We report on second-epoch imaging of two candidate planet-hosting white dwarf (WD) stars, WD 2105−82 and WD 1202−232. Both stars showed evidence of resolved, planet-mass candidate companions in observations using the MIRI mid-infrared imager on JWST. WD 2105 also showed evidence of an infrared excess consistent with an unresolved 1.4 M _J companion with an orbital separation of <4 au. Our second epoch observations confirm that the source of the excess shares common proper motion with the star. The excess is almost certainly due to a companion planet or debris disk. However, neither of the two resolved sources with projected separations of >1″ in the first epoch of JWST observations show measurable proper motion and are thus likely faint, unresolved background galaxies. We also search for common proper-motion companions out to hundreds of astronomical unit, but find no evidence of widely separated companions.

Context. With day-side temperatures elevated enough for all atmospheric constituents to be present in gas form, ultra-hot Jupiters offer a unique opportunity to probe the composition of giant planets. Aims. We aim to infer the composition and thermal structure of the day-side atmosphere of the ultra-hot Jupiter WASP-121b from two NIRISS/SOSS secondary eclipses observed as part of a full phase curve. Methods. We extracted the eclipse spectrum of WASP-121b with two independent data reduction pipelines and analysed it using different atmospheric retrieval prescriptions to explore the effects of thermal dissociation, reflected light, and titanium condensation on the inferred atmospheric properties. Results. We find that the observed day-side spectrum of WASP-121b is best fit by atmosphere models possessing a thermal inversion with temperatures reaching over 3000 K, with spectral contributions from H2O, CO, VO, and H−, along with either titanium oxide (TiO) or reflected light. We found the atmosphere of WASP-121b to be metal-enriched (~10× stellar), but comparatively titanium-poor (≲1× stellar), potentially due to partial cold-trapping. The inferred C/O depends on model assumptions, such as whether reflected light is included, ranging from being consistent with stellar, if a geometric albedo of zero is assumed, to being super-stellar for a freely fitted value of Ag = 0.16−0.02+0.02. The volatile-to-refractory ratio was found to be consistent with the stellar value. Conclusions. From the NIRISS eclipse spectrum, we infer that WASP-121b has an atmosphere that is enriched in both volatile and refractory metals, but not in ultra-refractory titanium, suggesting the presence of a night-side cold-trap. Considering H2O dissociation is critical in free retrieval analyses, leading to order-of-magnitude differences in retrieved abundances for WASP-121b if neglected. Simple chemical equilibrium retrievals that assume all species are governed by a single metallicity parameter tend to drastically overpredict the TiO abundance, strongly biasing the inferred atmospheric composition.

The MIRI Excesses Around Degenerates (MEAD) Survey is a Cycle 2 JWST program designed to image nearby white dwarfs with MIRI at 10 and 15 μ m. This survey targeted 56 white dwarfs within 25 pc to search for mid-infrared excesses, flux deficits from collision-induced absorption, and resolved substellar companions. In this paper we present our analysis of WD 0644+025, an unusually massive white dwarf (0.95 M _⊙ ) and the MEAD target exhibiting the most significant mid-infrared excess. The observed JWST MIRI photometry shows a 7.3 σ excess at 15 μ m and a 3.6 σ excess at 10 μ m, which may be associated with either a planetary companion or a circumstellar dust disk. This excess corresponds to a companion mass of 6.8 M _Jup ( T _eff = 261 ±9 K) with orbital distance <11.8 au, although substantially lower masses are possible if we consider a closely orbiting isolated companion. No spatially resolved sources are detected within 200 au, with contrast curve analysis excluding planets more massive than 2 M _Jup beyond ∼12 au. Metal pollution is confirmed in both archival Keck HIRES spectra from 1999 and new observations from 2025, with no evidence suggesting that the accretion rate has substantially changed over the decades. We explore possible dust disk morphologies to describe the observed IR excess and find that traditional debris disks struggle to fit our data. WD 0644+025 thus represents a compelling case study in the growing population of white dwarfs with cold infrared excesses and highlights JWST’s ability to probe planetary system remnants inaccessible to prior infrared observatories.

