WISPIT: Wide Separation Planets in Time
- Wide Separation Planets in Time (WISPIT) is a survey that detects planetary-mass companions at extreme separations using time-domain high-contrast imaging.
- The survey employs repeated VLT/SPHERE imaging, Hα accretion mapping, and ALMA disk observations to estimate masses and track orbital motion.
- WISPIT's discoveries, including the WISPIT 1 and WISPIT 2 systems, offer new insights into exoplanet formation, planet-disk interactions, and formation pathways.
Wide Separation Planets In Time (WISPIT) is a survey program centered on the detection and characterization of wide-separation planetary-mass companions around young stars, especially solar-type hosts, through time-domain high-contrast imaging and subsequent multi-wavelength follow-up. In its published implementation, WISPIT combines repeated VLT/SPHERE imaging for common-proper-motion confirmation with color-based mass estimation, and extends to accretion-sensitive H imaging, interferometric spectroscopy, and ALMA disk imaging for selected systems. Its early results include the two-planet circumbinary system WISPIT 1 and the embedded multi-planet system WISPIT 2, which together situate WISPIT at the intersection of exoplanet demographics, planet-disk interaction, and formation-pathway inference (Capelleveen et al., 25 Aug 2025, Capelleveen et al., 26 Aug 2025, Lawlor et al., 23 Mar 2026).
1. Survey definition, scope, and nomenclature
The WISPIT survey aims to detect and characterize wide-separation planetary-mass companions over a range of ages from to $20$ Myr around solar-type host stars at distances of $75$–$500$ pc, with a median distance of $140$ pc. Target selection retains stars younger than $20$ Myr, of solar-type mass, and suitable for adaptive-optics imaging with mag; additional cuts based on youth indicators, stellar mass, proper-motion suitability, and SPHERE observability yield a sample of 178 stars with median age $8.5$ Myr (Capelleveen et al., 25 Aug 2025).
The scientific motivation is the difficulty of explaining wide-separation gas giants within standard formation frameworks. In the WISPIT 1 context, the survey is explicitly framed around companions at au, where the relevant possibilities include in situ top-down formation through disk gravitational instability or cloud fragmentation, formation at smaller radii followed by outward scattering, or capture (Capelleveen et al., 25 Aug 2025). In the broader exoplanet-demographics literature, “wide separation” is often defined more generally as beyond the snow line, roughly 0 au for a Sun-like star, so WISPIT occupies an especially extreme direct-imaging subset of that parameter space (Gaudi, 2021).
The acronym is not fully unique across the literature. In directly imaged exoplanet studies it denotes WIde Separation Planets In Time, whereas a white-dwarf timing study used “WISPIT-type” in the distinct sense of “White-dwarf Investigation by Survey and Precise Infrared Timing” (Kubiak et al., 2023). The published exoplanet survey results associated with WISPIT use the former expansion.
2. Observational architecture and analysis strategy
The baseline WISPIT observing strategy uses VLT/SPHERE with the IRDIS camera in Classical Imaging mode under pupil-stabilized observations. The survey obtains two 5-minute 1-band exposures separated by at least six months, followed by 2-band imaging. Candidate companions are confirmed through proper-motion analysis by testing whether their measured positions follow the host-star motion rather than the expected background track (Capelleveen et al., 25 Aug 2025).
Photometric characterization is based on aperture photometry in 3 and 4, referenced to the unresolved system magnitude, and companion masses are inferred by comparison to AMES-COND and AMES-DUSTY evolutionary tracks. In the WISPIT 1 analysis, masses are derived by random sampling of 5, 6, and age, interpolation of the observed absolute 7-band magnitude onto the 8 Myr isochrones, and interpolation between dust-free and dusty models according to 9 color (Capelleveen et al., 25 Aug 2025).
WISPIT is not restricted to blind detached-companion searches. In the WISPIT 2 branch, the program targets young stars with large, structured transitional disks and uses H$20$0 direct imaging to isolate actively accreting protoplanets. The MagAO-X discovery data for WISPIT 2b employed Angular Spectral Differential Imaging, combining simultaneous narrowband H$20$1 and continuum imaging with angular differential imaging and KLIP-based PSF subtraction. For the inner companion WISPIT 2c, confirmation proceeded through $20$2-band SPHERE recovery and VLTI/GRAVITY $20$3-band interferometry, including medium-resolution spectroscopy and atmospheric-grid fitting with nested sampling via the species tool (Close et al., 26 Aug 2025, Lawlor et al., 23 Mar 2026).
This tiered design makes time a structural element of the survey rather than merely a scheduling detail. Proper-motion baselines, multi-epoch astrometry, and follow-up spectroscopy are all integral to the survey logic.
