Tootfinder

Astronomers have categorized this object as interstellar
because of the hyperbolic shape of its orbital path.
(It does not follow a closed orbital path about the Sun.)
3I/ATLAS will reach its closest point to the Sun around Oct. 30, 2025,
at a distance of about 1.4 au
(130 million miles, or 210 million kilometers)
— just inside the orbit of Mars.

Comet 3I/ATLAS
NASA missions are working together to track and study this rare, interstellar comet as it passes through our solar system.

Keine Außerirdischen: NASA zeigt Bilder von 3I/ATLAS
Nach dem Ende des Shutdowns hat die NASA endlich Bilder des Kometen 3I/ATLAS gezeigt. Das lange Schweigen der Raumfahrtbehörde hatte zu Spekulationen geführt.
https:…

Whoa, the #InterstellarComet 3I/ATLAS clearly has a tail now! A raw image taken minutes ago with the GMOS instrument on Gemini South and shared live during the Shadow the Scientists event - I raised the contrast slightly.

Astronomie: ESA-Missionen fotografieren 3I/ATLAS, die der NASA vielleicht auch
Der interstellare Komet 3I/ATLAS hat den Mars passiert und Sonden haben versucht, ihn zu fotografieren. Die ESA zeigt die Bilder, bei der NASA muss man suchen.

All the NASA s/c images of #3IATLAS shared today (and some more) can be found at https://science.nasa.gov/solar-system/comets/3i-atlas/comet-3i-atlas-image-gallery/ now - including this spectrum from the Imaging Ultraviolet Spectrograph on MAVEN taken on 28 September, showing hydrogen emitted from different sources, namely the comet (dim spot on the far left), hydrogen from Mars (bright emission on the right), and hydrogen flowing through our solar system between the planets (dim emission in the middle).

3I/ATLAS: Auch chinesische Marssonde fotografiert interstellaren Kometen
Weil die größte Annäherung von 3I/ATLAS an die Sonne von der Erde aus nicht sichtbar war, mussten Sonden einspringen. Das hat auch eine aus China getan.

SPHEREx and JWST reveal what comet 3I/ATLAS is... and isn't - Big Think #astronomy

SPHEREx and JWST reveal what comet 3I/ATLAS is... and isn't
Designed to map galaxies, the SPHEREx mission's first science result is instead about interstellar interloper 3I/ATLAS. No, it's not aliens.

ATLAS Photometry of Interstellar Object 3I/ATLAS
John Tonry, Larry Denneau, Miguel Alarcon, Alejandro Clocchiatti, Nicolas Erasmus, Alan Fitzsimmons, Javier Licandro, Karen Meech, Robert Siverd, Henry Weiland
https://arxiv.org/abs/2509.05562

ATLAS Photometry of Interstellar Object 3I/ATLAS
We present calibrated ATLAS photometry of the interstellar comet 3I/ATLAS (C/2025 N1) from 28 March through 29 Aug 2025, obtained with the five-site, robotic ATLAS network in the c (420-650~nm), o (560-820~nm), and Teide w (420-720~nm) bands. Stacked difference images yield reliable light curves measured in four fixed apertures that capture the evolving coma. We observe 3I/ATLAS transitioning in color from red (c-o)~0.7 before MJD 60860 to near-solar (c-o)~0.3 after MJD 60870, coincident with t…

ESA’s space probe #JUICE is headed towards a truly unexpected encounter: on November 2nd, observations of interstellar object #3IATLAS will begin. Read more about contributions from #mpsgoettingen

All eyes on #3I/ATLAS ☄️
Our Mars Express & ExoMars Trace Gas Orbiter will observe the comet around its closest approach to Mars on 3 October 2025, when 3I/ATLAS will be around 30 million km from the red planet.

ESA observations of interstellar comet 3I/ATLAS
The European Space Agency (ESA) reacted promptly to the discovery of comet 3I/ATLAS on 1 July 2025. Soon after they were alerted to its existence by automated detection systems, ESA astronomers began using ground-based telescopes in Hawaii, Chile, and Australia to monitor its progress.Since then, the comet has been observed by space telescopes close to Earth, including the NASA/ESA Hubble Space Telescope and the NASA/ESA/CSA James Webb Space Telescope.In the coming months, ESA will turn interp…

Interstellarer Komet 3I/ATLAS: Jetzt sind die Weltraumsonden dran
Der interstellare Besucher 3I/ATLAS rast weiter durchs Sonnensystem, von der Erde aus ist er aber gerade nicht zu sehen. Deshalb übernehmen jetzt Raumsonden.