The MIRI Excesses Around Degenerates Survey is a Cycle 2 James Webb Space Telescope (JWST) survey program designed to image nearby white dwarfs in the mid-IR with the MIRI imaging mode. Only a handful of white dwarfs have previously been observed beyond 8 mu m. This survey gathered observations for 56 white dwarfs within 25 pc at 10 and 15 mu m, probing each white dwarf for unresolved IR excesses, IR flux deficits indicative of collision-induced absorption, or resolved substellar companions. This paper presents observations of our first target, 2MASS J09424023-4637176 (also UCAC4 217-039132), henceforth called MEAD 62. This is a magnetic DA white dwarf with an estimated age of 6.5-2.0+4.0 Gyr. A red candidate companion, MEAD 62 B, about 2 mag fainter than its host white dwarf, is detected at an apparent separation of 1 .'' 95. If confirmed, MEAD 62 B would be a 0.014-0.003+0.002 M circle dot brown dwarf with T eff=343-11+7 K, according to ATMO2020 evolutionary models. Also, at 20.48 +/- 0.01 pc, it would be the third nearest substellar companion to a white dwarf. While the red F1000W - F1500W color of MEAD 62 B is similar to background galaxies, it is also consistent with being an unresolved point source from empirical point-spread function fitting. A false positive analysis yields an expectation number of 0.66 red (F1000W - F1500 >= +0.80 mag) unresolved sources within the same separation (r <= 2 '') for the entire MEAD survey. Thus, this candidate companion is as likely to be an actual companion as a false positive unresolved background galaxy. Follow-up JWST observations to measure common proper motion and sample the spectral energy distribution are warranted to confirm the nature of MEAD 62 B.

From the onset of observations of JWST we have discovered unexpectedly luminous galaxies at redshifts z>10 and as high as z=14. With their discovery, the question immediately followed as to where their progenitors are, since such progenitors should be within reach of existing surveys. However, the discovery of several bright candidates at z>15 may indicate further discrepancies between pre-JWST model predictions and current observations. Progenitors of the bright z∼ 14 galaxies should be visible at redshifts as high as z∼ 20-30, showing in the data as F277W and F356W dropouts. We identify two such candidates in the Bullet Cluster JWST data; however, subsequent NIRSpec follow-up data show spectra that can be well fit with Y dwarf templates with temperatures 272351 and 445525 (using ATMO2020 and Sonora Elf Owl models) and distances of ∼ 150650. The first is one of the lowest-temperature brown dwarfs known, and the lowest-temperature brown dwarf detected spectroscopically outside the solar neighborhood. With additional NIRCam imaging taken ∼ 1 year later, we also detect their proper motions of (49 ± 8) and (24 ± 3), further indicating that at least some F277W and F356W dropouts are sub-stellar cold Milky Way objects such as brown dwarfs.

In just over three years of operation, JWST has observed all seven planets of the TRAPPIST-1 system. The two innermost planets were found to have little to no atmosphere, barring the presence of high-altitude aerosols. Here we present the first JWST transit spectra of the habitable-zone exoplanet TRAPPIST-1 f, which were obtained with NIRISS SOSS over the course of five transits. At least one stellar flare occurred in each visit, but unlike observations of closer-in TRAPPIST-1 planets, no evidence for contamination of the transit spectra from unocculted stellar surface heterogeneities was found. This non-detection does not guarantee the absence of unocculted heterogeneities in all future transit observations of this planet, and it could be explained by the transit chord of TRAPPIST-1 f having properties similar to the average, out-of-transit, visible stellar hemisphere at the time of observation. The transit spectra exhibit slopes ranging from -365 ppm/um down to 15 ppm/um, which we attribute to stellar variability, that is, flares and/or smaller-scale events. The visits least affected by flares rule out H2/He-dominated atmospheres with surface pressures higher than about 20 mbar at 95

