Metal-poor stars are more ‘friendly’ to life

2023-04-18 17:00:04

Los planets located in habitable zones around metal poor stars are the best targets for seek life potential outside of Earth, according to the study that researchers from two Max Planck Institutes (Germany) and other international centers publish this week in the journal Nature Communications.

The authors have focused on the metallicity, the abundance of elements heavier than hydrogen and helium in a star. Our Sun, where there are more than 31,000 hydrogen atoms for each iron atom, has served as a reference, considering stars rich in metals to those with more than the Sun, and poor those with less.

Planets located in habitable zones around metal-poor stars are the best targets for searching for potential life beyond Earth.

They have also verified that the amount of metals in a star is related to its emissions of ultraviolet radiation and that this, in turn, in its two modalities (B and C) affects the ozone layer that the planets can generate.

“The key lies in the different distribution of energy in metal-rich and metal-poor stars towards their stellar atmospheres,” explains the lead author, SINC. Anna Shapirofrom the Max Planck Institute for Solar System Research, “and that the thickness of the ozone layer is proportional to the ratio between radiation UV- C (that produces ozoneby photolysis of oxygen) and radiation UV-B (that destroys ozone).

“This relationship decreases with metallicity: it is higher in metal-poor stars than in rich ones”, underlines the researcher. In the former, UV-C radiation predominates, which allows the formation of a dense layer of ozone, protective for life.

However, in those with more metals, although they emit less UV radiation, UV-B prevails, associated with a scarcer and ineffective ozone envelope to support life.

The protection of the planetary atmosphere from harmful ultraviolet stellar radiation depends to a great extent on the metallicity of the host star. / MPS/hormesdesign.de

The researchers have reached these conclusions after modeling the atmospheres of hypothetical planets Earth-like hosted in stars with different metallicities, thus confirming that the worlds located around metal-poor stars are the ones with more UV protectionit has implications in the search for potential life outside our planet.

This finding could be useful for future space missionslike the mission PLATO of the European Space Agency (ESA), which from 2026 will search a vast array of stars in search of signs of habitable exoplanets.

Increasingly difficult scenario for life

Furthermore, the study yields a paradoxical conclusion: as the universe ages, it is likely to become increasingly hostile to life. Metals and other heavy elements form inside stars at the end of their lives of several billion years and, depending on their mass, are released into space in the form of stellar winds or a supernova explosion. They are the building material for the next generation of stars.

The study yields an almost paradoxical conclusion: as the universe ages, it is likely to become increasingly hostile to life.

Therefore, each newly formed star has more metal-rich building material than their predecessors: the stars in the universe are richer in metals with each generation,” says Shapiro.

According to the authors, the probability of star systems producing life also decreases as the universe ages. However, his search outside of Earth is not in vain.

After all, many stars that host exoplanets are similar in age to the Sun, and we know that our star harbors complex and interesting life forms on at least one of its planets.

Rights: Creative Commons.