Astronomers have announced that the James Webb Space Telescope has successfully captured its first direct images of carbon dioxide gas on a planet beyond our solar system. The findings are both a testament to the telescope’s power in direct imaging and provide valuable insights into how planets form, both within our solar system and across the universe.
The latest James Webb Space Telescope (JWST) observations focused on the HR 8799 system, which consists of four planets orbiting their host star about 130 light-years from Earth in the constellation Pegasus. Previous observations have shown four of them are more massive than Jupiter, and are in orbits with periods that range from decades to centuries.
This system has long intrigued astronomers studying planet formation, largely because of its youth — at just 30 million years old, these planets still radiate leftover heat from their births, which JWST was able to observe in wavelengths that tease out the specific gases and other atmospheric details.
The newly detected carbon dioxide in one of the planets, HR 8799 e, shows there is a significant amount of heavy metals in the planet’s atmosphere, which aligns with the leading, “bottom up” theory of planet formation: Worlds gradually clump together over millions of years from the disk of gas and dust swirling around a young star, similar to how planets in our own solar system formed.
But recent research offered compelling evidence that planet-forming material around a young star can also collapse rapidly into a massive planet, suggesting there’s more than one way to form a planet and that the process is more complex than astronomers thought. Pinning down which process is more common among planets across the universe can give scientists clues to tease out between the types of exoplanets they discover in distant solar systems.
“Our hope with this kind of research is to understand our own solar system, life, and ourselves in comparison to other exoplanetary systems,” William Balmer, an astronomer at the Johns Hopkins University in Maryland, who led the new research, said in a statement. “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 really is — or how normal.”
JWST’s observations revealed that the HR 8799 planets contain more abundances of heavy elements than previously thought, suggesting they formed in a similar way to our solar system’s gas giants, Jupiter and Saturn.
JWST also detected infrared light emanating from the innermost planet in the system, named HR 8799 e, according to a study published today in The Astrophysical Journal. These findings, which highlight the telescope’s sensitivity in observing faint planets huddled close to their typically bright stars, hold significance because very few exoplanets have been directly imaged — a particularly challenging task because faraway planets are easily outshined by their bright host stars.
“We have been waiting for 10 years to confirm that our finely tuned operations of the telescope would also allow us to access the inner planets,” Rémi Soummer of the Space Telescope Science Institute, who previously led Webb’s coronagraph operations, said in the statement. “Now the results are in, and we can do interesting science with it.”
JWST also imaged 51 Eridani, a star system 97 light-years away. The telescope was able to directly image 51 Eridani b, a cool, young planet that circles its host star at some 11 billion miles (17.7 billion kilometers), a distance roughly equivalent to that at which Neptune and Saturn orbit our sun.
In forthcoming observations, Soummer and his colleagues hope to use Webb’s starlight-blocking coronagraphs to analyze a larger number of giant exoplanets and compare their composition to various theoretical models.
Additionally, the new observations also pave the way for more detailed observations that could determine whether exoplanet candidates are truly giant planets or objects like brown dwarfs, which form like stars do but lack the mass necessary to ignite nuclear fusion. Their nature can play a consequential role in the potential for habitability within the solar systems, Balmer said in the statement.
“If you have these huge planets acting like bowling balls running through your solar system, they can either really disrupt, protect, or do a little bit of both to planets like ours,” he said.
“Understanding more about their formation is a crucial step to understanding the formation, survival and habitability of Earth-like planets in the future.”
A new study of Eridani 51 b and HR 8799 e including these JWST observations was published today in The Astrophysical Journal.
