SPHEREx Discovery of Strong Water Ice Absorption and an Extended Carbon Dioxide Coma in 3I/ATLAS
Year: 2025
Type: article
Abstract: In mid-August 2025, 0.75–5.0 μm SPHEREx imaging spectrophotometric and ancillary NASA-IRTF/SpeX 0.7–2.5 μm low-resolution spectral observations of 3I/ATLAS were obtained. The combined spectrophotometry is dominated by features due to water ice absorption and CO2 gas emission. A bright, ∼3′ radius CO2 gas coma was clearly resolved, corresponding to Q gas,CO2∼9.4 × 1026 molecules s−1. From the SPHEREx photometry, we put conservative, preliminary 3σ upper limits on the gas production rates for H2O and CO of 1.5 × 1026 and 2.8 × 1026 molecules s−1, respectively. No obvious jet, tail, or trail structures were found in SPHEREx images. If we assume all observed 1 μm flux is scattered light from a p v = 0.04 albedo spherical nucleus, then the radius would be R nuc ∼ 23 km. Given the nucleus size limit R nuc < 2.8 km from D. Jewitt et al., we conclude >99% of the measured SPHEREx continuum flux is from coma dust.
Source: Research Notes of the AAS
Authors: C. M. Lisse, Y. P. Bach, S. Bryan, B. P. Crill, A. Cukierman, O. Doré, B. Fabinsky, A. Faisst, P. M. Korngut, G. Melnick, Z. Rustamkulov, V. Tolls, M. Werner, M. L. Sitko, C. Champagne, M. Connelley, J. P. Emery, Y. R. Fernandez, B. Yang, the SPHEREx Science Team
Institutions: Johns Hopkins University, Johns Hopkins University Applied Physics Laboratory, Korea Astronomy and Space Science Institute, Arizona State University, California Institute of Technology, Jet Propulsion Laboratory, Infrared Processing and Analysis Center, Center for Astrophysics Harvard & Smithsonian, Space Science Institute, Northern Arizona University, University of Hawaii System, University of Hawaii at Hilo, University of Central Florida, Planetary Science Institute
Language: English
Topic: Astro and Planetary Science
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
SDG: Climate action
Open Access status: hybrid
OpenAlex ID: W4414156387