Laudatio PNW

Laudatio for Peter Norman Wilkinson
on the occasion of awarding Him
a honorary degree of
Nicolaus Copernicus University in Toruń

by Andrzej Kus

Today, I have a great honour to present the scientific achievements of professor Peter Norman Wilkinson to whom the Senate of Nicolaus Copernicus University has awarded a honorary degree.

Professor Wilkinson is a distinguished scientist who has collaborated with the world’s best radio astronomy institutes whose achievements opened new areas of the research in this domain of science. He co-authored more than 300 publications that were cited 6,000 times. For his notable contribution to the development of high-resolution interferometry, he is highly ranked in the astronomical community. Developing and refining the techniques of image reconstruction as well building new instruments are among his major achievements. The very long baseline interferometry (VLBI) and application of those image reconstruction methods has made it possible to investigate a number of astronomical objects with the highest angular resolution ever attainable in astronomy. After more than 20 years, Wilkinson’s extremely accurate images of quasars like 3C273, 3C147, 3C309.1, and 3C380 are still recognised as the greatest accomplishment in the field and are regarded as a quality standard. The core ingredient of interferometric observational data reduction process proposed by Wilkinson is to eliminate the errors, introduced by the atmosphere and equipment, by means of a novel treatment of phases and amplitudes of the received signal. This approach is commonly used nowadays not only in astronomical research, but in other domains as well. Computed tomography is a good example here.

Application of VLBI and the new methods of image reconstruction is of tremendous importance for the understanding of the physical processes of extreme states of matter taking place in active galactic nuclei. Those objects are the most distant and powerful sources of electromagnetic radiation we observe in the Universe. The physical conditions inside them are so unusual that we will never be able to reconstruct and investigate them in our laboratories here on Earth. Thus, we have to use the Universe itself as such laboratory so that eventually the Grand Unification Theory of interactions could be verified.

Now, let me enumerate a few examples of investigations of those intriguing objects. The results of professor Wilkinson’s work were published in the best scientific journals such as Nature, Astrophysical Journal, and Monthly Notices of the Royal Astronomical Society. He was the leader of a group who analysed the properties of a selected sample of very compact (i.e. of very small angular sizes) radio sources. Based on the observations thereof, the number of supermassive black holes existing in the early stages of the evolution of the Universe shortly after the so-called Big Bang, could be estimated. These investigations put constrains on the galaxy formation theory.

Another important Wilkinson’s achievements was the discovery of a population of young (aged less than 100 years) extragalactic radio sources labelled compact symmetric objects. They turned out to be precursors of the well-known giant double radio sources. That discovery helped us understand the processes of galaxy evolution better. The role of black holes in those processes is substantial albeit still not fully recognised.

Professor Wilkinson played a key role in the investigations of the phenomenon of gravitational lensing in which light as well as radio waves coming from distant quasars are bent when passing through the gravitational field of massive galaxies located on their way towards the observer. Independently of cosmological considerations, the statistical analysis of observations of such “lenses” provided the evidence for the existence and the predominant role of dark matter in the global mass-energy budget of the Universe.

As I mentioned before, a major part of professor Wilkinson’s activity was pertinent to the development of existing astronomical instruments and the construction of new ones. Among his notable accomplishments in this category was a co-ordination of the expansion of interferometric network MERLIN in the ’80-ies and the upgrade of 76-metre radio telescope in Jodrell Bank. He also participated in developing the modern technologies of the construction of wide-angle radio cameras – the radio equivalents of opto-electronic converters (CCD) used in digital photographic cameras. However, perhaps his most outstanding achievement in the field of modern instrumentation was a proposal of the concept of a supersensitive radio telescope to be used for observations of neutral hydrogen in the whole Universe, the so-called “hydrogen array”. Later, this concept – still with Wilkinson’s co-authorship – became a world-wide Square Kilometre Array (SKA) project. SKA is expected to be a new generation radio telescope, whose sensitivity will outperform that of the existing ones by a factor of a hundred.

The VLBI-related collaboration of professor Wilkinson with Toruń radio astronomy group dates back to 1979. Thanks to Peter’s help and encouragement, we included our radio telescopes in the European VLBI Network and began to carry out ambitious joint scientific projects. This collaboration, in turn, made it possible to extend our scientific ties with leading radio astronomy centres like Caltech and National Radio Astronomy Observatory in the USA.

A decade ago, professor Wilkinson’s and our groups started a new project named One-Centimetre Receiver Array (OCRA). Thanks to the funding from the European Commission and both our institutes, we succeeded in building a state-of-the-art receiving matrix, specifically designed for the 32-metre radio telescope in Toruń. The ultimate scientific goal of the whole endeavour was to carry out a unique whole-sky survey at one-centimetre wavelength. A prototype called OCRA-p has been working successfully on Toruń radio telescope for already six years. This year, we launched a matrix labelled OCRA-f consisting of 8 receivers out of 16 planned. This unique programme could not have been even started at Nicolaus Copernicus University if it was not for the long-standing collaboration with Peter Wilkinson and his British colleagues. The research conducted within the framework of OCRA project provides new data on the populations of the youngest objects in the Universe and the distribution of gas in clusters of galaxies. Thanks to this unprecedented project, Toruń Radio Astronomy Observatory has entered the club of the world’s top institutes of this kind.

And finally, I have to mention professor Wilkinson’s role in the concept study of a 90-metre radio telescope for Polish astronomers and developing an ambitious scientific programme for such an instrument.

Let me conclude by quoting the opinions of the reviewers invited by Nicolaus Copernicus University when setting out with the aim of awarding the honorary degree to professor Wilkinson.

Professor Kazimierz Stępień wrote: Professor Wilkinson is a world-wide recognised scientist with appreciable scientific record in astrophysics. His fondness for Poland and willingness to collaborate with us is exceptional. With no doubt, his personality, scientific record, and contribution to Toruń radio astronomy fully justify awarding him the honorary degree of the university bearing the name of Nicolaus Copernicus – the greatest Polish astronomer.

Professor Jerzy Machalski wrote: Professor Peter N. Wilkinson is a well-known scientist and outstanding constructor of astronomical instruments. His contributions to radio astronomy are exceptional.

And finally, professor Andrzej Woszczyk from our university wrote: Awarding a honorary degree of Nicolaus Copernicus University to Peter Wilkinson will be a fitting token of our appreciation of his contribution to the development of modern astronomy as well as international scientific collaboration.

From the present perspective, it is perfectly clear that our collaboration with Jodrell Bank Observatory of the University of Manchester resulted in a remarkable development in many fields of radio astronomical research in Toruń Centre for Astronomy of Nicolaus Copernicus University. Therefore, awarding a honorary degree to professor Wilkinson is the right way to appreciate his unique contribution to the advancement of science and promoting the international collaboration that is so important and fruitful for Nicolaus Copernicus University. Today, the noble community of the scientists to whom Nicolaus Copernicus University has awarded the honorary degree, accepts a distinguished personality, propagator of scientific collaboration with our university and its ambassador in the world.