Search for Past Stellar Encounters and the Origin of 3I/ATLAS
Yiyang Guo, Luyao Zhang, Fabo Feng, Zhao-Yu Li, Anton Pomazan, Xiaohu Yang
https://arxiv.org/abs/2509.03361 https:/…

Search for Past Stellar Encounters and the Origin of 3I/ATLAS
3I/ATLAS, the third discovered interstellar object, has a heliocentric speed of 58 km/s and exhibits cometary activity. To constrain the origin of 3I/ATLAS and its past dynamical evolution, we propagate the orbits of 3I/ATLAS and nearby stars to search for stellar encounters. Integrating orbits in the Galactic potential and propagating the astrometric and radial-velocity uncertainties of 30 million Gaia stars, we identify 25 encounters with median encounter distances less than 1 pc. However, be…

Interstellar Comet 3I/ATLAS Stuns Scientists with Surprising Bright Outburst and Ancient Origins https://ground.news/article/interstellar-comet-3i-atlas-stuns-scientists-with-surprising-bright-outburst-and-ancient-origins_cafba4

Nachfolger von 3I/ATLAS: Raumsonde könnte interstellarem Kometen besuchen
Für einen Besuch beim interstellaren Kometen 3I/ATLAS ist es zu spät, aber Nachfolger wären erreichbar. Das hat ein Forschungsteam aus den USA bestätigt.

#3iatlas
I've read that we can't observe 3I/Atlas from earth because it will be behind the sun, but according to SkyLive it looks like i should be possible to spot it from Norway still at around 1730.
If I had had a telescope, I would have tried(and likely failed).
#3i_atlas

Spatial Profiles of 3I/ATLAS CN and Ni Outgassing from Keck/KCWI Integral Field Spectroscopy
W. B. Hoogendam, B. J. Shappee, J. J. Wray, B. Yang, K. J. Meech, C. Ashall, D. D. Desai, K. Hart, J. T. Hinkle, A. Hoffman, E. M. Hu, D. O. Jones, K. Medler
https://arxiv.org/abs/2510.11779

Spatial Profiles of 3I/ATLAS CN and Ni Outgassing from Keck/KCWI Integral Field Spectroscopy
Cometary activity from interstellar objects provides a unique window into the environs of other stellar systems. We report blue-sensitive integral field unit spectroscopy of the interstellar object 3I/ATLAS from the Keck-II-mounted Keck Cosmic Web Imager on August 24, 2025 UT. We confirm previously reported CN and Ni outgassing, and present, for the first time, the radial profiles of Ni and CN emission in 3I/ATLAS. We find a characteristic $e$-folding radius of $593.7\pm14.8$ km for Ni and $841…

Astronomie: Interstellarer Komet 3I/ATLAS wieder von der Erde aus sichtbar
Ein Astronom aus den USA hat in den frühen Morgenstunden mehrere Aufnahmen des interstellaren Kometen 3I/ATLAS gemacht. Er war vorher nicht für uns sichtbar.

☄️ Comet #3I/ATLAS is currently making its closest approach to the Sun.
#ESAJuice might catch the best view of this comet in a very active state. Juice will attempt observations in November 2025, with data received on Earth in February 2026
👉

Comet 3I/ATLAS – frequently asked questions
Note that this list is regularly updated as we learn more about comet 3I/ATLAS

Is 3I Atlas adjusting its course towards Mars?
#3iAtlas #news
https://youtu.be/_NnccpJLxBk?si=T4X41l0yh7A62_h1

3I/ATLAS: Aufnahme zeigt gewachsenen Schweif des interstellaren Kometen
Der dritte bekannte interstellare Komet im Sonnensystem steht jetzt zu nah an der Sonne. Vorher ist noch eine beeindruckende Aufnahme des Schweifs gelungen.

