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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

UFS works closely with employees in the post-Reitz settlement process
2013-05-20

20 May 2013

In the light of an article in IOL News on 18 and 19 May 2013 and in Sunday Independent and Sunday Tribune on 19 May 2013 in which it is alleged that the University of the Free State (UFS) has failed to honour its commitment to the five Reitz employees we are pleased to report on the ongoing process and progress made with respect to their employment.

The university remained consistently true to the settlement agreement and High Court order of 2011 and cannot apologise for complying with the law. It was therefore impossible for us to talk to our colleagues directly until last week when we had a breakthrough meeting, which was cleared by the Human Rights Commission (HRC), and matters were resolved.

The UFS continues to work closely and now directly with the five employees to ensure that their rights as employees remain the highest priority in the post-settlement process.
 
All but one of the conditions of the Reitz settlement (own business) has already been met; however, we are in the process of providing training and support for the establishment of an independent business led by the employees.

After some delays, and frustration on all sides, we have found the right training provider for them and are satisfied that the process remains on track. The business office (furnished) has been allocated at the South Campus in Bloemfontein.

Already in late 2012 the Chair of the HRC expressed his satisfaction with the commitments made by the university to the process. By 30 June 2013 this outstanding commitment to establish an independent company with trained employees would also have been met in full.

Beyond the settlement agreement, the UFS has also committed to providing free education and training to the children of the employees so that their next generation of families emerge as strong, independent, well-trained and productive members of society. The child of one of the colleagues is in fact finishing Grade 12 this year and we are in discussion about possible studies at the UFS. This is our pledge and commitment as a university.

This final step in the post-Reitz settlement is being led by Dr Choice Makhetha, Vice-Rector of the University of the Free State.

 

Issued by: Lacea Loader
Director Strategic Communication
Tel: +27 (0) 51 401 2584 / +27 (0) 83 645 2454
E-mail: news@ufs.ac.za
Fax: +27 (0) 51 444 6393
Web: www.ufs.ac.za

 

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