Top 10 Exoplanets the James Webb Space Telescope Is Targeting

#1: TRAPPIST-1e (39 light-years, radius ~5,777 miles)

TRAPPIST-1e is one of seven Earth-sized planets orbiting the ultra-cool red dwarf star TRAPPIST-1, located about 39 light-years away in the constellation Aquarius. What makes TRAPPIST-1e stand out—and why JWST has devoted significant time to observing it—is its location in the star’s habitable zone, where temperatures could allow liquid water to exist on the surface. This planet is slightly smaller than Earth, with a radius of approximately 5,777 miles, and has a rocky composition, making it one of the most Earth-like exoplanets discovered so far. Interestingly, TRAPPIST-1e is tidally locked, meaning one side always faces its star while the other remains in perpetual darkness. Despite this odd configuration, climate models suggest that an atmosphere with even a modest amount of greenhouse gases could distribute heat and make parts of the surface habitable. JWST has targeted TRAPPIST-1e with its Near Infrared Spectrograph (NIRSpec) to search for carbon dioxide, methane, and other molecules that might indicate the presence of a stable atmosphere. Scientists are especially interested in whether the planet shows signs of volcanic outgassing or if it’s been stripped bare by its star’s high levels of radiation. Early JWST data have revealed tantalizing signs that TRAPPIST-1e may possess a compact atmosphere different from Earth’s but not inconsistent with potential habitability. Hidden beneath the excitement is the fact that this system was originally studied using a 24-inch ground-based telescope in Chile. The discovery of not just one but seven planets around this tiny star was a turning point in exoplanet research, and TRAPPIST-1e quickly became the poster child for habitable exoplanet exploration. Anecdotally, the discovery team was so stunned by the presence of multiple terrestrial worlds that they spent months double-checking the data before going public. With JWST now offering a clearer look than ever before, TRAPPIST-1e remains a top-tier target in the quest to find life beyond Earth.

#2: WASP-39b (700 light-years, radius ~55,800 miles)

WASP-39b, also nicknamed “Bocaprins,” is a bloated gas giant nearly 1.3 times the diameter of Jupiter, yet only about a quarter of its mass. Located approximately 700 light-years away in the constellation Virgo, this exoplanet orbits so close to its sun-like star that a single year on WASP-39b lasts only four Earth days. While it’s far too hot to be habitable—boasting temperatures above 1,650 °F—it has become one of JWST’s primary targets due to its puffy atmosphere, which makes it easier to study. In 2022, JWST made headlines when it detected sulfur dioxide in WASP-39b’s atmosphere, marking the first confirmed photochemical reaction on an exoplanet. This finding was groundbreaking: it showed that ultraviolet light from the host star is actively shaping the planet’s atmosphere, similar to how sunlight drives atmospheric chemistry on Earth. Interestingly, JWST also found evidence of water vapor, carbon monoxide, and sodium—making WASP-39b a chemical playground for atmospheric scientists. This exoplanet essentially functions as a lab for testing the accuracy of planetary climate models. Hidden gem: WASP-39b’s inflated nature isn’t fully understood—scientists still debate whether internal heat, tidal forces, or other mechanisms keep the planet’s atmosphere so puffed up. The planet’s study has deep historical roots in the shift from simple detection to atmospheric analysis, a change that Webb is accelerating. For planetary scientists, WASP-39b is more than a curiosity—it’s a validation of the tools and theories that will eventually be applied to Earth-like worlds.

#3: LHS 475b (41 light-years, radius ~5,490 miles)

LHS 475b is a rocky exoplanet just slightly smaller than Earth and orbits a red dwarf star about 41 light-years away in the constellation Octans. In early 2023, JWST confirmed the existence of this planet, making it one of the first rocky worlds studied by the telescope. Its compact size—just over 5,490 miles in radius—coupled with its proximity and short orbital period (just two Earth days) made it an ideal candidate for atmospheric analysis. One of the most surprising things about LHS 475b is that, despite its closeness to its host star, JWST observations have so far found no obvious atmosphere. This was unexpected, as many astronomers had hoped to detect at least a thin layer of carbon dioxide or water vapor. However, the absence of a detectable atmosphere doesn’t close the book—it might simply mean the planet has an exotic, hard-to-detect atmosphere composed of hydrogen, helium, or other molecules outside JWST’s immediate sensitivity range. Anecdotally, the planet sparked buzz in the scientific community because it demonstrates how JWST can detect even subtle variations in planetary light curves. Historically, this marks a shift toward precision measurements of rocky worlds—something Hubble and Spitzer couldn’t do effectively. LHS 475b might not have the fireworks of gas giants, but its simplicity is scientifically rich. Hidden gem: some models suggest it could have once had a dense atmosphere, now stripped away by its star’s high-energy radiation, making it a relic of early planetary evolution.