We present JWST/NIRSpec IFU spectroscopy of the central 618×618 pc^2 (∼3”×3”) of NGC 4696, the BCG in the Centaurus cluster. Leveraging the ∼0.1” (20.6 pc) pixel size of JWST, we resolve a compact circumnuclear rotating disk (radius of ∼120 pc) traced by Paα and H_2 1-0 S(1) emission, which allows a reassessment of the AGN position based on the kinematic centre of this disk. A central Paα velocity dispersion reaching σ∼449 km s^-1 implies a SMBH mass of ∼10^9 M_⊙, corresponding to a sphere of influence of r_inf∼60 pc, resolved by our observations. Position-velocity diagrams reveal an increase from ∼-200 to ∼600 km s^-1 on scales of ∼150 pc (a gradient of 4.7 km s^-1 pc^-1) and an accretion rate of ∼18 M_⊙ yr^-1 feeding the CND. The Paα emission shows a double-component in the core, with a high-dispersion redshifted component reaching σ∼600 km s^-1. In contrast, MUSE Hα observations covering the ∼10 kpc-scale filamentary structure recover only weak velocity gradients (≲150 km s^-1) within ∼300×300 pc^2 and do not resolve the disk due to larger PSFs and pixel sizes. ALMA CO(2-1) data reveal only compact molecular clumps within a ∼410×410 pc^2 region, with no extended counterpart to the structures traced by Paα and H_2 1-0 S(1). Stellar kinematics show a smooth velocity field and broad dispersion profile, clearly decoupled from both the multiphase gas and the hot ICM probed by XRISM. These results provide a direct, spatially resolved view of gas dynamics within the inner few hundred parsecs, demonstrating the power of JWST/NIRSpec to probe SMBH feeding.

The formation and evolution of giant planets remain incompletely understood, with mounting evidence that many close-in giants may have migrated from their birth locations. The detection of helium escaping the atmosphere of exoplanets has provided a powerful new tracer of atmospheric escape and exoplanetary evolution. Here, using high-precision spectroscopic observations from the James Webb Space Telescope (JWST) Near Infrared Imager and Slitless Spectrograph (NIRISS) in single-object slitless spectroscopy mode (SOSS) mode, we report the detection of substantial helium absorption during the pre-transit phase of WASP-107 b (17 sigma), as well as in the transit and post-transit phases. This unique continuous helium absorption begins approximately 1.5 h before the planet's ingress and reveals the presence of an extended thermosphere. The observations show a maximum transit depth of 2.395 +/- 0.01% near the helium triplet (36 sigma; at the NIRISS-SOSS resolution of similar to 700). Our ellipsoidal model of the planetary thermosphere matches the measured light curve well, suggesting an outflow extending to tens of planetary radii. Furthermore, we confidently detect water absorption (log(10)H(2)O = -2.5 +/- 0.6), superimposed with a short-wavelength slope that we attribute to a prominent signature from unocculted stellar spots (5.2 sigma), rather than a small-particle haze slope. We place an upper limit on the abundance of K (log(10)K < -4.86, or K/H < 75x stellar) at 2 sigma, which is consistent with the O/H supersolar metallicity estimate. Together with the supersolar water abundance and the evidence for vigorous atmospheric escape, these findings suggest that WASP-107 b has undergone inward migration in its recent past, probably accompanied by strong tidal heating that continues to sustain its inflated atmosphere and mass loss. This investigation underscores the transformative potential of JWST for investigating planetary evolution.