3. WISPIT 1 and the directly imaged wide-orbit circumbinary system
WISPIT 1 is a previously unrecognized stellar binary composed of a K4V primary with $20$4 K and an M5.5V secondary with $20$5 K. Its age is $20$6 Myr, its Gaia DR3 distance is $20$7 pc, and the stellar projected separation is at least $20$8 au, implying an orbital period of at least 34 years. No significant orbital motion between the stellar components was reported over the observed baseline (Capelleveen et al., 25 Aug 2025).
Against that binary host, WISPIT identified two common-proper-motion planetary companions. WISPIT 1b lies at $20$9, corresponding to $75$0 au projected, and WISPIT 1c at $75$1, corresponding to $75$2 au projected. Their reported photometric and model-derived properties are as follows (Capelleveen et al., 25 Aug 2025):
| Object | Projected separation | Reported properties |
|---|---|---|
| WISPIT 1b | 338 au | $75$3, $75$4 |
| WISPIT 1c | 840 au | $75$5, $75$6 |
Both companions are red, with $75$7, and their color-magnitude positions were reported to cluster with other directly imaged gas giants. The survey paper states that these targets are well suited to follow-up characterization with ground-based and space-based facilities, including orbital monitoring with GRAVITY and spectroscopy for atmospheric composition and metallicity (Capelleveen et al., 25 Aug 2025).
WISPIT 1 is significant because it couples very large projected separations with a binary host. The published interpretation emphasizes that such companions are difficult to reconcile with classical core accretion or pebble accretion at those radii because of low surface densities and long formation timescales. The same study notes that gravitational instability is more plausible at wide orbits, while scattering remains possible, especially in binary systems; it also remarks that more than half of the widest-separation directly imaged planets orbit binary or multiple stars, suggesting a possible role for multiplicity in producing or retaining such architectures (Capelleveen et al., 25 Aug 2025).
4. WISPIT 2: gap-clearing planet, H$75$8 protoplanet, and inner spectroscopic companion
WISPIT 2 is the young ($75$9 Myr), nearby ($500$0 pc) solar-type star TYC 5709-354-1. SPHERE observations obtained in four independent epochs revealed an extended $500$1 au disk in scattered light with a multi-ringed substructure. The disk has an average inclination of $500$2 and position angle $500$3, and the scattered-light morphology includes prominent rings at approximately $500$4, $500$5, $500$6, and $500$7 au. The deepest gap lies between the $500$8 au and $500$9 au rings, is centered near $140$0 au, and has a width of $140$1 au in $140$2 band (Capelleveen et al., 26 Aug 2025).
Within that gap, SPHERE directly detected WISPIT 2b and established that it is co-moving with the star. Multi-epoch astrometry showed orbital motion consistent with Keplerian motion in the disk gap, and OFTI orbit fitting under a coplanarity assumption yielded a most probable semimajor axis of $140$3 au, with low eccentricity for most solutions. From $140$4- and $140$5-band photometry and comparison with AMES-COND and AMES-DUSTY evolutionary models at an age of $140$6 Myr, the adopted planet mass is $140$7. The same work states that this mass is consistent with the observed gap width as interpreted with hydrodynamic models (Capelleveen et al., 26 Aug 2025).
A second view of WISPIT 2b came from MagAO-X H$140$8 imaging. On 2025 April 13 and 16, WISPIT 2b was detected as an accreting H$140$9-emitting protoplanet at $20$0 mas, with $20$1, corresponding to $20$2 au deprojected for $20$3. The detection had SNR $20$4, an H$20$5 ASDI contrast of $20$6, and an H$20$7 line flux of $20$8 erg s$20$9 cm0. Coupled with 1 mag and DUSTY evolutionary models, that analysis yielded a mass estimate of 2 and an accretion rate of 3 (Close et al., 26 Aug 2025).
The H4 study further emphasized that WISPIT 2b is the first H5 protoplanet found between two bright ring features rather than inside a large central cavity. It also reported that the four robust H6 protoplanet systems then known had disk inclinations clustered between 7 and 8, with a simulated chance probability of 9 ($8.5$0); the authors speculated that magnetospherical accretion might have a preferred inclination range for a direct, low-extinction line of sight to the H$8.5$1 shock region (Close et al., 26 Aug 2025).
WISPIT 2 was later shown to host a second planet, WISPIT 2c. Using SPHERE $8.5$2-band dual-polarisation imaging and VLTI/GRAVITY $8.5$3-band interferometry, the inner companion was confirmed as a point-like, bound source at $8.5$4 au. Its extracted $8.5$5-band spectrum shows CO band-head absorption at $8.5$6 and a continuum shape consistent with a young giant planet. Atmospheric-model fitting yielded $8.5$7–$8.5$8 K, radius $8.5$9–0, and 1 between 2 and 3; comparison with evolutionary tracks implied a mass of 4–5 (Lawlor et al., 23 Mar 2026).
Taken together, these results make WISPIT 2 a rare directly imaged multi-planet system inside a protoplanetary disk. The published comparison is to PDS 70: WISPIT 2 is described as a second laboratory for studying the formation and early evolution of a multi-planet system within its natal disk (Lawlor et al., 23 Mar 2026).
