Zitat Apache Point Observatory Colors of Interstellar Comet 3I/ATLAS on 13 Jul 2025; 17:27 UT Credential Certification: Bryce Bolin (bolin.astro@gmail.com)
We report color measurements of interstellar comet 3I/ATLAS from g, r, i, and z band photometry taken with the Astrophysical Research Consortium 3.5-m telescope (ARC 3.5-m) at Apache Point Observatory (observatory code 705). We used the ARC Telescope Imaging Camera (ARCTIC) to observe 3I/ATLAS on 2025 July 06 03:23 UTC. The comet appears to be extended in the ARCTIC images, with a coma having a FWHM between 1.8-2.3 arcsec in the g, r, i, and z images compared to the FWHM measured for nearby background stars of ~1.5 arcsec (see attached g, r, i, and z-band band image composite), confirming the results of recent ATels: ATel #17263 (Jewitt & Luu), ATel#17264 (Alacron et al.), ATel #17275 (Minev et al.), and ATel #17276 (Belyakov et al.). Using our multi-band images, we measured the following color indices using an aperture with a 4.1 arcsec, equivalent to 10,000 km at the 3.36 au geocentric distance of the comet: g-r = 0.81 +/- 0.06, r-i = 0.18+/-0.04, i-z = -0.02+/-0.07, and g-i = 0.99+/-0.08, equivalent to a spectral slope of 15.5+/-2.6 % / 100 nm. The r-i measurement made with the ARC 3.5-m/ARCTIC appears to be equivalent to the r-i measurement from photometry and spectroscopy described by Belyakov et al. in ATel #17276 of r-i = 0.16+/-0.02. However, our g-r measurement is significantly more red (g-r = 0.81 +/- 0.06 vs. g-r = 0.43 +/- 0.02). The g-r and overall color slope measured with the ARC 3.5/ARCTIC appear to be in line with the spectral slope measurements for the comet reported in other recent results (e.g., ATel #17283 by Champagne et al.). Based on observations obtained with the Apache Point Observatory 3.5-meter telescope, which is owned and operated by the Astrophysical Research Consortium.
FWHM steht für "Full Width at Half Maximum" und wird zur Abgabe des Seeing, der atmosphärischen Sichtbedingungen, verwendet. Es bezeichnet die Breite (bzw. "Verschmierung") des einfallenden Lichts bei der Hälfte der maximalen Helligkeit. Je kleiner der Wert, desto punktschärfer erfolgt die Abbildung.
"Les hommes seront toujours fous; et ceux qui croient les guérir sont les plus fous de la bande." - Voltaire
Image Credit: Gemini Observatory/NOIRLab/NSF/AURA/K. Meech (IfA/U. Hawaii) Processing: Jen Miller, Mahdi Zamani (NSF/NOIRLab)
Also known as C/2025 N1, 3I/ATLAS is clearly a comet, its diffuse cometary coma, a cloud of gas and dust surrounding an icy nucleus, is easily seen in these images from the large Gemini North telescope on Maunakea, Hawai‘i. The left panel tracks the comet as it moves across the sky against fixed background stars in successive exposures. Three different filters were used, shown in red, green, and blue. In the right panel the multiple exposures are registered and combined to form a single image of the comet.
Die gleiche Aufnahme des Gemini-North-Telescope auf dem Maunakea (anscheinend ist die Schreibweise in den letzten Jahren geändert worden), mit einem Hauptspiegel-⌀ von 8,1 m, vom 15. Juli in höherer Auflösung (1800 x 1800 Pixel): https://upload.wikimedia.org/wikipedia/c...22c%29.tiff.jpg
RE: JWST, HST
Zitat Astronomers race to study interstellar interloper
Phalanx of instruments scrutinize 3I/ATLAS for clues about planet formation elsewhere in the galaxy 11 Jul 20259:00 AM ET
The main thing scientists want to figure out is 3I/ATLAS’s composition. Comets and asteroids represent the leftovers of planet formation—making ATLAS a discarded sample of alien worlds, flung out from the dusty disk surrounding a distant star. By comparing its ratios of things such as carbon monoxide, water, ammonia, and salts with those of our local comets and asteroids, researchers hope to learn whether other planetary systems have ingredients like our own. “If we see that this building block looks like all the building blocks in our Solar System, that’s good news,” says Karen Meech, an astronomer at the University of Hawaii at Manoa. “That’s encouraging for the potential for life” elsewhere in the Galaxy.
Already ATLAS appears to have a reddish color, which means its surface probably contains organic materials such as methane, typical for both comets in our Solar System and ‘Oumuamua and Borisov. More detail is likely to come as larger instruments such as the Hubble Space Telescope and JWST swing into action. A team of astronomers has submitted a request to target the object with JWST next month. Noonan has sent a similar proposal to Hubble, with the goal of observing 3I/ATLAS near the beginning of December.
