WISPIT 2c: Confirmed Young Giant Planet

• The paper confirms WISPIT 2c as a self-luminous young giant planet using VLTI/GRAVITY interferometric spectroscopy that detects CO band-head absorption in the K-band.
• Atmospheric modeling with Drift-Phoenix and ExoRem indicates a cloudy/dusty atmosphere with an effective temperature range of 1500–2600 K and a radius between 0.91–2.20 R_Jup.
• Positioned at about 14 au, WISPIT 2c lies within a structured, multi-ringed protoplanetary disk, making the WISPIT 2 system a benchmark for studying planet-disk interactions.

WISPIT 2c is the second confirmed planet in the young, disk-hosting WISPIT 2 system. It was established as a bound, self-luminous planetary-mass companion through spatially resolved interferometric spectroscopy with VLTI/GRAVITY, supported by new VLT/SPHERE $H$-band imaging and earlier $z'$ and $L$-band detections. The defining observational result is a point-like K-band coherent source whose extracted spectrum shows CO band-head absorption near $2.3\,\mu\mathrm{m}$ and a continuum shape consistent with a young giant planet. The companion lies at a projected separation of about $14$ au, has an inferred mass of $8$–$12\,M_{\rm Jup}$, and, together with WISPIT 2b, makes WISPIT 2 an analogue to PDS 70 and only the second known system hosting multiple directly imaged young giant planets still associated with a natal disk (Lawlor et al., 23 Mar 2026).

1. Designation and system context

In the WISPIT survey nomenclature, host stars are designated WISPIT NNN, and planets are designated WISPIT NNNb, WISPIT NNNc, and so forth (Capelleveen et al., 25 Aug 2025). Within that convention, WISPIT 2c is the inner confirmed planet of WISPIT 2, the young solar-type star also identified as TYC 5709-354-1. The system is described as a young, nearby, solar-analog or young solar-type star at about $133$ pc, with an age of about $5.1$ Myr and a multi-ringed protoplanetary disk extending to about $380$ au in scattered light (Capelleveen et al., 26 Aug 2025).

Before WISPIT 2c was confirmed, the system already hosted one established planet, WISPIT 2b, embedded in a prominent disk gap. That outer planet is reported at a semi-major axis of about $z'$0 au and has a mass of $z'$1 from SPHERE $z'$2- and $z'$3-band photometry (Lawlor et al., 23 Mar 2026). The broader system architecture includes multiple rings, intermediate gaps, and a central cavity, making WISPIT 2 a particularly structured laboratory for planet-disk interaction studies (Capelleveen et al., 26 Aug 2025).

2. From CC1 to WISPIT 2c

WISPIT 2c was not initially introduced as a confirmed planet. In the 2025 MagAO-X and LMIRCam study, the inner source was presented as CC1, a close companion candidate at about $z'$4 mas, corresponding to about $z'$5 au deprojected. It was detected in $z'$6 at SNR $z'$7 and in $z'$8 at SNR $z'$9, but it showed no significant H$L$0 emission and no significant 668 nm continuum detection. That paper explicitly treated the source as ambiguous, allowing that it could be an inner planet, an unusually red compact dust clump, or a protoplanet still somewhat embedded inside its CPD (Close et al., 26 Aug 2025).

This status distinction is important. In that earlier work, “WISPIT 2c” was only a conditional label for what future data might establish. The 2026 spectroscopic study changed the object’s status fundamentally: it confirmed that the former CC1 is a planet through VLTI/GRAVITY interferometric spectroscopy and additional SPHERE $L$1-band imaging. The confirmation was not based merely on re-detection, but on the combination of compact coherent emission, a planet-like K-band spectrum, and astrometry inconsistent with a background source (Lawlor et al., 23 Mar 2026).

A recurrent misconception is therefore to retroactively treat the 2025 candidate stage as already secure. The candidate paper did not do so; the planet status follows from the later spectroscopic confirmation (Close et al., 26 Aug 2025).

3. Interferometric and imaging basis of the confirmation

The decisive dataset is the VLTI/GRAVITY observation obtained on 2025-10-05 with the four Unit Telescopes in dual-field on-axis mode at spectral resolution $L$2. The fringe-tracker fiber followed the host star, while the science fiber alternated between star and planet. The observation used GRAVITY+ extreme AO (GPAO), and the data were reduced with the ESO GRAVITY pipeline and the exogravity pipeline. The companion is reported at S/N $L$3 in each of the 12 GRAVITY exposures (Lawlor et al., 23 Mar 2026).

The GRAVITY analysis models the planet as a point-like coherent source,

$L$4

with

$L$5

and phase

$L$6

The detection map is defined through

$L$7

and shows a strong central peak with side lobes characteristic of the VLTI $L$8 coverage (Lawlor et al., 23 Mar 2026).

