{"id":250265,"date":"2025-10-30T05:34:15","date_gmt":"2025-10-30T05:34:15","guid":{"rendered":"https:\/\/www.newsbeep.com\/au\/250265\/"},"modified":"2025-10-30T05:34:15","modified_gmt":"2025-10-30T05:34:15","slug":"a-q-a-on-3i-atlas-at-perihelion-by-avi-loeb-oct-2025","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/au\/250265\/","title":{"rendered":"A Q & A on 3I\/ATLAS at Perihelion | by Avi Loeb | Oct, 2025"},"content":{"rendered":"

\"Avi<\/a>Press enter or click to view image in full size\"\"A series of images captured on Aug. 22, 2021 by Goldstone\u2019s 70-meter radio antenna, showing asteroid 2016 AJ193 rotating. The 1.3-kilometers wide object was the 1,001st near-Earth asteroid to be measured by planetary radar since 1968. (Credit: NASA\/JPL-Caltech<\/a>)<\/p>\n

When exactly did 3I\/ATLAS make its closest approach to the Sun?<\/p>\n

The perihelion time for 3I\/ATLAS<\/a> was today, October 29, 2025, at 7:47AM Eastern Time, according to the JPL Horizons fit to its trajectory. The timing uncertainty is only a few minutes.<\/p>\n

Did anything happen to 3I\/ATLAS at perihelion?<\/p>\n

We do not know since it is hidden from our terrestrial telescopes behind the Sun.<\/p>\n

Can we possibly map 3I\/ATLAS with a radar system?<\/p>\n

A radar system with a radio telescope was used<\/a> in the past to image asteroids and comets from the Solar System. The same technique can be applied to large interstellar objects, like 3I\/ATLAS. The first radar observation was of the asteroid 1566 Icarus<\/a> in 1968. I calculated today that we could have imaged 3I\/ATLAS with existing radar systems if Earth was located on the opposite side of its orbit around the Sun, corresponding to where Earth had been 6 months ago or will be again 6 months from now. At that location, 3I\/ATLAS would have passed within 54 million kilometers from Earth. Assuming a minimum diameter of 5 kilometers for 3I\/ATLAS (as derived here<\/a>), the interstellar object would have been detectable by existing radar systems on Earth. This would have given us a direct measurement of its size and images of its three-dimensional shape through multiple snapshots taken as it rotates every 16.2 hours. The observed radio flux scales in proportion to the object\u2019s diameter squared and inversely with its distance to the fourth power. The latter dependence stems from the fact that the radio flux impinging on its surface declines inversely with distance squared and the observed flux from its reflective surface adds another inverse dependence on distance squared. The steep dependence on distance makes the radar detection of 3I\/ATLAS unfeasible even at its closest distance of 269 million kilometers from Earth on December 19, 2025.<\/p>\n

Do we know about whether it really is a natural comet or something else?<\/p>\n

3I\/ATLAS is most likely a comet of natural origin, but there are 8 anomalies that endow it with a rank of 4 on the Loeb scale (quantified here<\/a> and here<\/a>), where a rank of 0 is for a definitely natural interstellar object and a rank of 10 is for a definitely technological object. The 8 surprising properties of 3I\/ATLAS are as follows:<\/p>\n

\u00b7 Its 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

\u00b7 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

\u00b7 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

\u00b7 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

\u00b7 The gas plume around 3I\/ATLAS 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

\u00b7 The gas plume of 3I\/ATLAS contains only 4% water by mass, a primary constituent of familiar comets (see here<\/a>).<\/p>\n

\u00b7 3I\/ATLAS showed extreme negative polarization, unprecedented for all known comets, including 2I\/Borisov, with a likelihood below 1% (see here<\/a>).<\/p>\n

\u00b7 3I\/ATLAS 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

Multiplying these small probabilities yields a cumulative likelihood lower than a part in ten quadrillion (10^{16}).<\/p>\n

After asking radio observers to monitor 3I\/ATLAS because of the last anomaly, I was assured yesterday that this is being done. Congresswoman Anna Paulina Luna is graciously helping to get the HiRISE images of 3I\/ATLAS from October 2, 2025 released to the scientific community.<\/p>\n

If 3I\/ATLAS maneuvers, releases mini-probes, or transmits radio signals, then we will know that it is technological in origin. Other technological signatures include artificial lights or excess heat from an engine. If 3I\/ATLAS is a natural comet glued together by weak forces, its heating by 770 watts per square meter at perihelion may break it up into fragments which evaporate more quickly. The resulting fireworks might generate a much brighter cometary plume of gas and dust around it.<\/p>\n

What do you think it is?<\/p>\n

We have to collect as much data as possible to figure out the nature of this anomalous object. The implication of alien technology would be huge and therefore we must take this possibility seriously. Our biggest rocket, Starship, is a hundred times smaller than 3I\/ATLAS, so in case 3I\/ATLAS is technological \u2014 its senders master capabilities that go well beyond our technologies.<\/p>\n

How does the technological scenario compare to science fiction films?<\/p>\n

Science is better than fiction, because nature might be more imaginative than the best script writers for science fiction movies in Hollywood. Rather than imagine who might be our dating partner, we better observe it.<\/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 sizeA series of images captured on Aug. 22, 2021…\n","protected":false},"author":2,"featured_media":250266,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[64,63,128,285],"class_list":{"0":"post-250265","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-space","8":"tag-au","9":"tag-australia","10":"tag-science","11":"tag-space"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/250265","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/comments?post=250265"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/250265\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media\/250266"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media?parent=250265"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/categories?post=250265"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/tags?post=250265"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}