Karl R. Stapelfeldt

We present near- and mid-infrared broadband imaging observations of the edge-on protoplanetary disk 2MASS J16281370-2431391, a.k.a. the “Flying Saucer,” obtained with NIRCam and MIRI on board JWST. These data are combined with archival optical and near-IR broadband imaging from Hubble Space Telescope (HST), millimeter dust continuum emission from Atacama Large Millimeter/submillimeter Array, and optical lightcurves from the K2 and TESS for a comprehensive multiwavelength study. The JWST observations reveal a reversal of the flux ratio between the two reflection nebulae at near-infrared wavelengths (2–3 μ m), which can be explained by a misaligned inner disk. For the first time, JWST reveals the bright lining along the disk edge at 2 and 3 μ m, arising from forward-scattering of background photons by dust grains near the τ ≈ 1 layer. By combining the dust lane thickness measured with HST and JWST, we find the dust grains up to at least ∼3 μ m are vertically mixed throughout the disk and have undergone significant growth. In addition, a comparison of earlier HST/NICMOS J - and K -band images with those from JWST/NIRCam reveals variability in the scattered-light morphology, as well as measurable proper motion of the system with respect to the background stars, confirming that the Flying Saucer is comoving with the young star population of ρ Ophiuchus.

NASA is embarking on an ambitious program to develop the Habitable Worlds Observatory (HWO) flagship to perform transformational astrophysics, as well as directly image ∼25 potentially Earth-like planets and spectroscopically characterize them for signs of life. This mission was recommended by the Astro2020 decadal survey, which additionally recommended a new approach for flagship formulation based on increasing the scope and depth of early, pre-phase A trades and technology maturation. A critical capability of the HWO mission is the suppression of starlight. To inform future architecture trades, it is necessary to survey a wide range of candidate technologies, from the relatively mature ones such as the ones described in the LUVOIR and HabEx reports to the relatively new and emerging ones, which may lead to breakthrough performance. We present a summary of an effort to survey potential coronagraph options for HWO. In particular, our results consist of (1) a database of different coronagraph designs sourced from the world-wide coronagraph community that are potentially compatible with HWO; (2) evaluation criteria, such as expected mission yields and feasibility of maturing to TRL 5 before phase A; (3) a unified modeling pipeline that processes the designs from (1) and outputs values for any machine-calculable criteria from (2); (4) assessments of maturity of designs, and other criteria that are not machine-calculable; and (5) findings and emerging trends and patterns (some of which overturn prior conventional wisdom). Although not charged to down-select or prioritize the different coronagraph designs, the products of this survey were designed to facilitate future HWO trade studies.

We present the first discoveries from Keck Observations in the Infrared of Taurus and ρ Oph Exoplanets and Ultracool dwarfs (KOINTREAU), an adaptive optics imaging survey of young stars in the Taurus and ρ Oph star-forming regions using the Keck infrared pyramid wavefront sensor. We have found two faint (Δ K ∼7 mag), wide-separation companions to two ≈3 Myr old Taurus members. Relative astrometry for these systems shows that both companions are bound to their host stars. We obtained near-infrared spectra of these companions using the Infrared Telescope Facility/SpeX ( R ∼100) and the Gemini North InfraRed Spectrograph (Gemini/GNIRS; R ∼ 1000–2000), and combined these with photometry from our NIRC2 imaging, the Pan-STARRS survey, and Spitzer/IRAC archival imaging to constrain their properties. One companion, KOINTREAU-1b (at a projected separation of 690 au), has an average near-infrared spectral type of M9 ± 2, a gravity classification of vl-g , and a changing spectral type between the SpeX (M7) and GNIRS (L1) observations. We estimate this object’s mass to be 10 . 6 − 2.3 + 2.5 M _Jup , making KOINTREAU-1b the fifth planetary-mass companion found in Taurus. The other companion, KOINTREAU-2b (projected separation 560 au), has a spectral type of M4.5 ± 1 but is ≈4 mag underluminous relative to other Taurus stars of the same spectral type. We detect exceptionally strong He I 1.083 μ m emission from this object, indicative of outflows driven by ongoing accretion, but with a conspicuous lack of accompanying H emission. We conclude that KOINTREAU-2b is a young star obscured by an edge-on disk and observed in scattered light. Finally, we derive a distortion solution for NIRC2 imaging, which shows a 0 . ° 118 difference in position angle from the previous distortion solution.

