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Detecting exoplanets is one thing, but imaging them is another thing entirely. Astronomers can detect them by the way they block their star's light and by the way they make their stars wobble, and from that they can infer a lot. But that's not the same as seeing them.

The search for exoplanets—including by the transit method and the radial velocity method—is beset by observational biases, and scientists know that. All methods face limitations. The gold standard for exoplanet detection is probably direct imaging, which is much less susceptible to biases.

When the JWST was being designed, it was given four science themes. One of them is the Birth of Stars and Protoplanetary Systems. "JWST is uniquely primed to solve these mysteries given the combination of its high-resolution observing modes, imaging, spectroscopy, and coronagraphic capabilities, and superb near and mid-IR sensitivity," the Space Telescope Science Institute wrote.

The powerful telescope has lived up to the challenge in many ways. It has used its NIRCam and MIRI coronagraphy to directly image young sub-Jupiter-mass exoplanets and mature gas giant exoplanets. But those modes haven't been able to detect planets like Jupiter and Saturn in our solar system, which are cooler and farther from their star.

New research says that there might be a way the JWST can detect planets like our gas giants.

Titled "" the research is published in The Astrophysical Journal Letters. The lead author is Rachel Bowens-Rubin. Bowens-Rubin is a post-Doctoral researcher in the Department of Astronomy at the University of Michigan.

"NIRCam and MIRI coronagraphy has successfully demonstrated the ability to directly image young sub-Jupiter-mass and mature gas giant exoplanets," the authors write. "However, these modes struggle to reach the sensitivities needed to find the population of cold giant planets that are similar to our own solar system's giant planets (Teff = 60–125 K, a = 5–30 au)."

The authors write that this is the first time they're exploring using JWST's high-contrast MIRI imaging without coronagraphy to image exoplanets. It's based on the JWST's general observing program.

That program focuses on gas giant and ice giant exoplanets orbiting low-mass stars with 0.08—0.45 solar masses. These are red dwarf stars (M dwarfs) within 6 parsecs (19.5 light-years.)

The authors write "we demonstrate that 21 μm MIRI imaging can detect planets with the same temperature, mass, age, and orbital separations as Saturn and Jupiter."

Exoplanet scientists want a method of finding these planets because they're under-represented in the known exoplanet population. Our solar system could be an oddball, but there are hints that cold giants like Jupiter and Saturn exist in other systems.

based on a microlensing survey showed there could be an average of 1.5 low-mass giant planets in every solar system. Radial velocity surveys also indicated that giant planets less massive than Jupiter are more prevalent than giant planets more massive than Jupiter. They may be clustered near the water snowline.

"If these trends hold, low-mass cold giant exoplanets may be among the most common types of exoplanets in the galaxy," the authors write.

The researchers focused on three systems from the JWST's Cool Kids on the Block observing program: Wolf 359, EV Lac, and AD Leo, though NIRCam coronagraphy was unable to complete its observations of AD Leo. The JWST's Mid-Infrared Instrument has four observing modes, and the researchers used its F2100W broadband imaging mode in their work.

"The MIRI F2100W imaging mode was chosen in order to take advantage of JWST's sensitivity at the wavelengths at which cold (80–200 K) planets are expected to be the brightest and clouds do not suppress emission," the researchers explain in their letter.

The researchers also investigated how cloudy exoplanet atmospheres could affect giant planet detection, since clouds can block infrared light. They generated a grid of models with both cloudy and cloud-free atmospheres. "We find that the measured spectra of Jupiter and Saturn are best reproduced by a combination of clear and cloudy atmospheric models," they explain.

MIRI imaging was superior to NIRCam coronagraphy for systems within about 20 parsecs (65 ly). This breakthrough shows that MIRI's standard imaging mode at 21 μm performs better than coronagraphy at detecting cold giants. MIRI's longer wavelengths create a contrast ratio between the planet and the star that is better than in the NIR.

This work shows that the JWST is capable of imaging Jupiter and Saturn analogs. It also shows that future JWST observations, combined with ongoing efforts to improve data-reduction methods, could improve the sensitivity of the MIRI imaging.

"This breakthrough enables a path toward the first direct characterization of cold giant exoplanets that are analogous to the solar system's giant planets," the researchers write. They've demonstrated that the JWST can directly image planets like Jupiter and Saturn, which are likely under-represented in our understanding of the exoplanet population.

Compared to other solar systems and the exoplanet architectures we've observed, our solar system can seem like an oddball. But if MIRI direct imaging can uncover more exo-Jupiters and exo-Saturns, our system will seem more "normal."

"The strategies outlined in this work point the way toward uncovering a potentially substantial population of cold, low-mass giant exoplanets, and future direct imaging of these planets offers a path to placing our own solar system in the broader context of planetary systems throughout the galaxy," the researchers conclude.