Researchers from Yale University found that compact systems with several planets are more likely to form around stars with fewer heavy elements than the Sun, which prevents many projects that currently focus on stars with higher metallicities.

The research team examined 700 stars and their surrounding planets. The researchers took in the role of heavy metals any elements heavier than helium, including iron, silicon, magnesium and carbon, that is, the main components of the small stony worlds. They revealed a lot of compact multi-planet systems around stars with low metallicities, from which several conclusions can be drawn.

Firstly, this may indicate that there are many more such systems than previously thought. Until recently, research tools did not have the necessary accuracy for detecting small planets and instead focused on finding giant planets. Now, with the advent of technologies such as the Extreme Precision Spectrometer (EXPRES), developed by a team at Yale University, astronomers can detect small worlds.

Secondly, the new study suggests that a compact structure may be a defining feature of the primary type of planetary systems, which makes them an ideal place to look for life outside the solar system.

Back in 2005, it was found that the higher metallicity of stars increases the likelihood of the formation of huge planets like Jupiter. The discovery provided substantial support for the nuclear expansion model in the formation of gas giants. Understanding the birth and evolution of relatively small planets was not available at that time.

Our surprising result, that compact systems with several small worlds are more likely around stars with low metallicities, offers a new important key to the study of the most common type of planetary systems in our galaxy.

-Songhu Wang

Further, the team plans to investigate the relationship between iron and silicon at the birth of planets, since the current work also shows a high ratio of these elements in stars with less metallicity.

Silicon can be a secret ingredient. So far we see that the ratio of silicon to iron acts as a thermostat in the formation of planets: the higher it is, the more small worlds originate in the star’s orbit.

Professor Debra Fisher

Multi-planet systems are not heavily metallic
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