Astronomers utilizing the Immersion Grating Infrared Spectrometer (IGRINS) at the International Gemini Observatory’s Gemini South Telescope have made groundbreaking discoveries regarding WASP-189b’s atmospheric composition. Their findings indicate that the planet’s elemental composition closely aligns with that of its host star, offering compelling evidence that the planet inherits its chemical makeup from the protoplanetary disk from which it formed.

WASP-189, classified as a 730-million-year-old A-type star, is located 322 light-years away in the constellation Libra.

Also known as HD 133112, this star is significantly larger than our Sun and boasts a temperature exceeding 2,000 degrees Celsius.

First discovered in 2018, WASP-189b is a gas giant that orbits its star at a distance roughly 1.6 times that of Jupiter.

This exotic planet lies about 20 times closer to its star than Earth is to the Sun, completing an orbit in a mere 2.7 days.

According to Arizona State University graduate student Jorge Antonio Sanchez and colleagues, “Superhot Jupiter has temperatures sufficient to vaporize rock-forming elements, such as magnesium, silicon, and iron. This presents a unique opportunity to observe these elements through spectroscopy, a technique that identifies chemicals by analyzing light spectra.”

The astronomers harnessed the IGRINS instrument to capture high-resolution thermal emission spectra of WASP-189b.

They successfully identified neutral iron, magnesium, silicon, water, carbon monoxide, and hydroxyl groups within the exoplanet’s atmosphere.

“The IGRINS data reveals that WASP-189b exhibits a magnesium to silicon ratio identical to that of its host star,” they noted.

This pivotal finding offers the first observational evidence supporting a commonly held hypothesis regarding planetary formation, paving the way for deeper insights into exoplanet creation and evolution.

Gas giants like WASP-189b are believed to possess outer gas layers whose chemical makeup is heavily influenced by the protoplanetary disk from which they originated.

Researchers suspect that the ratio of rock-forming elements in the protoplanetary disk mirrors that of the host star, as they formed from the same primordial matter cloud.

This inferred chemical connection between a star and its surrounding planets is frequently utilized to model the composition of rocky exoplanets.

Previously observed only within our solar system, this link has now been directly documented on distant planets.

“WASP-189b represents a critical observational milestone in understanding terrestrial planet formation, as it allows for measurable quantities to confirm the similarities in stellar composition and the proportion of rocky materials that form alongside planets,” Sanchez stated.

Dr. Michael Rhine, an astronomer at Arizona State University, added, “Our study showcases the capabilities of ground-based, high-resolution spectrometers to analyze key species like magnesium and silicon, two essential elements in rocky planet formation. This advancement opens a new frontier in exoplanet atmospheric studies.”

The findings of this research were published in a paper in the journal Nature Communications on February 18, 2026.

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JA Sanchez et al. 2026. The magnesium to silicon ratio in the exoplanet’s atmosphere. Nat Commune 17, 2902; doi: 10.1038/s41467-026-69610-x