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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

Student leaders 2012/13 announced
2012-08-30

Ready for the task - Sabelo Khumalo, SRC President of the Qwaqwa Campus and William Clayton, SRC President of the Bloemfontein Campus.
Photo: Johan Roux
31 August 2012

The 2012/13 elections for the Student Representative Councils (SRC) of the University of the Free State were completed successfully and show meaningful support for the changes in student governance adopted by students across campuses over the past two years.

The SRC elections at the Qwaqwa Campus were completed on 23 August 2012, while the elections at our Bloemfontein Campus took place on 27 and 28 August 2012.

The SRC Elections at our Bloemfontein Campus showed a voter turnout of 4516 votes (30.8%), with the elections at the Qwaqwa Campuses showing 1753 votes (46%) – both campuses reached the required quorums and the IEA (Bloemfontein Campus) and IEC (Qwaqwa Campus) declared the elections free and fair and announced the results as a true reflection of the will of the student bodies at the campuses.

The full SRC at Bloemfontein Campus now consists of 62% black and 38% white, and 53% female and 47% male members.

In the Qwaqwa elections, SADESMO achieved 46, 38% of the vote, with SASCO, PASMA and NASMO each achieving 30,23% and 8,39% and 14,26%, respectively.

The successful elections at Bloemfontein Campus show that the detailed transformation of student governance introduced by students at the Campus in 2010 and adopted by the university in 2011, succeeded in mobilizing greater participation of students in governance and representation. These changes in the main included a shift to independent candidacy for elective portfolios (12 seats) and organizational candidacy in nine sub-councils that holds ex officio seats on the SRC. Changes also included the establishment of student representative seats in faculty governance and management forums and the adoption of a reviewed Central SRC Constitution. Ex officio seats hold full and equal constitutional authority in the SRC.

Students at Qwaqwa Campus introduced additional portfolios to its SRC, including ex-officio seats for academic affairs, arts and culture, commuter students, Rag Community Service, religious affairs, residences and sports.

A joint sitting of the Campus SRCs will establish the Central SRC 2012/13 on 9 September 2012.

As a further opportunity for participation in and the development of student governance and representation, the current Central SRC herewith also announces its recent adoption of a student governance advisory programme, namely the UFS Student Elders Council (SEC).

The SEC is established as a combined programme between the Central SRC and the Dean of Student Affairs and will consist of selected senior student leaders from all campuses who completed their terms of office, apply and are appointed to the Elders Council by the Central SRC.

The Council will serve as an advisory structure to the Central SRC and other student structures in support of the continuous development of student governance and representation of the student body at the university.

The SEC will advise the Central SRC to be constituted following the constitution of the respective Campus SRCs.

The SRC members at the Bloemfontein Campus are:

President: Mr William Clayton

Vice-President: Mr Bonolo Thebe

Secretary: Ms Karis-Robin Topkin

Treasurer: Mr Pieter Coetzee

Arts & Culture: Ms Chanmari Erasmus

Accessibility & Student Support: Ms Gene McCaskill

First-generation Students: Ms Tanya Calitz

Legal and Constitutional Affairs: Ms Nokuthula Sithole

Media, Marketing & Liaison: Ms Neo Chere

Sport: Mr Tshepo Moloi

Student Development & Environmental Affairs: Ms Thabisile Mgadi

Transformation: Ms Koketso Mofokeng

Dialogue & Ex officio: Associations Council: Mr Anesu Ruswa

Academic Affairs & Ex officio: Academic Affairs Council: Ms Nombuso Ndlovu

Residence Affairs & Ex officio: Residences Council: Mr Johann Steyn

City Residence Affairs & Ex officio: Commuter Council: Mr Michael van Niekerk

Postgraduate Affairs & Ex officio: Postgraduate Council: Mr Fadeyi Akinsuyi

International Affairs & Ex officio: International Council: Ms Tumelo Moreri

Student Media Affairs & Ex officio: Media Council: Mr Jamal-Dean Grootboom

RAG Community Service & Ex officio: RAG Fundraising Council: Mr Jaco Faul

RAG Community Service & Ex officio: RAG Community Service Council: Ms Keneue Mahloana

The SRC members at the Qwaqwa Campus are:

President General: Mr S Khumalo

Deputy President: Mr P T Lenka

Secretary General: Mr D Khethang

Treasurer General: Mr S I Sithole

Media & Publicity: Mr S N Ntombela

Politics & Transformation: Tbc

Student Development & Evironmental Affairs: Tbc Academic Affairs: Mr T Molawude

Arts & Cultural Affairs: Mr T Nkohli

Off-Campus Students: Mr B Mtshali

RAG, Community Service & Dialogue: Ms S F Mlotya

Religious Affairs: Ms D C Khau

Residence & Catering Affairs: Ms Z Mzolo

Sports Council: Mr S Mngomezulu

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