First standardised way to measure stars

The same way we need values to measure everything from temperature to time, astronomers have now developed a new stellar scale as a "ruler" to help them classify and compare data on star discoveries.

Previously, as with the longitude problem 300 years earlier for fixing locations on earth, there was no unified system of reference for calibrating the heavens.

The astronomers selected 34 initial 'benchmark' stars to represent the different kinds of stellar populations in our galaxy, such as hot stars, cold stars, red giants and dwarfs, as well as stars that cover the different chemical patterns - or "metallicity" in their spectrum, as this is the "cosmic clock" which allows astronomers to read a star's age.

This detailed range of information on the 34 stars form the first value set for measuring the millions of stars that the Gaia satellite, an unmanned space observatory of the European Space Agency, aims to catalogue.

Many of the benchmark stars can be seen with the human eye, and have been studied for most of human history - dating to the very first astronomical records from ancient Babylon.

"We took stars which had been measured a lot so the parameters are very well-known, but needed to be brought to the same scale for the new benchmark - essentially, using the stars we know most about to help measure the stars we know nothing about," said Paula Jofre from Institute of Astronomy at Britain's University of Cambridge.

"This is the first attempt to cover a wide range of stellar classifications, and do everything from the beginning - methodically and homogenously," Jofre added.

The study appeared in the journal Astronomy & Astrophysics.