Non-Gravitational Acceleration in 3I ATLAS: Constraints on Exotic Volatile Outgassing in Interstellar Comets
Florian Neukart
https://arxiv.org/abs/2511.07450 https://arxiv.org/pdf/2511.07450 https://arxiv.org/html/2511.07450
arXiv:2511.07450v1 Announce Type: new
Abstract: The interstellar comet 3I/ATLAS exhibited a measurable nongravitational acceleration similar in form to that of 1I/'Oumuamua but of smaller magnitude. Using thermophysical and Monte Carlo models, we show that this acceleration can be fully explained by anisotropic outgassing of conventional volatiles, primarily CO and CO2, under realistic surface and rotational conditions. The model includes diurnal and obliquity-averaged energy balance, empirical vapor-pressure relations, and collimated jet emission from localized active regions. Mixed CO-CO2 compositions reproduce both the magnitude and direction of the observed acceleration with physically plausible active fractions below one percent for nucleus radii between 0.5 and 3 km. Less volatile species such as NH3 and CH4 underproduce thrust at equilibrium temperatures near 1 AU. These results eliminate the need for nonphysical or exotic explanations and define thermophysical limits for natural acceleration mechanisms in interstellar comets.
toXiv_bot_toot

Or friend @… seems to be getting a wee bit exhasperated with all the silly people that are saying nonsense about 3I Atlas. :) https://youtu.be/O0Q4agPyUqI

Prediscovery Activity of New Interstellar Object 3I/ATLAS: A Dynamically-Old Comet?
Quanzhi Ye, Michael S. P. Kelley, Henry H. Hsieh, Eric C. Bellm, Tracy X. Chen, Richard Dekany, Andrew Drake, Steven L. Groom, George Helou, Shrinivas R. Kulkarni, Thomas A. Prince, Reed Riddle
https://arxiv.org/abs/2509.08792…

Prediscovery Activity of New Interstellar Object 3I/ATLAS: A Dynamically-Old Comet?
We report on the prediscovery observations and constraints of the new interstellar comet 3I/2025 N1 (ATLAS), made by the Zwicky Transient Facility (ZTF), for the inbound leg of the comet out to a heliocentric distance of $r_\mathrm{h}=17$ au, or approximately a year before its discovery. We find that 3I/ATLAS has been active inward of a heliocentric distance of at least $r_\mathrm{h}=6.5$ au. The comet followed a brightening rate of $\propto r_\mathrm{h}^{-3.8}$, which is significantly steeper …

3I/ATLAS: In Search of the Witnesses to Its Voyage
X. P\'erez-Couto, S. Torres, E. Villaver, A. J. Mustill, M. Manteiga
https://arxiv.org/abs/2509.07678 https://

3I/ATLAS: In Search of the Witnesses to Its Voyage
3I/ATLAS is the third interstellar object discovered to date, following 1I/'Oumuamua and 2I/Borisov. Its unusually high excess velocity and active cometary nature make it a key probe of the Galactic population of icy planetesimals. Understanding its origin requires tracing its past trajectory through the Galaxy and assessing the possible role of stellar encounters, both as a potential origin and a perturber to its orbit. We integrated the orbit of 3I/ATLAS backward in time for 10 Myr, together …

And here comes ... another light curve of interstellar comet #ATLAS through much of October, now based on the satellite coronagraphs LASCO C3 and CCOR-1, with observations up to and including October 26th! From the paper "Rapid Brightening of 3I/ATLAS Ahead of Perihelion" - https://arxiv.org/abs/2510.25035 - out minutes ago: it finds that "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."

Our solar system’s interstellar interloper, 3I/ATLAS,
showed strong ultraviolet emissions that are unmistakable telltales of hydroxyl gas (OH), a byproduct of water,
when astronomers imaged it with the with NASA’s Neil Gehrels Swift space telescope before it disappeared behind the Sun.
Their findings, detailed in a new studypublished in The Astrophysical Journal Letters, argue that the presence of all this OH indicates
the comet is ejecting water vapor at a torrentia…

Crosslisted article(s) found for astro-ph.SR. https://arxiv.org/list/astro-ph.SR/new
[1/1]:
- Spatial Profiles of 3I/ATLAS CN and Ni Outgassing from Keck/KCWI Integral Field Spectroscopy
Hoogendam, Shappee, Wray, Yang, Meech, Ashall, Desai, Hart, Hinkle, Hoffman, Hu, Jones, Medler

The Physics of Cometary Anti-tails as Observed in 3I/ATLAS
Eric Keto, Abraham Loeb
https://arxiv.org/abs/2509.07771 https://arxiv.org/pdf/2509.07771…

