{"id":251193,"date":"2025-11-08T12:11:10","date_gmt":"2025-11-08T12:11:10","guid":{"rendered":"https:\/\/www.newsbeep.com\/uk\/251193\/"},"modified":"2025-11-08T12:11:10","modified_gmt":"2025-11-08T12:11:10","slug":"first-radio-signal-from-3i-atlas-absorption-by-hydroxyl-radicals-oh-molecules-by-avi-loeb-nov-2025","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/uk\/251193\/","title":{"rendered":"First Radio Signal from 3I\/ATLAS: Absorption by Hydroxyl Radicals (OH Molecules) | by Avi Loeb | Nov, 2025"},"content":{"rendered":"

\"Avi<\/a>Press enter or click to view image in full size\"\"The MeerKAT Radio Telescope in South Africa. (Credit: Wikimedia<\/a>)<\/p>\n

MeerKAT<\/a>, a radio telescope with a diameter of 13.5 meters operated by the South African Radio Astronomy Observatory, detected radio absorption lines by hydroxyl radicals, namely OH molecules, from the interstellar object 3I\/ATLAS<\/a>. The report by D.J. Pisano and collaborators was posted on The Astronomer\u2019s Telegram here<\/a>.<\/p>\n

MeerKAT observed 3I\/ATLAS on October 24, 2025 when the angular separation of 3I\/ATLAS from the Sun was 3.76 degrees, just 7 times the diameter of the Sun in the sky. The OH absorption signal was detected in two spectral lines at radio frequencies of 1.665 and 1.667 gigahertz. The two lines revealed absorption at Doppler velocity shifts of -15.59 (+\/-0.16) and -15.65(+\/-0.17) kilometers per second, respectively. The full-width-at-half-maximum of the absorption lines were 0.88(+\/-0.37) and 1.26(+\/-0.40) kilometers per second, respectively. Previous attempts to detect these lines with MeerKAT on September 20 and 28, 2025 were not successful.<\/p>\n

The solar conjunction of 3I\/ATLAS relative to Earth occurred a few days earlier, on October 21, 2025, when the object was traveling very close to the orbital plane of the Earth around the Sun. Given that the velocity vector of 3I\/ATLAS was nearly perpendicular to MeerKAT\u2019s line-of-sight, the Doppler shift of the OH absorption results from the full speed of 3I\/ATLAS relative to Earth of (30+68)=98 kilometers per second, times the sine of the angle between the direction of relative motion and MeerKAT\u2019s line-of-sight to 3I\/ATLAS on October 24. This angle was apparently 9.2 degrees.<\/p>\n

Given that 3I\/ATLAS was separated from the Sun by 1.38 times the Earth-Sun separation, its surface temperature was smaller than that of Earth by roughly the square root of 1.38. This is because the solar heating rate scales inversely with separation squared, whereas surface cooling scales as temperature to the 4th power. The resulting thermal speed of the OH molecules shed from the surface of 3I\/ATLAS at a temperature of ~230 degrees Kelvin, yields thermal broadening of the OH lines by a full-width at half maximum of ~0.8 kilometers per second \u2014 in agreement with the observed widths. Coincidentally, I taught thermal broadening in my class \u201cRadiative Processes in Astrophysics\u201d at the Harvard Astronomy department a month ago.<\/p>\n

This absorption signal constitutes the first radio detection of 3I\/ATLAS. Five weeks ago, I encouraged radio observatories like MeerKAT to search for radio emission from 3I\/ATLAS given that the arrival direction of 3I\/ATLAS coincided to within 9 degrees with the arrival direction of the Wow! Signal<\/a> detected in 1977 at a frequency of 1.4204556 gigahertz (as discussed here<\/a>). In response, I was assured that 3I\/ATLAS will be monitored by radio observatories like MeerKAT. So far there was no report on a radio detection of 3I\/ATLAS other than the OH absorption signal.<\/p>\n

On March 16, 2026, 3I\/ATLAS is expected to pass within 53 million kilometers from Jupiter. At that time, the Juno spacecraft will use its dipole antenna to search for a radio signal from 3I\/ATLAS at low frequencies ranging from 50 hertz to 40 megahertz.<\/p>\n

