{"id":"c04fb7c6-4a5b-4e50-9688-79ca078b9bc2","arxiv_id":"2508.19053","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":7.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":6,"one_line_summary":"Direct imaging of the young star WISPIT 2 reveals a 380-au multi-ringed disk and a co-moving, gap-embedded companion consistent with a 4.9-MJup planet in Keplerian motion.","lead":"Four VLT/SPHERE observing runs of a young, nearby solar-type star reveal a disk with at least four rings and a bright point-like companion inside the widest gap. The companion moves with the star, shows apparent orbital motion, and its brightness matches a young giant planet of about five Jupiter masses, making it the first secure planet found inside a multi-ringed disk.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Planet classification depends on an adopted age at the low end of the group-age range; the mass at older allowed ages is not computed, so the 'unambiguous planet' claim is not yet secured.","rationale":"The paper has strong positive evidence: the companion is detected in multiple independent reductions (RDI, cADI, PCA-ADI, iRDI), it is inconsistent with a stationary background source, and its colors and position in the disk gap are consistent with a young giant planet. The multi-epoch astrometry, especially the large deviation from the stationary-background track, makes the co-moving nature of the source quite secure. The reader's CONDITIONAL verdict is therefore appropriate. However, the step that most directly supports the word 'unambiguous planet' is the mass estimate, and that estimate is anchored to an adopted stellar age of 5.1 Myr. The paper's own appendix shows that the likely parent group has a much wider and older age range, and the SED/isochrone age is model-dependent. The planet-mass uncertainties quoted in Table 4 propagate only photometric and age uncertainties within the nominal 5.1 Myr assumption; they do not include the systematic shift that would result from adopting an allowed older age. Since the deuterium-burning boundary at 13 MJup is the formal planet/brown-dwarf dividing line, and the paper does not show that the mass remains below this boundary for the older group ages, the 'unambiguous planet' claim is not fully closed. A simple grid recomputation at 17, 20, and 35 Myr would settle this directly. If the mass remains below 13 MJup, as I suspect it may, the concern is resolved and the CONDITIONAL verdict can be upgraded; if not, the headline claim must be weakened. I therefore keep the reader's CONDITIONAL verdict unchanged rather than moving to ACCEPT or REJECT on the basis of the present manuscript alone.","tokens_in":35716,"tokens_out":20698,"duration_ms":228746,"concrete_test":"Using the same species/AMES-COND and AMES-DUSTY grids as §5.2, recompute the companion mass from MKs = 11.95 mag and the observed H-Ks color at ages of 17 Myr (upper EAGLES v2.0), 20 Myr (Kerr et al. 2021), and 35 Myr (Hunt & Reffert 2024). If the central mass remains below 13 MJup at all three ages, the planetary classification survives and the concern is refuted. If any age gives a central mass at or above 13 MJup, then the classification is age-dependent, and the 'unambiguous planet' claim should be downgraded to 'substellar companion' pending a dynamical mass or a direct stellar age measurement.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim that WISPIT 2b is a planet, not a brown dwarf, rests on converting MKs = 11.95 mag and the H-Ks color into a mass using AMES-COND/DUSTY at a stellar age of 5.1+2.4/-1.3 Myr (§5.2, Table 4). That age is the low end of the constraints for the likely parent group Theia 53/OCSN 8/TLC-7: EAGLES v2.0 gives 11.1+5.9/-8.1 Myr, and literature group ages range from ~20 to ~35 Myr (Appendix A.2, A.3). The SED/isochrone age is model-dependent (BHAC15/PARSEC/SPOTS span 4.0-6.7 Myr, Table 7), and the SED fit excludes WISE W1-W3 as an excess, so a modest bias in Teff/Lbol or unresolved disk/companion flux would move the age upward. At fixed absolute magnitude, the implied companion mass increases with adopted age. The quoted uncertainties (0.6-0.9 MJup) do not include this age systematic, and the paper itself cautions that the uncertainty may be underestimated and that spectral analysis is needed. If the true age is near 17-20 Myr, the same photometry would imply a higher mass, and the paper provides no calculation showing that it remains below the 13-MJup deuterium-burning boundary. Since the abstract's 'first unambiguous planet detection in a multi-ringed disk' depends on the object being planetary, this missing calculation is the load-bearing step.