#4: GJ 1214b (48 light-years, radius ~16,100 miles)

GJ 1214b is a super-Earth that has puzzled astronomers since its discovery in 2009. About 2.7 times Earth’s radius and 8 times its mass, it lies 48 light-years away in the constellation Ophiuchus. It was one of the first known exoplanets to have a “transiting” orbit, meaning it passes in front of its star from our point of view—perfect for atmospheric study. However, for over a decade, attempts to decode its atmosphere using Hubble and Spitzer were foiled by thick clouds or hazes that obscured its spectral features. Then came JWST. In 2023, JWST’s infrared instruments finally pierced the cloud cover, detecting signs of water vapor and suggesting a steamy, hydrogen-rich atmosphere. One interpretation is that GJ 1214b could be a “water world”—a planet with a global ocean or layers of hot steam and ice. With a temperature of about 530 °F, it’s not Earth-like, but its composition could offer insights into planet formation. Hidden gem: some researchers speculate GJ 1214b could have formed beyond the ice line of its star system and migrated inward, bringing volatile materials with it—offering a glimpse into dynamic planetary evolution. Historically, it’s a symbol of persistence; dozens of failed atmospheric readings finally paid off with Webb’s powerful optics.

#5: K2-18b (124 light-years, radius ~17,200 miles)

K2-18b orbits a red dwarf star in the constellation Leo and is about 2.6 times the size of Earth and roughly 8.6 times as massive. Located 124 light-years away, this planet has intrigued astronomers because it lies in the habitable zone, where temperatures could allow liquid water to exist. In 2019, Hubble hinted at water vapor in its atmosphere, and JWST was called in to settle the debate. In 2023, JWST made a breakthrough by confirming not just water vapor, but also methane and carbon dioxide—suggesting the presence of a possible “Hycean” atmosphere, a term coined for hydrogen-rich worlds that may also have vast oceans. K2-18b’s moderate temperature, estimated at around 270 °F, makes it a compelling target despite its larger-than-Earth size. Anecdotal twist: this planet sparked controversy over the limits of habitability—critics argue that a thick hydrogen envelope could make surface life impossible, while others believe it could offer the right chemistry in a dense ocean. The JWST’s findings rekindled debate over what kinds of planets we should classify as “potentially habitable.” Hidden gem: if confirmed, K2-18b may become the archetype for a new class of planets that don’t resemble Earth, yet could still support life in ways we haven’t yet imagined.

#6: WASP-96b (1,120 light-years, radius ~69,000 miles)

WASP-96b is a massive gas giant nearly 1.2 times the size of Jupiter but far less dense, orbiting a yellow dwarf star about 1,120 light-years away in the Phoenix constellation. This puffy world was among the very first exoplanets observed by JWST during its initial science operations in 2022. What makes WASP-96b remarkable is the clarity of its atmosphere. Unlike many gas giants that have hazes and clouds obscuring observations, WASP-96b has a largely transparent atmosphere, making it ideal for spectroscopy. JWST’s early images showed a detailed water vapor spectrum, and the planet quickly became a benchmark for what infrared observation can accomplish. The atmospheric data also showed sodium signatures, suggesting a rich chemistry. Anecdotally, the excitement around WASP-96b was so high that it was featured in the very first public JWST release, symbolizing a new era in exoplanetary science. Hidden gem: the planet orbits its star every 3.4 days and is heated to around 1,120 °F, making it an excellent model for studying hot-Jupiter dynamics and cloud formation. Its transparency lets astronomers test and refine atmospheric models that can later be used on smaller, Earth-like planets.

#7: TOI-700d (101 light-years, radius ~6,100 miles)

TOI-700d is a potentially habitable Earth-sized exoplanet located 101 light-years away in the constellation Dorado. Discovered by NASA’s TESS mission, it orbits a quiet M-dwarf star and resides squarely in the habitable zone. Its Earth-like radius of about 6,100 miles and 37-day orbit make it an ideal candidate for JWST follow-up studies. Scientists believe TOI-700d could sustain liquid water on its surface, especially if it has an atmosphere. Webb’s infrared instruments are now being used to search for gases like carbon dioxide and methane, which could reveal not just habitability but possibly even signs of life. Anecdotal buzz: TOI-700d is among the rare few Earth-size planets in the habitable zone of a nearby star, and it was discovered by citizen scientists using public data—a reminder that major discoveries sometimes begin with amateur astronomers. Hidden gem: its sibling planets, TOI-700b and TOI-700c, are too close to the star to be habitable, giving researchers a perfect laboratory to compare different planetary climates within the same system.

