Making measurements in space yet more accurate
An international team of astronomers led by the Polish Araucaria group from the PAS Copernicus Astronomical Center announced another important discovery in the field of measuring distances across the Universe. Based on very precise measurements of the distances to the near galaxies of the Large Magellanic Cloud and the Small Magellanic Cloud, the researchers were able to determine how the luminosity of Cepheids depends on metallicity.
Cepheids are stars changing their dimensions periodically, which results in variations of luminosity. More than 100 years ago, the connection between Cepheids’ luminosity and period of pulsation was discovered. Since then, Cepheids have become the basic tool for measuring distances in space, allowing for a number of revolutionary discoveries.
Cepheids are also involved in determining the Hubble parameter, which is used to described the physical scale of the Universe and its evolution. Determining how the luminosity of Cepheids depends on metallicity has been one of the main obstacles in the procedure.
The Araucaria group confirmed that the impact of metallicity on luminosity is very small. This discovery will lay the ground for attempts to improve the accuracy of the Hubble parameter to an unprecedented 1% – says project leader Prof. Grzegorz Pietrzyński.
Araucaria project (https://araucaria.camk.edu.pl) aims at improving the calibration of the cosmic distance scale in the Universe. In recent years, it has succeeded in determining precise distances to other galaxies, including the Large Magellanic Cloud. The group’s leader, Prof. Grzegorz Pietrzyński, has recently received the Advanced Grant of the European Research Council.
The results will be published in the Astrophysical Journal.
They are also available at arXiv:1705.10855.
