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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

Address by the first Inaugural President of the Central SRC

2005-08-03

The UFS Central SRC

Address by the first Inaugural President of the Central SRC of the University of the Free State, Mr Tello Motloung on Wednesday 3 August 2003

The Chairperson of the UFS Council, Judge Faan Hancke,
The Vice-chancellor and Rector of the UFS, Prof Frederick Fourie
The Vice-Rector Student Affairs of the UFS, Dr Ezekiel Moraka
The Presidents of the main campus SRC and the Vista campus SRC
Colleagues in the Central SRC, campus SRCs, students and fellow South Africans

Please receive my heartfelt revolutionary greetings

Vice-chancellor and rector what I bring here with me assisted by facts, is just the work of my imagination. Like a love letter addressed to a sweetheart miles away, even though you do not know how she feels, what she wants to hear, and do not even know what she looks like.

I value speech as just an honest intimation, that’s why I got into a habit of establishing a dialogue with people, looking at each other’s face, and persuading one another of what we are saying.

Vice-chancellor, today marks an important milestone in the history of the existence of the UFS. Today reflects the confidence and trust that students of the UFS have placed in us. They are confident that the Central SRC has both the will and the capacity to take our university forward as we confront the challenge of transformation.

Students are confident that they are correct to trust the Central SRC as the principal agent of change in our university that is genuinely committed to the objective of building a non-racial, non-sexist and democratic university. We need to frankly ask ourselves, as CSRC members, whether are we up to all these challenges?

All Central SRC members have to understand this fully, internalize it, and ensure that everything we do, does not betray the confidence and trust of students, or disappoint their expectations. I say this knowing that all Central SRC members have committed themselves to serve the students of the UFS, black and white, and no one among us (CSRC) needs any special lectures about this central commitment.

The UFS should be an omnibus, welcoming everybody on board. But we should be a bus with a clear direction. We will certainly lose our way if we, as an institution, don’t have a clear road map spelling out where we are heading to.

There should be clear guidelines on the role of students in the transformation process. Students should also be viewed as role players in transformation along with the University management, and not just opposing forces. There is no right time, other than this one, to move away from the politics of opposition to politics of transformation.

However, we need the support of management to do so. The University should value the role and contribution of student leaders, hear our legitimate claims and consider them as part of political and policy decision making.

Vice-chancellor and Rector, it remains our task to ensure that the UFS is transformed into an institution that is seen to be playing a vigilant role in developing students academically, intellectually, socially, culturally, politically and otherwise. The process of transformation is not ending tonight, it is just beginning tonight.

Judge Hancke, Prof Fourie, Dr Moraka, fellow students and fellow South Africans, I lead students at this university with a sense of pride and duty, and I know very well that I lead men and women, students who are all determined that we reach our destination safely and on time.

A navy divided within its ranks will be destroyed and vanquished by the enemy, but the navy united in purpose and action, loyalty and commitment will not sink but sail on to victory.

It is befitting to mention that every drop of my blood is telling me that the UFS is my home. I firstly became a student here, I became the SRC treasurer in my first year here, I became the deputy president here, and I became the first president of the Central SRC of the UFS.

Therefore you should never doubt my commitment towards the transformation of this university. To paraphrase what was said by students at another institution, “If there is no UFS in heaven, then I am not going.”

Let me conclude by thanking my ancestors for teaching me that even if I wined and dined with kings and queens, I am not a king myself, so I should not turn my back on people who made me what I am today.

Most importantly, I would like to thank the Almighty God and the grace of our Lord Jesus Christ for giving me time and power to lead this university.

It will be theoretically irresponsible if I ended my speech without indicating that “Only a Kovsie knows the feeling”.

I thank you.

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