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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

In January 1, 2003, the Qwa-Qwa campus of the University of the North (Unin) was incorporated into the University of the Free State (UFS).
2003-02-07


FREDERICK FOURIE

IN January 1, 2003, the Qwa-Qwa campus of the University of the North (Unin) was incorporated into the University of the Free State (UFS).

While this is merely the beginning of a long and complex process, it does represent a major milestone in overcoming the apartheid legacy in education, realising the anti-apartheid goal of a single non-racial university serving the Free State.

The incorporation is also part of the minister's broader restructuring of the higher education landscape in South Africa - a process which aims to reshape the ideologically driven legacy of the past.

In contrast to the past educational and social engineering that took place, the current process of incorporating the Qwa-Qwa campus of Unin into the UFS is informed by three fundamentally progressive policy objectives, clearly outlined in the education white paper 3: (A framework for the transformation of higher education):

To meet the demands of social justice to address the social and structural inequalities that characterise higher education.

To address the challenges of globalisation, in particular the role of knowledge and information processing in driving social and economic development.

To ensure that limited resources are effectively and efficiently utilised, given the competing and equally pressing priorities in other social sectors.

Besides informing the way the UFS is managing the current incorporation, these policy objectives have also informed the transformation of the UFS as an institution over the past five years.

In 2001, former president Nelson Mandela lauded the success of the UFS in managing this transformation, by describing the campus as a model of multiculturalism and multilingualism. This was at his acceptance of an honorary doctorate from the UFS.

Indeed our vision for the Qwa-Qwa campus as a branch of the UFS is exactly the same as it is for the main UFS campus - a model of transformation, academic excellence, community engagement and financial sustainability, building on the histories and strengths of both the Qwa-Qwa campus and the UFS (Bloemfontein campus).

Realising this vision will be a giant leap forward in establishing a unified higher education landscape in the Free State.

In more concrete terms, the UFS is working towards this vision by focusing on the following areas of intervention: access and equity; academic renewal; investment in facilities; and sound financial management.

These interventions are being made not to preserve any vestiges of privilege or superiority, but precisely to increase access for students from poor backgrounds and to promote equity and representivity among all staff.

The current growth phase of the UFS has seen student enrolment almost double over the past five years, in particular black students, who now constitute approximately 55 percent of the student population of nearly 18 000 (including off-campus and online students).

But it has not just been a numbers game. Our approach has been to ensure access with success.

Our admissions policy, coupled with the academic support and "career preparation" programmes we offer, have resulted in significant successes for students who otherwise would not have been allowed to study at a university.

This will be continued at Qwa-Qwa as well.

Our academic offerings too have undergone dramatic change. We have become the first university in the country to offer a degree programme based on the recognition of prior learning (RPL).

This is not just a matter of academic renewal but of access as well, especially for working adults in our country who were previously denied a university education.

As for the sound financial management of the UFS (including the Qwa-Qwa campus), this is being done not for the sake of saving a few rands and cents, but for the greater value to our society that comes from having sustainable institutions.

It is sustainable universities that can make long-term investments to fund employment equity, provide information technology for students, upgrade laboratories, construct new buildings, develop research capacity, and provide a safe environment for students and staff, as is happening now at the UFS.

As a result of such management, a practical benefit for prospective students at the Qwa-Qwa campus of the UFS will be lower academic fees in some cases compared with the Unin fees.

As is the case with all these processes, there are concerns from staff and students at Qwa-Qwa and the broader community of the region that the Qwa-Qwa campus serves.

To get the campus viable and to ensure its continuation in the short term, tough choices had to be made by the minister of education regarding which programmes to offer and fund.

But we have been encouraged by the community's understanding that these concerns can be addresed over time as the campus becomes financially viable.

Meetings between the top mangement of the UFS and community representatives, staff and students at Qwa-Qwa have laid the basis for building a climate of trust in such a complex process.

We should not be captives of the past divisions but build this new unified higher education landscape that can meet our country's developmental needs.

It should be a higher education landscape that is based on broadening access, promoting equity and social justice, developing academic excellence, and the effective and efficient management of scarce resources. This should be our common common objective.

Professor Frederick Fourie the rector and vice-chancellor of the University of the Free State (UFS)

 

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