Astronomers have set a record with the James Webb Space Telescope (JWST), capturing direct images of four gas giant planets 130 light-years away in the HR 8799-star system. The four young planets at about 30 million years have been the focus of much attention, but the new images provide unparalleled data, including the detection of carbon dioxide being present in their atmospheres. This discovery brings a positive view into the formation of the planets, that they might have been created in the same way Jupiter and Saturn were created in the neighboring solar system to us.
HR 8799 located in the constellation Pegasus is one of only a few such systems where various exoplanets are visible to be seen directly, and for this reason, it is of extra interest to researchers. The discovery was enabled through the aid of a coronagraph, a specific tool in JWST’s Near-Infrared Camera (NIRCam) that blocks out the star-blinking light so that the telescope may point towards the weak light being emitted by the planets themselves. The scientists were able to capture “the light emitted from the planet itself, instead of the host star’s fingerprint of that light,” lead author William Balmer, an astrophysicist at Johns Hopkins University, said.
The presence of carbon dioxide in the atmospheres of the planets provides key evidence that the exoplanets contain heavier elements like carbon, oxygen, and iron. This is evidence for the standard gas giant formation model known as “core accretion,” where heavy, solid cores form first and afterward sweep up lighter gases, including carbon dioxide, into their atmospheres.
While the finding reinforces the core accretion paradigm, it contributes to the controversy over how the gas giants are formed. The other, yet controversial, speculation is that the gas giants can form through a collapse of a star’s material in its protoplanetary disk. These new observations suggest core accretion as the more likely process for the planet HR 8799, although more work will have to be done to assess how widespread this process is across the universe.
The findings open the door for future studies of planet building and the diversity of gas giants in other star systems. Scientists already are planning follow-up JWST observations to determine how common these formation sequences are.