5. Disk structure, circumplanetary limits, and unresolved architecture
ALMA 0.88 mm observations of WISPIT 2, obtained at 6 mas resolution (7 au), revealed a single narrow continuum ring with deprojected radius 8 au and width 9 au. No circumplanetary emission was detected within the cavity. Injection-recovery tests set a 00 upper limit of 01 for point-like emission at the location of WISPIT 2b, sufficient to rule out PDS 70c-like circumplanetary emission, though still consistent with empirical mass-flux relations extrapolated from the stellar regime (Facchini et al., 22 Jan 2026).
The ALMA analysis sharpened the architectural problem. Visibility modeling showed that WISPIT 2b lies significantly interior to the mm dust ring, raising doubts about its ability to be the sole driver of the dust structure. The paper proposed two classes of explanation: either another lower-mass companion resides between WISPIT 2b and the cavity edge, likely in the scattered-light gap seen at 02 au, or WISPIT 2b is either substantially more massive than the IR-photometry-based estimate, at 03, or on a moderately eccentric orbit (Facchini et al., 22 Jan 2026).
The scattered-light and mm views are also not redundant. SPHERE resolved multiple rings from 04 to 05 au, whereas ALMA recovered essentially the outermost narrow ring. The ALMA paper interpreted this as evidence that small grains remain coupled to the gas while larger grains are trapped at an outer pressure maximum (Facchini et al., 22 Jan 2026). This suggests that WISPIT 2 is not simply a case of one imaged planet mapping one dust feature; rather, it is a dynamically structured system in which different diagnostics sample different particle populations and potentially different sculpting agents.
A common simplification is to treat directly imaged wide-separation planets as self-contained point sources whose interpretation rests only on age and luminosity. WISPIT 2 shows a more complex regime in which astrometry, accretion tracers, scattered-light morphology, mm continuum structure, and non-detections of circumplanetary emission all materially affect the inferred system architecture.
6. Formation implications and position within the wider field
WISPIT was designed in a part of parameter space where planet-formation theory is under particular strain. The WISPIT 1 discovery paper states that core accretion and pebble accretion are unlikely at separations of hundreds of au because of low surface densities and long formation timescales, whereas gravitational instability is more plausible there, and scattering remains possible in the presence of binaries or other massive bodies (Capelleveen et al., 25 Aug 2025). WISPIT 2, by contrast, directly probes giant-planet formation during the disk phase, with an embedded gap-clearing planet at 06 au and a second inner giant at 07 au (Capelleveen et al., 26 Aug 2025, Lawlor et al., 23 Mar 2026).
These systems therefore do not point to a single universal formation channel. For WISPIT 1, the published discussion explicitly weighs in situ top-down formation, scattering, and capture (Capelleveen et al., 25 Aug 2025). For the most extreme separations in the general wide-orbit population, an additional theoretical framework exists in which free-floating planets are recaptured during cluster dispersal, producing planetary companions on 08–09 au orbits with thermal eccentricity distributions; this provides a possible interpretive context for very wide directly imaged companions, although no WISPIT object has been demonstrated to originate in that way (Perets et al., 2012).
WISPIT also sits naturally within the direct-imaging regime highlighted by demographic reviews. Direct imaging is most sensitive to massive, young, self-luminous planets at 10 au, whereas radial velocity, transits, and microlensing probe different combinations of mass, separation, age, and host-star type (Gaudi, 2021). WISPIT’s discoveries at 11, 12, 13, and 14 au therefore complement, rather than duplicate, the broader exoplanet census.
Future characterization is central to the program’s scientific value. The WISPIT 1 paper emphasizes spectroscopy and interferometric monitoring as routes to composition, metallicity, and eccentricity constraints (Capelleveen et al., 25 Aug 2025). That emphasis aligns with a broader synthesis of wide-separation gas giants, which found atmospheric C/O ratios clustering near or slightly above the presumed stellar value, with a range of elemental C/H; in that framework, if such planets formed by core accretion, they must have acquired their metals from pebble or planetesimal accretion, while gravitational instability cannot yet be ruled out (Bergin et al., 2024). WISPIT targets are thus positioned not only as detections, but as test cases for composition-based formation diagnostics.
The survey also belongs to a wider strategic push toward wide-orbit planet discovery. A JWST white paper advocated a large-scale NIRCam dual-band coronagraphic survey of 15 nearby young targets to detect sub-Jovian planets beyond 16, with expected yields of 10–70 companions depending on the underlying population (Carter et al., 2024). Separately, deep archival JWST/MIRI 17 imaging of M-dwarfs has been presented as a “powerful window” on cold wide-orbit giants and discussed in synergy with programs such as the upcoming WISPIT survey (Li et al., 9 Apr 2026). In that landscape, WISPIT functions as a concrete, already productive example of time-domain high-contrast imaging applied to the wide-separation frontier.