Rapid Brightening of 3I/ATLAS Ahead of Perihelion
2025/10/28 by Qicheng Zhang, Karl Battams, Zhang, Qicheng +1 · 10 voices · 4 citations
Physics and Astronomy · #Astro and Planetary Science #Solar and Space Plasma Dynamics #Stellar, planetary, and galactic studies
paper · pdf · doi:10.1088/1538-3873/ae2e88
Abstract
Abstract 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 of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>∼</mml:mo> <mml:msup> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo accent="true">′</mml:mo> </mml:mrow> </mml:msup> </mml:math> in diameter. Furthermore, LASCO/CCOR-1 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.
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- Rapid Brightening of 3I/Atlas Ahead of Perihelion [hn, 31 points, 78 comments]
- We now have roughly complete magnitude data for our interstellar visitor 3I / ATLAS, up to its perihelion This includes SOHO LASCO and GOES-19 CCOR-1 data from arxiv.org/abs/2510.25035 This plot looks [bsky, 9 points, 1 comments]
- Loeb highlighted today in his blog this unusual brightening. If he stays true to form, he'll spend a while thinking why this "anomaly" argues it's an alien spaceship, then add it to his list and updat [bsky, 8 points, 1 comments]
- Rapid Brightening of 3I/ATLAS Ahead of Perihelion Qicheng Zhang, Karl Battams arxiv.org/abs/2510.25035 ☄️🔭 [bsky, 7 points, 0 comments]
- Der interstellare Komet ATLAS gestern im sonnennächsten Punkt seiner Bahn - von der Erde aus unbeobachtbar, da zu nahe neben der Sonne am Himmel, aber kein Problem für die PUNCH-Satelliten. Auch ander [bsky, 4 points, 1 comments]
- An interstellar visitor lighting up as it swings by — nature’s fireworks, with a cosmic story to tell. arxiv.org/abs/2510.25035 [bsky, 1 points, 0 comments]
- LOTS more 3I/ATLAS October data points from LASCO C3 and CCOR-1 in the paper arxiv.org/pdf/2510.25035 the alert of which reached me 10 minutes ago! [bsky, 1 points, 1 comments]
- Rapid Brightening of 3I/Atlas Ahead of Perihelion https://arxiv.org/abs/2510.25035 [bsky, 0 points, 0 comments]
- Rapid Brightening of 3I/Atlas Ahead of Perihelion #HackerNews https://arxiv.org/abs/2510.25035 [bsky, 0 points, 0 comments]
- Rapid Brightening of 3I/Atlas Ahead of Perihelion https://arxiv.org/abs/2510.25035 (https://news.ycombinator.com/item?id=45763367) [bsky, 0 points, 0 comments]
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