Yurii Nikolaevich Pariiskii

Yurii Nikolaevich Pariiskii (born on 23 May 1932 in Moscow) was a leading Soviet and Russian radio astronomer whose work shaped modern centimetre-wave radio astronomy and cosmology. He was born into a distinguished scientific family: his father, Nikolai Nikolaevich Pariiskii, was a Corresponding Member of the USSR Academy of Sciences, and his mother, Lidiya Viktorovna Pariiskaya, worked at the Lebedev Physical Institute (FIAN) in close collaboration with Andrei D. Sakharov. Close family ties with Igor E. Tamm and Mikhail A. Leontovich strongly influenced Pariiskii's scientific outlook from an early age.

Pariiskii graduated from Moscow State University in 1955 with a degree in astronomy, having also studied at the Moscow Institute of Mechanics and the Moscow Electrotechnical Institute of Communications. Among his most influential teachers was Iosif S. Shklovskii, who introduced radio astronomy lectures at the university. His fellow students included Nikolai Kardashev, Vladimir Kurt and Nataliya Soboleva, who later became his lifelong scientific collaborator and wife.

While completing his diploma work at FIAN under Alexander E. Salomonovich in 1954, Pariiskii independently constructed an 8-mm radiometer to observe a solar eclipse and obtained improved data on the structure of the solar chromosphere. After graduation, he joined the newly established Department of Radio Astronomy at the Pulkovo Observatory, headed by Semyon E. Khaikin, the founder of experimental radio astronomy in the USSR.

At Pulkovo, Pariiskii played a key role in developing high-sensitivity broadband radiometers for the Large Pulkovo Radio Telescope (BPR), a novel variable-profile antenna that began operation in 1956. These instruments enabled high-resolution centimetre-wave observations and were crucial for early studies of solar radio emission. In 1961, the first high-resolution survey of the Milky Way revealed compact radio structure at the Galactic Centre, an observation that attracted wide international attention.

Using the BPR, Pariiskii also conducted detailed studies of radio sources from the Westerhout catalogue, demonstrating that many were supernova remnants rather than H II regions. In 1962, he published a seminal paper on the radio brightness distribution of Venus, showing that the observations supported a hot-surface model with extremely high surface pressure (~100 atm). Although this result reached Soviet space planners too late, it was later confirmed by NASA’s Mariner II mission.

Pariiskii defended his PhD thesis in 1962 and, following Khaikin's resignation, became Head of the Pulkovo radio astronomy department. His methodological work clarified fundamental sensitivity limits of metre-wave radio telescopes and demonstrated the advantages of centimetre wavelengths. He was also a co-author of a pioneering international project for a giant radio telescope, presented at the IAU in 1964.

These ideas culminated in the construction of the RATAN-600 radio telescope at the Special Astrophysical Observatory (SAO) in Nizhny Arkhyz, where first observations were carried out in 1974. Pariiskii was deeply involved in commissioning the instrument and defining its scientific programme. Under his leadership, RATAN-600 produced the first radio detections of several Galilean satellites of Jupiter, including Europa and Io, revealing the unique physical properties of Io well before their direct confirmation by spacecraft.

In 1969, Pariiskii defended his Habilitation thesis on one-dimensional radio imaging and the future of multi-dimensional radio astronomy. From the late 1960s onward, his career was closely linked to RATAN-600 and the SAO. In the early 1980s, he led the "Cold" experiment to study cosmic microwave background (CMB) anisotropy, resulting in a deep centimetre-wave sky survey and the establishment of the international Big Trio programme (RATAN-600, VLA, and the SAO 6-m optical telescope). This programme produced a comprehensive atlas of FRII radio galaxies and led to the discovery of the extremely distant and luminous radio galaxy RCJ0311+0507 at z = 4.515, hosting a giant black hole with a mass exceeding 10¹⁰ solar masses.

Pariiskii devoted much of his later work to studies of the early Universe and the CMB. His research at RATAN-600 refined models of Galactic foreground emission, identified optimal frequency ranges for deep cosmological observations, and confirmed key predictions of primordial density oscillations first proposed by Andrei Sakharov. These results demonstrated the feasibility of precision CMB studies from the ground and contributed to the interpretation of data from major space missions, including Planck.

Pariiskii's scientific legacy includes more than two hundred publications and two monographs: Radio Telescopes and Radiometers (1973, with N.A. Esepkina and D.V. Korol'kov) and Radio Galaxies and Cosmology (2009, with O.V. Verkhodanov). He was elected a Corresponding Member of the USSR Academy of Sciences in 1979 and a Full Member of the Russian Academy of Sciences in 1992. He served as Chair of IAU Commission 40 on Radio Astronomy and of the Radio Astronomy Commission of URSI. His achievements were recognised with numerous state honours, including the Order of Lenin and the Order of Merit for the Fatherland (Fourth Class).

Yurii Pariiskii passed away in St. Petersburg after a long illness on 31 July 2021.