- Taking direct images of exoplanets is difficult, due to their great distances and dimness. Astronomers have only photographed a small number of exoplanets so far.
- NASA’s Webb space telescope has obtained new images of five young, giant planets in the HR 8799 and 51 Eridani planetary systems. They look like bright dots in various colors.
- All the planets have carbon dioxide-rich atmospheres. This suggests they formed in a manner similar to Jupiter and Saturn in our own solar system.
See colorful giant exoplanets in new Webb images
It’s difficult for astronomers to take direct images of planets orbiting distant stars, or exoplanets. Even the largest exoplanets present a challenge because of how much fainter they are than their host stars. Now, NASA’s Webb space telescope has obtained new direct images of not just one but two planetary systems, HR 8799 and 51 Eridani. Between them, Webb imaged five young giant planets, scientists said on March 17, 2025. Webb also confirmed that the atmospheres of all five planets are rich in carbon dioxide.
The researchers published the peer-reviewed details about the new images and other data in The Astrophysical Journal on March 17, 2025.
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5 colorful giant exoplanets in 2 planetary systems
Webb imaged the five planets in two different planetary systems. It used its NIRCam (Near-Infrared Camera) coronagraph, which blocks light from bright stars, to reveal the hidden planets. The planets appear as bright dots in blue, green and red.
The first system, HR 8799, has four known planets and is 130 light-years from Earth. The second system, 51 Eridani, is 97 light-years away and has one young giant planet.
HR 8799 is still young compared to our own solar system, only about 30 million years old. Our solar system, on the other hand, is 4.6 billion years old. This means the planets are still forming and are hot. As a result, they release a lot of infrared radiation, which Webb can analyze.
Rémi Soummer, director of STScI’s Russell B. Makidon Optics Lab and former lead for Webb’s coronagraph instrument, said:
We knew Webb could measure colors of the outer planets in directly imaged systems. 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. Now the results are in and we can do interesting science with it.
The James Webb Space Telescope imaged young, giant exoplanets and detected carbon dioxide! The findings suggest that the giant exoplanets in the HR 8799 system likely formed like Jupiter and Saturn. (1/5) ? ? ?
— spacetelescope.bsky.social (@spacetelescope.bsky.social) 2025-03-17T18:56:22.515Z
Carbon dioxide-rich atmospheres
By using NIRCam and other instruments, Webb analyzed the planets’ atmospheres. It looked for infrared light emitted in wavelengths that are absorbed by specific gases. This can tell the astronomers what the atmospheres are composed of.
Webb found that all five planets have atmospheres rich in carbon dioxide. The atmospheres also contain more heavy elements overall than scientists had previously thought.
How did the planets form?
The results suggest that the planets formed in a manner similar to Jupiter and Saturn in our solar system, in a process called core accretion. They are gradually building solid cores that then attract more gas from the original planet-forming disk, or protoplanetary disk. That disk is the swirling cloud of gas and dust that planets are born in around stars. Lead author William Balmer, at Johns Hopkins University in Baltimore, Maryland, said:
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.
Giant planets can also form through disk instability, when particles of gas rapidly coalesce into massive objects (the young planets) from a cooling disk of material around a new-born star. But in the case of HR 8799 and 51 Eridani, it seems the planets formed through core accretion.
Understanding our own solar system
Knowing more about how other planetary systems form can also help scientists better understand how our own solar system came to be. Balmer said:
Our hope with this kind of research is to understand our own solar system, life and ourselves in the 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 really is, or how normal.
The astronomers are planning additional observations of HR 8799 and 51 Eridani. It’s possible that some of the observed planets might actually be brown dwarfs, but only more observations can confirm that, or not. Brown dwarfs are unusual objects, kind of halfway between the smallest stars and the largest planets. They don’t have enough mass to become fully ignited stars. As co-author Laurent Pueyo, an astronomer at the Space Telescope Science Institute in Baltimore, Maryland, noted:
We have other lines of evidence that hint at these four HR 8799 planets forming using this bottom-up approach. How common is this for planets we can directly image? We don’t know yet, but we’re proposing more Webb observations to answer that question.
Bottom line: NASA’s Webb space telescope has obtained stunning new images of five young and colorful giant exoplanets. All of them have carbon dioxide-rich atmospheres.
Source: JWST-TST High Contrast: Living on the Wedge, or, NIRCam Bar Coronagraphy Reveals CO2 in the HR 8799 and 51 Eri Exoplanets’ Atmospheres
Via Webb Space Telescope
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