Y dwarfs represent the coldest class of brown dwarfs, with effective temperatures below 500 K, and provide unique analogues to cold giant exoplanets. We present a large compilation of uniform nearinfrared photometry from the Hubble Space Telescope for 21 Y-dwarfs across multiple WFC3/IR filters, including the F105W, F125W, and F160W bands. We employed refined Point Spread Function fitting and calibration procedures to reach photometric uncertainties at the 0.02-0.05 mag level for most targets. Combined with precise parallax measurements, our data reveal well-defined Y-dwarf sequences in near-infrared colour-magnitude diagrams, observed with a markedly improved tightness. Known photometric trends emerge with minimal scatter, including the continuous redward progression in F125W-F160W with decreasing temperature, and the blueward trend in F105W-F125W with possible hints of a reversal around 350 K. Comparisons to the ATMO, Sonora Elf Owl, and Lacy & Burrows atmospheric models highlight systematic discrepancies, in particular F105W-F125W and F105W-F160W colours predicted to be too red. Low-metallicity grids provide the best fits to the global Y-dwarf population, although closer inspection across wavelengths shows that these preferences likely reflect compensating effects in missing or incomplete physics rather than true population level abundances. While some atmospheric diversity is expected among Y dwarfs, their tight observational sequences and systematic offsets from model predictions reveal that key physical and chemical processes remain inadequately captured in current grids. Our results underscore the importance of high precision, internally consistent data sets in robustly tracing the Y-dwarf cooling sequence and providing the empirical constraints needed to advance theoretical models at the lowest temperatures.

Attempts to probe the atmospheres of rocky planets around M dwarfs present both promise and peril. While their favorable planet-to-star radius ratios enable searches for even thin secondary atmospheres, their high activity levels and high-energy outputs threaten atmosphere survival. Here we present the 0.6–2.85 μ m transmission spectrum of the 1.1 R _⊕ , ∼ 340 K rocky planet TRAPPIST-1 c obtained over two JWST NIRISS/SOSS transit observations. Each of the two spectra displays 100–500 ppm signatures of stellar contamination. Despite being separated by 367 days, the retrieved spot and facula properties are consistent between the two visits, resulting in nearly identical transmission spectra. Jointly retrieving for stellar contamination and a planetary atmosphere reveals that our spectrum can rule out hydrogen-dominated, ≲300× solar metallicity atmospheres with effective surface pressures down to 10 mbar at the 3 σ level. For high mean molecular weight atmospheres, where O _2 or N _2 is the background gas, our spectrum disfavors partial pressures of more than ∼10 mbar for H _2 O, CO, NH _3 , and CH _4 at the 2 σ level. Similarly, under the assumption of a 100% H _2 O, NH _3 , CO, or CH _4 atmosphere, our spectrum disfavors thick, >1-bar atmospheres at the 2 σ level. These nondetections of spectral features are in line with predictions that even heavier, CO _2 -rich atmospheres would be efficiently lost on TRAPPIST-1 c given the cumulative high-energy irradiation experienced by the planet. Our results further stress the importance of robustly accounting for stellar contamination when analyzing JWST observations of exo-Earths around M dwarfs, as well as the need for high-fidelity stellar models to search for the potential signals of thin secondary atmospheres.

Brown dwarfs lack nuclear fusion and cool with time; the coldest known have an effective temperature below 500 K, and are known as Y dwarfs. We present a James Webb Space Telescope (JWST) photometric data set of Y dwarfs: 23 were imaged in wide-field mode, 20 using NIRCam with the F150W and F480M filters, and three using NIRISS with the F480M filter. We present an F480M versus F150W – F480M color–magnitude diagram for our sample, and other brown dwarfs with F150W and F480M colors synthesized from JWST spectra by S. A. Beiler et al. For one target, WISEA J083011.95+283716.0, its detection in the near-infrared confirms it as one of the reddest Y dwarfs known, with F150W – F480M = 9.62 mag. We provide its updated parallax and proper motion. One of the Beiler et al. Y dwarfs, CWISEP J104756.81+545741.6, is unusually blue, consistent with strong CO absorption seen in its spectrum, which the F480M filter is particularly sensitive to. The strong CO and the kinematics of the object suggest it may be very low mass and young. We update the resolved photometry for the close binary system WISE J033605.05–014350.4 AB, and find that the secondary is almost as cold as WISE 085510.83–071442.5, with T eff ≲ 300 K, however the F150W – F480M color is significantly bluer, possibly suggesting the presence of water clouds. Astrometry is measured at the JWST epoch for the sample which is consistent with parallax and proper motion values reported by J. D. Kirkpatrick et al. and F. Marocco et al.

