Brazilian study points out where to look for systems similar to solar – 12/11/2023 – Messenger Sideral

Studying a sample of 192 stars similar to the Sun, a trio of researchers in Brazil managed to establish a strong link between the amount of lithium in the stellar composition and the presence of planets. Apparently, stars with low levels of lithium, like ours, have a greater chance of being surrounded by a planetary system.

The work was carried out by Anne Rathsam, Jorge Meléndez and Gabriela Carvalho Silva, all three from the Institute of Geophysics, Astronomy and Atmospheric Sciences at the University of São Paulo (IAG/USP), and published in the British journal Monthly Notices of the Royal Astronomical Society .

The link between the abundance of lithium and the existence of planets has long been studied by astronomers, but it is not easy to unequivocally establish that it exists. After all, many different things can influence the amount of this metal in the stellar composition, from the age of the star itself (we know that lithium is destroyed within it over time) to the impact of objects that can “pollute” its upper atmosphere. with metal. This is why it is difficult to see the correlation with clarity and mathematical rigor. But apparently this new work has gotten there.

To do this, the trio explored the spectrum (the light signature, which denotes the composition) of 36 stars that are known to have planets, in addition to another 156 without detected planetary companions. Care was taken to only choose stars that were similar in mass, age and abundance of heavy elements in both groups, to avoid any bias that would create a false correlation.

Data collected with the Harps spectrograph, specialized in the study of exoplanets and installed at the ESO (European Southern Observatory) 3.6-meter telescope in La Silla, Chile, revealed that stars without planets have about twice the abundance of lithium than their planet counterparts.

Furthermore: statistical analyzes carried out by researchers indicate that the chance of this correlation being spurious, pure coincidence, is something like 1%. In other words, we now have good reasons to believe that the phenomenon is real – less lithium in the star, more planets around it.

The explanation for this is not yet completely clear, but it is speculated that it occurs because the formation of planets ends up incorporating much of the lithium present in the accretion disk that would give rise to the system in question. This, in turn, reduces the amount that ends up in the star.

The most interesting thing, however, is that the result indirectly helps in the search for exoplanets in stars similar to the Sun. Detecting these stars sometimes requires years of observations, while the chemical composition of stars can be determined much faster. By taking a look at the Sun’s twins scattered throughout the Milky Way, astronomers can focus their searches on those that have less lithium and, therefore, a greater chance of harboring a planetary system similar to ours.

This column is published on Mondays in print, in Folha Corrida.

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