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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 unveils portrait of Ms Winkie Direko
2005-11-28

During the unveiling ceremony were from the left Prof Frederick Fourie (Rector and Vice-Chancellor of the UFS), Mrs Direko, Judge Faan Hancke (Chairperson of the UFS Council) and Dr Charles Nwaila (Director-General of the Free State Provincial Government and Vice-Chairperson of the UFS Council). The blue background of the portrait depicts Ms Direko's philosophy of "the sky is the limit".  She also wore the same outfit as what she has on in the portrait. Photo:  Stephen Collett

UFS unveils portrait of Ms Winkie Direko  
A portrait of Ms Winkie Direko, former Chancellor of the University of the Free State (UFS) and Premier of the Free State Province and currently a Member of Parliament, was unveiled today during the last session of the UFS Council for this year on the Main Campus in Bloemfontein.

The portrait, painted by the gifted artist Ms Reshada Crouse, now hangs in the Council Chambers of the UFS.

Ms Direko was sworn in as Chancellor of the UFS in August 1999.  She was the first black person and first woman in this position at the UFS. She was succeeded by Dr Franklin Sonn.

“Ms Direko had an exceptional legitimacy in the black community because of her role in black education in the Free State (as principal) and community leader in the difficult ‘struggle’ period.  This former principal’s simultaneous insistence on transformation as well as discipline and order at an educational institution was exactly what the UFS needed at that stage,” said Prof Frederick Fourie, Rector and Vice-Chancellor, during the unveiling ceremony.

“She also played a special role to bring the UFS and the Free State Provincial Government closer to each other.  Her comprehension for the own nature of a university helped in times when difficult decisions had to be made.  She also realised the value of the university’s expertise for her government.  The Premier’s Economic Advisory Council, with the UFS rector and academics like Lucius Botes and James Moses in leading roles, was formed to undertake important research on economic development strategies in the Free State,” said Prof Fourie.

In her speech Ms Direko said that it is an unique experience for her to be catalogued in the history of the UFS.  “I am humbled and proud to be associated with the UFS,” she said.

Ms Direko said that the UFS is on the right track with its transformation process.  “I will continue to convince people that the UFS is for everyone and will fight for that until the end.  But, it is important to see a visible change concerning transformation.  The UFS must bring its side and speed up the transformation process.  I know that it is a difficult road, but we cannot hide from the realities of our time,” she said.
 

Media release
Issued by: Lacea Loader
Media Representative
Tel:  (051) 401-2584
Cell:  083 645 2454
E-mail:  loaderl.stg@mail.uovs.ac.za
25 November 2005

 

 

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