New study measures carbon and oxygen in six K-dwarf stars

Researchers led by David R. Coria have measured carbon and oxygen abundances in six K-dwarf stars that host exoplanets targeted for JWST characterization, in work accepted 11/3/2026 for publication in ApJ, Astrobiology Web reported.

Astrobiology Web reports that K-dwarf stars cooler than 4,700 K have few published chemical abundance measurements. Standard optical techniques fail on these cooler stars, since molecular lines crowd their optical spectra. Astronomers as a result lack the baseline chemistry needed to read observations of exoplanets around these common stars.

The outlet names the six stars as K2-141, NGTS-10, WASP-43, WASP-69, WASP-80, and HATS-72. Each system includes an exoplanet already chosen for JWST characterization, so astronomers need precise stellar chemistry to interpret the planetary data. The host star’s carbon and oxygen content gives astronomers a baseline for reading what the planets are made of and how they formed.

The team derived carbon-to-hydrogen and oxygen-to-hydrogen abundance ratios using MARCS model atmospheres, the TurboSpectrum spectral synthesis code, and near-infrared IGRINS spectra, the outlet reports. Near-infrared H+K band spectroscopy offers a substitute for optical atomic-line techniques when measuring carbon and oxygen in these cool stars. That makes the approach a practical alternative where molecular lines dominate optical spectra, and a more reliable route to stellar abundances.

The team looked at whether carbon-12/carbon-13 and oxygen-16/oxygen-18 ratios could be measured using 13C16O and 12C18O lines from the carbon monoxide bandhead near 2.3 microns, according to Astrobiology Web. They chose the near-infrared lines because optical atomic lines do not suit these cool stars. The spectra proved too noisy for oxygen-16/oxygen-18 measurements, so none resulted for any of the six stars.

Astrobiology Web reports sub-solar carbon-12/carbon-13 ratios for five out of the six targets, a signature the team can compare across the sample and against galactic chemical evolution models. The researchers also derived uniform gyrochronological ages — ages estimated from stellar rotation — for every host star. Using consistent ages across the sample let them hunt for abundance-age trends and place the elemental and isotopic abundances within the wider story of how galactic chemistry changes over time.

Researchers say the catalog backs continued companion observations with a reference to the stars’ chemical makeup, origin, and evolution, according to Astrobiology Web. Those abundances add to the exoplanet observations already under way and give a baseline for tracing how each planet and its star formed together.

The accepted paper runs 32 pages with six figures and five tables, Astrobiology Web reports. The preprint, arXiv:2611.08676, was submitted Nov. 5, 2026 by David R. Coria and nine co-authors, including Neda Hejazi, Ian J. M. Crossfield, and Diana Dragomir.