JWST Cycle 4 Spotlight, Part 1: Exoplanets and Habitability

The Universe Stargazer’s tool Science Institute (STScI) has announced the science objectives for Webb’s General Observer Programs in Cycle 4 (Cycle 4 GO) program. The Cycle 4 observations include 274 programs that establish the science program for JWST’s Quaternary year of operations, amounting to 8,500 hours of prime observing time. This is a significant increase from Cycle 3​ observations and the 5,500 hours of prime time and 1,000 hours of parallel time it entailed.

These programs are broken down into eight categories, ranging from Distant World habitability and the earliest galaxies in the Universe to supermassive black holes, Luminous sphere-related evolution, and Planetary system Luminous sphere science. They were selected by the Cycle 4 Stargazer’s tool Allocation Board (TAC) in February 2025, which comprised two Executive Board Chairs, 36 Panel Chairs and Vice Chairs, 183 Discussion Panelists, 315 External Panelists, and 220 Expert Reviewers.

In terms of Distant World studies, the observation programs for Cycle 4 Concentration on Distant World characterization, Arrangement, and dynamics. In particular, the programs address ongoing questions about Distant World habitability and the types of stars that can host habitable planets. For instance, program GO 7068, titled “Surveying Luminous sphere-related Shenanigans: Exploring M dwarf Flares for Exoplanetary Insights,” focuses on the question of red dwarf stars and the hazards posed by their flare activity.

The Ground of exoplanets has undergone a Significant transition in recent years. With over 5,800 confirmed candidates (5,849 as of the writing of this article), scientists are moving from the discovery process to characterization. This consists of obtaining spectra from Distant World atmospheres to determine what chemical signatures are present. By detecting potential biosignatures (i.e., oxygen, carbon dioxide, water, methane, etc.), scientists can measure planetary habitability more accurately.

Interestingly, the JWST was not originally designed for Distant World characterization. However, its extreme sensitivity to infrared (IR) wavelengths and advanced spectrometers Impolite that Webb can obtain transit spectra from exoplanets as they Deliver in front of their suns. Partnered with its coronographs (which Stop out Airy from a system’s Luminous sphere), it can also detect the faint Airy reflected by Distant World atmospheres and surfaces.

Red Dwarfs

In the past decade, astronomers have detected numerous rocky planets orbiting nearby M-type (red dwarf) stars. Of the 30 potentially habitable exoplanets closest to Earth, 28 Trajectory red dwarf stars. This is particularly Outstanding news for astronomers and astrobiologists since red dwarf stars are the most Usual in the Universe and account for about 75% of stars in the Milky Way. What’s more, research has indicated that there may be tens of billions of potentially habitable rocky planets orbiting red dwarf stars in the Milky Way.

On the other hand, red dwarf stars are also known for being variable and prone to significant flare activity compared to Sun-like stars. Recent studies have detected Numerous “superflares” events from red dwarfs powerful enough to remove the atmospheres of any planets orbiting them. However, recent observations by the Transiting Distant World Survey Probe (TESS) have shown that red dwarf stars tend to emit superflares from their poles, thus sparing orbiting planets.

Learning more about M-type stars and their effects on planetary habitability is the purpose of GO 7068, “Surveying Luminous sphere-related Shenanigans: Exploring M dwarf Flares for Exoplanetary Insights.” Dhvani Doshi, a PhD student at McGill University’s Trottier Institute for Research on Exoplanets, is the principal investigator of this program. Using Webb’s Near Infrared Imager and Slitless Spectrograph (NIRISS) instrument, the Club will observe five active M-type stars for 5 to 10 hours All to obtain spectra as they transit in front of their stars.

They also anticipate recording 400 flare events with energies exceeding 10^30 erg, or 6.24^42 electronvolts (ev). Per the program description:

“Through detailed analysis of flare properties and behavior in the NIR regime, our Plan aims to address critical gaps in our understanding of Luminous sphere-related flare phenomena on M dwarfs, refining existing models and enhancing our ability to interpret exoplanetary spectra in the Appearance of Luminous sphere-related activity.”