#8: HD 209458b (159 light-years, radius ~85,700 miles)

HD 209458b, famously nicknamed “Osiris,” was the first exoplanet ever observed transiting its host star, and it remains a key object of study even decades after its discovery. This gas giant, roughly 1.4 times the size of Jupiter and located 159 light-years away in the constellation Pegasus, has been instrumental in helping scientists understand how planetary atmospheres evolve. What makes HD 209458b so iconic is that it was the first planet outside our solar system where an atmosphere was directly detected—Hubble spotted sodium in its skies back in 2002. Now, with JWST’s vastly superior sensitivity, astronomers are revisiting Osiris to dive deeper into its atmospheric makeup. Webb is probing for carbon-based molecules, silicates, and metallic compounds that might hint at high-temperature chemistry. HD 209458b orbits extremely close to its star, completing a full revolution in just 3.5 Earth days and reaching surface temperatures over 2,000 °F. Anecdotally, scientists have found evidence that this planet is literally evaporating—its atmosphere is being blown into space, forming a comet-like tail of hydrogen. The nickname “Osiris” comes from Egyptian mythology, referencing the god who was torn apart—an apt metaphor for this disintegrating giant. Hidden gem: the planet’s mass loss rate may eventually cause it to shrink into a Neptune-like world, making it a rare real-time example of planetary evolution.

#9: HAT-P-18b (531 light-years, radius ~69,600 miles)

HAT-P-18b is a Saturn-sized gas giant orbiting a sun-like star in the constellation Hercules. It lies about 531 light-years away and boasts a radius just over 69,600 miles. Unlike many gas giants that circle their stars in scorching proximity, HAT-P-18b has a longer orbit of 5.5 days and cooler temperatures of around 1,080 °F. This makes it an excellent candidate for studying how cooler atmospheres compare to those of hotter hot Jupiters. What intrigues scientists most is the recent JWST observation of methane in its atmosphere—a key molecule in planetary chemistry that could have broader implications when detected in other environments. While not habitable, HAT-P-18b is a testbed for understanding cloud formation and photochemical reactions at cooler atmospheric thresholds. Anecdotally, it’s often used in astronomy classrooms because its transit light curve is so clean and predictable—making it a textbook example for students learning how to identify exoplanets. Hidden gem: HAT-P-18b is part of a slowly growing class of “intermediate” temperature exoplanets that may serve as stepping stones to understanding the atmospheric dynamics of Earth-like planets.

#10: GJ 367b (31 light-years, radius ~3,700 miles)

GJ 367b is one of the smallest and densest exoplanets ever discovered, with a radius of just 3,700 miles—smaller than Earth’s Moon—and about 55% the mass of Earth. Orbiting an M-dwarf star only 31 light-years away in the constellation Vela, it completes a full orbit in just 7.7 hours, making it an ultra-short-period planet. JWST’s interest in GJ 367b stems from its composition: it appears to be mostly made of iron, similar to Mercury in our solar system. The planet is scorched by its star’s proximity, with temperatures likely exceeding 2,700 °F, meaning its surface could be molten. Yet this searing heat provides an opportunity—JWST is trying to determine whether GJ 367b has any remnant atmosphere or if it’s a completely stripped, bare core. Hidden gem: scientists believe GJ 367b might be the remnant of a once-larger planet whose outer layers were blasted away by stellar flares or catastrophic collisions. Anecdotally, its discovery was a surprise to many astronomers, who didn’t expect such a small world to be detectable with existing tools before JWST. Now that it’s in Webb’s sights, it may offer answers about how planetary systems strip, sculpt, and reshape their inner worlds.

Eyes on Other Worlds: A New Chapter in Exoplanet Exploration

The James Webb Space Telescope is more than just a powerful tool—it’s a time machine, a chemistry lab, and a planetary detective rolled into one. By targeting exoplanets of all shapes, sizes, and distances, JWST is not only enriching our understanding of the cosmos but also reshaping the fundamental question of whether we are alone in the universe. From the steamy skies of WASP-39b to the potentially ocean-covered surface of K2-18b, these ten exoplanets represent a diverse cross-section of the galaxy’s planetary zoo. They offer clues about planetary birth, atmospheric loss, volcanic activity, water chemistry, and maybe—just maybe—the first whispers of alien life. Each world brings a new puzzle piece, and JWST is helping assemble the broader picture of what it means to be a planet orbiting a distant star. As observations continue and data accumulates, our understanding of these distant realms will only deepen, pushing the frontier of discovery beyond what we once thought possible. The universe is speaking—we just needed the right telescope to listen.