In a groundbreaking discovery, the James Webb Space Telescope has captured the first direct images of carbon dioxide in a planetary system beyond our own, located 130 light-years away in HR 8799. This finding provides compelling evidence that the giant planets in HR 8799 formed through core accretion, a process similar to the formation of Jupiter and Saturn, according to NASA.
The breakthrough was enabled by Webb's advanced coronagraphs, which selectively block the intense light from bright stars, much like a solar eclipse, to uncover hidden planets. This innovative technology permitted the team to focus on specific infrared wavelengths, unveiling the presence of particular gases and other atmospheric features.
Furthermore, these findings demonstrate Webb's capability to directly analyse the chemical composition of exoplanet atmospheres, moving beyond indirect inferences from starlight measurements.
"By spotting these strong carbon dioxide features, we have shown there is a sizable fraction of heavier elements, like carbon, oxygen, and iron, in these planets' atmospheres. Given what we know about the star they orbit, that likely indicates they formed via core accretion, which is an exciting conclusion for planets that we can directly see," said William Balmer, of Johns Hopkins University in Baltimore.
The HR 8799 system, a mere 30 million years old, is a cosmic youngster compared to our 4.6 billion-year-old solar system. Its planets, still radiating heat from their turbulent formation, emit substantial infrared light, providing scientists with a unique opportunity to study their formation mechanisms and contrast them with those of stars and brown dwarfs.
Giant planets form through two distinct processes: core accretion, where solid cores gradually accumulate gas, as seen in our solar system, or disk instability, where massive objects rapidly collapse from a cooling disk. Determining the prevalence of these formation models can provide scientists with valuable insights to categorize and understand the diverse range of planets discovered in other star systems.
"Our hope with this kind of research is to understand our solar system, life, and ourselves in comparison to other exoplanetary systems, so we can contextualize our existence. We want to take pictures of other solar systems and see how they're similar or different when compared to ours. From there, we can try to get a sense of how weird our solar system is—or how normal," Mr Balmer said.
Only a few exoplanets have been directly imaged due to their faintness compared to their stars. The James Webb Space Telescope's ability to capture direct images at specific wavelengths is paving the way for distinguishing between giant planets and objects like brown dwarfs.
