{"id":"03fef5ca-9217-45ab-91dd-abaec212d3f3","arxiv_id":"2411.18683","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":7.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":9,"one_line_summary":"IRAS 04125+2902 b is a Jupiter-radius, likely low-mass planet transiting a 3 Myr star in Taurus, the youngest transiting planet found to date.","lead":"Astronomers found a planet about the size of Jupiter transiting a star only about three million years old in the Taurus star-forming region. It is the youngest transiting planet known, and its misaligned disk makes it a unique testbed for how planets form and migrate.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The inferred 3 Myr age of the host star is the load-bearing link; if the pre-main-sequence tracks are biased, the 'youngest transiting planet' claim and the 2–3 Myr formation inference weaken.","rationale":"The reader's weakest assumption identifies the stellar age as the load-bearing element, and my reading agrees. The transit detection itself is well supported: 18 TESS transits over six sectors, consistent depths and durations across four years, ground-based multi-wavelength follow-up, deep high-resolution imaging, and a thorough false-positive analysis that rules out eclipsing binaries, background/foreground stars, and transient dippers. What would have to be true for the 'youngest transiting planet' claim is that the host star is genuinely a few Myr old, not merely consistent with a young association. The PARSECv1.2S age is model-dependent, and young accreting, spotted stars are known to bias isochronal ages. At the same time, the paper provides independent support for youth: membership in the 2.49 Myr D4-North subgroup, a transitional disk, and a transit-derived stellar density (ρ*=0.284+0.031/−0.068) consistent with the SED-based radius and a young pre-main-sequence structure. These do not fully remove the concern but substantially weaken it, so the appropriate stance remains the reader's conditional acceptance rather than rejection. The title's use of 'giant planet' despite the authors' own conclusion that the object is not a true giant is a secondary overclaim that should also be corrected, but it is not the load-bearing assumption for the discovery itself. Therefore I leave the reader's verdict unchanged.","tokens_in":20218,"tokens_out":14556,"duration_ms":141978,"concrete_test":"Re-derive the host star age using independent pre-main-sequence model grids that include starspots and/or accretion (e.g., MIST, BHAC15, or SPOTS) with the same photometry, Gaia parallax, and AV prior as in the paper. If all model families return best-fit ages below 6 Myr, the age concern is resolved; if any credible grid yields a best-fit age of 10 Myr or older, the 'youngest transiting planet' claim and the 2–3 Myr formation-timescale inference should be qualified in the title and abstract.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim of 'youngest transiting planet' depends on the stellar age of 3.3+0.6/−0.5 Myr derived in Methods (Host star properties) by fitting PARSECv1.2S tracks to photometry, Gaia parallax, and an AV prior. For low-mass pre-main-sequence stars, such ages are sensitive to starspot coverage, magnetic activity, and accretion; the host is a disk-bearing, highly variable (1–10%) T Tauri star, so the track-based age could be systematically biased. If the true age were ≳10 Myr, IRAS 04125+2902 b would no longer be the youngest transiting planet, since the paper itself notes a population of transiting planets at 10–40 Myr, and the claim that a super-Earth/sub-Neptune formed and migrated within 2–3 Myr would lose its timescale anchor. The D4-North association age of 2.49 Myr and the presence of a transitional disk make a much older system unlikely, but these are consistency arguments, not independent age measurements. The transit detection, period, radius, and false-positive rejection do not depend on this age and appear robust; the concern is specifically about the headline youth claim and its evolutionary interpretation.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports the discovery of IRAS 04125+2902 b, a transiting planet with an orbital period of 8.83498 days and a radius of 0.97 Jupiter radii, orbiting a ~3 Myr, 0.7 solar-mass pre-main-sequence star in the Taurus Molecular Cloud. The detection is based on 18 TESS transits across six sectors and is confirmed by multi-wavelength ground-based photometry from LCO. An extensive false-positive analysis using AO imaging, radial velocities, color constraints, and companion-search modeling rules out most alternative interpretations. The paper additionally characterizes a wide binary companion and a misaligned outer disk, and derives a 95% upper limit on the planet mass of 0.3 Jupiter masses. The authors argue this is the youngest transiting planet known and a possible precursor of super-Earths or sub-Neptunes, implying that planet formation and migration can occur within 2–3 Myr.","tokens_in":20471,"tokens_out":12210,"duration_ms":113720,"significance":"If correct, this constitutes a benchmark discovery: the youngest transiting planet known, providing a unique window into planetary