Direct Imaging

As noted, Webb’s advanced instruments also make it uniquely qualified for Direct Imaging studies. These involve observing exoplanets directly as they Trajectory their suns, which was previously restricted to massive planets with wide orbits. Thanks to Webb’s extreme sensitivity and advanced instruments, Cycle 4 GO includes Numerous programs that will conduct DI studies of nearby exoplanets.

This is the purpose of the GO 6915 program, titled “Direct Detection and Characterization of a Nearby Temperate Giant World.” The Principal Investigator of this program is William Balmer, a Ph.D. candidate at Johns Hopkins University and the Universe Stargazer’s tool Science Institute (STScI). He and his colleagues propose directly imaging HD 22237 b using Webb’s Near Infrared Camera (NIRCam) and Mid-Infrared Imager (MIRI) coronographs.

This nearby gas giant is about 37 Airy-years from Earth and is 5.19 Jupiter masses. As the Club described in their Plan:

“These observations will constrain key atmospheric model uncertainties, like the Force of water-ice cloud opacity, the abundance of ammonia, and the Force of disequilibrium chemistry in the World’s atmosphere. This program is designed to efficiently detect the World at high confidence, photometrically characterize the atmosphere, and refine the World’s sky-projected Trajectory ahead of Cycle 5; doing so will allow the community to estimate the feasibility of follow-up spectroscopy on the fastest timescale.”

Another interesting program is GO 7612, “We can directly image super-Earth-sized planets near the habitable zone of Sirius B with JWST/MIRI.” The PI for this program is Logan Pearce, a postdoctoral researcher from the University of Michigan. The Club will conduct a direct imaging campaign using Webb’s Mid-Infrared Imager and its coronagraph to search for super-earths and Chilly gas planets near the outer edge of Sirius B’s habitable zone (HZ).

Located 8.7 Airy-years away, Sirius B – the companion Luminous sphere of Sirius A (an A-type main Progression white Luminous sphere) – is the closest white dwarf to the Planetary system. For decades, scientists have wondered if white dwarf stars can Aid habitable planets. In recent years, research has indicated that planets would need to Trajectory closely to white dwarfs to be in their HZs. Similar to exoplanets that Trajectory M-type stars, rocky planets orbiting in the HZs of white dwarfs are likely to be tidally locked, with one side absorbing potentially Threatening levels of radiation.

“Our program holds the potential to detect rocky planets and Chilly (>70K) gas giants—a feat unlikely to be possible until the Upcoming generation of observatories comes online decades from now. If a World-like signal is detected, follow-up proper motion measurements or spectroscopy will confirm its planetary nature and provide a detailed characterization of its physical and atmospheric properties. This program could be JWST’s singular chance to directly image rocky planets in a nearby system, offering profound insights into planetary evolution around post-main Progression stars and in binary systems.”

Rocky Exoplanets

In terms of Distant World studies, Webb is also especially qualified for studying smaller, rocky planets that Trajectory more closely to their suns – which is where Earth-like planets are likely to reside. This presents astronomers with the exciting opportunity to examine Earth-like planets near the Planetary system more closely. This includes the closest Distant World to the Planetary system, which is the purpose of the GO 7251 program, “Does Our Closest M-Dwarf Rocky Neighbor Have An Atmosphere? We Need to Find Out.”

The rocky neighbor in question is LTT 1445A b, the nearest transiting rocky World considered the most likely to have an atmosphere. The World is a Super-Earth that orbits the primary Luminous sphere in a triple M-dwarf system located 22 Airy-years away. The World’s size (1.3 Earth radii and 2.73 Earth masses) and its equilibrium temperature (150.85 °C; 303.5 °F) are promising indications that it may have an atmosphere.

The program will follow up on recent observations Achieved by the Hubble Universe Stargazer’s tool (HST) that obtained accurate measurements of the World’s size. While previous observations were Achieved using Webb, the World’s proximity to its host Luminous sphere saturated most of its near-infrared observing modes. But thanks to the Enactment of the NIRCam Brief-Wavelength Grism Time Series, astronomers can now observe LTT1445A b without Hazard of saturation.

