{"id":"63d9646d-5a7c-42d6-84f9-539ff13e1248","arxiv_id":"2505.15995","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":7.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":5,"one_line_summary":"MIRI F2100W imaging can detect 95-125 K giant exoplanets around nearby M-dwarfs, including Saturn analogs, and beats NIRCam coronagraphy for cloudy cold planets within about 20 pc.","lead":"JWST's simple MIRI camera at 21 microns can see cold planets like Saturn and Jupiter around the very nearest stars, a job once thought to require high-tech coronagraphs. First real telescope measurements show this mode wins for cold, cloudy planets within about 20 light-years, opening a new way to find solar-system analogs.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Figure 6's 70 pc tradespace applies background-limited F2100W sensitivity at all separations, ignoring the measured inner-working-angle degradation; the 'MIRI advantage within 20 pc' claim therefore rests on an unverified extrapolation.","rationale":"The Reader's conditional verdict identifies the same load-bearing weakness: Section 5.2 applies background-limited apparent magnitude limits uniformly across the 70 pc tradespace without folding in the inner working angle. This matters because the paper's headline claim includes orbital separations of 5-30 AU, which at distances of 7-20 pc fall at angular separations of 0.25-1.5 arcsec, precisely where the paper's own MIRI data show degraded sensitivity from the brighter-fatter effect. The concern is concrete and testable: replacing the scalar background limit with the actual separation-dependent contrast curves would determine whether the 'MIRI advantage within 20 pc' conclusion survives. The near-field Wolf 359 result is on firmer ground because 4.8 AU corresponds to about 2.0 arcsec at 2.4 pc, outside the worst residual region. I would keep the verdict at CONDITIONAL rather than moving to ACCEPT or REJECT, because the fix is straightforward and the central observational sensitivity measurement appears credible. A secondary overreach in the abstract's 'same mass, age' phrasing is real but less central than the IWA omission, since the paper's quantitative detectability claims are framed in terms of effective temperature and separation.","tokens_in":19455,"tokens_out":5636,"duration_ms":51318,"concrete_test":"Recompute Figure 6 using the measured, separation-dependent EV Lac contrast curves from Figure 2 instead of a single scalar background-limit magnitude. For each distance d and orbital radius a, compute theta = a/d, read the 3-sigma F2100W and F444W sensitivity limits at that angular separation, and re-derive the cold-planet detectability map. In parallel, inject negative fake companions at 0.3, 0.6, 1.0, and 1.5 arcsec in the real MIRI F2100W images to measure the actual recovery limits at these inner working angles. If the sensitivity inside 1.5 arcsec is more than about 0.5-1 magnitude worse than the background-limited value, the claimed 20 pc MIRI advantage region and the 7 pc Jupiter-temperature boundary will shift or disappear.","verdict_should_be":"UNCHANGED","load_bearing_attack":"Section 5.2 and Figure 6 are constructed from the EV Lac background-limited apparent magnitude limits (F2100W = 15.75, F444W = 20.8) applied as though they were reachable at every projected separation. The measured MIRI F2100W contrast curves in Figure 2 only reach the background-limited regime by roughly 2.5 arcsec, and Section 3.2 explicitly reports unresolved residuals inside <~1.2 arcsec caused by MIRI's brighter-fatter effect. For an M4V star at 20 pc, the 5-30 AU orbital separations highlighted in the abstract subtend only 0.25-1.5 arcsec, which is mostly inside the degraded inner-working-angle region. Consequently, the statements that 'MIRI F2100W provides a detection advantage that is independent of atmospheric conditions for systems within 20 pc' and that a Jupiter-temperature planet can be detected within 7 pc extrapolate a small-separation sensitivity that the presented data do not actually establish. The central Wolf 359 result near 4.8 AU (2.0 arcsec at 2.4 pc) is less affected and remains credible, but the 20 pc tradespace and any 5 AU claims around EV Lac are not protected by the measured curves. This is a limitation of the tradespace construction rather than an internal inconsistency, and it is correctable by folding the separation-dependent contrast curves into Figure 6 or by explicitly labeling the figure as background-limited only.