structure and migration at ages when protoplanetary disks are still present. The paper is thorough in its vetting: the transit is recovered in independent TESS and ground-based datasets, the false-positive scenarios are addressed individually with quantitative constraints, and the key parameters (disk inclination, binary inclination, stellar rotation, planet mass limit) come from independent datasets, mitigating concerns about circularity. The data and code availability statements meet reproducibility standards. The main scientific payoff, that such compact planets can form and migrate within a few million years, is significant for planet formation theory.","major_comments":[],"minor_comments":[{"comment":"The term 'protostar' in the title is inappropriate for a 3 Myr pre-main-sequence star that no longer has a dense envelope; 'young star' or 'pre-main-sequence star' would be more accurate. Additionally, the title calls the object a 'giant planet' while the paper argues that it is likely a sub-Neptune precursor; the title may mislead readers about the inferred nature.","section":"Title and Abstract"},{"comment":"The age estimate of 3.3+0.6/-0.5 Myr is derived from a single set of pre-main-sequence evolutionary tracks (PARSECv1.2S). Systematic uncertainties from starspots, magnetic activity, and accretion are not discussed. Since the 'youngest transiting planet' claim rests on this age, the paper would be strengthened by a caveat and, ideally, a comparison with other evolutionary models (e.g., BHAC15 or SPOTS) to demonstrate that the conclusion is not track-dependent.","section":"Methods: Host star properties"},{"comment":"The mass upper limit of <0.3 M_J at 95% confidence is derived from only six HPF radial-velocity epochs using a white-noise jitter model. Given the star's strong photometric variability (1–10%) and 11.3-day rotation period, correlated activity signals could plausibly influence the posterior. The paper notes that more complex jitter models increase the limit to <2 M_J, but presenting the K posterior and a rotation-phased RV diagnostic would make the robustness of the <0.3 M_J constraint more transparent.","section":"Methods: Radial Velocities and RV analysis"},{"comment":"The binary orbital inclination is reported as 94.5+10.9/-4.7 degrees based on astrometry covering only a small orbital arc. The text correctly notes the eccentricity is unconstrained, but the inclination constraint also relies on the assumption of purely radial motion; the uncertainty should be emphasized so that 'consistent with edge-on' is not overstated.","section":"Methods: Star-binary alignment"},{"comment":"There are a few typographical issues: 'preformed' should be 'performed' in the Author Contributions; Extended Data Table 3 lists 'W 3 (mag)' twice with different values, one of which is presumably W4; and the abstract uses 'i ∼ 30°' for the disk without explicitly stating that this is the inclination angle (measured from face-on), which may confuse readers.","section":"Author Contributions and tables"}],"recommendation":"minor_revision","confidential_remarks":"The paper is generally strong and the central claim is well supported. The only substantive risk is the model-dependent stellar age, but the independent group-age and disk evidence make a much older system unlikely. The requested changes are mostly clarifications and robustness checks, not corrections to the derivation. I believe the paper will be suitable for publication after minor revision."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The short version: this is the strongest case yet for a transiting planet around a ~3 Myr star, and the transit detection should survive referee scrutiny. The part to scrutinize is the age, not the planet.\n\nWhat is actually new: a transiting planet with an 8.83-day period around a pre-main-sequence star in Taurus, with a nearly face-on outer disk that lets the transit be seen. If the age holds, it is the youngest transiting planet by a factor of three, and the first one found through a depleted inner disk / misaligned outer disk geometry. The paper does a lot right. The transit is supported by 18 TESS transits across six sectors, ground-based confirmation in three filters with consistent depths, a careful treatment of stellar variability with GPs, and a genuinely thorough false-positive analysis: archival and new AO imaging rules out background/foreground sources, multi-wavelength depth limits rule out eclipsing binary scenarios, and MOLUSC plus RV constraints rule out bound stellar companions. The mass upper limit of 0.3 M_J from HPF RVs is honest; they show the signal is not detected, only bounded.\n\nThe soft spots are real but mostly minor. The stellar age is the load-bearing one. It comes from fitting PARSEC pre-main-sequence tracks to photometry, Gaia parallax, and an A_V prior. For a spotted, accreting T Tauri star that is a model-dependent estimate, and the stress-test is right that if the tracks are biased the 'youngest' headline weakens. But the star is a member of the D4-North subgroup with an independent association age of 2.49 Myr, and the presence of a transitional disk is hard to reconcile with an age much older than the disk lifetime, so the youth claim is likely correct, just not ironclad. Minor: the title calls it a 'giant planet,' but the paper's own mass upper limit and radius argument say it is probably a sub-Neptune or sub-Saturn precursor. That is an overclaim. Also 'protostar' is loose for a 3 Myr T Tauri star. The claim that this planet formed and migrated within 2–3 Myr is reasonable but depends on the age and on pebble-accretion models, so it should stay clearly labeled as model-dependent.