Carey Michael Lisse

The SPHEREx all-sky survey has now measured the R ∼ 40–100 infrared spectra of thousands of nearby brown dwarfs in the chemically rich 0.75–5 μ m range. The survey’s wide spectral coverage and high S/N permits flux measurements that capture several broadband molecular absorption features and upwards of 80% of the total bolometric luminosity of most brown dwarfs. Atmospheric models are known to yield systematic disagreements in the inferred temperatures and radii of brown dwarfs, necessitating benchmarking against observations. In this work, we present SPHEREx spectra across a broad sequence of 33 nearby field brown dwarfs, ranging from L0 to Y4 (∼2500–250 K) and compare them to theoretical expectations. We additionally compile spectra for separate low-gravity and low-metallicity objects, and show how they trend with constant spectral type. We fit the measured spectra to the well-known forward model grids Sonora Diamondback, Elf Owl, BT-Settl, ATMO2020, and ATMO2020++ and compare their goodness-of-fit as a function of wavelength, spectral type, and treatment of clouds and chemistry. We find that the models continue to struggle to simultaneously fit the J / H / K peaks and the 4 μ m opacity window, especially in L/T transition objects. The largest deviations appear around the chemistry-sensitive CO ₂ and CO features. Despite these offsets, the models broadly capture their trends across the L/T transition, with the observed sample of field dwarfs strongly preferring the weak vertical mixing ( k _zz = 10 ⁴ cm ² s ⁻¹ ) Elf Owl models over strong mixing. The spectra shown here along with future SPHEREx data will help guide improvements to models.

We present the first spectroscopic mineralogical analysis of the dust coma of an interstellar object (ISO) from JWST mid-infrared spectroscopy of 3I/ATLAS (3I). 3I exhibits a strong 9–11 μ m emissivity feature due to Si–O vibrational stretching modes that is commonly seen in asteroids, comets, disks, and the interstellar medium. Characterization of this 10 μ m emissivity maximum reveals that 3I’s dust composition is dominated by amorphous silicates, and that 3I is unlike solar system comets, which show significant crystalline silicate dust. Instead, 3I’s dust composition is more similar to circumstellar transition disks and the interstellar medium. We suggest 3I may have formed in a distant part of its home system out of interstellar medium–like material, without substantial incorporation of silicates condensed near its host star, unlike the mixing scenarios commonly suggested for the solar system. Alternatively, 3I’s original crystalline silicates may have been amorphized during its Gyr-long journey, although we find this alternative less likely due to 3I’s mass-loss rate and distinct 10 μ m feature as compared to observed solar system comets.

We present measurements of near‐infrared (NIR) terrestrial airglow produced by helium and oxygen in the exosphere as observed by the Spectro‐Photometer for the History of the Universe, Epoch of Reionization, and ices Explorer (SPHEREx). Using 8 months of survey data obtained from a 680‐km low‐Earth orbit, emission from He i , O i , and O i is mapped with both global spatial and multiseason temporal coverage. These measurements are obtained along upward looking lines of sight as part of the astrophysical survey, in contrast to conventional nadir‐viewing Earth remote sensing, which probes the behavior of low‐density material in the thermo‐ and exosphere. We describe an analytical framework to extract atmospheric emission lines in the presence of astrophysical backgrounds including stars, resolved galaxies, and the diffuse zodiacal light. The resulting global measurements reveal temporal variability over the survey period and systematic dependencies on geographic locations. We interpret these variations in the context of the variable solar illumination and seasonal effects. SPHEREx, an astrophysical space observatory, is demonstrated to be a promising new platform for monitoring NIR airglow and investigating its coupling to solar activity and global geophysical processes.

