Rapid Brightening of 3I/ATLAS Ahead of Perihelion
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866908804134731776 |
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| author | Zhang, Qicheng Battams, Karl |
| author_facet | Zhang, Qicheng Battams, Karl |
| contents | Interstellar comet 3I/ATLAS has been approaching its 2025 October 29 perihelion while opposite the Sun from Earth, hindering ground-based optical observations over the preceding month. However, this geometry placed the comet within the fields of view of several space-based solar coronagraphs and heliospheric imagers, enabling its continued observation during its final approach toward perihelion. We report photometry from STEREO-A's SECCHI HI1 and COR2, SOHO's LASCO C3, and GOES-19's CCOR-1 instruments in 2025 September--October, which show a rapid rise in the comet's brightness scaling with heliocentric distance r as r^(-7.5+/-1.0). CCOR-1 also resolves the comet as an extended source with an apparent coma ~4' in diameter. Furthermore, LASCO color photometry shows the comet to be distinctly bluer than the Sun, consistent with gas emission contributing a substantial fraction of the visible brightness near perihelion. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2510_25035 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Rapid Brightening of 3I/ATLAS Ahead of Perihelion Zhang, Qicheng Battams, Karl Earth and Planetary Astrophysics Astrophysics of Galaxies Interstellar comet 3I/ATLAS has been approaching its 2025 October 29 perihelion while opposite the Sun from Earth, hindering ground-based optical observations over the preceding month. However, this geometry placed the comet within the fields of view of several space-based solar coronagraphs and heliospheric imagers, enabling its continued observation during its final approach toward perihelion. We report photometry from STEREO-A's SECCHI HI1 and COR2, SOHO's LASCO C3, and GOES-19's CCOR-1 instruments in 2025 September--October, which show a rapid rise in the comet's brightness scaling with heliocentric distance r as r^(-7.5+/-1.0). CCOR-1 also resolves the comet as an extended source with an apparent coma ~4' in diameter. Furthermore, LASCO color photometry shows the comet to be distinctly bluer than the Sun, consistent with gas emission contributing a substantial fraction of the visible brightness near perihelion. |
| title | Rapid Brightening of 3I/ATLAS Ahead of Perihelion |
| topic | Earth and Planetary Astrophysics Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2510.25035 |