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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

Questions about racial integration in residences answered

2007-07-31

Answers to frequently asked questions about the racial integration of student residences at the UFS

1. Why does the UFS want to change the current situation in the student residences?

There are many reasons why a new approach to placement in the student residences is necessary. However, the main reason is of an educational nature. As a university, the UFS should create an environment in its residences where students can learn to appreciate and respect the rich diversity that is on offer at the university. A university accommodates students from many different backgrounds in terms of race, language, religion, economic status, culture and other aspects. If a student can learn to appreciate the value in this rich diversity at university, he or she will also be able to appreciate the value of this diversity in the workplace and broader society.

The current situation of predominantly white and predominantly black residences has not been able to cultivate such an appreciation for diversity and respect for one another as human beings, and will not equip students with the knowledge and skills required to manage diversity.

Besides this, there are many other areas of life in the residences that need attention. For one, we need to urgently establish a human rights culture in the residences so that the rights of all students can be respected. We need to address the abuse of alcohol, provide disabled students with their rightful place, and last but not least, really entrench a culture of learning in student residences.

Let us make the residences places we can be proud of – places of learning, of diversity, of respect; places of growth and development. This is the ideal we should all strive to achieve.

2. Why does the management want to force us to integrate?

It is a false argument to debate the issue in terms of “force”. Any decision by a University, or any other organisation, regarding matters of policy, rules and regulations implies a restriction on the choice of an individual and an obligation to comply. What we should focus on is whether this decision of the Council is in the best interests of our students.

The management of the university believes that it has a responsibility to give students the best education possible, not only in terms of what you learn in the lecture rooms, but especially in the residences as well. The residences can be very powerful places of learning about matters of great importance, both academic and non-academic.

The parallel-medium language policy separates students into largely white/Afrikaans and black/English classes. Efforts are being made to bridge this divide in the classroom, but we can also try to eliminate it in the residences.

The university is committed to building a new culture for the entire institution that is based on values and principles – such as an academic culture, non-racialism, respect for human rights and diversity – among staff and students.

In the context of student residences, the application of these values and principles still allows substantial room for the voluntary exercising of choice by individuals as well as by Residence Committees, notably with regard to the placement of students (they can still place 50 percent of first-year students), as well as the determination of the future character and traditions of a diverse residence.

Furthermore, students can still choose their residences (subject to availability of places), can choose a roommate, and so forth.

3. What about freedom of association?

The rights we enjoy in a democracy must be balanced against other rights, as well as the laws of the country. This means that the right to freedom of association must be balanced against laws that make it illegal to discriminate against other people on the basis of race, language or religion, for instance.

Freedom of association pertains to the right of individuals to form voluntary organisations such as clubs or private boarding houses, or their right to join or not join existing organisations. You exercise that right when you decide to become a student of the UFS, and again when you choose to live in one of its residences.

However, once you have decided to join an organisation voluntarily, you cannot subsequently demand that that organisation should provide a “club” or residence to your liking where, for instance, you only associate with your choice of co-members. You must accept the policies of that organisation.

In any case, how would that right of yours be balanced against the right of another individual who wishes to associate with a different set of co-members? (For instance – what about the freedom of a student to associate with students NOT from his own background, but indeed from another language, cultural, racial or economic background?)

The constitutional right to freedom of association can, in any case, not be used to exclude or discriminate on the basis of race or religion (Section 18 of the Bill of Rights).

Besides, the new policy guidelines will still make provision for freedom of association. This right can be exercised freely within a diverse residence with regard to friendships, joint academic work, socialising, sport, etc.

4. Will residences not lose their traditions?

The University appreciates that there are many valuable elements of tradition in residences. However, we must bear in mind that the traditions and character of student residences have evolved and changed over time, and they will continue to evolve and to change. In addition, we do not need to accept all aspects of residence life purely on the basis of tradition, including the unacceptably high level of alcohol abuse and unsavoury, humiliating and discriminatory orientation practices. The new approach to integrated residences provides the opportunity to retain the positive aspects of the current traditions and character, but also to develop new traditions and give residences a new character.

We can now establish a tradition and a character for each residence that are reconcilable with the values of the University as a place of scholarship and are aligned with the human rights approach of our country’s Constitution, the laws of our country and the strengths and diversity of the students in a particular residence.

5. Have students been involved in this process? Is there a role for them to play after the decision has been taken by the Council of the UFS?

In the first semester of 2007, during two rounds of consultations, the primes, SRC and student organisations were consulted about the proposed new placement policy to increase diversity in residences. Some residences also made written submissions on the matter (such as Madelief, Soetdoring, Wag-'n-bietjie, Vergeet-my-nie, Emily Hobhouse). Other residences requested and were granted more time, but did not make any submissions in the end (such as Reitz and Armentum).

Management also had several meetings with the above-mentioned structures to hear first-hand from students their concerns and solutions regarding possible challenges presented by integration in residences.

During these interactions, several excellent ideas and proposals were put forward by students. These views had a definite impact on the eventual proposal that was taken to the University Council, in particular regarding the minimum level of diversity (30%) in junior residences and the fact that residences still want to have a say in the placement of students, rather than the placement decision being left in the hands of Management alone (hence the 50% placement portion of residences). Management values the effort that was put into the process by the primes and residence committees, and thanks them for their contributions.

However, it should be stressed that consultation should not be understood as a process of negotiation, nor does it imply that consensus must be reached. What it means is that Management must take a considered decision after hearing the views of stakeholders.

Management would like students to continue to provide input and ideas regarding the implementation details of the policy guidelines. Task teams have been established and students will be informed about how they can interact with the task teams on an ongoing basis.

6. But integration in the residences was tried in the past (in the late 1990s), and then it failed. Why will it work now?

Yes, the University of the Free State did integrate its residences as far back as 1993, and for a few years it worked. The UFS did it at that time and is now doing so again, because it is the right thing to do. Yet it is important to understand why the previous attempt at racial integration in residences was not successful.

Firstly, both black and white students were much polarised because of the apartheid past. Secondly, there was insufficient management support for students in the residences, the student leaders generally as well as residence heads, in terms of dealing with diversity and related issues. Thirdly, the institutional culture of the UFS and the residences in particular was not addressed as part of broader transformation and integration in residences, whereas it is now being addressed.

In addition, the current decision to integrate residences has the benefit of being implemented after several more years of integration in schooling, sport, workplaces and other aspects of life.

This decision is also based on Management’s commitment to give all the possible support it can to this process.

This is a very important initiative that the UFS is undertaking. Management, in co-operation with students, must ensure that it succeeds. Integrated residences that produce high-quality graduates equipped to deal with the challenges of the workplace and our society is a worthwhile ideal we should all strive to achieve.

If you would like to make a proposal regarding the implementation and practical aspects of the new policy, please send it to the following email address: rector@ufs.ac.za

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