Chemical makeup of planet hosting red dwarfs reveals insights into their planetary systems

Analysis of 42 red dwarf stars reveals new details about their chemical compositions and the potential structures of the planets orbiting them. By measuring elements like magnesium, silicon, and iron, the study identifies specific stars belonging to the thick disk of the Milky Way and estimates that planets around these stars likely possess core-mass fractions ranging from 20 to 40 percent.

Star system: Gliese 1252 | Distance from the Sun: 66.5 light years

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Chemical makeup of planet hosting red dwarfs reveals insights into their planetary systems

Star system: Gliese 1252 | Distance from the Sun: 66.5 light years

Red dwarfs are the most common stars in the Milky Way, yet their complex light patterns make them difficult to study. Their atmospheres are often dominated by dense molecular absorption, which masks the signatures of individual elements. To bypass this, researchers analyzed infrared light, which provides a clearer view of the stellar composition. By observing 40 planet-hosting red dwarfs and two additional stars in binary systems, the team successfully measured the levels of oxygen, magnesium, silicon, and iron within these stars.

To determine these chemical abundances, the team compared the observed infrared light spectra against synthetic models of stellar atmospheres. They measured temperatures using water and hydroxyl molecules and calculated iron content using specific iron and iron-hydride markers. This data allows for a better understanding of how these stars formed and evolved. By combining this chemical information with measurements of how the stars move through the galaxy, the team identified Gliese 1252 and L181-1 as likely members of the Milky Way's thick disk, an older population of stars located in the galaxy's central plane.

The findings also have implications for the planets orbiting these stars. By calculating the ratios of silicon, magnesium, and iron, researchers estimated the internal composition of the orbiting planets. These calculations suggest that the rocky cores of these exoplanets account for 20 to 40 percent of their total mass. This data provides a foundational step in linking the chemistry of host stars to the physical characteristics of the small planets they frequently host.

Key findings
Gliese 1252 and L181-1 were identified as members of the thick disk stellar population.
Kepler 42 is likely a member of the thick disk based on its velocity and low iron content.
Planets orbiting the surveyed red dwarfs are estimated to have core-mass fractions between 20 and 40 percent.
Infrared spectroscopy provides a reliable way to measure chemical abundances in red dwarfs.

Scientific study

The Composition of M-dwarf Exoplanet Hosts: Atmospheric Parameters and O, Mg, Si, and Fe Abundances from IR Spectroscopy