\n\nBottom line: this deserves a serious referee. The transit and false-positive work are solid; the age should be handled with explicit caveats and the title qualified. I would cite it and bring it to reading group.","headline":"A robust young transiting planet whose age claim, not the transit, is the part to scrutinize; the paper earns a serious referee.","tokens_in":21216,"tokens_out":2197,"would_cite":true,"duration_ms":37472,"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":"IRAS 04125+2902 b is the youngest transiting planet known, a Jupiter-radius world orbiting a 3-million-year-old star.","keywords":["transiting exoplanet","youngest planet","TESS","Taurus molecular cloud","pre-main-sequence star","transitional disk","pebble accretion","planet migration"],"falsifier":"A radial-velocity campaign dense enough to detect a companion more massive than 0.3 Jupiter masses at 95% confidence would overturn the sub-Neptune-precursor interpretation, as would a measurement showing the transit comes from a close stellar or brown-dwarf companion. Alternatively, an independent stellar age estimate (for example from lithium depletion or a revised pre-main-sequence grid) placing the star above 10 Myr would remove the 'youngest transiting planet' record while leaving the transit detection intact.","tokens_in":20001,"feed_emoji":"🪐","tokens_out":6963,"duration_ms":62383,"temperature":0.7,"pith_summary":"IRAS 04125+2902 b is a transiting planet with an 8.83-day period and a radius of 0.97 Jupiter radii, orbiting a roughly 3-million-year-old, 0.7-solar-mass pre-main-sequence star at 160 parsecs in Taurus. The paper argues this is the youngest transiting planet found to date, about three times younger than the previous record holders, and that its low mass upper limit (<0.3 Jupiter masses) makes it a likely precursor of the super-Earths and sub-Neptunes common around mature stars. The existence of such a planet so early matters because it shows that planetary cores of tens of Earth masses can assemble and migrate inward within a few million years, and that young planets can present clean, sharply-edged transits. The detection was made possible by a rare geometry: the outer disk is nearly face-on and the inner disk is depleted out to roughly 20 AU, so the edge-on orbit of the planet is not hidden by disk material.","feed_headline":"Youngest transiting planet yet orbits a 3-million-year-old star","feed_subtitle":"The Jupiter-radius world likely shrinks to a super-Earth, showing planets form and migrate within a few million years.","key_machinery":"The load-bearing mechanism is the system's geometry plus a sharp planetary transit signal. IRAS 04125+2902 hosts a transitional disk with an inner cavity out to about 20 AU and an outer disk inclined only about 30 degrees to our line of sight, so an edge-on planetary orbit is not occulted by optically thick material. The transit analysis uses a Gaussian-process model of the 11.3-day stellar rotation variability in the TESS light curves, with the MISTTBORN/BATMAN transit model to extract the period, depth, and impact parameter; the flat, sharply-edged shape and wavelength-independent depth separate the signal from dust-dipper variability, while radial velocities from HPF, APOGEE, and IGRINS place the mass limit.","core_discovery":"The central discovery is that a planet can be caught transiting its host star while the protoplanetary disk is still present, at an age near 3 Myr. The authors report 18 TESS transits plus ground-based multiwavelength follow-up, yielding period $P = 8.834976 \\pm 2.4 \\times 10^{-5}$ days, radius $R_P = 0.97 \\pm 0.06\\,R_J$, and a 95% confidence mass limit below $0.3\\,M_J$ from radial velocities. They reject the usual false-positive scenarios (background eclipsing binary, blended source, stellar variability, and transient dipper behavior) using the consistency of the transit across instruments and filters, the flat-bottomed trapezoidal shape, and high-resolution imaging limits. Because the host is a known member of the 2.5-Myr D4-North subgroup of Taurus-Auriga and fits pre-main-sequence tracks to an age of $3.3^{+0.6}_{-0.5}$ Myr, the planet becomes the youngest transiting planet known, and its radius combined with the mass limit points to an inflated sub-Neptune or sub-Saturn that will shrink as it cools.","pith_inferences":["If this geometry is not extraordinarily rare, many young planets orbiting inside depleted, nearly face-on disks may be hiding in plain sight; targeted searches of transition-disk members in young associations could find more such systems.","The misaligned outer disk, if caused by infall rather than the binary companion, would imply that