The near-ultraviolet (NUV) wavelength range contains a valuable ozone absorption feature for characterizing the atmospheric composition of Earth-like exoplanets. Both the LUVOIR and HabEx decadal mission concept studies baseline instrumentation for obtaining photometry of directly imaged exoplanets down to wavelengths of 200 nm. Both of their proposed implementations present challenges: in the case of the HabEx starshade occulter, a separate spacecraft is required; in the case of a NUV channel within the main coronagraph instrument, non-UV-optimized optics limit the performance. However, the science requirements allow the relaxation of some of the trades of a dedicated near-UV coronagraph. For instance, given that the inner working angle (IWA) of the coronagraph is a function of the wavelength, and one would only consider the characterization of planets detected in the visible, the IWA of the NUV coronagraph can be relaxed to meet the IWA of the visible coronagraph. In addition, given that a NUV coronagraph would be used for a follow-up observation after a visible detection, it could be designed to produce a half dark zone, allowing the simplification of the optical design. Here, we present the case for a standalone NUV coronagraph instrument for the Habitable Worlds Observatory based on the science requirements, developed as part of the Coronagraph Technology Roadmap study commissioned by NASA’s Exoplanet Exploration Office. We describe the trades and rationale behind the recommendation of having a separate NUV coronagraph instrument and show the evaluation of several coronagraph designs in the NUV. We assess the effect of polarization aberrations, discuss relevant technologies, and describe potential NUV detectors and wavefront sensing and control strategies.

We present high-resolution ( ≲ 0 . ″ 1 ) Hubble Space Telescope/Wide Field Camera 3 imaging of the near edge-on ( i ∼ 80°) protoplanetary disk IRAS23077+6707 (“Dracula’s Chivito”), obtained across six broadband filters spanning 0.4–1.6 μ m. These observations unveil the scattered light from this unusually large disk (∼14″, or ∼4200 au at 300 pc) in remarkable detail, revealing a rich tapestry of substructures, including brightness asymmetries and signatures of dynamical activity. Extended filaments are detected extending ∼10″ from the northern edges of both nebulae, while no comparable southern features are observed. In addition to large-scale asymmetries, the disk exhibits prominent wispy features that extend well above the midplane and are visible in all filters, suggesting a complex, possibly turbulent outer disk atmosphere shaped by infall, dynamical stirring, or gravitational instability. The central dark lane narrows from optical to near-IR wavelengths, and high-resolution millimeter data reveal compact midplane emission. Although our radiative transfer simulations show that the current data cannot yet distinguish between dust settling and no-settling scenarios, they underscore the need for resolved midinfrared observations of this unique system. IRAS23077 thus represents a rare and valuable laboratory for studying the vertical structure, asymmetries, and evolutionary state of protoplanetary disks.

The upcoming Roman Coronagraph will be the first high-contrast instrument in space capable of high-order wave front sensing and control technologies, a critical technology demonstration for the proposed Habitable Worlds Observatory (HWO) that aims to directly image and characterize habitable exoEarths. The nominal Roman Coronagraph observing plan involves alternating observations of a science target and a bright, nearby reference star. High contrast is achieved using wave front sensing and control, also known as “digging a dark hole,” where performance depends on the properties of the reference star, requiring V < 3, a resolved stellar diameter <2 mas, and no stellar multiplicity. The imposed brightness and diameter criteria limit the sample of reference star candidates to high-mass main-sequence and post-main-sequence objects, where multiplicity rates are high. A future HWO coronagraph may have similarly restrictive criteria in reference star selection. From an exhaustive literature review of 95 stars, we identify an initial list of 40 primary and 18 reserve reference star candidates relevant to both the Roman Coronagraph and HWO. We present results from an initial survey of these candidates with high-resolution adaptive optics imaging and speckle interferometry and identify no new companions. We discuss the need for higher-contrast observations to sufficiently vet these reference star candidates prior to Roman Coronagraph observations, along with the implications of reference star criteria on observation planning for Roman and HWO.