The detection of helium escaping the atmosphere of exoplanets has revolutionized our understanding of atmospheric escape and exoplanetary evolution. Using high-precision spectroscopic observations from the James Webb Space Telescope (JWST) NIRISS-SOSS mode, we report the detection of significant helium absorption during the pre-transit phase of WASP-107b (17σ), as well as in the transit and post-transit phases. This unique continuous helium absorption begins approximately 1.5 hours before the planet's ingress and reveals the presence of an extended thermosphere. The observations show a maximum transit depth of 2.395%± 0.01% near the helium triplet (36σ; at NIRISS-SOSS resolution ∼ 700). Our ellipsoidal model of the planetary thermosphere matches well the measured light curve suggesting an outflow extending to tens of planetary radii. Furthermore, we confidently detect water absorption (log10 H2O=-2.5 ± 0.6), superimposed with a short-wavelength slope which we attribute to a prominent signature from unocculted stellar spots (5.2σ), rather than a small-particle haze slope. We place an upper limit on the abundance of K (log10 K<-4.86, or K/H< 75× stellar) at 2σ, which is consistent with the O/H super-solar metallicity estimate. This study underscores the transformative potential of JWST for tracing atmospheric and mass-loss processes, while offering a benchmark for future studies targeting helium escape and its implications for planetary evolution.

Zodiacal light – arising from both the thermal emission and scattered sunlight by interplanetary dust – is the dominant component of the sky background in NIRISS Single Object Slitless Spectroscopy (SOSS) observations. The GR700XD grism disperses the zodiacal background across multiple diffraction orders, producing a characteristic two-dimensional, spectral order-dependent background pattern on the detector that reflects the combined contribution of overlapping orders. Observations reveal significant variability in background intensity driven by JWST's sky pointing and seasonal changes, underscoring the need for precise background subtraction during SOSS data reduction. Current methods rely on a generic background template derived during commissioning, scaled to match individual exposures. However, mis-scaled templates can leave behind structured residuals that may compromise the precision of exoplanet transit depth measurements. To improve background modeling, we conducted two calibration programs (PID 4479 and 6658) using the FULL frame readout mode and a 5-row by 2-column mosaic pattern to sample a range of sky positions. These observations enable empirical reconstruction of the sky background and provide detailed insights into its spatial and spectral characteristics. We present a library of empirically derived background templates and evaluate their performance, alongside the current template, by benchmarking against the PID 2113 dataset, which includes contemporaneous background exposures. This work supports aims to enhance background subtraction for SOSS time-series to achieve higher-precision exoplanet spectroscopy with JWST.

