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The USP scientist shows how stars like the Sun will absorb their planets – 2021

Publicado em 30 agosto 2021

Por brazil

In planetary systems made up of stars like the Sun, but which have serious dynamic processes that reconfigure their structure, some planets are “devoured” by the receiving star.

Led by an international astronomical team, Lorenzo Spina, from the Italian Istituto Nazionale di Astrofisica (INAF) in Padua, including Jorge Meléndez, staff at the Institute of Astronomy, Geophysics and Atmosphere of the University of São Paulo (IAG-USP)), more than a hundred b studied the chemical composition of Sun-type stars in order to identify the signatures of the planets eventually “swallowed”. An article about it was published in the journal Nature Astronomy (August 30, 2008).

“In a binary system, two stars are made of the same material, so they must be chemically identical. However, when a planet falls into a star, it dissolves in the outermost region of the star, called the convective zone, and modifies the composition of that region, increasing the” refractory “The content of the chemical elements, which are abundant on the rocky planets. In the stars, whose signature indicates the absorption of the planets, higher amounts of lithium and iron can be observed in connection with its twin companion star,” Meléndez Agência tells FAPESP.

According to the researcher, lithium is destroyed inside the stars, but remains in the material that makes up the planets. Therefore, the abnormally high abundance of this chemical element in a star may indicate that it has swallowed the substance of the planet.

The study was based on observations of 31 binary pairs, i.e. 62 stars, obtained using the HARPS spectrograph in a 3.6-meter telescope at the La Silla Observatory operated by the European Southern Observatory (ESO). The data collected on site were supplemented with previous results already recorded in the literature.

La Silla Observatory is located in the Atacama Desert, in the Chilean Andes, in an extremely dry, lonely countryside, away from light pollution, with one of the darkest night skies on Earth.

“This was the largest sample of similar stars in binary systems ever studied, and the results showed that at least a quarter of solar-type stars” devour “their own planets. The finding suggests that a significant portion of planetary systems were very dynamic — unlike our solar system, which has preserved the orderly architecture, “says Meléndez.

According to study coordinator Lorenzo Spina, “finding planets like Earth is like” looking for a needle in a haystack. “However, this result opens up the possibility of using plenty of chemical elements to identify similar stars. stars incomplete in elements are more likely to receive structures similar to our solar system.

A well-studied binary system is 16 Cygni, which is about 69 light-years from Earth. The system consists of two yellow Sun-like dwarf stars, 16 Cygni A and 16 Cygni B. It may also contain a red dwarf star.

The distance between 16 Cygni A and 16 Cygni B is estimated at 860 AU [sendo UA, a unidade astronômica, definida pela distância entre a Terra e o Sol]. By comparison, the distance between the Sun and the so-called Heliopause, the farthest boundary of the Solar System, is between 110 and 160 AU.

Although the twin stars are separated by a huge distance from each other, the highly eccentric orbit of a planet larger than Jupiter orbiting the 16 Cygni B stars is probably due to the gravitational disturbance caused by the 16 Cygni A stars.

“It’s interesting to note that the Cygni A 16 component, which has no detected planets, is overly abundant in refractory elements, suggesting that perhaps this star has already swallowed the planets,” comments Meléndez.

The research was supported by FAPESP through the thematic project “High Precision Spectroscopy: From the First Stars to the Planets”, coordinated by Meléndez.

Chemical evidence for the ingestion of a quarter of stars similar to the Sun on the planet is available at