This morning, I have found the following letters in my inbox.<\/p>\n

Letter 1<\/p>\n

\u201cDear Prof. Loeb,<\/p>\n

I was reading your latest post on Medium during my breakfast, and I noticed that you mentioned at the end a few letters that had arrived in your inbox, so I decided to write to you a few lines of appreciation.<\/p>\n

I am an Italian teacher with a strong passion for astronomy. I teach math, science, and coding in middle school. Before teaching, I was a visiting professor in marine microbiology at the University of Genoa, and after starting a family with children, I decided to begin a career in teaching. I am very happy with this decision, and I enjoy teaching science (a bit less math, mostly because it is a difficult subject for many children here in Italy).<\/p>\n

This is just to introduce myself. The purpose of my email is to congratulate you for your passion, transparency, scientific rigor, and above all, your curiosity. These are the qualities I try to teach my students as well. As a microbiologist, I am sure that microbes must exist on other planets or moons, as long as there is liquid water \u2014 even if there is no light, no oxygen, and other conditions that are not necessary for many microbes that also live on Earth. As for intelligent life, I hope it exists, just as you often mention in your reflections. Mainly for the technology they could teach us and for the possibility that our human race could grow in stability and peace if we found our superior neighbors.<\/p>\n

I would like to conclude by saying that I hope to be a good example of a scientist and teacher for my students, just as you are for many people around the world.<\/p>\n

Best regards, ciao<\/p>\n

Stefania\u201d<\/p>\n

Letter 2<\/p>\n

\u201cDear Professor Avi Loeb,<\/p>\n

I am writing to you from Mexico City, Mexico.<\/p>\n

I hope this message finds you well.<\/p>\n

I would like to express my deepest appreciation for the dedicated and valuable work you are carrying out in the study of the interstellar object 3I\/ATLAS. Although I am not a student of astronomy, I have a strong interest and genuine fascination with space and the many questions that remain unanswered about our universe. Your research allows people like me, outside of the academic scientific field, to approach these topics with inspiration, clarity, and enthusiasm.<\/p>\n

I am grateful for the legacy your work is building \u2014 not only in terms of scientific knowledge, but also in encouraging curiosity, critical thinking, and openness to new possibilities. I deeply share your view on the importance of remaining inquisitive about the phenomena of the cosmos and being willing to explore what we do not yet fully understand.<\/p>\n

Thank you for expanding the boundaries of our understanding of the universe and for inspiring so many people, both within and beyond academia, to keep asking questions.<\/p>\n

I send you my best wishes and my admiration for your present and future work.<\/p>\n

With respect and gratitude,<\/p>\n

Alfonso Guti\u00e9rrez\u201d<\/p>\n

Letter 3<\/p>\n

\u201cGood Day Professor Loeb.<\/p>\n

I trust that you are well.<\/p>\n

My name is Chad Plaatjies, I\u2019m a content creator from Cape Town South Africa.<\/p>\n

I\u2019m doing my due diligence and I\u2019ve been creating awareness around 3I Atlas and your work.<\/p>\n

If in any way I could doing anything more to help, please feel free to contact me. I would love to either join your research team or do what I can in order to help.<\/p>\n

You\u2019ve been doing an amazing job keeping the world informed. We thank you sir.<\/p>\n

Kindest Regards.<\/p>\n

Chad Plaatjies\u201d<\/p>\n

Letter 4<\/p>\n

\u201cHello Dr Loeb,<\/p>\n

I have been following your papers on medium and watching all of your recent interviews to get the latest up-to-date information on the interstellar object 3I Atlas. I must say, I am grateful for your continued work to gather and analyze the data with transparency, educating us on possibly the most important and interesting astrological event to happen in my lifetime to date. With so much suppression of data and censorship in our media, it is refreshing to have someone that we can trust to relay the truth to us all. I think we all have come to rely on you and genuinely want to support you in any way we can. After watching the LBC interview that you did with the British journalist, I must say I was appalled at where the interviewer was initially headed, but your integrity and professionalism shone through as it always does. The ignorance of other scientists to conclusively state that 3I is simply a comet or natural object, this early on, is frankly shameful. I wanted to take a moment to tell you that myself, and my family watching, were very proud of the way that you explained the anomalies and the reason that it is so important to not make a determination this early in the game. Way to go! Though the interviewer seemed arrogant, I think you really opened him up to see that there is much more to the story. I read that there was another object detected, and I am hoping that you will give us some information on that object and whether or not it may be related to 3I\u2026I only trust what I read in your papers or see in your interviews\u2026after working in healthcare most of my life, you have inspired me to dabble in astronomy again. I am purchasing another telescope that I may can use to observe 3I on its closest approach to Earth and hopefully get some images. Thank you for being an inspiration to us all. What you said in reference to the scientific community around the world coming together despite our differences, was very moving. Thank you for making the world a better place.<\/p>\n