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper presents first performance measurements from JWST GO 6122, comparing NIRCam F444W coronagraphy with MIRI F2100W imaging for Wolf 359 and EV Lac, with the goal of detecting cold giant exoplanets at Teff = 60-125 K and separations of 5-30 AU. The authors reduce real JWST data with standard pipelines, compute contrast curves with small-sample statistics, and convert them into effective-temperature detection limits using custom PICASO/Virga cloudy models anchored to measured Jupiter and Saturn spectra. They find that MIRI F2100W imaging can detect companions as cold as ~94 K around Wolf 359 and ~114 K around EV Lac in all atmospheric cases, whereas NIRCam F444W coronagraphy reaches such temperatures only for clear atmospheres. The paper then extrapolates background-limited apparent magnitude limits to a 70 pc tradespace and claims MIRI imaging is advantageous within ~20 pc.","tokens_in":19827,"tokens_out":7089,"duration_ms":59984,"significance":"If the central Wolf 359 result holds, the paper is significant: it is the first demonstration that MIRI F2100W imaging, rather than coronagraphy, can reach the flux levels of Saturn-temperature planets around the nearest M dwarfs, and it outlines a concrete survey strategy for a population that microlensing suggests is common. The use of real flight data, standard pipelines, small-sample statistics, and empirical Jupiter/Saturn anchors is a genuine strength, and the custom cold-atmosphere models will be useful to the community. The paper also makes falsifiable predictions, such as the detectability of a Saturn-temperature companion around Wolf 359 at ~9.5 AU. However, the quantitative extrapolation in Figure 6 is not protected by the measured contrast curves at small inner working angles, and the abstract overstates the mass and age reach. These issues are correctable and do not invalidate the core observational result.","major_comments":[{"comment":"The 70 pc tradespace is constructed by applying the background-limited apparent magnitude limits for EV Lac (F2100W = 15.75, F444W = 20.8) at every projected separation and distance. The measured MIRI F2100W contrast curves reach the background-limited regime only at roughly 2.5 arcsec, and Section 3.2 explicitly reports unresolved PSF-subtraction residuals inside <~1.2 arcsec due to MIRI's brighter-fatter effect. For an M4V star at 20 pc, the 5-30 AU separations emphasized in the abstract subtend only 0.25-1.5 arcsec, mostly inside the degraded inner-working-angle region. The claims that 'MIRI F2100W provides a detection advantage that is independent of atmospheric conditions for systems within 20 pc' and that a Jupiter-temperature planet is detectable within 7 pc therefore rest on an unverified extrapolation of small-separation sensitivity. The Wolf 359 result near 4.8 AU (2.0 arcsec at 2.4 pc) is less affected, but Figures 5 and 6 should either fold in the separation-dependent contrast curves or be explicitly labeled as background-limited only.","section":"Section 5.2 and Figure 6"},{"comment":"The abstract and title claim detection of planets with 'the same temperature, mass, age, and orbital separation as Saturn and Jupiter,' but the analysis measures flux sensitivity at an assumed radius of 1 R_Jup and effective temperature; it does not present a mass sensitivity calculation or evolutionary tracks. Section 4.3 itself states that for Wolf 359, which is less than one-third the age of the Solar System, the 95 K temperature limit corresponds to 'sub-Saturn masses including masses in the ice-giant regime.' A sub-Saturn-mass, ~1 Gyr old object is not the same mass and age as Saturn. The abstract should be revised to claim temperature and orbital-separation analogs, with mass and age qualified, or a mass sensitivity calculation should be added.","section":"Abstract and Section 4.3"},{"comment":"The quoted Teff limits (94 K for Wolf 359, 114 K for EV Lac) are presented without propagated uncertainties. The conversion from measured contrast to effective temperature depends on the assumed planetary radius, the model grid (fsed, [M/H] = +0.5), and the measured contrast values, none of which enter the figure as error bars or ranges. Because these numbers are the paper's headline quantitative claims, the authors should quantify the sensitivity of the Teff limits to the model assumptions and to the contrast-curve uncertainties, or clearly state that the limits are model-dependent point estimates.","section":"Figure 5 and Section 4.3"}],"minor_comments":[{"comment":"There is a typo, 'effective temperture,' and inconsistent spacing in 'Tef f' throughout the section; please proofread.","section":"Section 4.3"},{"comment":"The figure mixes measured GO 6122 limits with 'approximate' JWST Helpdesk