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper presents VLT/SPHERE observations of the young solar-type star WISPIT 2, resolving a ~380 au scattered-light disk with four rings and a wide gap, and directly detecting a point source (WISPIT 2b) inside that gap. The authors argue that the source is co-moving with the star, that its H and Ks photometry imply a ~4.9 MJup mass at an adopted stellar age of 5.1 Myr, that its astrometry is consistent with a Keplerian orbit in the disk plane, and that the width of the disk gap is consistent with the planet's mass according to gap-opening models. The abstract concludes that WISPIT 2b is the first unambiguous planet detection in a multi-ringed disk and a laboratory for planet-disk interaction.","tokens_in":36068,"tokens_out":5048,"duration_ms":51359,"significance":"If the central claim holds, the paper is a significant step: it would add a rare, directly imaged embedded protoplanet in a multi-ringed disk around a young solar analog, complementing PDS 70 and providing a direct test of gap-opening theory. The observational work is substantial: four SPHERE epochs, careful RDI/PDI/ADI reductions, a multi-epoch background-source rejection, and an independent comparison to hydrodynamical gap-width models. The photometric interpretation is internally consistent, and the authors are appropriately cautious in several places, including flagging that the mass uncertainty may be underestimated and that spectral characterization is needed. The main weakness is that the 'unambiguous planet' and 'Keplerian orbital motion' claims are not yet fully supported by the presented analysis.","major_comments":[{"comment":"The planetary classification rests on converting M_Ks = 11.95 mag and M_H = 12.8 mag into a mass with AMES-COND/DUSTY at an adopted age of 5.1^{+2.4}_{-1.3} Myr. This age sits at the lower end of the EAGLES v2.0 group age (11.1^{+5.9}_{-8.1} Myr) and below the older literature group ages (~20-35 Myr) listed in Appendix A.2. At fixed absolute magnitude, the inferred mass increases with adopted age, and the quoted 0.6-0.9 MJup uncertainties do not include this age systematic. The paper should explicitly compute the companion mass at 11, 17, 20, and 35 Myr and show that it remains below the deuterium-burning limit. Without that calculation, the abstract's 'first unambiguous planet' and §8's 'consistent with a planetary-mass object' are not secured; the authors' own caution that 'the reported uncertainty may be underestimated' supports this concern.","section":"§5.2, Table 4; Appendix A.3"},{"comment":"After excluding the 2024 epoch, the 'orbital motion consistent with Keplerian motion' claim rests on only two epochs (2023-10-19 and 2025-04-26). Two astrometric points cannot demonstrate Keplerian motion; any two points are consistent with some Keplerian orbit. The posterior peak at a~57 au is obtained with inclination/node fixed to the disk orientation and with a post-fit down-selection to a<=70 au. Please (i) include the 2024 epoch in the orbit fit or quantitatively justify its exclusion for the orbit determination, (ii) report the sensitivity of the semi-major axis posterior to the 70 au cut and to the disk-orientation assumptions, and (iii) temper the abstract/conclusion language from 'demonstrate' to 'is compatible with' a Keplerian orbit. The background rejection itself is more robust because it uses all three epochs against the stationary-source track, but that is a separate stat","section":"§5.1, Table 3, Figure 8"},{"comment":"The gap-opening consistency claim is weaker than stated. With alpha spanning 10^-4 to 10^-2, the Kanagawa et al. model gives 0.5-5.3 MJup and the Zhang et al. model gives 4-16 MJup; the photometric 4.9 MJup overlaps only a portion of the combined model range, and the scattered-light gap width is not obviously the same quantity as the gas/dust gap width in the Zhang et al. model. The statement in §8 that the mass is 'consistent with the modeled planet mass required to open such a gap' should be qualified by the strong alpha and model dependence, or the range of allowed masses should be propagated into the comparison.","section":"§6, Eqs. (2)-(3), Figure 10"}],"minor_comments":[{"comment":"The column header 'Mass M_Jup' appears to be a