Cosmology—the study of the Universe as a whole—requires accurate measurements of the distances to galaxies and other objects billions of light-years away. However, the reliability of those estimates depends on how accurately we know the distance to closer objects, such as the Milky Way’s satellite galaxy known as the Large Magellanic Cloud (LMC). A new study has obtained the most accurate distance to the LMC yet, which in turn leads to better cosmological measurements. The key to the new distance measure: binary systems in the LMC consisting of two aging stars in relatively large orbits.

The researchers used data from the Optical Gravitational Lensing Experiment (yes, it’s nicknamed OGLE), which was designed to look for fluctuations in dark matter density by observing stars in the LMC. While OGLE hasn’t succeeded in its primary goal of spotting clumps of dark matter, it has amassed a lot of data from 35 million stars, going back as far as 1992.

From those 35 million stars, the astronomers identified 12 eclipsing binary stars; of those, they analyzed data from eight pairs for a period of eight years. These pairs they chose are rare, consisting of stars in the helium-burning stage, which occurs after they have exhausted their core’s hydrogen fuel. Aging stars of this type have well-known intrinsic brightness in relation to their color. [Read more…]

Aging binaries provide new calibration for cosmic distances