coronagraphic limits and STScI background values; the provenance of each curve should be stated directly in the figure caption.","section":"Figure 3 and Section 4.2"},{"comment":"The reference list has Balmer et al. 2025a and 2025b with the same journal citation (AJ, 169, 209); please verify and distinguish the two entries.","section":"References"},{"comment":"Section 2 reports that the NIRCam observations of AD Leo were not completed, but Section 2.2 lists an AD Leo MIRI exposure time; clarify that the AD Leo MIRI data were used only as reference images.","section":"Section 2"},{"comment":"The phrase 'same age' is inconsistent with Wolf 359's age of 0.1-1.5 Gyr; consider 'comparable to' or specify that the host-star age is younger than the Solar System's.","section":"Abstract and Conclusion"}],"recommendation":"major_revision","confidential_remarks":"The paper is well suited to ApJ Letters if the abstract overclaim and the Figure 6 inner-working-angle extrapolation are fixed. The core observational result for Wolf 359 appears credible and is the main value of the paper; the broader 20 pc tradespace claim is the key risk. If the authors can show that the within-20 pc MIRI advantage survives when separation-dependent sensitivity is included, or if they re-label Figure 6 as background-limited only and soften the claims accordingly, the paper would be accept-worthy. No concerns about novelty or citation patterns."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The core result is credible and useful. The paper uses real GO 6122 data to show MIRI F2100W imaging reaches background-limited contrast around 2.5 arcsec and, because cold-planet flux at 21 microns is nearly insensitive to cloud cover, it can detect a Saturn-temperature (95 K) planet around Wolf 359 at ~2 arcsec in all three atmospheric cases they consider. That is a genuinely new capability demonstration, supported by measured contrast curves, negative fake-companion injection, and public data.\n\nWhat's new: first systematic MIRI F2100W imaging contrast curves for exoplanet work; same-target comparison with NIRCam F444W coronagraphy; and a low-temperature PICASO grid down to 50 K that the community lacks. The cloudy vs clear contrast at F444W versus F2100W is well made and empirically anchored to Jupiter/Saturn SEDs. The data handling is careful and the citation pattern is appropriate.\n\nSoft spots, in order:\n1. The abstract says 'same mass, age' as Saturn/Jupiter. The observation gives temperature and luminosity; mass comes from assumed age and evolution models. The body is more careful and says sub-Saturn masses. That sentence should be tempered.\n2. Figure 6 and the 20 pc/7 pc claims use EV Lac's background-limited apparent magnitude limits as if they apply at every separation. The measured curves don't reach the background limit until ~2.5 arcsec, and inside ~1.2 arcsec the brighter-fatter effect leaves residuals. For a 20 pc M4V, 5-30 AU subtends 0.25-1.5 arcsec; so the 'MIRI advantage within 20 pc' region applies only to planets outside ~50 AU, not the 5-30 AU window the paper highlights. The Wolf 359 result (2 arcsec at 2.4 pc) sits outside the worst residuals and holds; the extrapolated distance claims do not. The figure is labeled background-limited, but the text draws conclusions that ignore that label.\n3. Minor: the model grid has only water clouds, one metallicity, and fixed 1 Rjup; the fractional cloudy/clear fits to F444W are a bit circular as evidence for cloud suppression, though the F2100W sensitivity does not depend on them.\n\nNet: the central near-field result is solid and important. The 70 pc tradespace is an extrapolation that needs either an IWA penalty term or an explicit statement that it is a wide-separation upper limit. Given the real data and the utility for planning JWST programs, this deserves peer review, but with requested revisions.","headline":"Solid real-data sensitivity study: MIRI F2100W imaging genuinely opens a window to cold giants around the nearest M-dwarfs, but the 70 pc tradespace overreaches by ignoring inner-working-angle losses.","tokens_in":20394,"tokens_out":3935,"would_cite":true,"duration_ms":34499,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"JWST MIRI imaging at 21 microns can directly detect giant exoplanets as cold as Saturn (about 95 K) around the nearest M-dwarf stars, in every cloudy and clear atmospheric case considered, and does so where NIRCam coronagraphy is blinded…","keywords":["direct imaging","extrasolar gaseous giant planets","extrasolar ice giants","James Webb Space Telescope","high contrast techniques","MIRI F2100W","cold giant exoplanets","M-dwarf