Searching for life elsewhere in the universe is one of the most highly prioritized pursuits in astronomy today. However, the ability to observe evidence of Earth-like life through biosignatures is limited by the number of planets in the solar neighborhood with conditions similar to Earth. The occurrence rate of Earth-like planets in the habitable zones of Sun-like stars, η _⊕ , is therefore crucial for addressing the apparent lack of consensus on its value in the literature. Here we present a review of the current understanding of η _⊕ . We first provide definitions for parameters that contribute to η _⊕ . Then, we discuss the previous and current estimated parameter values and the context of the limitations on the analyses that produced these estimates. We compile an extensive list of the factors that go into any calculation of η _⊕ , and how detection techniques and surveys differ in their sensitivity and ability to accurately constrain η _⊕ . Understanding and refining the value of η _⊕ is crucial for upcoming missions and telescopes, such as the planned Habitable Worlds Observatory and the Large Interferometer for Exoplanets, which aim to search for biosignatures on exoplanets in the solar neighborhood.

We present JWST NIRCam coronagraphic observations of the HD 141569A circumstellar disk, obtained as part of the JWST Early Release Science program. The observations recover the multi-ringed structure seen in previous shorter-wavelength observations, but at filters centered on the ∼3 μ m water ice absorption feature and a complementary continuum region (F300M and F360M, respectively). The observations reveal apparent absorption between the F300M and F360M filters that decreases with radius, with a notable change around 200 au, between the innermost and outermost two rings. These results are consistent whether the data is reduced via deconvolution or through a forward-modeling approach. We demonstrate that these changes suggest a radial decrease in the water ice mass fraction by a factor of ∼3–10 and possibly a change in minimum grain size. We do not detect any point sources within the system and can exclude planetary companions 2 Jupiter masses and greater beyond 1 ″ radius (∼111 au). These observations and the subsequent analysis illustrate a robust pathway for using JWST/NIRCam to characterize the distribution of water ice in other circumstellar disks. We highlight some of the early lessons learned from this work that we hope will be useful for future circumstellar disk observation planning and analysis.

The upcoming Roman Coronagraph will be the first high-contrast instrument in space capable of high-order wavefront sensing and control technologies, a critical technology demonstration for the proposed Habitable Worlds Observatory (HWO) that aims to directly image and characterize habitable exoEarths. The nominal Roman Coronagraph observing plan involves alternating observations of a science target and a bright, nearby reference star. High contrast is achieved using wavefront sensing and control, also known as "digging a dark hole", where performance depends on the properties of the reference star, requiring V<3, a resolved stellar diameter <2 mas, and no stellar multiplicity. The imposed brightness and diameter criteria limit the sample of reference star candidates to high-mass main sequence and post-main sequence objects, where multiplicity rates are high. A future HWO coronagraph may have similarly restrictive criteria in reference star selection. From an exhaustive literature review of 95 stars, we identify an initial list of 40 primary and 18 reserve reference star candidates relevant to both the Roman Coronagraph and HWO. We present results from an initial survey of these candidates with high-resolution adaptive optics imaging and speckle interferometry and identify no new companions. We discuss the need for higher-contrast observations to sufficiently vet these reference star candidates prior to Roman Coronagraph observations along with the implications of reference star criteria on observation planning for Roman and HWO.