typo; the listed masses (0.93-1.14) are clearly in solar masses. Please correct to M_sun.","section":"Table 7"},{"comment":"The pixel scales are quoted as '12.246 ± 0.009 mas yr^-1' and '12.266 ± 0.009 mas yr^-1'; the units should be mas pixel^-1, not mas yr^-1.","section":"§3.2"},{"comment":"The 2024 H-band astrometry is used in Figure 7 for background rejection but excluded from the orbital fit. The text explains the exclusion, but the abstract and §8 should avoid implying that all three epochs contribute to the 'Keplerian motion' statement. A sentence distinguishing 'background rejection' from 'orbit fit' would prevent confusion.","section":"§5.1, Table 3"},{"comment":"The composite image shifts the 2023 H-band planet position to the 2025 Ks-band position for display. This is stated in the appendix, but the main-text Figure 1 caption should also note that the planet position shown is for 2025-04-26 and that the H-band emission was shifted.","section":"Appendix G"}],"recommendation":"major_revision","confidential_remarks":"The manuscript is a strong direct-imaging discovery paper, but the 'first unambiguous planet in a multi-ringed disk' claim is conditional on the age-dependent mass estimate. The age systematic is not a minor caveat because the adopted 5.1 Myr age is at the low end of the available constraints and the paper does not show that the mass remains below the deuterium-burning limit at the older allowed ages. A revision that adds the requested age-mass calculation, hedges the orbital claims to two epochs, and qualifies the gap-width consistency would make the paper suitable for publication. I would also encourage the editor to ensure that the companion H-alpha letter (Close et al., submitted) is either available for cross-checking or explicitly marked as not used in the present conclusions."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Colleague,\n\nThe headline is that this is a real discovery: the first directly imaged co-moving point source sitting in the gap of a multi-ringed scattered-light disk, and if it holds, the second embedded protoplanet system after PDS 70. That alone makes it worth a serious referee.\n\nWhat the paper does well: the background rejection is solid. Three epochs of SPHERE astrometry are inconsistent with a stationary background object, and the photometry is internally consistent across H and Ks. The gap-width comparison to Kanagawa and Zhang models is independent of the photometric mass estimate, which is a nice check. The appendices show care with the RDI/PCA subtractions and the astrometric calibration. The authors are also honest about the weak spots, which I appreciate.\n\nThe soft spots are in the mass and orbit sections, and they are real. The mass of 4.9 MJup comes from converting H and Ks photometry via AMES isochrones at a stellar age of 5.1 Myr. That age sits at the low end of the group age range for Theia 53/OCSN 8, which EAGLES v2.0 puts at 11.1 Myr with a tail up to ~19 Myr. At those older ages the same photometry would give a higher mass. The paper does not show that the mass stays below 13 MJup—the deuterium-burning boundary—over the allowed age range. The authors even caution that their uncertainty may be underestimated. That is the load-bearing step, and it needs a sensitivity calculation.\n\nThe orbital motion claim rests on two epochs, since the 2024 epoch is excluded as too noisy. That is defensible—the astrometry shows it—but it means the Keplerian orbit is not yet demonstrated. The orbit fit also down-selects to a<70 au to keep the planet in the gap. Mild circularity, but the co-motion detection does not depend on it.\n\nOne more thing: the 'unambiguous' claim leans partly on an H-alpha detection in a companion paper that is submitted, not yet public. The current preprint alone doesn't close that case.