stars"],"falsifier":"A decisive test is an injection-recovery experiment on the actual Wolf 359 MIRI frames: place a model of Saturn's measured spectrum, scaled to 2.41 pc and set at 9.5 AU (about 3.9 arcsec), into the raw frames and run the same PSF-subtraction pipeline; if the synthetic Saturn is not recovered at 3-sigma, the headline detectability claim fails. A second, survey-level falsifier is a complete MIRI F2100W search of every known M-dwarf within 10 pc; if no companion at Saturn-like temperatures brighter than the background limit appears in a statistically complete sample, the combination of the detectability claim and the microlensing occurrence rate is contradicted.","tokens_in":19282,"feed_emoji":"🪐","tokens_out":9655,"duration_ms":74065,"temperature":0.7,"pith_summary":"This paper establishes that plain MIRI imaging at 21 microns — no coronagraphic mask — is the JWST mode best suited to directly detect cold giant exoplanets around the nearest low-mass stars. Using GO 6122 observations of Wolf 359 and EV Lac, it shows MIRI reaches 3-sigma sensitivity to planets as cold as 94 K around Wolf 359 and 114 K around EV Lac, colder than Saturn and Jupiter respectively, for every atmospheric model considered. The reason matters: NIRCam F444W coronagraphy, the usual direct-imaging workhorse, only reaches comparable temperatures if the planet's atmosphere is cloud-free, and cold giants are expected to be cloudy. If the claim holds, a substantial population of Solar-System-like giants that microlensing surveys predict to be common becomes accessible to direct imaging and first-time characterization.","feed_headline":"MIRI imaging finds cold Saturn-like worlds NIRCam misses","feed_subtitle":"At 21 microns, clouds stop hiding cold giants; JWST MIRI outdoes NIRCam for planets under 300 K within 20 pc.","key_machinery":"The load-bearing element is the 21-micron photometric band ($F2100W$ on MIRI). Cold giant planets with $T_{\\rm eff}$ between 60 and 300 K emit most of their thermal radiation near 20 microns, so their $F2100W$ flux changes by less than a factor of about 0.4 between the clearest and cloudiest model atmospheres, whereas the 4.4-micron ($F444W$) flux changes by more than a factor of 10,000. The argument then runs on a measured-detection chain: reference-star differential imaging with principal-component PSF subtraction yields contrast curves; contrast curves are converted into apparent-magnitude limits; and a custom grid of one-dimensional radiative-convective equilibrium atmosphere models — clear, cloudy with $f_{\\rm sed}=8$, and a blackbody 'maximally cloudy' bound — converts those limits into coldest-detectable effective temperatures. The measured spectra of Jupiter and Saturn serve as empirical anchors showing that real cold giants are best represented by cloudy solutions.","core_discovery":"The central discovery is that MIRI F2100W imaging outperforms NIRCam F444W coronagraphy for detecting planets cooler than roughly 300 K in nearby systems, and the gap comes from cloud physics. In the measured contrast curves, MIRI reaches the background-limited regime near 2.5 arcsec at an apparent magnitude limit of about 15.5–16, which converts to a coldest-detectable effective temperature of 94 K for Wolf 359 and 114 K for EV Lac at 3 S/N. These limits hold for clear, moderately cloudy ($f_{\\rm sed}=8$), and maximally cloudy atmospheres alike, because flux at 21 microns is nearly insensitive to clouds. NIRCam F444W matches MIRI only for clear atmospheres; under the $f_{\\rm sed}=8$ cloudy model its limit degrades to 185 K for Wolf 359, and a blackbody-like maximally cloudy planet widens the gap beyond 130 K. Anchoring with the measured SEDs of Jupiter and Saturn, the paper shows that a true Saturn analog at Wolf 359 would be undetectable by NIRCam coronagraphy unless clear, but is straightforwardly within MIRI's reach.","pith_inferences":["The 20-pc boundary is probably optimistic: the 70-pc trade space applies background-limited magnitude limits at every separation, but at 20–70 pc a 5–30 AU orbit is inside roughly an arcsecond, where PSF-subtraction residuals and MIRI's brighter-fatter effect have not been folded in; applying an inner-working-angle penalty would likely move the MIRI advantage to closer systems.","If the brighter-fatter effect is mitigated by matching the detector count of reference stars, the effective inner working angle could approach 0.2 arcsec, extending MIRI searches to 5 AU separations across the full 10-pc sample; this is an extrapolation the paper flags as promising but does not demonstrate.","The model grid condenses only water ice; including