The HR 8799 planetary system is one of the most intriguing and well-studied exoplanet systems, known for its young age and dynamic planetary orbits. Located 130 light-years away from Earth, it is home to four massive gas giants, making it a prime target for understanding planetary formation.
NASA’s James Webb Space Telescope has provided stunning images of these gas giants, offering new insights into the system’s structure. The observations reveal that the atmospheres of the HR 8799 planets contain significant amounts of carbon dioxide, supporting the theory that they formed in a similar way to Jupiter and Saturn—by gradually building solid cores that attracted gas from the surrounding protoplanetary disk, a process known as core accretion.
These findings also highlight Webb’s ability to analyze exoplanet atmospheres through imaging, complementing its spectroscopic capabilities, which provide further details on their chemical composition.
Lead author William Balmer from Johns Hopkins University explained, “By detecting carbon dioxide, we can infer that these planets’ atmospheres contain significant amounts of heavier elements like carbon, oxygen, and iron. Given the nature of their host star, this strongly suggests the planets formed via core accretion, a key insight for worlds we can directly observe.”
In addition to HR 8799, Balmer’s team also studied the 51 Eridani system, located 97 light-years away, with Webb capturing valuable data about this distant world as well. The exoplanets in HR 8799 vary in distance from their sun, with the closest planet (HR 8799 e) orbiting at a distance between Saturn and Neptune, while the most distant planet (HR 8799 b) orbits at a distance twice as far from its star as Neptune is from our Sun, making it one of the most distant planets directly imaged by Webb.
The results of this study were published in The Astrophysical Journal.
