Spectroscopic Characterization of Interstellar Object 3I/ATLAS: Water Ice in the Coma
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arXiv
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| Auteurs principaux: | , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866912593968365568 |
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| author | Yang, Bin Meech, Karen J. Connelley, Michael Zhao, Ruining Keane, Jacqueline V. |
| author_facet | Yang, Bin Meech, Karen J. Connelley, Michael Zhao, Ruining Keane, Jacqueline V. |
| contents | We present optical and near-infrared spectroscopy of the interstellar object 3I/ATLAS, obtained with Gemini-S/GMOS and NASA IRTF/SpeX on 2025 July 5 and July 14. The optical spectrum shows a red slope of approximately 10% per 1000 angstroms between 0.5 and 0.8 microns, closely resembling that of typical D-type asteroids. At longer wavelengths, the near-infrared spectrum flattens significantly to approximately 3% per 1000 angstroms from 0.9 to 1.5 microns, consistent with the spectral behavior of large water ice grains in the coma. Spectral modeling with an areal mixture of 70% Tagish Lake meteorite and 30% 10-micron-sized water ice successfully reproduces both the overall continuum and the broad absorption feature near 2.0 microns. The 1.5-micron water ice band, however, is not detected, likely due to the limited signal-to-noise of the IRTF data and dilution by refractory materials. The ~30% ice fraction should be interpreted as an approximate, order-of-magnitude estimate of the coma composition. The agreement between the GMOS and SpeX spectra, taken nine days apart, suggests short-term stability in the coma's optical properties. Our observations reveal that 3I/ATLAS is an active interstellar comet containing abundant water ice, with a dust composition more similar to D-type asteroids than to ultrared trans-Neptunian objects. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_14916 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Spectroscopic Characterization of Interstellar Object 3I/ATLAS: Water Ice in the Coma Yang, Bin Meech, Karen J. Connelley, Michael Zhao, Ruining Keane, Jacqueline V. Earth and Planetary Astrophysics Astrophysics of Galaxies We present optical and near-infrared spectroscopy of the interstellar object 3I/ATLAS, obtained with Gemini-S/GMOS and NASA IRTF/SpeX on 2025 July 5 and July 14. The optical spectrum shows a red slope of approximately 10% per 1000 angstroms between 0.5 and 0.8 microns, closely resembling that of typical D-type asteroids. At longer wavelengths, the near-infrared spectrum flattens significantly to approximately 3% per 1000 angstroms from 0.9 to 1.5 microns, consistent with the spectral behavior of large water ice grains in the coma. Spectral modeling with an areal mixture of 70% Tagish Lake meteorite and 30% 10-micron-sized water ice successfully reproduces both the overall continuum and the broad absorption feature near 2.0 microns. The 1.5-micron water ice band, however, is not detected, likely due to the limited signal-to-noise of the IRTF data and dilution by refractory materials. The ~30% ice fraction should be interpreted as an approximate, order-of-magnitude estimate of the coma composition. The agreement between the GMOS and SpeX spectra, taken nine days apart, suggests short-term stability in the coma's optical properties. Our observations reveal that 3I/ATLAS is an active interstellar comet containing abundant water ice, with a dust composition more similar to D-type asteroids than to ultrared trans-Neptunian objects. |
| title | Spectroscopic Characterization of Interstellar Object 3I/ATLAS: Water Ice in the Coma |
| topic | Earth and Planetary Astrophysics Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2507.14916 |