Laureates of the 2022 Marie Skłodowska-Curie and Pierre Curie Polish-French Science Award: Pierre Kervella and Grzegorz Pietrzynski

Pierre Kervella and Grzegorz Pietrzynski, laureates for the 2022 Maria Sklodowska-Curie and Pierre Curie award in recognition of their combined complementary expertise in stellar interferometry and in observations of binary stars, in order to precisely determine the distance to the Large Magellanic Cloud, hence creating a benchmark for measuring distances between galaxies, which would allow better measurements of expansion of the Universe.

Grzegorz Pietrzynski, full professor at the Nicolaus Copernicus Astronomical Center of the Polish Academy of sSciences and Pierre Kervella, full Pprofessor at Lesia (Observatoire de Paris), both renowned scientists in their own country, have worked for many years on an innovative research project, based on their complementary expertise.

The aim of the project is to first calibrate new distance estimators between galaxies, and use them for a precise measurement of the Hubble constant (which is a measure of the expansion of the Universe). Current estimates of the Hubble constants differ, they depend on the method used. Further, the expansion of the Universe seems to be increasing, which in turn seems to evidence the existence of a mysterious “dark energy”. It may explain the acceleration of the expansion and therefore the discrepancies in the estimated values of the Hubble constant. Any further research of this cosmological phenomenon requires a high precision in determination of distances between galaxies. This is the aim of this outstanding collaboration. The first step is a precise determination of the distance of nearby galaxies. After 13 years of work, the Polish-French team and collaborators set up a precise benchmark for measuring intergalactic distances:, the distance to the Large Magellanic Cloud, with an accuracy of 1% (distance of 49.6 kpc). The methods used involve stellar interferometry for the French team and observations of eclipsing binary stars orbiting around their center of mass for the Polish team. Merging the information reached by complementary observations, they calibrated the surface brightness-color relations of red giants with unprecedented accuracy. Their new precisely calibrated distance indicators will allow to get distances of other galaxies, and the information would constitute a test for the standard cosmological model and contribute to solve the mystery of dark energy and matter. This next aim is of profound astronomical, physical and philosophical consequences.