Recent transit observations of K2-18 b and TOI-270 d revealed strong molecular absorption signatures, lending credence to the idea that temperate sub-Neptunes (equilibrium temperature Teq = 250-400 K) have upper atmospheres mostly free of aerosols. These observations also indicated higher-than-expected CO2 abundances on both planets, implying bulk compositions with high water mass fractions. However, it remains unclear whether these findings hold true for all temperate sub-Neptunes. Here we present the JWST NIRSpec/PRISM 0.7-5.4-mu m transmission spectrum of a third temperate sub-Neptune, the 2.4 R circle plus planet LP 791-18 c (Teq = 355 K), which is even more favourable for atmospheric characterization thanks to its small M6 host star. Intriguingly, despite the radius, mass and equilibrium temperature of LP 791-18 c being between those of K2-18 b and TOI-270 d, we find a drastically different transmission spectrum. Although we also detect methane on LP 791-18 c, its transit spectrum is dominated by strong haze scattering and there is no discernible CO2 absorption. Overall, we infer a deep metal-enriched atmosphere (246-415 times solar) for LP 791-18 c, with a CO2-to-CH4 ratio smaller than 0.07 (at 2 sigma), indicating less H2O in the deep envelope of LP 791-18 c and implying a relatively dry formation inside the water-ice line. These results show that sub-Neptunes that are near analogues in density and temperature can show drastically different aerosols and envelope chemistry and are intrinsically diverse beyond a simple temperature dependence.

Ultra-hot Jupiters exhibit day-to-night temperature contrasts upwards of 1000 K due to competing effects of strong winds, short radiative timescales, magnetic drag, and H 2 dissociation/recombination. Spectroscopic phase curves provide critical insights into these processes by mapping temperature distributions and constraining the planet’s energy budget across different pressure levels. Here, we present the first NIRISS/SOSS phase curve of an ultra-hot Jupiter, WASP-121 b. The instrument’s bandpass [0.6–2.85 μ m] captures an estimated 50%–83% of the planet’s bolometric flux, depending on orbital phase, allowing for unprecedented constraints on the planet’s global energy budget; previous measurements with HST/WFC3 and JWST/NIRSpec/G395H captured roughly 20% of the planetary flux. Accounting for the unobserved regions of the spectrum, we estimate effective day- and nightside temperatures of T day = 2717 ± 17 K and T night = 156 2 − 19 + 18 K corresponding to a Bond albedo of A B = 0.277 ± 0.016 and a heat recirculation efficiency of ϵ = 0.246 ± 0.014. Matching the phase-dependent effective temperature with energy balance models yields a similar Bond albedo of 0.3 and a mixed layer pressure of 1 bar consistent with photospheric pressures, but unexpectedly slow winds of 0.2 km s −1 , indicative of inefficient heat redistribution. The shorter optical wavelengths of the NIRISS/SOSS Order 2 yield a geometric albedo of A g = 0.09 3 − 0.027 + 0.029 (3 σ upper limit of 0.175), reinforcing the unexplained trend of hot Jupiters exhibiting larger Bond than geometric albedos. We also detect near-zero phase curve offsets for wavelengths above 1.5 μ m, consistent with inefficient heat transport, while shorter wavelengths potentially sensitive to reflected light show eastward offsets.

Highly irradiated gas giant exoplanets are predicted to show circulation patterns dominated by day-to-night heat transport and a spatial distribution of clouds that is driven by advection and local heating. Hot Jupiters have been extensively studied from broadband phase-curve observations at infrared and optical wavelengths, but spectroscopic observations in the reflected light are rare and the regime of smaller and higher-metallicity ultrahot planets, such as hot Neptunes, remains largely unexplored. Here we present the phase-resolved reflected light and thermal emission spectroscopy of the ultrahot Neptune LTT 9779 b, obtained through observing its full phase curve from 0.6 mu m to 2.8 mu m with the NIRISS/SOSS instrument onboard the JWST. We detect an asymmetric dayside in reflected light (3.1 sigma significance) with highly reflective white clouds on the western dayside (albedo A = 0.79 +/- 0.15) and a much lower-albedo eastern dayside (A = 0.41 +/- 0.10), resulting in an overall dayside albedo of A = 0.50 +/- 0.07. The thermal phase curve is symmetric about the substellar point, with a dayside effective temperature of T-eff,T-day=2,260(-50)(+40)K and a cold nightside (T-eff,T-night < 1,330 K at 3 sigma confidence), indicative of short radiative timescales. We propose an atmospheric circulation and cloud distribution regime in which heat is transported eastwards from the dayside towards the cold nightside by an equatorial jet, leading to a colder western dayside where temperatures are sufficiently low for the condensation of silicate clouds.