The Physics of Cometary Anti-tails as Observed in 3I/ATLAS
Observations of interstellar comet 3I/ATLAS at 3.8 au show an elongated coma similar to a cometary tail but pointing in the direction of the Sun. This type of anti-tail, not a result of perspective, may not have been previously observed. We explain the anti-tail as an anisotropic extension of the snow line, or survival radius of a sublimating ice grain, in the direction of the Sun. The anisotropy is due to the difference in the sublimation mass flux in the solar and perpendicular directions cau…

Extreme Negative Polarisation of New Interstellar Comet 3I/ATLAS
Zuri Gray, Stefano Bagnulo, Galin Borisov, Yuna G. Kwon, Alberto Cellino, Ludmilla Kolokolova, Rosemary C. Dorsey, Grigori Fedorets, Mikael Granvik, Eric MacLennan, Olga Mu\~noz, Philippe Bendjoya, Maxime Devog\`ele, Simone Ieva, Antti Penttil\"a, Karri Muinonen
https://…

Extreme Negative Polarisation of New Interstellar Comet 3I/ATLAS
We present the first polarimetric observations of the third discovered interstellar object, 3I/ATLAS (C/2025 N1), obtained pre-perihelion with FORS2/VLT, ALFOSC/NOT, and FoReRo2/RCC, over a phase angle range of 7.7-22.4°. This marks the second ever polarimetric study of an interstellar object, the first distinguishing 2I/Borisov from most Solar System comets by its higher positive polarisation. Our polarimetric measurements as a function of phase angle reveal that 3I is characterised by an dee…

Replaced article(s) found for astro-ph.EP. https://arxiv.org/list/astro-ph.EP/new
[1/1]:
- Spectroscopic Characterization of Interstellar Object 3I/ATLAS: Water Ice in the Coma
Bin Yang, Karen J. Meech, Michael Connelley, Ruining Zhao, Jacqueline V. Keane

And here now is the color composite of the famous images of the #InterstellarComet 3I/ATLAS taken in the night 27/28 August in u, g, r and i: https://noirlab.edu/public/news/noirlab2525/ - the tail measures about 30 arc seconds. Amateur astronomers caught it as well, with a 12-inch telescope, only a few hours later: https://groups.io/g/comets-ml/message/33921

Near-Discovery SOAR Photometry of the Third Interstellar Object: 3I/ATLAS
Tessa T. Frincke, Atsuhiro Yaginuma, John W. Noonan, Henry H. Hsieh, Darryl Z. Seligman, Carrie E. Holt, Jay Strader, Thomas Do, Peter Craig, Isabella Molina
https://arxiv.org/abs/2509.02813

Near-Discovery SOAR Photometry of the Third Interstellar Object: 3I/ATLAS
3I/ATLAS was discovered on UT 2025 July 1 and joins a limited but growing population of detected $\sim10^2-10^3$ m scale interstellar objects. In this paper we report photometric observations of 3I/ATLAS from the nights of UT 2025 July 3, UT 2025 July 9, and UT 2025 July 10 obtained with the Southern Astrophysical Research Telescope (SOAR). The photometric observations are taken with the Goodman High Throughput Spectrograph (HTS) in the $r'$-band. These data provide 28 photometric data points t…

JCMT detection of HCN emission from 3I/ATLAS at 2.1 AU
Iain M. Coulson, Yi-Jehng Kuan, Steven B. Charnley, Martin A. Cordiner, Yo-Ling Chuang, Yueh-Ning Lee, Min-Kai Lin, Stefanie N. Milam, Bannawit Pimpanuwat, Nathan X. Roth, Micha{\l} \.Z\'o{\l}towski
https://arxiv.org/abs/2510.02817

JCMT detection of HCN emission from 3I/ATLAS at 2.1 AU
We report the detection of HCN ($J=3-2$) rotational emission from comet 3I/ATLAS at a heliocentric distance of 2.13 AU with the James Clerk Maxwell Telescope (JCMT). Observations were conducted from 07 August 2025 (UT) using the $^{\prime}\overline U^{\prime}\overline u$ heterodyne receiver and ACSIS spectroscopic backend. The HCN line was detected at $>5σ$ on 14 Sep 2025 (UT) and a production rate of $Q({\rm HCN})=(4.0\pm1.7)\times10^{25}\ {\rm s}^{-1}$ was derived by non-LTE radiative transf…

Images of the #InterstellarComet 3I/ATLAS taken in u, g, r, and i bands on 2025 August 27 UTC with GMOS on Gemini South during the "Shadow the Scientists" event - see https://www.astronomerstelegram.org/?read=17363 for what's seen here.