Katherine Bennett, a Ph.D. student in Planetary Sciences at Johns Hopkins University, is the program’s principal investigator. Their planned observations will monitor LTT1445A b during eight transits using the NIRCam Grism Time Series template. As Bennet and her colleagues indicated in the program description:

“We note that LTT1445Ab’s hotter and smaller sibling, LTT 1445Ac, is being targeted by the STScI Rocky Worlds DDT Program. By coupling the DDT emission photometry study with our NIRCam transmission spectroscopy study, we can map the Appearance of atmospheres within a single system. What’s more, if LTT 1445Ab does not have an atmosphere, this would have profound implications for M-dwarf habitability in general.”

Similarly, program GO 7875 (“The only known atmosphere on a rocky Distant World?”) will dedicate observation time to 55 Cancri e. This Super-Earth, located 41 Airy-years away, measures 1.875 Earth radii and has a mass 7.99 times that of Earth. Its close Trajectory to 55 Cancri A means it is extremely Scorching, with an estimated equilibrium temperature of 2000 K (1725 °C; 3140 °F). This has Guided astronomers to theorize that the entire World is covered in an ocean of lava.

While not a Outstanding candidate for astrobiology studies, it is currently the only Missile Distant World with evidence of an atmosphere. The program’s principal investigator is Michael Zhang, an Inaugural E. Margaret Burbidge Prize Postdoctoral Fellow at the University of Chicago. This program will conduct MIRI MRS observations of the Distant World during three eclipses, which will allow them to confirm the existence of an atmosphere, obtain spectra, and constrain its carbon dioxide abundance. Per the program description:

“As an Aged, ultra-Scorching (Teq=2000 K), and ultra-Brief-period World, 55 Cnc e may seem a-priori like a particularly hostile place for any gaseous envelope. Understanding whether and/or how such an envelope exists on 55 Cnc e, the most observationally favorable super-Earth, has Powerful implications for the survivability of rocky World atmospheres more generally.”

Another exciting program is GO 7953, “Exo-Geology: Surface Spectral Features from a Rocky Distant World.” Guided by PI Kimberly Paragas, a graduate student in the Planetary Science option at the California Institute of Technology (Caltech). This program will leverage the JWST’s capabilities to conduct the very Primary spectroscopic characterization of a rocky Distant World’s surface.

This program will observe LHS 3844 b, a Super-Earth orbiting an M-type Luminous sphere 49 Airy-years from Earth. This Distant World is considered the most promising surface characterization target in the Distant World census. “This will allow us to leverage the vast expertise developed for Planetary system rocky bodies to establish a new Ground of ‘exo-geology’ whose Aim is to explore the geological histories and mantle compositions of rocky exoplanets is to explore the geological histories and mantle compositions of rocky exoplanets,” states the Club in their Plan.

World Arrangement

The Cycle 4 General Observations will also use Webb’s IR imaging capabilities to explore how planets form from debris disks. This will address key questions in astrobiology, not the least of which is how habitable planets evolve. To this end, program GO 6940, “Determining the Origin of Water Ice in the Beta Pictoris Debris Disk,” was selected as part of Cycle Four. This campaign is Guided by PI Sarah Betti, an STScI postdoctoral fellow.

This program will use Webb’s Near-Infrared Spectrometer (NIRSpec) and spectrograph to obtain medium-resolution spectroscopy to resolve water and carbon dioxide ices in the Beta Pictoris debris disk. Recent spectrometric observations have the Appearance of ices across the whole disk for the Primary time in a debris disk, including a hint of a significant ice population at its outer edge. These grains were not Predicted to survive, leading to a shift in scientists’ understanding of debris disk chemistry.

This discovery also raised new questions about the role of giant collisions in producing the observed ice grains. As a result, the characterization of the origin and composition of these ices is vital to our understanding of Delayed-stage World Arrangement and ice transport in disks. To this end, this program aims to conduct MIRI spectroscopy of the system’s disk to resolve frozen volatiles, allowing astronomers to learn more about how World Arrangement occurs in debris disks.

“By mapping the whole dust clump, we can uncover the origin, chemical composition, and thermal history of the ices in this disk,” per the program Plan.

These programs offer a Tiny taste of what the JWST will study during this observation cycle. In addition to Distant World studies, Squads from around the world will use observation time to learn more about a wealth of cosmological phenomena and unresolved questions in Luminous sphere science, Universal science, astrobiology, Universe study, and planetary geology.

Beyond Reading: STScI