, she went on to say that if we really want to show our commitment towards fighting this disease at our institution a number of problem areas should be addressed:

  • Around half of all students under the age of 20 have had sex before and this increased to almost three-quarters of students older than 20.

     
  • The majority of staff and a third of students had ever been tested for HIV.

     
  • More than 50% of students drink more than once per week and 44% of students reported being drunk in the past month. Qualitative data suggests that binge drinking over weekends and at campus ‘bashes’ is an area of concern.

Recommendations of the study:

  • Emphasis should be on increased knowledge of sexual risk behaviours, in particular those involving a high turnover of sexual partners and multiple sexual partnerships. Among students, emphasis should further be placed on staying HIV negative throughout university study.

     
  • The distribution of condoms on all campuses should be expanded, systematised and monitored. If resistance is encountered, attempts should be made to engage and educate dissenting institutional members about the importance of condom use in HIV prevention.

     
  • The relationship between alcohol misuse and pregnancy, sexually transmitted infections (STIs), HIV and AIDS needs to be made known, and there should be a drive to curb high levels of student drinking, promote non-alcohol oriented forms of recreation, and improve regulation of alcohol consumption at university-sponsored “bashes”.

     
  • There is need to reach out to students and staff who have undergone HIV testing and who know their HIV status, but do not access or benefit from support services. Because many HIV-positive students and staff are not receiving any kind of support, resources should be directed towards the development of HIV care services, including support groups.

Says Heideman, “If we really want to prove that we are serious about an HIV/AIDS-free campus, these results are a good starting point. It definitely provides us with a strong basis from which to work.” Since the study was done in 2008 the UFS has committed itself to a more comprehensive response to HIV/AIDS. The current proposed ‘HIV/AIDS Institutional response and strategic plan’, builds and expands on work that has been done before, the lessons learned from previous interventions, and a thorough study of good practices at other universities.

Media Release
Issued by: Mangaliso Radebe
Assistant Director: Media Liaison
Tel: 051 401 2828
Cell: 078 460 3320
E-mail: radebemt@ufs.ac.za  
10 May 2010

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