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The Araucaria Project is an international science collaboration focused on improving the calibration of the extragalactic distance scale based on observations of major distance indicators in several nearby
galaxies A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar Sys ...
.


Project

The Araucaria Project is a collaboration between astronomers from institutions in
Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...
,
Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...
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 Hubble's law, also known as the Hubble–Lemaître law, is the observation in physical cosmology that galaxies are moving away from Earth at speeds proportional to their distance. In other words, the farther a galaxy is from the Earth, the faste ...
lies in the determination of accurate absolute distances to nearby galaxies. The principal reason for this persisting difficulty is in the unknown dependencies of stellar
standard candles The cosmic distance ladder (also known as the extragalactic distance scale) is the succession of methods by which astronomers determine the distances to celestial objects. A ''direct'' distance measurement of an astronomical object is possible ...
, 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 variable A Cepheid variable () is a type of variable star that pulsates radially, varying in both diameter and temperature. It changes in brightness, with a well-defined stable period (typically 1–100 days) and amplitude. Cepheids are important cosmi ...
s, RR Lyrae stars,
red clump The red clump is a clustering of red giants in the Hertzsprung–Russell diagram at around 5,000 K and absolute magnitude (MV) +0.5, slightly hotter than most red-giant-branch stars of the same luminosity. It is visible as a denser region of ...
giants, and
blue supergiant A blue supergiant (BSG) is a hot, luminous star, often referred to as an OB supergiant. They are usually considered to be those with luminosity class I and spectral class B9 or earlier, although sometimes A-class supergiants are also deemed blu ...
s which all have the potential to provide accurate distance determinations to nearby galaxies once their environmental dependencies are well calibrated. The sample of galaxies include NGC 6822, IC 1613 and NGC 3109 in the
Local Group The Local Group is the galaxy group that includes the Milky Way, where Earth is located. It has a total diameter of roughly , and a total mass of the order of . It consists of two collections of galaxies in a " dumbbell" shape; the Milky Way ...
, and
NGC 55 NGC 55, also known as the String of Pearls Galaxy, is a Magellanic type barred spiral galaxy located about 6.5 million light-years away in the constellation Sculptor. It was discovered on 7 July 1826 by Scottish astronomer James Dunlop. Along ...
, NGC 247, NGC 300 and NGC 7793 in the Sculptor Group.


Main discoveries

* The dynamical mass of a classical Cepheid variable star in an eclipsing binary system * RR-Lyrae-type pulsations from a 0.26-solar-mass star in a binary system * An eclipsing-binary distance to the Large Magellanic Cloud accurate to two per cent, to one per cent


References

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External links


Araucaria Project Homepage

Nicolaus Copernicus Astronomical Center Homepage
Astronomy projects