News Release 

Recipients of Gruber Foundation 2019 Cosmology Prize announced

Nicholas Kaiser and Joseph Ivor Silk are honoured for their seminal work on cosmological structure formation and dark matter

International Astronomical Union


IMAGE: Nicholas Kaiser, recipient of the Gruber Foundation 2019 Cosmology Prize. view more 

Credit: Gruber Foundation

The recipients of this year's Gruber Foundation Cosmology Prize were announced today. The prize is awarded annually to leading scientists and cosmologists who have made groundbreaking discoveries that change or challenge our understanding of the Universe.

The recipients of the 2019 prize are Nicholas Kaiser and Joseph Silk, both of whom have made seminal contributions to the theory of cosmological structure formation and to the creation of new probes of dark matter. Though they have worked mostly independently of each other, the two theorists' results are complementary in these major areas, and have transformed modern cosmology -- not once but twice.

The two recipients will share the $500,000 award, and each will be presented with a gold medal at a ceremony that will take place on 28 June at the CosmoGold conference at the Institut d'Astrophysique de Paris in France.

The physicists' independent contributions to the theory of cosmological structure formation have been instrumental in building a more complete picture of how the early Universe evolved into the Universe as astronomers observe it today. In 1967 and 1968, Silk predicted that density fluctuations below a critical size in the Cosmic Microwave Background, the remnant radiation "echoing" the Big Bang, would have dissipated. This phenomenon, later verified by increasingly high precision measurements of the CMB, is now called "Silk Damping".

In the meantime, ongoing observations of the large-scale structure of the Universe, which evolved from the larger CMB fluctuations, were subject to conflicting interpretations. In a series of papers beginning in 1984, Kaiser helped to resolve these debates by providing statistical tools that would allow astronomers to separate "noise" from data, reducing ambiguity in the observations.

Kaiser's statistical methodology was also influential in dark matter research; the DEFW collaboration (Marc Davis, George Efstathiou, Carlos Frenk, and Simon D. M. White) utilised it to determine the distribution and velocity of dark matter in the Universe, and discovered its non-relativistic nature (moving at a velocity not approaching the speed of light). Furthermore, Kaiser devised an additional statistical methodology to detect dark matter distribution through weak lensing -- an effect by which foreground matter distorts the light of background galaxies, providing a measure of the mass of both. Today weak lensing is among cosmology's most prevalent tools.

Silk has also been impactful in dark matter research, having proposed in 1984 a method of investigating dark matter particles by exploring the possibilities of their self-annihilations into particles that we can identify (photons, positrons and antiprotons). This strategy continues to drive research worldwide.

Both Kaiser and Silk are currently affiliated with institutions in Paris, Kaiser as a professor at the École Normale Supérieure, and Silk as an emeritus professor and a research scientist at the Institut d'Astrophysique de Paris (in addition to a one-quarter appointment at The John Hopkins University). Among their numerous significant contributions to their field, their work on the CMB and dark matter has truly revolutionised our understanding of the Universe.

In addition to the cash award, each recipient will receive a gold laureate pin and a citation that reads:

The Gruber Foundation is pleased to present the 2019 Cosmology Prize to Nicholas Kaiser and Joseph Ivor Silk, for their seminal contributions to the theory of cosmological structure formation and probes of dark matter.

Kaiser provided the mathematical description of primordial density fluctuations that have evolved into large-scale structure, while Silk predicted the eponymous damping scale imprinted on the cosmic microwave background anisotropies. Kaiser pioneered the analysis of weak gravitational lensing of light from distant galaxies by dark matter, while Silk recognized dark matter's indirect signatures such as antiprotons in cosmic rays and high energy neutrinos from the Sun. Their work has transformed modern cosmology.


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The IAU is the international astronomical organisation that brings together more than 13 500 professional astronomers from more than 100 countries worldwide. Its mission is to promote and safeguard astronomy in all its aspects, including research, communication, education and development, through international cooperation. The IAU also serves as the internationally recognised authority for assigning designations to celestial bodies and the surface features on them. Founded in 1919, the IAU is the world's largest professional body for astronomers.

The Gruber International Prize Program honours individuals in the fields of Cosmology, Genetics and Neuroscience, whose groundbreaking work provides new models that inspire and enable fundamental shifts in knowledge and culture. The Selection Advisory Boards choose individuals whose contributions in their respective fields advance our knowledge and potentially have a profound impact on our lives.


A. Sarah Hreha
Executive Director, The Gruber Foundation, Yale University
New Haven, USA
Tel: +1 203-432-6231

Lars Lindberg Christensen
IAU Press Officer
Garching bei München, Germany
Tel: +49 89 320 06 761
Cell: +49 173 38 72 621

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