Professor Grzegorz Pietrzyński from the Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences in Warsaw received the 2021 FNP Prize in mathematical, physical, and engineering sciences for the precise distance determination to the Large Magellanic Cloud.

Grzegorz Pietrzyński was born in 1971 in Nowy Dwór Mazowiecki. In 1995, he graduated in astronomy from the Faculty of Physics at the University of Warsaw. In 1999, he received a Ph.D. degree for a dissertation prepared under the supervision of Professor Andrzej Udalski. He received a habilitation degree in 2006 from the Faculty of Physics at the University of Warsaw for the work “Projekt Araucaria – poprawa kalibracji skali odległości we Wszechświecie na podstawie obserwacji świec standardowych w pobliskich galaktykach” (The Araucaria Project: The Improvement of the Calibration of the Cosmic Distance Scale Based on Observations of Standard Candles in Nearby Galaxies.” He received full  professorship in 2014.

Pietrzyński is currently working at the Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences in Warsaw. He has founded and directs the international Araucaria Project, which aims to calibrate the cosmic distance scale.

Furthermore, Pietrzyński did postdoctoral training in Chile at Universidad de Conception. He cooperated with Princeton University, European Southern Observatory, and for twenty years worked at the Warsaw University Observatory. He has lectured at research institutions in Japan, Germany, France, Belgium, Italy, and China, among other places.

Pietrzyński authored or co-authored more than 400 scientific publications, which appeared in the most prestigious journals, such as Nature, Science, Astrophysical Journal, or Astronomical Journal, accruing more than 23,000 citations.

Moreover, Pietrzyński won many prestigious Polish and international research grants, including the European Research Council grant (ERC), the Nature magazine award for outstanding scientific contribution,  Maria Skłodowska-Curie Award in physics from the Polish Academy of Sciences, and the Rector of the University of Warsaw Award. In 2011, together with Dr. Igor Soszyński, Pietrzyński received the Marian Mięsowicz Prize for outstanding achievements in physics from the Council of the Polish Academy of Arts and Sciences. He is a laureate of FOCUS and TEAM programmes of the Foundation for Polish Science.

 

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Professor Grzegorz Pietrzyński is a leading researcher in the field of observational astrophysics. He has become a world expert in space distance measurements. The Foundation for Polish Science awarded him for the precise determination of the distance to the Large Magellanic Cloud.

The Large Magellanic Cloud (LMC) is the closest satellite galaxy to the Milky Way and the most important calibrator of the cosmic distance scale, the standard for distance in the universe. The distance to the LMC now forms the basis for almost all empirical determinations of the Hubble Constant using supernovae. In turn, the value of the Hubble Constant is necessary to be able to learn about the evolution of our universe and to study the nature of dark energy. Each refinement of the Hubble Constant leads to further discoveries and important findings. One of the main problems of determining the Hubble Constant was the precision of measuring the distance to the LMC.

Professor Pietrzyński’s achievement lies in the measurement of the distance to the Large Magellanic Cloud galaxy with the highest accuracy ever: just 1 percent. His findings show that the LMC is located 49.59 kiloparsecs from Earth or about 161,000 light-years.

Pietrzyński together with his team has improved methods for measuring cosmic distances to a level that is now a standard in astrophysics. The process of measuring the distance to the LMC consisted of several components that led to the estimation of the distance to twenty eclipsing binary star systems that orbit each other in the Large Magellanic Cloud. Scientists measured these stars’ eclipses, velocities, and then using simple laws of physics, determined their precise physical parameters and distance.

All this was possible thanks to the Araucaria Project, which has been going on for more than two decades and is headed by Professor Pietrzyński (together with Professor Wolfgang Gieren). The goal of the project is to calibrate the cosmic distance scale. The results of the work so far have already been presented in many publications, including several times in the prestigious journal Nature.

Measurement of absolute distances is one of the biggest problems in cosmology. In order to measure the most distant objects, scientists must first precisely measure the distance to the Large Magellanic Cloud. Knowing the distance, they calculate the absolute luminosity of the bright pulsating stars in the Large Magellanic Cloud (and other galaxies), which are called cepheids. They are called “standard candles” for measuring distances in the universe because we can calculate the distance to them by knowing their absolute brightness and measuring the observed brightness.

Observing the brightness of cepheids in other galaxies allows us to measure distances to even further objects, namely galaxies where Type Ia supernovae were observed. These measurements are used to determine the absolute brightness of the supernovae. If we know the absolute luminosity of the supernovae, we can compare it with the observed luminosity and determine their distances. Supernovae Ia are one of the brightest objects in the universe, so they allow us to determine distances to very distant parts of the universe, and thus to determine the Hubble Constant.

The precise measurement of the LMC distance now provides a solid foundation for determining the Hubble Constant with an accuracy of about 3%.

For their research, scientists from the Araucaria Project used various telescopes located in several observatories including: the European Southern Observatory in Chile, Las Campanas Observatory in Chile, and South African Astronomical Observatory in Cape Town, South African Republic. Some observations were made at the Cerro Armazones Observatory belonging to the Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences. Moreover, the scientists used data from the Polish Optical Gravitational Lensing Experiment (OGLE).

 

Photo: prof. Grzegorz Pietrzyński_fot. Magdalena Wiśniewska-Krasińska_Archiwum FNP

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