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| NASA’s James Webb Space Telescope has captured the clearest infrared images yet of the HR 8799 system, showcasing the intrinsic differences of its planets. HR 8799 e orbits 1.5 billion miles from its star, while HR 8799 b orbits 6.3 billion miles away. The image uses colors applied to Webb’s NIRCam filters—blue for 4.1 microns, green for 4.3 microns, and red for 4.6 microns—to reveal the planets' unique characteristics. The host star’s light is blocked by the coronagraph. |
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| Webb’s NIRCam captured this image of 51 Eridani b, a cool, young exoplanet orbiting 890 million miles from its star, similar to Saturn’s orbit. The 51 Eridani system is located 97 light-years from Earth. The image uses a 4.1-micron light filter, with the red background resulting from light subtraction during processing, not from other planets. |
NASA's James Webb Space Telescope (JWST) has captured groundbreaking images of multiple gas giant planets within the HR 8799 system, located 130 light-years away. This young planetary system, just 30 million years old, has long been a focal point for studying planet formation processes.
The recent observations provide critical insights into the composition of these exoplanets, revealing that the planets in HR 8799 are rich in carbon dioxide. This discovery strengthens the hypothesis that the system’s four gas giants formed similarly to Jupiter and Saturn, through the process of core accretion. This mechanism involves the gradual accumulation of solid cores, which then attract gas from a protoplanetary disk, leading to the formation of gas giants.
“The presence of significant carbon dioxide features in these planets’ atmospheres suggests a sizable fraction of heavier elements, like carbon, oxygen, and iron,” said William Balmer, a researcher at Johns Hopkins University and lead author of the study published today in The Astrophysical Journal. “This finding implies that the HR 8799 planets likely formed through core accretion, providing an exciting glimpse into planet formation that we can directly observe.”
Balmer and their team also analyzed Webb's observations of another system, 51 Eridani, located 97 light-years away. The results underscore Webb’s ability to discern the chemical makeup of exoplanet atmospheres, enhancing our understanding of planet formation in distant star systems.
Revealing the Secrets of Young Planetary Systems.
HR 8799 is a particularly valuable system for scientists, as its planets are still hot from their formation, emitting large amounts of infrared light. This allows researchers to study the early stages of planetary development in detail. The planets' infrared emissions provide essential data on how these giant planets formed, shedding light on the processes that may have shaped our own solar system.
There are two main theories for how giant planets form: core accretion, where solid cores build up and attract gas, and disk instability, where gas rapidly condenses into massive planets directly from the cooling disk around a young star. By confirming that the HR 8799 planets likely formed through core accretion, the findings support the idea that this may be the dominant formation method for giant planets.
“Our goal is to understand our own solar system and life by comparing it to other exoplanetary systems,” Balmer explained. “We want to take pictures of other solar systems, comparing them to ours to see how common or unique our solar system is in the broader universe.”
Webb’s Role in Exoplanet Exploration.
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| This graph shows the spectrum of HR 8799 e, revealing spectral fingerprints of carbon dioxide and carbon monoxide, as captured by Webb’s NIRCam. |
Despite nearly 6,000 exoplanets having been discovered, only a handful have been directly imaged, due to the immense challenge of capturing the faint light emitted by planets that are many thousands of times dimmer than their stars. JWST’s Near-Infrared Camera (NIRCam) coronagraph, which blocks out the light from bright stars, has allowed scientists to directly capture infrared images of the HR 8799 and 51 Eridani systems.
The new images provide unprecedented details on the HR 8799 planets, revealing that they contain more heavy elements than previously believed. This breakthrough could help distinguish between giant planets and brown dwarfs—objects that form like stars but do not accumulate enough mass to start nuclear fusion.
Next Steps in Exoplanet Research.
Laurent Pueyo, an astronomer at the Space Telescope Science Institute, emphasized that these findings are just the beginning. “We have other evidence suggesting that the HR 8799 planets formed through core accretion, but how common is this for planets that we can directly image? We are planning additional Webb observations to answer this crucial question.”
Rémi Soummer, director of the Russell B. Makidon Optics Lab at the Space Telescope Science Institute, echoed this optimism: “For 10 years, we’ve been refining our techniques to capture detailed images of outer planets. Now, we are able to study even the inner planets, revealing new insights about these distant worlds.”
The NIRCam observations of HR 8799 and 51 Eridani were conducted as part of JWST's Guaranteed Time Observations programs 1194 and 1412, respectively, and pave the way for future exoplanet studies that will deepen our understanding of planet formation across the galaxy.
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