_version_ 1866912556448219136
author Bolin, Bryce T.
Belyakov, Matthew
Fremling, Christoffer
Graham, Matthew J.
Abdelaziz, Ahmed. M.
Elhosseiny, Eslam
Gray, Candace L.
Ingebretsen, Carl
Jewett, Gracyn
Karpov, Sergey
Kilic, Mukremin
Mašek, Martin
Molham, Mona
Roderick, Diana
Takey, Ali
Lisse, Carey M.
Abron, Laura-May
Coughlin, Michael W.
Hsieh, Cheng-Han
Noll, Keith S.
Wong, Ian
author_facet Bolin, Bryce T.
Belyakov, Matthew
Fremling, Christoffer
Graham, Matthew J.
Abdelaziz, Ahmed. M.
Elhosseiny, Eslam
Gray, Candace L.
Ingebretsen, Carl
Jewett, Gracyn
Karpov, Sergey
Kilic, Mukremin
Mašek, Martin
Molham, Mona
Roderick, Diana
Takey, Ali
Lisse, Carey M.
Abron, Laura-May
Coughlin, Michael W.
Hsieh, Cheng-Han
Noll, Keith S.
Wong, Ian
contents We describe the physical characteristics of interstellar comet 3I/ATLAS, discovered on 2025 July 1 by the Asteroid Terrestrial-impact Last Alert System. The comet has eccentricity, $e$ $\simeq$ 6.08 and velocity at infinity, v$_{\infty}$ $\simeq$ 57 km/s, indicating an interstellar origin. \textbf{We obtained B,V, R, I, g, r, i, and z photometry with the Kottamia Astronomical Observatory 1.88-m telescope, the Palomar 200-inch telescope, and the Astrophysical Research Consortium 3.5-m telescope on 2025 July 2, 3, and 6. We measured colour indices B-V=0.98$\pm$0.23, V-R=0.71$\pm$0.09, R-I=0.14$\pm$0.10, g-r=0.84$\pm$0.05 mag, r-i=0.16$\pm$0.03 mag, i-z=-0.02$\pm$0.07 mag, and g-i=1.00$\pm$0.05 mag and a spectral slope of 16.0$\pm$1.9 $\%$/100 nm.} We calculate the dust cross-section within 10,000 km of the comet to be 184.6$\pm$4.6 km$^2$, assuming an albedo of 0.10. 3I/ATLAS's coma has FWHM$\simeq$2.2 arcsec and A(0$^\circ$)f$ρ$=280.8$\pm$3.2 cm. \textbf{We estimate that 3I/ATLAS's \textmu m-scale to mm-scale dust is ejected at $\sim$0.01-1 m/s, implying a dust production of $\sim$0.1 - 1.0 kg/s.
format Preprint
id arxiv_https___arxiv_org_abs_2507_05252
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Interstellar comet 3I/ATLAS: discovery and physical description
Bolin, Bryce T.
Belyakov, Matthew
Fremling, Christoffer
Graham, Matthew J.
Abdelaziz, Ahmed. M.
Elhosseiny, Eslam
Gray, Candace L.
Ingebretsen, Carl
Jewett, Gracyn
Karpov, Sergey
Kilic, Mukremin
Mašek, Martin
Molham, Mona
Roderick, Diana
Takey, Ali
Lisse, Carey M.
Abron, Laura-May
Coughlin, Michael W.
Hsieh, Cheng-Han
Noll, Keith S.
Wong, Ian
Earth and Planetary Astrophysics
Astrophysics of Galaxies
Instrumentation and Methods for Astrophysics
We describe the physical characteristics of interstellar comet 3I/ATLAS, discovered on 2025 July 1 by the Asteroid Terrestrial-impact Last Alert System. The comet has eccentricity, $e$ $\simeq$ 6.08 and velocity at infinity, v$_{\infty}$ $\simeq$ 57 km/s, indicating an interstellar origin. \textbf{We obtained B,V, R, I, g, r, i, and z photometry with the Kottamia Astronomical Observatory 1.88-m telescope, the Palomar 200-inch telescope, and the Astrophysical Research Consortium 3.5-m telescope on 2025 July 2, 3, and 6. We measured colour indices B-V=0.98$\pm$0.23, V-R=0.71$\pm$0.09, R-I=0.14$\pm$0.10, g-r=0.84$\pm$0.05 mag, r-i=0.16$\pm$0.03 mag, i-z=-0.02$\pm$0.07 mag, and g-i=1.00$\pm$0.05 mag and a spectral slope of 16.0$\pm$1.9 $\%$/100 nm.} We calculate the dust cross-section within 10,000 km of the comet to be 184.6$\pm$4.6 km$^2$, assuming an albedo of 0.10. 3I/ATLAS's coma has FWHM$\simeq$2.2 arcsec and A(0$^\circ$)f$ρ$=280.8$\pm$3.2 cm. \textbf{We estimate that 3I/ATLAS's \textmu m-scale to mm-scale dust is ejected at $\sim$0.01-1 m/s, implying a dust production of $\sim$0.1 - 1.0 kg/s.
title Interstellar comet 3I/ATLAS: discovery and physical description
topic Earth and Planetary Astrophysics
Astrophysics of Galaxies
Instrumentation and Methods for Astrophysics
url https://arxiv.org/abs/2507.05252