The paper is explicit that GRAVITY provides the key confirmation because interferometry is sensitive to the coherent signal of a point-like source, thereby separating the source from extended disk emission. The source is stated to be consistent with a point-like emitter, not a broad disk asymmetry. SPHERE/IRDIS $L$9-band data from 2025-03-21 and 2025-09-24 supplied independent re-detections in total intensity after RDI plus PCA subtraction, with photometry and astrometry extracted by negative planet injection, simplex minimization, and MCMC (Lawlor et al., 23 Mar 2026).

Polarized intensity was also examined, but the authors report no strong dust-scattering signal at the companion location. That non-detection in polarized light supports the interpretation that the detected K-band coherent flux is planetary rather than dominated by scattered light (Lawlor et al., 23 Mar 2026).

4. Spectrum, atmospheric fits, and physical parameters

The extracted medium-resolution K-band spectrum is the central physical diagnostic. It shows CO band-head absorption at $2.3\,\mu\mathrm{m}$0, additional CO overtones around $2.3\,\mu\mathrm{m}$1–$2.3\,\mu\mathrm{m}$2, and a positive continuum slope from $2.3\,\mu\mathrm{m}$3 to $2.3\,\mu\mathrm{m}$4. The source is described as having a spectrum characteristic of a young, low-gravity giant planet. The authors compare it to ExoGRAVITY spectra and note that WISPIT 2c resembles HR 8799 e in continuum shape and CO depth, whereas PDS 70b has a flatter K-band spectrum without strong CO (Lawlor et al., 23 Mar 2026).

Atmospheric fitting was carried out with the species package using nested sampling with dynesty. The fit combined the GRAVITY K-band spectrum with $2.3\,\mu\mathrm{m}$5 and $2.3\,\mu\mathrm{m}$6 photometry from the earlier candidate study and new SPHERE $2.3\,\mu\mathrm{m}$7-band photometry. Model grids included Drift-Phoenix, Sonora-Diamondback, ExoRem, BT-Dusty, Sonora-Bobcat, BT-Settl, and ATMO. The best-performing models were Drift-Phoenix and ExoRem, and the authors infer that WISPIT 2c likely has a cloudy/dusty atmosphere (Lawlor et al., 23 Mar 2026).

The maximum-likelihood Drift-Phoenix fit yielded $2.3\,\mu\mathrm{m}$8 K and $2.3\,\mu\mathrm{m}$9, but these uncertainties are described as purely statistical. The paper therefore adopts broader model-encompassing intervals: $14$0–$14$1 K, $14$2–$14$3, and $14$4 to $14$5. It further emphasizes a bimodal solution family, with a low-temperature, inflated-radius branch and a high-temperature, small-radius branch; the authors regard the low-$14$6, larger-radius branch as physically favored for such a young planet (Lawlor et al., 23 Mar 2026).

Quantity	Value	Source of estimate
Projected separation	$14$7 au	Abstract
Apparent $14$8 magnitude	$14$9	GRAVITY spectrum integrated over $8$0
Apparent $8$1 magnitude	$8$2; $8$3	SPHERE $8$4-band epochs
Apparent $8$5 magnitude	$8$6	Earlier candidate detection
Apparent $8$7 magnitude	$8$8	Earlier candidate detection
$8$9	$12\,M_{\rm Jup}$0–$12\,M_{\rm Jup}$1 K	Atmosphere-model range
Radius	$12\,M_{\rm Jup}$2–$12\,M_{\rm Jup}$3	Atmosphere-model range
Luminosity	$12\,M_{\rm Jup}$4 to $12\,M_{\rm Jup}$5	Atmosphere-model range
Mass	$12\,M_{\rm Jup}$6–$12\,M_{\rm Jup}$7	Luminosity-age evolutionary tracks

The mass estimate comes from comparison of the inferred luminosity with age-dependent evolutionary isochrones at $12\,M_{\rm Jup}$8, $12\,M_{\rm Jup}$9, and $133$0 Myr. The preferred result is $133$1–$133$2, and the paper notes that the dominant uncertainty is the system age rather than the choice of evolutionary grid (Lawlor et al., 23 Mar 2026).

5. Astrometry and orbital status

The highest-precision astrometry comes from GRAVITY, which gives

$133$3

equivalent to

$133$4

The SPHERE $133$5-band epochs yielded $133$6 mas, $133$7 on 2025-03-21 and $133$8 mas, $133$9 on 2025-09-24. These measurements are consistent with the earlier $5.1$0 and $5.1$1 candidate detections at about $5.1$2 mas (Lawlor et al., 23 Mar 2026).