\n\nBottom line: the detection of a co-moving source is solid, the planetary interpretation is plausible, and the classification as a sub-13-MJup planet is not yet secured. This is a natural candidate for peer review—send it, but ask for the age-mass curve and a clear statement of what the two-epoch orbit does and does not constrain.","headline":"A genuinely new discovery that deserves referee time, but the planet classification hinges on an age systematic the authors should quantify.","tokens_in":36702,"tokens_out":2412,"would_cite":true,"duration_ms":23779,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"WISPIT 2b is a directly imaged, gap-clearing ~4.9-Jupiter-mass proto-planet co-moving with its young solar-type host star.","keywords":["exoplanet formation","circumstellar disks","direct imaging","polarimetry","protoplanets","planet-disk interaction","multi-ringed disks","scattered light"],"falsifier":"A dynamical mass for WISPIT 2b from high-precision astrometry (for example VLTI/GRAVITY) or radial velocities over several years, combined with a spectroscopic age for the host star: if the mass exceeds the deuterium-burning limit (~13 Jupiter masses) or the orbit is not coplanar with the disk, the planetary and gap-opening interpretations fail.","tokens_in":35552,"feed_emoji":"🪐","tokens_out":9490,"duration_ms":81982,"temperature":0.7,"pith_summary":"The paper sets out to prove that a point source seen inside the widest gap of the multi-ringed disk around the young solar-type star WISPIT 2 is a genuine young planet, not a background star or a disk artifact. Using four epochs of high-contrast near-infrared imaging, it resolves the disk for the first time—out to roughly 380 au, with at least four concentric rings—and shows that the companion, WISPIT 2b, moves with the star and on an orbit consistent with Keplerian motion inside the gap. Its H- and Ks-band brightness, interpreted with young-object evolutionary models, gives a mass of about 4.9 Jupiter masses, and the measured gap width agrees with hydrodynamic predictions for a planet of that mass opening the gap. If correct, this is the first unambiguous planet detected in a multi-ringed disk, making WISPIT 2 a direct laboratory for how embedded planets carve their natal disks and a calibration point for indirect planet detections in other ringed disks.","feed_headline":"First unambiguous planet spotted inside a multi-ringed disk","feed_subtitle":"Near-infrared imaging resolves a 4.9-Jupiter-mass companion moving inside the widest gap of a 380-au disk.","key_machinery":"The argument rides on four coupled pieces: multi-epoch, multi-mode high-contrast imaging that detects the same point source in several independent reductions; astrometry showing the source is neither stationary nor background, with the orbit fitted under a disk-aligned, co-planar assumption; H- and Ks-band photometry placed on a color-magnitude diagram against AMES-COND and AMES-DUSTY, two grids of young-object evolutionary models; and the gap-width-versus-planet-mass scaling relations of Kanagawa et al. (2016) and Zhang et al. (2018) that tie the observed 59-au gap to the inferred mass. The planet WISPIT 2b itself, sitting in the cleanest gap, is the object that binds these pieces together.","core_discovery":"The central claim is that WISPIT 2b is a directly imaged young proto-planet embedded in the widest gap of the disk and co-moving with its host star. The companion is recovered in multiple independent reductions—RDI in H-band and cADI, PCA-ADI, and iRDI in Ks-band—and its positions are inconsistent with a stationary background object. The two cleanest epochs yield an orbital fit with a most probable semi-major axis of about 57 au, placing the planet inside the gap. H- and Ks-band photometry matches a 4.9+0.9/-0.6 Jupiter-mass object on the AMES-COND and AMES-DUSTY young-object tracks at the adopted stellar age of 5.1 Myr. The paper further argues that this mass is consistent with the observed","pith_inferences":["If the host-star age is pinned down spectroscopically and the companion's dynamical mass is measured, WISPIT 2b would provide a rare test of whether young-object evolutionary tracks over- or under-predict masses near the deuterium-burning boundary—a test the paper does not perform.","The tentative detection of the inner disk's bottom side through the gap implies the gap is nearly devoid of small dust; a high-resolution ALMA map would test whether dust filtration at the planet's gap is as efficient as the scattered-light morphology suggests.","The morphological similarity to HD 97048—nearly identical inclination and ring structure but a lower-mass host—hints that wide-orbit giant planets may form around low-mass T Tauri stars as readily as around Herbig stars, an occurrence-rate comparison the paper leaves implicit.","If the planet's orbit can be constrained to be exactly coplanar with the disk, WISPIT 2b could serve as a clean calibration target for kinematic planet-detection methods, because its gap is empty enough to give a direct view of the planet's influence on the