{"id":246037,"date":"2025-11-05T21:28:09","date_gmt":"2025-11-05T21:28:09","guid":{"rendered":"https:\/\/www.newsbeep.com\/uk\/246037\/"},"modified":"2025-11-05T21:28:09","modified_gmt":"2025-11-05T21:28:09","slug":"no-clear-cometary-tail-in-post-perihelion-images-of-3i-atlas-by-avi-loeb-nov-2025","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/uk\/246037\/","title":{"rendered":"No Clear Cometary tail in Post-Perihelion Images of 3I\/ATLAS | by Avi Loeb | Nov, 2025"},"content":{"rendered":"

\"Avi<\/a>Press enter or click to view image in full size\"\"Post-perihelion image of the interstellar object 3I\/ATLAS, taken on November 5, 2025 by the R. Naves Observatory, shows a fuzzy ball of light. The Sunward direction is towards the bottom left corner (with the arrow on the left pointing in the anti-Sun direction). No obvious cometary tail is seen. (Credit: R. Naves Observatory, Spain<\/a>)<\/p>\n

On November 5, 2025, two new images of the interstellar object 3I\/ATLAS<\/a> were released. They show a compact source of light without a clear cometary tail. The coma is not very different in morphology than its appearance in the Hubble Space Telescope on July 21, 2025 (accessible here<\/a>).<\/p>\n

Press enter or click to view image in full size\"\"Post-perihelion image of 3I\/ATLAS, reported on November 5, 2025 by the Virtual Telescope Project. (Credit: The Virtual Telescope Project<\/a>)<\/p>\n

This is surprising in view of NASA\u2019s JPL report here<\/a> of a non-gravitational acceleration \u2014 normalized<\/a> at a heliocentric value of 1 au:<\/p>\n

1. A radial acceleration away from the Sun of 1.1×10^{-6} au per day squared.<\/p>\n

2. A transverse acceleration relative to the Sun\u2019s direction of 3.7×10^{-7} au per day squared.<\/p>\n

Based on momentum conservation (as discussed here<\/a>), I derived here<\/a> that the mass fraction lost during the perihelion passage of 3I\/ATLAS is larger than 13%. For a typical comet, this should have resulted in a massive coma with dust and gas that would have been pushed by the solar radiation pressure and the solar wind to the shape of a typical cometary tail pointing away from the Sun. No such tail is visible in the new images from November 5, 2025.<\/p>\n

In comparison, I include below yesterday\u2019s image of the solar system\u2019s comet Lemmon<\/a>, taken by one of the telescopes that observed 3I\/ATLAS two days ago. Lemmon features a clear cometary tail pointing away from the Sun, as expected.<\/p>\n

Press enter or click to view image in full size\"\"Image of the comet Lemmon<\/a> from the solar system, taken on November 3, 2025 by the R. Naves Observatory, shows a clear cometary tail away from the Sun. (Credit: R. Naves Observatory, Spain<\/a>)<\/p>\n

The anomalies displayed so far by 3I\/ATLAS include:<\/p>\n

1. Its retrograde trajectory is aligned to within 5 degrees with the ecliptic plane of the planets around the Sun, with a likelihood of 0.2% (see here<\/a>).<\/p>\n

2. During July and August 2025, it displayed a sunward jet (anti-tail) that is not an optical illusion from geometric perspective, unlike familiar comets (see here<\/a>).<\/p>\n

3. Its nucleus is about a million times more massive than 1I\/`Oumuamua<\/a> and a thousand times more massive than 2I\/Borisov<\/a>, while moving faster than both, altogether with a likelihood of less than 0.1% (see here<\/a> and here<\/a>).<\/p>\n

4. Its arrival time was fine-tuned to bring it within tens of millions of kilometers from Mars, Venus and Jupiter and be unobservable from Earth at perihelion, with a likelihood of 0.005% (see here<\/a>).<\/p>\n

5. Its gas plume contains much more nickel than iron (as found in industrially-produced nickel alloys) and a nickel to cyanide ratio that is orders of magnitude larger than that of all known comets, including 2I\/Borisov, with a likelihood below 1% (see here<\/a>).<\/p>\n

6. Its gas plume contains only 4% water by mass, a primary constituent of familiar comets (see here<\/a>).<\/p>\n

7. It shows extreme negative polarization, unprecedented for all known comets, including 2I\/Borisov, with a likelihood below 1% (see here<\/a>).<\/p>\n

8. It arrived from a direction coincident with the radio \u201cWow! Signal\u201d to within 9 degrees, with a likelihood of 0.6% (see here<\/a>).<\/p>\n

9. Near perihelion, it brightened faster than any known comet and was bluer than the Sun (see here<\/a>).<\/p>\n

10. It exhibits non-gravitational acceleration which requires massive evaporation of at least 13%of its mass (as calculated here<\/a>), but preliminary post-perihelion images do not show evidence for it so far.<\/p>\n

This afternoon, I received the following email from Chile:<\/p>\n

\u201cDear Professor Loeb:<\/p>\n

I am writing to you from Santiago, Chile.<\/p>\n

My name is Dario Villal\u00f3n, and I\u00b4m a civil electrical engineer from the University of Chile.<\/p>\n

I wanted to express my sincere gratitude, as your work is proving very important, not only for your specific research on the 3I Atlas, but also because your approach to questions is motivating many ordinary people to become interested in and understand topics they previously thought they would never pay attention to. I would like to mention the case of my 18-year-old daughter, who was unsure about what career to pursue as she finished high school. She has become interested in your publications (she doesn\u2019t face a language barrier since she is fluent in English), and your opinions on social media have greatly motivated her towards astrophysics and astronomy. She will most likely pursue studies in that field.<\/p>\n

I want to thank you and please continue your work despite the well-known challenges.<\/p>\n

Best regards from Chile!<\/p>\n

Sincerely, Dario Villal\u00f3n\u201d<\/p>\n

ABOUT THE AUTHOR<\/p>\n

Press enter or click to view image in full size\"\"(Image Credit: Chris Michel, National Academy of Sciences, 2023)<\/p>\n

Avi Loeb is the head of the Galileo Project, founding director of Harvard University\u2019s \u2014 Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011\u20132020). He is a former member of the President\u2019s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of \u201cExtraterrestrial:<\/a> The First Sign of Intelligent Life Beyond Earth<\/a>\u201d and a co-author of the textbook \u201cLife in the Cosmos<\/a>\u201d, both published in 2021. The paperback edition of his new book, titled \u201cInterstellar<\/a>\u201d, was published in August 2024.<\/p>\n","protected":false},"excerpt":{"rendered":"Press enter or click to view image in full sizePost-perihelion image of the interstellar object 3I\/ATLAS, taken on…\n","protected":false},"author":2,"featured_media":246038,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[90,416,56,54,55],"class_list":{"0":"post-246037","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-space","8":"tag-science","9":"tag-space","10":"tag-uk","11":"tag-united-kingdom","12":"tag-unitedkingdom"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts\/246037","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/comments?post=246037"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts\/246037\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/media\/246038"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/media?parent=246037"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/categories?post=246037"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/tags?post=246037"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}