A planet 320 light-years away confirms what scientists long suspected
Astronomers have discovered that a scorching-hot planet 320 light-years away shares a striking chemical similarity with its host star, providing the first direct evidence for a fundamental assumption about planet formation. The breakthrough could help scientists predict what distant rocky planets are made of and identify worlds with conditions favorable for life.
Key points
- Astronomers measured magnesium and silicon together in WASP-189b's atmosphere for the first time.
- The planet's magnesium-to-silicon ratio closely matches that of its host star.
- This provides the first direct evidence for a long-assumed star-planet chemical link.
Astronomers have found the first direct evidence for a fundamental assumption about how planets form, using the ultra-hot Jupiter WASP-189b located nearly 320 light-years away in the Libra constellation. An international team led by Jorge Antonio Sanchez, a graduate student at Arizona State University, measured gaseous magnesium and silicon simultaneously in the planet's atmosphere with the Gemini South telescope in Chile.
The observations showed that the proportion of magnesium to silicon on WASP-189b closely matches the ratio in its parent star. This is the first time such a relationship has been directly measured in a planet outside our Solar System, according to the researchers.
A long-suspected connection
Scientists have long assumed that stars and the protoplanetary disks that form planets contain similar proportions of rock-forming elements, because they originate from the same cloud of material. Until now, that assumption was supported mainly by evidence from our own Solar System.
The WASP-189b result provides the missing observational evidence. It strengthens the basis for using stellar chemistry to predict the materials from which distant planets form, including rocky exoplanets.
WASP-189b gives us a much-needed observational anchor in our understanding of terrestrial planet formation since it offers a measurable quantity that validates the presumed resemblance of stellar composition and the proportion of rocky material around host stars used to form planets
— Jorge Antonio Sanchez
Implications for habitability
The chemical relationship is also relevant to astrobiology, which studies the possibility of life beyond Earth. By studying a star's elements, astronomers may estimate how much rock-forming material is available to its planets, influencing internal structure, geological activity, and chemical environment.
Earth illustrates how these elements shape plate tectonics, the protective magnetic field, and the movement of chemicals into the atmosphere and oceans. The team expects future multi-wavelength observations with precise instruments to reveal more elements in exoplanet atmospheres.
