A Stellar Magnesium to Silicon ratio in the atmosphere of an exoplanet
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| Main Authors: | , , , , , , , , , , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| author | Sanchez, Jorge A. Smith, Peter C. B. Kanumalla, Krishna Welbanks, Luis Line, Michael R. Pelletier, Stefan Desch, Steven Young, Patrick Patience, Jennifer Bean, Jacob Brogi, Matteo Jaffe, Dan Mace, Gregory N. Mansfield, Megan Weiner Panwar, Vatsal Parmentier, Vivien Pino, Lorenzo Savel, Arjun Baliga van Sluijs, Lennart Wardenier, Joost P. |
| author_facet | Sanchez, Jorge A. Smith, Peter C. B. Kanumalla, Krishna Welbanks, Luis Line, Michael R. Pelletier, Stefan Desch, Steven Young, Patrick Patience, Jennifer Bean, Jacob Brogi, Matteo Jaffe, Dan Mace, Gregory N. Mansfield, Megan Weiner Panwar, Vatsal Parmentier, Vivien Pino, Lorenzo Savel, Arjun Baliga van Sluijs, Lennart Wardenier, Joost P. |
| contents | The elemental compositions of exoplanets encode information about their formation environments and internal structures. While volatile ratios such as carbon-to-oxygen (C/O) are used to trace formation location, the rock-forming elements - magnesium (Mg), silicon (Si), and iron (Fe) - govern interior mineralogy and are commonly assumed to reflect the host star's abundances. Yet this assumption remains largely untested. Ultra-hot Jupiters, gas-giant exoplanets with dayside temperatures above 3000 K, provide rare access to refractory elements that remain gaseous. Here we present high-resolution thermal emission spectroscopy of the exoplanet WASP-189b (Teq = 3354^{+27}_{-34} K) obtained with the Immersion Grating Infrared Spectrometer (IGRINS) on Gemini South. We detect neutral iron (Fe I), magnesium (Mg I), silicon (Si I), water (H_2O), carbon monoxide (CO), and hydroxyl (OH) at signal-to-noise ratios exceeding 4, and retrieve their elemental abundances. We show that the Mg/Si, Fe/Mg, and Si/Fe ratios are consistent with stellar values, while the refractory-to-volatile ratio is enhanced by roughly a factor of ~2. These findings demonstrate that giant-planet atmospheres can preserve stellar-like rock-forming ratios, providing an empirical validation of the stellar-proxy assumption that underpins planetary composition and formation models across exoplanet systems. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2512_10904 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | A Stellar Magnesium to Silicon ratio in the atmosphere of an exoplanet Sanchez, Jorge A. Smith, Peter C. B. Kanumalla, Krishna Welbanks, Luis Line, Michael R. Pelletier, Stefan Desch, Steven Young, Patrick Patience, Jennifer Bean, Jacob Brogi, Matteo Jaffe, Dan Mace, Gregory N. Mansfield, Megan Weiner Panwar, Vatsal Parmentier, Vivien Pino, Lorenzo Savel, Arjun Baliga van Sluijs, Lennart Wardenier, Joost P. Earth and Planetary Astrophysics Solar and Stellar Astrophysics The elemental compositions of exoplanets encode information about their formation environments and internal structures. While volatile ratios such as carbon-to-oxygen (C/O) are used to trace formation location, the rock-forming elements - magnesium (Mg), silicon (Si), and iron (Fe) - govern interior mineralogy and are commonly assumed to reflect the host star's abundances. Yet this assumption remains largely untested. Ultra-hot Jupiters, gas-giant exoplanets with dayside temperatures above 3000 K, provide rare access to refractory elements that remain gaseous. Here we present high-resolution thermal emission spectroscopy of the exoplanet WASP-189b (Teq = 3354^{+27}_{-34} K) obtained with the Immersion Grating Infrared Spectrometer (IGRINS) on Gemini South. We detect neutral iron (Fe I), magnesium (Mg I), silicon (Si I), water (H_2O), carbon monoxide (CO), and hydroxyl (OH) at signal-to-noise ratios exceeding 4, and retrieve their elemental abundances. We show that the Mg/Si, Fe/Mg, and Si/Fe ratios are consistent with stellar values, while the refractory-to-volatile ratio is enhanced by roughly a factor of ~2. These findings demonstrate that giant-planet atmospheres can preserve stellar-like rock-forming ratios, providing an empirical validation of the stellar-proxy assumption that underpins planetary composition and formation models across exoplanet systems. |
| title | A Stellar Magnesium to Silicon ratio in the atmosphere of an exoplanet |
| topic | Earth and Planetary Astrophysics Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2512.10904 |