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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

Minister praises the Faculty of Law
2009-02-13

 
At the launch of the Faculty of Law at the UFS's celebration of 100 years of jurisprudence, under the theme "Iurisprudentia 100", were, from the left: Judge Faan Hancke, Extraordinary Professor in the Department of Criminal and Medical Law and Chairperson of the UFS Council, Judge Lex Mpati, President of the Highest Court of Appeal, Mr Surty, Judge Hendrik Musi, Judge President of the High Court of the Free State, and Prof. Henning.
Photo: Stephen Collett
The Minister of Justice and Constitutional Development, Mr Enver Surty, has praised the Faculty of Law at the University of the Free State (UFS) for producing lawyers, academics, judges, etc. of great note.

Mr Surty was guest speaker this week on the Main Campus in Bloemfontein at the launch of the faculty’s celebration of a century of excellence in legal education, training and research at the UFS. The theme of the celebration is “Iurisprudentia 100”.

“The faculty has throughout its existence demonstrated its capability and capacity to produce scholars, legal practitioners, academics, judges, politicians etc, of great note. The university can take pride in the fact that, as an institution, you have done so well,” said Mr Surty.

Mr Surty said that our judiciary must be adequately qualified and it must be representative of our nation. “We must therefore have more aspiring judges in our midst and we must have a more representative judiciary – in race and gender. This is where an institution like the UFS can play an important role,” said Mr Surty.

Mr Surty also commented on the university’s engagement with its communities.
“The UFS has begun to recognise the importance of community engagement. Unless community engagement is part of your curricular activity we would not be able to produce the judges of the caliber we need who are better able to understand the social and economic context of our society,” he said.

According to Prof. Johan Henning, Dean of the Faculty of Law at the UFS, the faculty has a distinguished history of excellence in theoretical and practical legal education and training, which can be traced as far back as the establishment of the Grey University College in 1904.

Over the years, student numbers grew considerably and today the faculty has over 2 700 graduate and postgraduate students.

“The faculty prides itself on the fact that some of its students and lecturers went on to hold some of the highest offices in the country. Under its alumni are state presidents, ministers of state, administrators, judges of appeal, judges, rectors, professors and lecturers at the UFS as well as at other universities, advocates, attorneys and legal advisors – in private practice as well as in government,” said Prof. Henning.

The faculty’s “Iurisprudentia 100” celebrations will take place throughout the year with activities such as breakfasts for the various alumni groups of the faculty and a series of inaugural lectures. Cum Laude awards will also be
handed to Judge Lex Mpati, President of the Supreme Court of Appeal, and Judge Louis Harms, Deputy President of the Supreme Court Appeal. The celebrations will be concluded in November with a prestige dinner.

Celebration programme:

26 February 2009: Visit by Prof. Fernand de Varennes (of the Murdoch Law School, Perth, Australia),
13 March 2009: Breakfast for all candidate attorneys
18 March 2009: Breakfast for judges and Cum Laude awards
15 May 2009: Breakfast for labour law certificate alumni
11 September 2009: Breakfast for diploma alumni (CFP)
16 October 2009: Breakfast for attorneys and advocates
9-12 November 2009: Inaugural and public lectures
13 November 2009: Centenary dinner

Media Release
Issued by: Lacea Loader
Assistant Director: Media Liaison
Tel: 051 401 2584
Cell: 083 645 2454
E-mail: loaderl.stg@ufs.ac.za  
18 February 2009

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