Gas Giant Planets in Our Galaxy Defy Solar System’s Atmospheric Composition Trend
The study, published in Nature on March 27, is a crucial first step towards obtaining similar measurements for a large sample of exoplanets to search for statistical trends. It also offers valuable insights into...
An international team of astronomers has found that the atmospheric compositions of giant planets in our galaxy do not follow the trend seen in our solar system. Using NASA’s James Webb Space Telescope (JWST), the researchers analyzed the atmosphere of exoplanet HD149026b, a “hot Jupiter” orbiting a star similar to our sun, and discovered its atmosphere is incredibly rich in heavier elements such as carbon and oxygen. This finding contradicts the solar system’s pattern, where the more massive a planet, the lower the percentage of heavy elements in its atmosphere.
The study, published in Nature on March 27, is a crucial first step towards obtaining similar measurements for a large sample of exoplanets to search for statistical trends. It also offers valuable insights into planet formation. “It appears that every giant planet is different, and we’re starting to see those differences thanks to JWST,” said Jonathan Lunine, a co-author of the study.
Jacob Bean, the lead author of the paper, explained that while extrasolar planets show a greater diversity of overall compositions, scientists were previously unaware of the variation in their atmospheric compositions. The research on HD149026b, also known as “Smertrios,” has demonstrated that the atmospheric compositions of giant extrasolar planets do not follow the same trend as those in our solar system.
Smertrios is particularly intriguing due to its super-enriched atmosphere compared to its mass. Although it has a mass similar to Saturn, its atmosphere contains up to 27 times the amount of heavy elements relative to its hydrogen and helium. This metallicity ratio is useful for comparing planets to their home stars or other planets within their system.
The carbon-to-oxygen ratio in Smertrios’ atmosphere is about 0.84, which is higher than that of our solar system. This suggests that the planet-forming disk around the star was rich in carbon-rich solids, and HD149026b acquired large amounts of this material during its formation. However, a high carbon-to-oxygen ratio may mean less water on a planet or in a planetary system, which could be problematic for life as we know it.
Lunine plans to observe five more giant exoplanets using JWST in the coming year. A larger sample size is necessary before astronomers can identify any patterns among giant planets or systems with multiple giant or terrestrial planets. Bean expressed hope that further atmospheric observations of extrasolar planets with JWST would better quantify this diversity and provide constraints on potential complex trends.