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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

Higher than expected prevalence of dementia in South African urban black population

2010-09-22

Prof. Malan Heyns and Mr Rikus van der Poel

Pilot research done by University of the Free State (UFS) indicates that the prevalence of dementia, of which Alzheimer’s disease is only one of the causes, is considerably higher than initially estimated. Clinical tests are now underway to confirm these preliminary findings.

To date it has been incorrectly assumed that dementia is less prevalent among urban black communities. This assumption is strongly disputed by the findings of the current study, which indicates a preliminary prevalence rate of approximately 6% for adults aged 65 years and older in this population group. Previous estimates for Southern Africa have been set at around 2,1%.

The research by the Unit for Professional Training and Services in the Behavioural Sciences (UNIBS) at the UFS and Alzheimer’s South Africa is part of the International 10/66 Dementia Research Group’s (10/66 DRG) initiative to establish the prevalence of dementia worldwide.

Mr Rikus van der Poel, coordinator of the local study, and Prof. Malan Heyns, Principal Investigator, say worldwide 66% of people with dementia live in low and middle income countries. It is expected that it will rise to more than 70% by 2040, and the socio-economic impact of dementia will increase accordingly within this period. 21 September marks World Alzheimer’s Day, and this year the focus is on the global economic impact of dementia. Currently, the world wide cost of dementia exceeds 1% of the total global GDP. If the global cost associated with dementia care was a company, it would be larger than Exxon-Mobil or Wal-Mart.

The researchers also say that of great concern is the fact that South Africa’s public healthcare system is essentially geared toward addressing primary healthcare needs, such as HIV/Aids and tuberculosis. The adult prevalence rate of HIV was 18,1% in 2007. According to UNAIDS figures more than 5,7 million people in South Africa are living with HIV/Aids, with an estimated annual mortality of 300 000. In many instances the deceased are young parents, with the result that the burden of childcare falls back on the elderly, and in many cases elderly grandparents suffering from dementia are left without children to take care of them. “These are but a few reasons that highlight the need for advocacy and awareness regarding dementia and care giving in a growing and increasingly urbanized population,” they say.

Low and middle income countries often lack epidemiological data to provide representative estimates of the regional prevalence of dementia. In general, epidemiological studies are challenging and expensive, especially in multi-cultural environments where the application of research protocols relies heavily on accurate language translations and successfully negotiated community access. Despite these challenges, the local researchers are keen to support advocacy and have joined the international effort to establish the prevalence of dementia through the 10/66 DRG.

The 10/66 DRG is a collective of researchers carrying out population-based research into dementia, non-communicable diseases and ageing in low and middle income countries. 10/66 refers to the two-thirds (66%) of people with dementia living in low and middle income countries, and the 10% or less of population-based research that has been carried out in those regions.

Since its inception in 1998, the 10/66 DRG has conducted population based surveys in 14 catchment areas in ten low and middle income countries, with a specific focus on the prevalence and impact of dementia. South Africa is one of seven LAMICs (low and medium income countries) where new studies have been conducted recently, the others being Puerto Rico, Peru, Mexico, Argentina, China and India.

Mr Van der Poel says participating researchers endeavour to conduct cross-sectional, comprehensive, one-phase surveys of all residents aged 65 and older within a geographically defined area. All centres share the same core minimum dataset with cross-culturally validated assessments (dementia diagnosis and subtypes, mental disorders, physical health, anthropometry, demographics, extensive non-communicable risk factor questionnaires, disability/functioning, health service utilization and caregiver strain).

The local pilot study, funded by Alzheimer’s South Africa, was rolled out through an existing community partnership, the Mangaung University of the Free State Community Partnership Programme (MUCPP).

According to Mr Van der Poel and Prof. Heyns, valuable insights have been gained into the myriad factors at play in establishing an epidemiological research project. The local community has responded positively and the pilot phase in and of itself has managed to promote awareness of the condition. The study has also managed to identify traditional and culture-specific views of dementia and dementia care. In addition, existing community-based networks are being strengthened, since part of the protocol will include the training and development of family caregivers within the local community in Mangaung.

“Like most developing economies, the South African population will experience continued urbanization during the next two decades, along with increased life expectancy. Community-based and residential care facilities for dementia are few and far between and government spending will in all probability continue to address the high demands associated with primary healthcare needs. These are only some of the reasons why epidemiological and related research is an important tool for assisting lobbyists, advocates and policymakers in promoting better care for those affected by dementia.”

Media Release
Issued by: Mangaliso Radebe
Assistant Director: Media Liaison
Tel: 051 401 2828
Cell: 078 460 3320
E-mail: radebemt@ufs.ac.za
21 September 2010

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