A team of researchers led by astronomer Ivan Ramirez of the University of Texas at Austin has identified the first Sun “sibling”. This star, identified as HD 162 826, almost certainly formed over 4.5 billion years ago in the same gas cloud in which the Sun formed along with thousands of other stars. The methods used to find it will help discover more of their “siblings” and also to understand in which part of the galaxy they formed.

HD 162826 is about 15% more massive than the Sun and its surface temperature is slightly higher. Because of its distance, it’s invisible to the naked eye but binoculars are enough to see it in the constellation of Hercules and apparently close to the star Vega.

The team that carried out the research examined 30 possible candidates identified by various groups looking for stars siblings of the Sun. They were studied using the Harlan J. Smith Telescope at McDonald Observatory at the University of Texas at Austin and the Clay Magellan Telescope at Las Campanas Observatory in Chile. In particular, high resolution spectroscopic analyzes were carried out to accurately detect the chemical make-up of those stars.

Other factors were considered in this research such as the orbits of the stars and their trajectories around the center of the Milky Way. Putting together all the information, the research focused on the star HD 162826. By a happy coincidence, it had already been extensively investigated at McDonald Observatory so we know that this star has no planets of the “hot Jupiter” kind and probably no gas giants like Jupiter but it’s possible that it has rocky planets like the Earth.

The near certainty that HD 162826 is a Sun sibling comes mainly from the chemical analysis of the two stars, which have a very similar composition. Stars contain traces of elements that are different in the various gas clouds in which they are born. That’ss because these clouds contain the elements produced by previous supernovae, which are different. Ivan Ramirez mentioned elements such as barium and yttrium as particularly useful for this type of analysis.

Finding the Sun siblings can help better understand the early stages of life in our solar system, which have greatly influenced its evolution. According to Ivan Ramirez, the survey that will be carried by the Gaia space probe will also help this kind of research. Stars like HD 162826, which also have a mass similar to the Sun, may have planets hosting life forms. This means that one day we might find our “cousins”.

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