ammonia and methane clouds in the coldest atmospheres is the natural next test and could shift the F2100W temperature limits by a modest amount at the coldest end.","A census of all M-dwarfs within 10 pc with about an hour of MIRI F2100W imaging each should yield multiple Saturn/Jupiter analogs if the microlensing occurrence rate of 1–2 low-mass giants per star is correct; a complete null result would pressure either the occurrence rate or the detectability assumptions."],"forward_implications":["Around the nearest systems (within 3 pc), MIRI F2100W imaging can detect planets colder than Saturn, including sub-Saturn and ice-giant masses, at separations beyond about 4.8 AU.","A Jupiter-temperature planet (124 K) is detectable with MIRI imaging out to about 7 pc, and a Saturn-temperature planet (95 K) out to about 3 pc, independent of atmospheric cloudiness.","For M-dwarf hosts within about 20 pc, MIRI F2100W imaging reveals more cold giants than NIRCam F444W coronagraphy; beyond about 61 pc the ordering reverses in favor of NIRCam for hotter planets.","Pairing F2100W and F444W photometry on the same planet yields a first-order atmospheric probe: brightness at 21 microns anchors the temperature while 4.4-micron brightness reports cloud cover or chemistry."],"supporting_citations":[{"why":"Eps Indi Ab, a directly imaged mature giant that is bright at mid-infrared but faint at 4 microns, is the empirical anchor for the MIRI-instead-of-NIRCam argument.","marker":"Matthews et al. 2024"},{"why":"Microlensing occurrence estimate of about 1–2 low-mass giant planets per system that motivates the search population.","marker":"Poleski et al. 2021"},{"why":"Measured Jupiter and Saturn spectra used to anchor the model flux comparison and the detectability conclusion.","marker":"Norwood et al. 2016"},{"why":"Calibration approach for NIRCam coronagraphic contrast curves, including throughput and KLIP-mode corrections.","marker":"Carter et al. 2023"},{"why":"Characterizes MIRI's brighter-fatter effect that sets the inner working angle limit in the MIRI imaging analysis.","marker":"Argyriou et al. 2023"},{"why":"EddySed sedimentation-parameter cloud model used to build the cloudy cold-planet atmosphere grid.","marker":"Ackerman & Marley 2001"},{"why":"PICASO model used to compute pressure–temperature profiles and emission spectra from 50 K upward.","marker":"Mukherjee et al. 2023"},{"why":"The GO 6122 program design and target sample from which the MIRI images and contrast curves are taken.","marker":"Bowens-Rubin et al. 2024"}],"fun_headline_variants":["MIRI imaging spots cold Jupiter analogs NIRCam misses","21-micron imaging finds Saturn-like exoplanets directly","JWST MIRI beats NIRCam for cold giant planets","MIRI captures Saturn twins in nearby systems","Cold giants revealed: MIRI imaging outshines coronagraphy"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The 20-pc MIRI advantage assumes the background-limited sensitivity already holds at the sub-arcsecond separations where 5–30 AU orbits appear around M-dwarfs beyond 20 pc, but the inner working angle and brighter-fatter residuals are not included in that trade space.","fun_headline_variants_meta":{"raw":{"variants":["MIRI imaging spots cold Jupiter analogs NIRCam misses","21-micron imaging finds Saturn-like exoplanets directly","JWST MIRI beats NIRCam for cold giant planets","MIRI captures Saturn twins in nearby systems","Cold giants revealed: MIRI imaging outshines coronagraphy"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000247,"raw_usage":{"total_tokens":1660,"prompt_tokens":1176,"completion_tokens":484,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":792,"completion_tokens_details":{"reasoning_tokens":398}},"tokens_in":792,"tokens_out":484,"duration_ms":4284,"temperature":1.0,"reasoning_tokens":398,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-07T15:09:03.264748+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A decisive test is an injection-recovery experiment on the actual Wolf 359 MIRI frames: place a model of Saturn's measured spectrum, scaled to 2.41 pc and set at 9.5 AU (about 3.9 arcsec), into the raw frames and run the same PSF-subtraction pipeline; if the synthetic Saturn is not recovered at 3-sigma, the headline detectability claim fails. A second, survey-level falsifier is a complete MIRI F2100W search of every known M-dwarf within 10 pc; if no companion at Saturn-like temperatures brighter than the background limit appears in a statistically complete sample, the combination of the detectability claim and the microlensing occurrence rate is contradicted.","supporting_citations":[],"review_version":1}