Araucaria Project

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The Araucaria Project - international science collaboration focused on improving calibration of the extragalactic distance scale based on observations of major distance indicators in several nearby galaxies.


The Araucaria Project is a collaboration between astronomers from institutions in Europe, Chile and the US. Its principal aim is to provide an improved calibration of the local extragalactic distance scale. In the process of setting up the extragalactic distance scale, the greatest difficulty leading to the currently largest contribution on the systematic uncertainty of the Hubble constant lies in the determination of accurate absolute distances to nearby galaxies. The principal reason for this persisting difficulty is in the unknown dependences of stellar standard candles, used to measure the distances of nearby galaxies, on the environmental properties of their host galaxies (metallicity, age of the stellar populations etc.). The Araucaria Project is an effort to remedy this situation for several of the most important stellar candles, including Cepheid variables, RR Lyrae stars, red clump giants, and blue supergiants which all have the potential to provide accurate distance determinations to nearby galaxies once their environmental dependences are well calibrated. Our strategy is to determine precise distances using the various stellar candles to handful of galaxies with widely different environmental parameters, carefully analyze the distance differences between the different stellar candles, and how they vary with the environmental parameters of their host galaxies.

The sample of galaxies include NGC 6822, IC 1613 and NGC 3109 in the Local Group, and NGC 55, NGC 247, NGC 300 and NGC 7793 in the Sculptor Group. All our target galaxies can be resolved into their stellar components with the modern telescopes and instruments available to the project.

Main discoveries[edit]

  • The dynamical mass of a classical Cepheid variable star in an eclipsing binary system[1]
  • RR-Lyrae-type pulsations from a 0.26-solar-mass star in a binary system[2]
  • An eclipsing-binary distance to the Large Magellanic Cloud accurate to two per cent[3]

Team members[edit]

PhD Students[edit]


  1. ^ Pietrzyński; et al. (2010). "The dynamical mass of a classical Cepheid variable star in an eclipsing binary system". Nature. 468 (7323): 542–544. arXiv:1012.0231. Bibcode:2010Natur.468..542P. doi:10.1038/nature09598. PMID 21107425.
  2. ^ Pietrzyński; et al. (2012). "RR-Lyrae-type pulsations from a 0.26-solar-mass star in a binary system". Nature. 484 (7392): 75–77. arXiv:1204.1872. Bibcode:2012Natur.484...75P. doi:10.1038/nature10966. PMID 22481359.
  3. ^ Pietrzyński; et al. (2013). "An eclipsing binary distance to the Large Magellanic Cloud accurate to 2 per cent". Nature. 495 (7439): 76–79. arXiv:1303.2063. Bibcode:2013Natur.495...76P. doi:10.1038/nature11878. PMID 23467166.

External links[edit]