Latest News Archive

Please select Category, Year, and then Month to display items
Previous Archive
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

Graduates should make a difference as leaders and be agents of change
2017-06-22

Description: Mid-year graduation read more 22 June 2017 Tags: Mid-year graduation read more 22 June 2017

More than 5 000 degrees will be conferred over six days
and eleven ceremonies at the UFS mid-year graduation
ceremonies.
Photo: Johan Roux

Livestream of Graduation Ceremonies

“Make the choice to make a difference as the leaders of the future.” These words of Dr Susan Vosloo, Cardiothoracic Surgeon and member of the University of the Free State (UFS) Council, echoed the call to graduates on the first three days of the UFS mid-year graduation ceremonies. The ceremonies are taking place in the Callie Human Centre on the Bloemfontein Campus from 19 to 26 June 2017.

Dr Vosloo, also an alumna of the UFS, was one of six guest speakers at the biggest set of graduation ceremonies in the university’s history. A spirit of excitement is part of the festivities, as a total of 5 258 degrees will be conferred over six days in eleven ceremonies. The graduation week will conclude on 26 June 2017, when 460 master’s and doctoral degrees will be conferred – 72 of these are doctoral degrees.

Stand up and be counted
Dr Vosloo urged the graduands at the afternoon session on 19 June 2017 to stand up and be counted. “What we need are leaders who treasure integrity, dignity, accountability, transparency, and who will focus on the common challenges which we all face today.”

Dr Khotso Mokhele, UFS Chancellor, also encouraged the graduates to be agents of change who shouldn’t conform to the current system. “Decide that it is your country and that you will decide what it should be. Then it will not be the corrupt experiment which the current government turned it into. We wish you well. Go and be the agents of transformation.”

Ambassadors of the UFS
Prof Francis Petersen, UFS Rector and Vice-Chancellor, asked the graduates to make a contribution: “Be excellent ambassadors of the UFS, and make the UFS, your families, and our country proud by your strong, innovative, ethical, and excellent contributions.” He was the guest speaker during the morning and afternoon sessions on 20 June 2017.

He also said that they should never forget the supporting role others played in their success, whatever form it took.

Do it for those who fought for SA
Justice Connie Mocumie, Judge of Appeal at the Supreme Court of Appeal, encouraged the graduates to go out and contribute to the development of the country. She was the guest speaker at the morning and afternoon ceremonies on 21 June 2017.

“It is important for you to continue being experts in your area of expertise,” she said.

“Today is the beginning of better days to come. Do it for the legacy of those who fought for our country in pursuit of a better South Africa.”

Dipiloane Phutsisi, Principal and Chief Executive Officer of the Motheo TVET College in the Free State, said everyone is destined for greatness. “In the words of Dr Martin Luther King: Everyone has the power for greatness, not for fame but greatness, because greatness is determined by service.” She was the guest speaker at the morning session on 19 June 2017.

Click here to see a list of Deans’ and Senate medals awarded.

We use cookies to make interactions with our websites and services easy and meaningful. To better understand how they are used, read more about the UFS cookie policy. By continuing to use this site you are giving us your consent to do this.

Accept