M dwarfs are the most common sites of planet formation in the Milky Way. Planet occurrence and composition are closely linked with the availability of metals in protoplanetary disks, which can be probed by measuring the metallicity of planet host stars. In this work, we measure the metallicities ([M/H] and [Fe/H]) of 59 M dwarfs hosting 76 planets and candidates using medium-resolution near-infrared spectra collected with IRTF/SpeX. We combine these results with literature metallicity measurements for planet-hosting cool dwarfs, and present a sample of 86 stars hosting 142 candidate, validated, and confirmed planets with homogeneously derived stellar parameters. Using our updated stellar radii, we calculate planet radii from TESS transit depths for both the confirmed ( N = 51, 0.6–12.5 R _⊕ , median R _p = 1.8 R _⊕ ) and candidate ( N = 25, 0.6–7.2 R _⊕ , median R _p = 2.1 R _⊕ ) planets. We compare the metallicity distributions of super-Earth and sub-Neptune host stars, finding that M dwarfs hosting sub-Neptunes are statistically more metal-rich than those hosting super-Earths. This result is robust to the radius valley prescription used and is likely not due to differences in the stellar samples considered. This result supports the hypothesized formation pathway whereby sub-Neptunes form beyond the water ice line where they can accrete volatiles before migrating inward to their observed locations. The enhanced inventories of refractory elements throughout the disk and of volatiles beyond the ice line in metal-rich disks around low-mass stars may contribute to the preference seen in the observed planet sample for sub-Neptunes to orbit metal-rich M dwarfs.

Launched in March 2025, NASA’s SPHEREx mission is currently conducting the first all-sky near-infrared spectral survey at wavelengths between 0.75μm and 5μm. Over its two-year nominal mission, SPHEREx acquires a spectrum for every 6.2” x 6.2” pixel on the sky, a transformative dataset for its primary science drivers in cosmology, galaxy formation, and interstellar ices [1]. However, this survey also provides an unprecedented opportunity for Solar System science, as exemplified by the recent SPHEREx discovery of a CO2 atmosphere around the interstellar comet 3I/ATLAS [2]. This presentation details the ongoing efforts of the SPHEREx Solar System Object Catalogue (SSOC) External Collaboration (XC) to extract, calibrate, and categorise these spectra, with a focus on the first-year asteroid results.The scientific significance of the SPHEREx dataset for minor bodies lies in its unique spectral coverage. While previous large-scale taxonomic efforts have focused on silicaceous compositions discernible in ground-based observations between 0.45μm and 2.45μm [3, 4], SPHEREx provides a critical window into the presence of volatiles, organics, and hydrated minerals identified at wavelengths beyond 2.45 μm (e.g. [5]). The sheer volume of high-quality spectra generated by this mission allows for a statistically robust ensemble analysis of the Main Belt and beyond, transitioning from individual case studies toward a holistic characterisation of the Solar System’s compositional landscape [6].Now, after more than one year of active operations and data processing, the SSOC XC presents a comprehensive status update. We showcase the first intermediate spectra derived from the mission pipeline, spanning diverse taxonomic classes including C-, S-, and M-complex asteroids. Extracting high-fidelity spectra for moving targets from a scanning mission presents unique data-reduction challenges; we discuss our solutions for these issues and address the remaining systematics currently present in the spectral products. Finally, we provide a timeline for the public release of the initial Solar System Object Catalogue. This work represents a major milestone in planetary astronomy, providing a rich, uniform spectral library that will serve as a cornerstone for Solar System studies for decades to come.

We present preliminary SPHEREx maps of diffuse Galactic emission tracing polycyclic aromatic hydrocarbons (PAHs) and ionized hydrogen gas, and we study their relationship across the Galactic plane. Since its launch in early 2025, the SPHEREx space telescope has been conducting an all-sky near-infrared spectral survey from 0.75 to 5.0 μ m. We produce a large-scale map of the 3.3 μ m PAH emission feature, which is bright and detectable throughout the Galactic plane, and find a strong correlation with the thermal dust radiance measured by Planck. We also trace ionized hydrogen gas by producing a map of Brackett- α emission at 4.05 μ m. By combining the two maps, we identify extended shells of PAH emission associated with photodissociation regions surrounding ionized gas. We construct a PAH abundance map and find a significant anticorrelation between PAH abundance and ionized hydrogen, indicating systematic PAH depletion within ionized gas regions across the Galactic plane and demonstrating that ionizing radiation is a dominant driver of PAH abundance variations. These early SPHEREx results provide a large-scale view of PAHs and ionized hydrogen and a preview of the capability of the mission to map diffuse emission in the interstellar medium.