The paper states that the astrometry rules out a distant background source. In particular, the expected separation evolution for a non-moving background object is not observed. The authors conclude that the GRAVITY and $5.1$3 data rule out a background object in position angle, while the GRAVITY, SPHERE $5.1$4-band, and $5.1$5 data rule it out in separation (Lawlor et al., 23 Mar 2026).

Orbital motion is reported as marginally detected. Trial Keplerian orbits were explored with orbitize! using EMCEE, with the orbital plane inclination fixed to the disk inclination of $5.1$6. The SPHERE $5.1$7-band points are said to be more consistent with prograde motion, in the same sense as WISPIT 2b, whereas the literature $5.1$8 and $5.1$9 measurements could suggest retrograde motion but are identified as more susceptible to systematics. The paper therefore favors the prograde interpretation but explicitly states that additional high-precision astrometry is required for confirmation (Lawlor et al., 23 Mar 2026).

6. Placement within the WISPIT 2 disk architecture

WISPIT 2c resides in a system whose scattered-light disk contains up to four confirmed rings, intermediate gaps, and a central cavity. WISPIT 2b occupies the large $380$0 au gap at about $380$1 au, whereas WISPIT 2c lies much farther inward, at about $380$2 au projected separation. The 2026 confirmation paper argues that, unlike PDS 70, a dust ring remains between the planets in WISPIT 2 because the planets are more widely spaced and have not cleared the intermediate ring as efficiently (Capelleveen et al., 26 Aug 2025).

An additional complication comes from the ALMA $380$3 mm continuum study, which resolved a single narrow ring at a deprojected radius of 144.4 au with width 7.2 au, and found no circumplanetary continuum emission at WISPIT 2b down to about 45 $380$4Jy at $380$5. That paper argued that the millimeter ring lies far beyond WISPIT 2b and raised doubts that WISPIT 2b alone could be the only driver of the dust structure. It proposed either another lower-mass companion between WISPIT 2b and the cavity edge, likely in the scattered-light gap at $380$6 au, or a more massive or moderately eccentric WISPIT 2b (Facchini et al., 22 Jan 2026).

A plausible implication is that the ALMA paper’s morphologically inferred additional companion and the later spectroscopically confirmed inner WISPIT 2c are distinct objects. The confirmed WISPIT 2c is the former inner candidate CC1 at $380$7 au, whereas the ALMA argument concerned a hypothetical companion near $380$8 au. On that reading, WISPIT 2c does not by itself resolve the millimeter-ring tension identified by ALMA; it instead strengthens the system’s status as a multi-planet, multi-gap architecture requiring further dynamical analysis (Facchini et al., 22 Jan 2026).

7. Interpretation, limitations, and significance

WISPIT 2c differs observationally from WISPIT 2b. WISPIT 2b previously showed strong H$380$9 accretion signatures, whereas WISPIT 2c has no significant H$z'$00 detection in current data. The confirmation paper offers two explanations: variable accretion and dust veiling or circumplanetary obscuration. It also notes that a compact CPD is not supported by the GRAVITY data down to scales of about 0.25 au, although a more extended dusty envelope or sub-micron CPD dust remains possible (Lawlor et al., 23 Mar 2026).

Several methodological limitations remain. The SPHERE $z'$01-band photometry is subject to residual systematic uncertainty because the companion lies near the $z'$02 coronagraph transmission region. The atmosphere fit is model-dependent, $z'$03 and metallicity were fixed rather than constrained, and the temperature-radius posterior is bimodal. The orbital motion is only marginally constrained. These caveats affect fine-grained characterization, but not the planet identification itself, which rests on compact coherent K-band emission, planet-like spectroscopy, and background-source rejection (Lawlor et al., 23 Mar 2026).

At the system level, WISPIT 2c is significant because it makes WISPIT 2 a rare benchmark for studying giant-planet formation inside an actively structured natal disk. The confirmation paper explicitly places the system alongside PDS 70 as only the second known system with multiple directly imaged young giant planets still associated with a natal disk. A further implication is that WISPIT 2 now provides a second empirical case for comparing embedded giant-planet spectra, accretion tracers, ring-gap morphologies, and early dynamical architecture in a multi-planet protoplanetary environment (Lawlor et al., 23 Mar 2026).

Future discriminants identified in the literature include higher-precision astrometry for WISPIT 2c, additional gas and dust observations on larger spatial scales, and dedicated hydrodynamical modeling of the full disk. Those steps are needed not only to refine the orbit and atmosphere of WISPIT 2c, but also to determine whether the known pair of planets fully explains the ring-gap structure or whether the WISPIT 2 disk still encodes additional unseen companions (Facchini et al., 22 Jan 2026).