In the era of exoplanet studies with JWST, the transiting, hot gas giant WASP-52 b provides an excellent target for atmospheric characterization through transit spectroscopy. WASP-52 b orbits an active K-type dwarf recognized for its surface heterogeneities, such as star-spots and faculae, which offers challenges to atmospheric characterization via transmission spectroscopy. Previous transit observations have detected active regions on WASP-52 through crossing events in transit light-curves and via the spectral imprint of unocculted magnetic regions on transmission spectra. Here, we present the first JWST observations of WASP-52 b. Our JWST NIRISS/SOSS transit observation, obtained through the GTO 1201 Program, detects two clear spot-crossing events that deform the 0.6-2.8 mu m transit light-curves of WASP-52 b. We find that these two occulted spots combined cover about 2.4 % of the stellar surface and have temperatures about 400-500 K colder than the stellar photosphere. Our NIRISS/SOSS transmission spectrum is best-fit by an atmosphere with H2O (10.8 sigma), He (7.3 sigma, with evidence of an escaping tail at similar to 2.9 sigma), hints of K (2.5 sigma), and unocculted star-spots and faculae (3.6 sigma). The retrieved H2O abundance (log H2O approximate to-4 +/- 1) is consistent with a subsolar or solar atmospheric metallicity for two independent data reductions. Our results underscore the importance of simultaneously modelling planetary atmospheres and unocculted stellar heterogeneities when interpreting transmission spectra of planets orbiting active stars and demonstrate the necessity of considering different stellar contamination models that account for both cold and hot active regions.

White dwarfs with metal pollution are caused by the accretion of rocky dust from tidally disrupted minor bodies and are signposts for planetary systems. These minor bodies are perturbed by planets that have survived post-main-sequence evolution. Open questions exist as to the typical mass of the perturbers and the specific planetary architectures that cause metal pollution. JWST’s sensitivity in the mid-IR has opened new doors to deciphering polluted white dwarfs. We present JWST Cycle 1 mid-infrared instrument imaging of four nearby metal-polluted white dwarfs with the goal of detecting and characterizing planetary companions. With deep mid-IR imaging we are sensitive to cold Jupiter-mass planet analogs. In addition to finding two candidate planetary companions, for the first time we detect significant excesses above the expected photospheric emission at 21 μ m for two of our targets, WD 2149+021 and WD 2105−820. WD 2105−820 has a candidate planetary companion at a projected separation of 34 au and an IR excess—if both candidates are confirmed, it would represent the first WD multiplanet system. We investigate whether these excesses could be caused by very low luminosity warm dust disks or planets. While both are likely, we argue that the most likely explanation for the excesses is that they are the thermal emission from Jovian-mass planets in orbits with semimajor axes <10 au, using a combination of observational constraints. If most of the candidate planets presented here are confirmed, it would suggest that metal-polluted white dwarfs are frequently orbited by at least one giant planet.

Atmospheric escape of close-in exoplanets, driven by stellar irradiation, influences their evolution, composition, and atmospheric dynamics. The near-infrared metastable helium triplet (10833 Å) has become a key probe of this process, enabling mass loss rate measurements for dozens of exoplanets. Only a few studies, however, have detected absorption beyond transit, supporting the presence of hydrodynamic outflows. None have yet precisely identified the physical extent of the out-of-transit signal, either due to non-continuous or short-duration observations. This strongly limits our ability to measure accurate mass-loss rates and to understand how the stellar environment shapes outflows. Here we present the continuous, full-orbit helium phase-curve observation of an exoplanet: the ultra-hot Jupiter WASP-121 b, obtained with the James Webb Space Telescope (JWST) and the Near Infrared Imager and Slitless Spectrograph (NIRISS). We detect significant helium absorption at > 3σ over nearly 60