Pierre Kervella, an astronomer at Observatoire de Paris - PSL at the Laboratoire d’études spatiales et d’instrumentation en astrophysique, and Grzegorz Pietrzyński, a professor at the Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences are both renowned in their respective countries. They have been working for many years on a research project aimed at improving the accuracy and reliability of distance measurements in the Universe.
Thanks to their combined complementary expertise in stellar interferometry and binary star observation, they have succeeded in determining, with great accuracy, the distance to the Large Magellanic Cloud (LMC), a satellite galaxy of the Milky Way. Thanks to this measurement, it is now possible to use the GNM as a solid reference for determining the distances to more distant galaxies. This will eventually allow the precise determination of the expansion rate of the Universe, the famous Hubble constant H0.
This work is important because the value of the Hubble constant H0, estimated from the cosmic microwave background - thanks to observations by the Planck space telescope - and that determined empirically by the study of galaxies, diverge. Obtaining an accurate empirical measurement of H0 is essential to resolve this tension.
Initially, the team’s work focused on the calibration of eclipsing binaries, valuable distance estimators that allow high-precision measurements. Using these stars, the Franco-Polish collaboration, which also involves researchers in Chile, was able to determine the distance of nearby galaxies with precision.
At the end of the thirteen years of this first stage, the Franco-Polish team and its collaborators succeeded in establishing a precise reference for measuring intergalactic distances.
The distance to the Large Magellanic Cloud is now known with an accuracy of 1% (distance of 49.6 kpc, or about 160,000 light years).
Two complementary methods were used to achieve this result : stellar optical interferometry for the French team and the observation of eclipsing binaries for the Polish team. By merging these approaches, the two teams were able to measure the surface brightness-color relationships of red giants with unprecedented accuracy, and thus convert them into high-precision distance indicators.
These initial results will make it possible to determine the distances of other galaxies in the near future.
Information that will be a test of the standard cosmological model and could help solve the mystery of energy and dark matter. A next goal that opens the door to fundamentally new considerations in astronomy, physics and philosophy.