Best regards,<\/p>\n

Melody Rongstad<\/p>\n

Cape Coral, FL\u201d<\/p>\n

Letter 5<\/p>\n

\u201cHey there Avi,
I just wanted to write to you to apologize on behalf of the way you were treated on the LBC interview that went live today.<\/p>\n

You are the single most honest, open minded and helpful person speaking up about ALL possibilities regarding interstellar visitors.<\/p>\n

I have never taken an interest in all things space and you have opened that door for me, and I have read and watched everything youve been involved in for the last 6 months.<\/p>\n

Can you promise me something?
Keep being AWESOME, because you are a voice amongst chaos that humanity needs.<\/p>\n

Many thanks,
Andy
(Bristol, UK)\u201d<\/p>\n

Letter 6<\/p>\n

\u201cHello Dr. Loeb,<\/p>\n

My name is Katana. I have no education in science, astronomy or anything of the sort. However, it piqued my interest as I have gotten older.<\/p>\n

I\u2019ve always been interested in space and \u201cwhat\u2019s out there\u201d. Lately, I\u2019ve been doing more and more reading on it, though much of the complex parts I don\u2019t quite understand. The articles I typically come across are \u201cclick bait\u201d and that\u2019s not the part I am interested in.<\/p>\n

Then recently I had come across your article about 3I\/ATLAS and even listened to your Joe Rogan interview (A podcast I\u2019ve never listened to before). It resonated with me because I agree so much with your outlook. It almost feels as though we are in a watered-down life experience of the movie \u201cDon\u2019t Look Up\u201d.<\/p>\n

I am an interested amateur in your field of work and definitely don\u2019t understand the scientific math of your articles but everything else is an easy read and you have the most interesting articles I\u2019ve come across so far.<\/p>\n

Thank you for sharing your knowledge and putting your voice out there. You sharing your knowledge has piqued my interest further in this field and I\u2019m excited to see how it will grow.<\/p>\n

I\u2019m looking forward to your future articles.<\/p>\n

Continued reader,<\/p>\n

Katana Webler\u201d<\/p>\n

Letter 7<\/p>\n

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

Thank you again for taking the time to speak with us today \u2014 it was a genuine honor.<\/p>\n

We were deeply inspired not only by your scientific perspective, but by your humility, open-mindedness, and your courage to question established assumptions. These qualities are rare, and they remind us of the spirit that moved humanity forward in the time of Galileo \u2014 a belief that knowledge is never complete, and that progress requires curiosity, honesty, and the willingness to explore beyond the boundaries of convention.<\/p>\n

Millions of our Chinese-speaking audience admire you for these very reasons. Your work \u2014 and the way you carry yourself \u2014 encourages people to think boldly, stay curious, and believe in a future built on exploration and collaboration, not fear or limitation.<\/p>\n

We would be truly honored to continue this conversation in the future, whenever the time feels right. It would mean a great deal to us, and to the audience who has been profoundly inspired by your vision.<\/p>\n

With heartfelt gratitude,
Mark & Minnie
Interstellar Archaeology Team\u201d<\/p>\n

Letter 8<\/p>\n

\u201cI don\u2019t have much to say other than thank you for enlightening humanity and your continued good work from science. Am from Nairobi Kenya no one in my country I have met is talking about 3I Atlas and the potential future of the discovery, I have been learning,<\/p>\n

Thank you<\/p>\n

Leonard Amimo<\/p>\n

Visual Artist & Writer\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 sizeThe MeerKAT Radio Telescope in South Africa. (Credit: Wikimedia)…\n","protected":false},"author":2,"featured_media":251194,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[24],"tags":[2302,90,56,54,55],"class_list":{"0":"post-251193","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-physics","8":"tag-physics","9":"tag-science","10":"tag-uk","11":"tag-united-kingdom","12":"tag-unitedkingdom"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts\/251193","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=251193"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts\/251193\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/media\/251194"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/media?parent=251193"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/categories?post=251193"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/tags?post=251193"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}