The frigid interiors of Trans-Neptunian objects (TNOs) and Centaurs, the dynamical descendants of TNOs scattered inward of Neptune’s orbit, preserve pristine material that have been shielded from cosmic rays and insolation since the planetary formation era. A small fraction of Centaurs provides means to study these otherwise inaccessible interiors during activity outbursts that expel subsurface material into a coma. Here we present observations of an outburst from the Centaur C/2023 RS61 (PANSTARRS) from the James Webb Space Telescope, Hubble Space Telescope, and Gemini North Telescope. We show that its unusual ultra-red coma dust grains are rich in organic and nitrogen-bearing compounds and have a reflectance spectrum remarkably similar to the surfaces of primitive Cold Classical TNOs, suggesting C/2023 RS61 (PANSTARRS) formed at the outermost edge of the protoplanetary disk. Our results further indicate that such pristine material can be preserved in objects later scattered into the giant-planet region. We found that the coma dust grains were excavated from a ∼30 m deep cavity, offering a first glimpse of preserved interior material from a small Cold Classical TNO. Finally, we conclude that the bulk composition of small Cold Classical TNOs is mostly homogeneous, based on the spectral similarity between the excavated dust grains and the surfaces of Cold Classical TNOs.

SPHEREx is a NASA mission designed to perform an all-sky spectroscopic survey in the 0.75–5 μ m wavelength range. Its primary science objectives are to investigate: (1) inflationary cosmology; (2) the history of galaxy formation; and (3) the abundance of molecular ices—critical for prebiotic chemistry—found on the surfaces of interstellar dust grains within planet-forming regions. This paper focuses on the third theme, the SPHEREx Ices Investigation, for which SPHEREx is conducting a spectroscopic survey of nearly 10 million preselected sources throughout the Milky Way and Magellanic Clouds, to characterize their ice absorption features. By selecting targets based on infrared color, spatial isolation, and brightness, the Ices Investigation secures high-signal-to-noise-ratio spectra across a broad range of astrophysical environments that are relatively free of spectral contamination. Rather than attempting to decompose each spectrum into its individual ice components, the Ices Investigation prioritizes accurate measurements of the integrated optical depths of key molecular ice absorption features. This approach enables statistically powerful correlation studies between ice abundances and environmental parameters—including extinction, temperature, gas composition, radiation field strength, cosmic-ray flux, and star formation activity. The data pipeline developed for this purpose incorporates machine learning for continuum estimation, drawing on both SPHEREx and ancillary data sets. Ultimately, the expansive spectral archive produced by SPHEREx, combined with targeted follow-up from facilities like JWST, will transform our understanding of Galactic ice formation, evolution, abundance, and their inheritance into planetary systems and prebiotic inventories.

The Spectro Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx) is conducting the first all-sky near-infrared spectral survey spanning 0.75–5.0 μ m with resolving power R ≈ 35–130. Linear variable filters mounted in front of six H2RG detectors produce a position-dependent spectral response across the focal plane. This paper presents the ground-based spectral calibration of SPHEREx, including the cryogenic apparatus, optical configuration, measurement strategy, analysis pipeline, and resulting calibration products. Monochromatic wavelength scans are used to derive the spectral response function, band center, and resolving power for every pixel. Band centers are measured to better than 1 nm for Bands 1 through 4 (0.75–3.82 μ m) and better than 10 nm for Bands 5 and 6 (3.82–5.0 μ m). Out-of-band leakage is negligible for detectors above 1.64 μ m and is present at the percent level below this wavelength. The resolving power is measured to within 5% and agrees with design expectations to within 10%. An on-sky spectrum of the Cat’s Eye Nebula (NGC 6543) constructed from repeated observations provides in-flight verification and shows agreement between ground-calibrated response and astrophysical emission features. Calibration products, including per-pixel band center and resolving power maps, are released through IPAC to support community use of SPHEREx data. The absolute spectral calibration will continue to improve through in-flight measurements, with further reductions in uncertainty expected for the longest-wavelength bands.