Upper Limit on the Non-Gravitational Acceleration and Lower Limits on the Nucleus Mass and Diameter of 3I/ATLAS
Richard Cloete, Abraham Loeb, Peter Vere\v{s}
https://arxiv.org/abs/2509.21408

Upper Limit on the Non-Gravitational Acceleration and Lower Limits on the Nucleus Mass and Diameter of 3I/ATLAS
We use astrometric data on 3I/ATLAS compiled by the Minor Planet Center from May 15 to September 23, 2025, and derive an upper limit on any statistically significant deviation from the best-fit gravity-based trajectory. The residuals imply that the non-gravitational acceleration is smaller than $\sim 3 \times 10^{-10}\,{\rm au\,d^{-2}}$. Based on the total mass-loss rate and outflow speed inferred from JWST data on August 6, 2025, we derive lower limits on the mass and diameter of 3I/ATLAS of $…

Here now is an edited recording of the "Shadow the Scientists" event last night during which Gemini South observed the #InterstellarComet 3I/ATLAS and detected its antisolar tail which hadn't been seen before: https://www.youtube.com/watch?v=5__AG5M5X8M - happens at 1:14:00.

Onset of CN Emission in 3I/ATLAS: Evidence for Strong Carbon-Chain Depletion
Luis E. Salazar Manzano, Hsing Wen Lin, Aster G. Taylor, Darryl Z. Seligman, Fred C. Adams, David W. Gerdes, Thomas Ruch, Tessa T. Frincke, Kevin J. Napier
https://arxiv.org/abs/2509.01647

Onset of CN Emission in 3I/ATLAS: Evidence for Strong Carbon-Chain Depletion
Interstellar objects provide a direct window into the environmental conditions around stars other than the Sun. The recent discovery of 3I/ATLAS, the second interstellar comet ever observed, offers a unique opportunity to investigate the physical and chemical properties of interstellar objects and to compare them with those of comets in our own Solar System. In this Letter we present the results of a 10-night spectroscopic and photometric monitoring campaign with the 2.4 m Hiltner and 1.3 m McG…

Extreme NiI/FeI abundance ratio in the coma of the interstellar comet 3I/ATLAS
Damien Hutsem\'ekers, Jean Manfroid, Emmanu\"el Jehin, Cyrielle Opitom, Michele Bannister, Juan Pablo Carvajal, Rosemary Dorsey, K Aravind, Baltasar Luco, Brian Murphy, Thomas H. Puzia, Rohan Rahatgaonkar
https://arxiv.org/abs/2509.26053

Extreme NiI/FeI abundance ratio in the coma of the interstellar comet 3I/ATLAS
Emission lines of FeI and NiI are commonly found in the coma of solar system comets, even at large heliocentric distances. These atoms are most likely released from the surface of the comet's nucleus or from a short-lived parent. The presence of these lines in cometary spectra is unexpected because the surface blackbody equilibrium temperature is too low to allow the sublimation of refractory minerals containing these metals. These lines were also found in the interstellar comet 2I/Borisov whic…

Quantitative Mapping of the Loeb Scale
Oem Trivedi, Abraham Loeb
https://arxiv.org/abs/2509.06253 https://arxiv.org/pdf/2509.06253

Quantitative Mapping of the Loeb Scale
The recent discovery of a third interstellar object (ISO) 3I/ATLAS, following 1I/`Oumuamua and 2I/Borisov, has raised questions about the nature and origin of these enigmatic objects. With the Vera C. Rubin Observatory expected to discover dozens of new ISOs over the next decade, it is timely to use a classification scheme for their nature in the context of the recently proposed Loeb scale. Here, we provide a formalism for ranking ISOs quantitatively on the Loeb Scale in analogy to Sagan's form…

Replaced article(s) found for astro-ph.EP. https://arxiv.org/list/astro-ph.EP/new
[1/1]:
- Water Production Rates of the Interstellar Object 3I/ATLAS
Zexi Xing, Shawn Oset, John Noonan, Dennis Bodewits

Crosslisted article(s) found for astro-ph.EP. https://arxiv.org/list/astro-ph.EP/new
[1/1]:
- VLT observations of interstellar comet 3I/ATLAS II. From quiescence to glow: Dramatic rise of Ni ...
Rohan Rahatgaonkar, et al.