planet formation and migration can proceed in disks not aligned with the final stellar spin, complicating spin-orbit interpretation of young systems.","A transmission spectrum of IRAS 04125+2902 b could test whether its extended atmosphere is still accreting or already escaping, directly connecting the observed inflated radius to the formation channel.","Future high-resolution disk mapping could distinguish the infall-warp scenario from binary-driven misalignment, a distinction the current data leave open."],"forward_implications":["This is the youngest transiting planet known, roughly three times younger than the previous record holders, giving a direct view of planetary structure shortly after formation.","The planet's existence supports models in which pebble accretion builds a tens-of-Earth-mass core and migrates it inside 0.2 AU within 2-3 million years.","The radius combined with the mass upper limit means IRAS 04125+2902 b is likely a precursor of the common super-Earths and sub-Neptunes, not a hot Jupiter, and will shrink as it cools.","The star, planet, and wide binary companion appear aligned while the outer disk is misaligned by about 4 sigma, leaving the origin of the disk warp unexplained.","Because the planet is large, low-density, and nearby, it is a strong target for atmospheric follow-up observations."],"supporting_citations":[{"why":"Defines the 20-Myr planet around AU Microscopii, the previous benchmark that IRAS 04125+2902 b now undercuts by a factor of about three.","marker":"1"},{"why":"Shows that outer disks are often warped, the geometric premise that makes a transiting planet visible through a depleted inner disk.","marker":"3"},{"why":"Establishes IRAS 04125+2902 as a transitional disk with a face-on outer disk and inner cavity, the key to why the transit is observable.","marker":"4"},{"why":"Places the host in the 2.49-Myr D4-North Taurus-Auriga subgroup, anchoring the young-age claim independent of evolutionary tracks.","marker":"5"},{"why":"Supplies the PARSECv1.2S pre-main-sequence tracks used to derive stellar mass and age.","marker":"6"},{"why":"Provides the pebble-accretion models that show a tens-of-Earth-mass core can form and migrate inside 0.2 AU within 2-3 Myr, the formation channel invoked for this planet.","marker":"18"},{"why":"Documents the candidate hot Jupiter PTFO 8-8695b, the classic young-planet signal later reinterpreted as a dipper, the main false-positive template the authors rule out.","marker":"90"},{"why":"Shows that PTFO 8-8695's dips are not a planet, anchoring the light-curve morphology criterion used to exclude dipper interpretations.","marker":"91"}],"fun_headline_variants":["Youngest transiting planet found around a 3-million-year-old star","3-million-year-old star hosts youngest transiting planet ever seen","Toddler planet caught in act of transiting its young star","Misaligned disk reveals newborn planet transiting its star","Record-breaking transiting planet found at just 3 million years"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The conclusion that this is the youngest transiting planet rests on the pre-main-sequence age estimate of about 3 Myr; if the evolutionary tracks used to date the star are biased for young, accreting stars and the star is actually substantially older, that headline claim and the inference of sub-Neptune formation within a few million years would weaken.","fun_headline_variants_meta":{"raw":{"variants":["Youngest transiting planet found around a 3-million-year-old star","3-million-year-old star hosts youngest transiting planet ever seen","Toddler planet caught in act of transiting its young star","Misaligned disk reveals newborn planet transiting its star","Record-breaking transiting planet found at just 3 million years"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000608,"raw_usage":{"total_tokens":2935,"prompt_tokens":1149,"completion_tokens":1786,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":765,"completion_tokens_details":{"reasoning_tokens":1698}},"tokens_in":765,"tokens_out":1786,"duration_ms":11246,"temperature":1.0,"reasoning_tokens":1698,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-12T10:59:31.341588+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A radial-velocity campaign dense enough to detect a companion more massive than 0.3 Jupiter masses at 95% confidence would overturn the sub-Neptune-precursor interpretation, as would a measurement showing the transit comes from a close stellar or brown-dwarf companion. Alternatively, an independent stellar age estimate (for example from lithium depletion or a revised pre-main-sequence grid) placing the star above 10 Myr would remove the 'youngest transiting planet' record while leaving the transit detection intact.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Shows that outer disks are often warped, the geometric premise that makes a transiting planet visible through a depleted inner disk."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Documents the candidate hot Jupiter PTFO 8-8695b, the classic young-planet signal later reinterpreted as a dipper, the main false-positive template the authors rule out."}],"review_version":1}