gas."],"forward_implications":["If WISPIT 2b is indeed a ~4.9-MJup planet in the gap, the system becomes the first case where a ring gap is unambiguously associated with an embedded planet, linking disk substructure to ongoing planet formation.","The gap-width analysis yields a disk viscosity constraint: the photometric mass matches a viscous alpha of ~1e-2 under the Kanagawa et al. (2016) model or ~1e-4 under the Zhang et al. (2018) model, offering a way to measure disk viscosity from an embedded planet.","The independent H-alpha detection indicates ongoing accretion and possibly a circumplanetary disk, making WISPIT 2b comparable to the PDS 70 planets and opening the door to detailed accretion studies.","The system supports in-situ formation of wide-separation gas giants by core accretion, without rapid migration, since the planet sits in a cleared and seemingly unperturbed gap.","Future ALMA and JWST observations of gas kinematics, dust structure, and atmospheric composition can calibrate indirect planet-detection techniques used on other multi-ringed disks."],"supporting_citations":[{"why":"Supplies the BHAC15 pre-main-sequence isochrones used to convert the SED position into the adopted stellar age and mass.","marker":"Baraffe et al. 2015"},{"why":"Supplies the AMES-COND model atmosphere isochrones whose H-Ks colors are interpolated for the planetary mass estimate.","marker":"Allard et al. 2001"},{"why":"Supplies the AMES-DUSTY evolutionary tracks, the second grid used to cross-check the planetary mass estimate.","marker":"Chabrier et al. 2000"},{"why":"Supplies the PynPoint/species machinery used for the companion's astrometry, photometry, and color-magnitude mass retrieval.","marker":"Stolker et al. 2020b"},{"why":"Supplies the orbitize! package and OFTI sampler used for the orbital fit that yields the ~57 au semi-major axis.","marker":"Blunt et al. 2020"},{"why":"Supplies the pixel-scale and true-north calibration that anchors the astrometric epochs.","marker":"Maire et al. 2021"},{"why":"Supplies the gas-only gap-width model used to check that a 4.9-MJup planet can open the observed gap.","marker":"Kanagawa et al. 2016"},{"why":"Supplies the gas-plus-dust gap-width model used as the second cross-check of the gap-opening mass.","marker":"Zhang et al. 2018"},{"why":"Provides the only other directly imaged embedded protoplanet system (PDS 70), the comparison on which the 'first unambiguous planet in a multi-ringed disk' claim rests.","marker":"Keppler et al. 2018"},{"why":"Independent H-alpha detection used to corroborate the planet interpretation via accretion emission.","marker":"Close et al. (submitted)"}],"fun_headline_variants":["Directly imaged planet found inside multi-ringed disk","Planet spotted carving gap in young star's disk","First unambiguous planet in a multi-ringed disk","Four Jupiter-mass planet seen in disk gap","Young planet imaged in ringed disk around solar twin"],"cache_read_input_tokens":2688,"weakest_assumption_plain":"The planetary classification rests on the host star being about 5 Myr old and on treating the two-epoch astrometric motion as Keplerian; if the star is actually about 19 Myr old, the same photometry would imply a mass above the deuterium-burning limit, and if the 2024 epoch is excluded the orbital constraint is thin.","fun_headline_variants_meta":{"raw":{"variants":["Directly imaged planet found inside multi-ringed disk","Planet spotted carving gap in young star's disk","First unambiguous planet in a multi-ringed disk","Four Jupiter-mass planet seen in disk gap","Young planet imaged in ringed disk around solar twin"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.0002,"raw_usage":{"total_tokens":1296,"prompt_tokens":910,"completion_tokens":386,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":654,"completion_tokens_details":{"reasoning_tokens":311}},"tokens_in":654,"tokens_out":386,"duration_ms":4629,"temperature":1.0,"reasoning_tokens":311,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-05T15:58:28.946430+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A dynamical mass for WISPIT 2b from high-precision astrometry (for example VLTI/GRAVITY) or radial velocities over several years, combined with a spectroscopic age for the host star: if the mass exceeds the deuterium-burning limit (~13 Jupiter masses) or the orbit is not coplanar with the disk, the planetary and gap-opening interpretations fail.","supporting_citations":[],"review_version":1}