Distance to neighbouring galaxy measured

Astronomers use the distance to the Large Magellanic Cloud galaxy as a basis to estimate more remote objects in outer space and the ultimate size of the Universe.

But this technique means that any error in the initial measurement is magnified over longer distances, meaning our estimates of the position of faraway galaxies are very uncertain.


Now researchers have made a much more accurate measurement of the space between Earth and the LMC – 163,000 light years – using observations of a rare type of “double star”.

By monitoring how the rare pairs of stars, known as eclipsing binaries, orbit one another the astronomers were able to figure out their size and mass.

Combining this information with measurements of their brightness and colour allowed the researchers to determine their distance from Earth to a high degree of accuracy.

They observed eight pairs of binary stars over an eight year period using the Las Campanas Observatory, and the European Southern Observatory’s La Silia site in Chile.

The new measurement also improves our estimates of the distance for bright, pulsating Cepheid variable stars which are used to tell the distance to other galaxies and calculate the expansion of the universe, known as the “Hubble Constant”, a process driven by a mysterious force known as “dark energy”.

Dariusz Graczyk, another author of the paper published in the Naturejournal, said: “We are working to improve our method still further and hope to have a one per cent [accurate] LMC distance in a very few years from now. This has far-reaching consequences not only for cosmology, but for many fields of astrophysics.

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