Work

Postperihelion Integral Field Spectroscopy of the Interstellar Comet 3I/ATLAS

Year: 2026

Type: article

Abstract: The environs of other stellar systems may be directly probed by analyzing the cometary activity of interstellar objects. The recently discovered interstellar object 3I/ATLAS was the subject of an intensive worldwide follow-up campaign in its preperihelion approach. Now, 3I/ATLAS has begun its postperihelion departure from the solar system. In this paper, we report the first postperihelion blue-sensitive integral-field unit spectroscopy of 3I/ATLAS using the Keck Cosmic Web Imager on 2025 November 16. We confirm previously reported CN, Fe, and Ni outgassing along with detections of carbon chain molecules C 2 and C 3 . We calculate production rates for each species. We find Fe and Ni production rates of Q Fe = (9.55 ± 3.96) × 10 25 atoms s −1 and Q Ni = (6.61 ± 2.74) × 10 25 atoms s −1 , resulting in a ratio of log ( Q Ni / Q Fe ) = − 0.16 ± 0.03 , which matches solar system comets well and continues the preperihelion trend of declining log ( Q Ni / Q Fe ) with r h . We investigate the radial distributions of these elemental species and find characteristic e -folding radii of 3880 ± 39 km for Ni, 6053 ± 68 km for CN, 4194 ± 45 km for C 2 , and 3833 ± 45 km for C 3 . Compared to preperihelion measurements, these radii have increased by a factor of ∼6.5–7. Our postperihelion observations reveal that 3I/ATLAS continues to exhibit cometary behavior broadly consistent with solar system comets.

Source: The Astrophysical Journal

DOI: 10.3847/1538-4357/ae6243

Authors: Willem B. Hoogendam, David O. Jones, Bin Yang, Benjamin J. Shappee, James J. Wray, Karen J. Meech, Christopher Ashall, Dhvanil D. Desai, Jason T. Hinkle, Andrew M. Hoffman, Kyle Medler, Cameron Pfeffer, Ruining Zhao

Institutions: University of Hawaiʻi at Mānoa, University of Hawaii System, Planetary Science Institute, Universidad Diego Portales, Georgia Institute of Technology, University of Illinois Urbana-Champaign, NSF-Simons AI Institute for the Sky, Chinese Academy of Sciences

Language: English

Topic: Astro and Planetary Science

Subfield: Space and Planetary Science

Field: Earth and Planetary Sciences

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $4,499

Funders: National Science Foundation, National Aeronautics and Space Administration, W. M. Keck Foundation, Simons Foundation, California Institute of Technology, Space Telescope Science Institute, NASA Exoplanet Science Institute, Science Foundation Ireland

Awards: G103270039, Collaborative Research: WoU-MMA: ASAS-SN in the Era of Multi-Messenger Astrophysics, G1590672606, G1848173918, G2054997787, G2453247062, G2468512172, G253522920, G2547019181, G256731684, G2952690682, G31735808, Cosmology in the Local Volume with Hawai'i Supernova Flows, G3388861423, G3514526295, G3534823121, G3614472770, G406396239, G433322167, G4704197846, G4776629850, Graduate Research Fellowship Program (GRFP), G4904421384, EPSCoR Research Fellows: NSF: Building a Duke University and University of Hawaii Collaboration for the Next Decade of Supernova Cosmology, Collaborative Research: The Connection between Astrophysical Transients and their Host Galaxies Across Cosmic Time, G58316358, G5875372848, G5897425255, G6273510985, G6372401702, G6565531537, G6910663132, G7066375774, G7431147399, G743399419, G7679015527, G7730037046, G806942708, G8107606116, G8182552442, G8302625262, G8376596093, G8717866391, G8862132048, G9000928711, G973579988

OpenAlex ID: W7162636673

FWCI: 40.45

Cites: 39

Cited by: 14

Related to: 10