An article published in the journal “Astronomy & Astrophysics” describes the discovery of a twin star of the Sun. It’s HD 186302, studied by a team of researchers led by Vardan Adibekyan of the Instituto de Astrofísica and Ciências do Espaço (IA), in Portugal, starting from the data collected by the AMBRE project that collected about 230,000 star spectra, along with other data collected by ESA’s Gaia space probe. HD 186302 is really similar to the Sun not only as an age and chemical composition but also in mass and size and this offers hopes that it has planets similar to the Earth.
About 184 light years away from Earth, the star HD 186302 was probably born in the same nursery of the Sun and who knows how many other stars born in the same cluster. In the course of over 4.5 billion years, they moved away so today it’s difficult to reconstruct the history of this cosmic family. AMBRE was defined as a galactic archeology project created from the collaboration between ESO and the Côte d’Azur Observatory to determine the atmospheric parameters of the stellar spectra in the archives of ESO’s FEROS, HARPS, UVES and GIRAFFE spectrographs.
The researchers made a series of selections between 17,000 stars in the AMBRE project archive based on their characteristics, from age to chemical composition. The first selection, also based on the Gaia’s mission Data Release 2, reduced the candidates to 55 and each parameter allowed to shrink the group to get very few stars of which the researchers tried to reconstruct the movements in the course of their lives to see if they formed in the same cluster as the Sun.
In the end, HD 186302 was found to be the star that has the characteristics with the highest compatibility with those of a Sun’s sibling. Other candidates show interesting characteristics but also greater differences with the Sun in terms of atmospheric parameters and chemical composition compared to HD 186302.
In May 2014, the announcement of the identification of the star HD 162826 as Sun’s sibling arrived. HD 186302 is even more similar to the Sun in size and mass so it was defined as its twin. Discovering the Sun’s siblings is important because it offers more information about its birth and the possibility that they have planets, with all the consequences that this entails.
Vardan Adibekyan mentioned the chance that in the period called the Late Heavy Bombardment, about 4 billion years ago, early life forms spread among different solar systems, since at that time they were much closer than today. In essence, not only those stars were born together with the Sun but there’s also the chance that they host some Earth’s sibling life forms.