Zitat "Assessing interstellar comet 3I/ATLAS with the 10.4 m Gran Telescopio Canarias and the Two-meter Twin Telescope"
Based on observations made with the Gran Telescopio Canarias (GTC) telescope (program ID 62-GTC55/24B), in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias (IAC), and the Two-meter Twin Telescope (TTT, PEI project PLANETIX25), in the Spanish Observatorio del Teide of the IAC.
R. de la Fuente Marcos et al., 17 Jul 2025
(Received 16 July 2025)
Abstract
Methods. We identified the spectral type of 3I/ATLAS from the visible reflectance spectrum and used photometric observations to derive its level of activity and rotational properties. Observational data were obtained with the OSIRIS camera spectrograph at the 10.4 m Gran Telescopio Canarias and the Two-meter Twin Telescope. We used N-body simulations and statistical analyses of Gaia DR3 data to investigate the origin of 3I/ATLAS and its Galactic background.
Results. Interstellar comet 3I/ATLAS has a visible spectrum consistent with that of a D-type asteroid, and has a spectral slope S′=14.6±0.2 %/1000 Å in the 5000–9000 Å range, which is similar to the one of ‘Oumuamua but redder than that of 2I/Borisov and most solar system comets. It has a conspicuous coma and its rotation period is 16.79±0.23 h. The heliocentric components of its Galactic velocity were (U,V,W)=(−51.25±0.02,−19.466±0.011,+18.94±0.014) km s-1 with a radiant in Sagittarius (295.∘050±0.∘008, −19.∘0693±0.∘0012). The analysis of a sample of kinematic analogs of 3I/ATLAS extracted from Gaia DR3 suggests that its parent system is part of the Galactic thin disk and includes a solar-like star with slightly sub-solar metallicity.
Conclusions. The results from the physical characterization of 3I/ATLAS further support the idea that extrasolar debris is not too different from the one found in the solar system and it is the result of similar formation processes.
Mein Beitrag fußt noch auf der Annahme, daß das Ursprungssystem in der Dicken Scheibe der Milchstraße lag/liegt. Wenn die chemische Zusammensetzung an schwereren Elementen nur knapp unter der des solaren Urnebels liegt, dann wäre damit wohl auch die Annahme, er sei erheblich älter als das Sonnensystem, hinfällig. Ein schönes Beispiel für den dynamischen Wissenszuwachs durch Empirie. Aus dem Paper:
Zitat Considering Nissen (2004), fig. 1.3, the components of the solar-motion corrected heliocentric Cartesian velocities of 3I/ATLAS place it in the thin disk as the value of (ULSR2+WLSR2)1/2 is 67.68 km s-1 and VLSR=−7.2 km s-1. The Toomre diagram indicates that the thin disk is inside (ULSR2+WLSR2)1/2< 85 km s-1 with the thick disk in the interval (85, 180) km s-1 and the halo outside 180 km s-1. In addition to this kinematic constraint, the analysis of a sample of kinematic analogues of 3I/ATLAS from Gaia DR3 gives a value of [Fe/H]=−0.04±0.14 (see Appendix F), which is somewhat sub-solar, but far from −1.2<[Fe/H]<−0.4 in the thick disk (see, e.g., Nissen 2004). An origin in the thick disk is favored by Hopkins et al. (2025).
Wie im Abstract angegeben, liegt der Radiant bei 19h67m R.A. und -19,06° Dekl. Das galaktische Zentrum liegt bei -17h45m40s R.A. und -29°0'26,95" Dekl.
"Les hommes seront toujours fous; et ceux qui croient les guérir sont les plus fous de la bande." - Voltaire
Zitat SPHEREx Discovers Extended Carbon Dioxide Coma in Interstellar Object 3I-ATLAS News Release • August 21st, 2025
SPHEREx has made detailed multi-spectral observations of interstellar comet 3I/ATLAS, detecting an abundance of carbon dioxide gas in its coma (the extended gaseous atmosphere of a comet) and water ice in its nucleus. The observations were made between Aug. 8 to Aug. 12, when the object was about 290 million miles (470 million kilometers) from the Sun. This discovery highlights SPHEREx unique capabilities: its spectral resolution allowed us to clearly detect the CO2 emission, while its wide field of view enabled us to map the coma over scales extending 10 arminutes. SPHEREx published a brief Research Notice of the American Astronomical Society, and plans to releave a more detailed publication soon.
Although further observations are needed to fully understand the interstellar object’s composition — many other NASA missions will be attempting to observe 3I/ATLAS as well — the discovery of an extended CO2 coma and the abundance of ice water shows that 3I/ATLAS may not be so different from the comets that formed around our Sun. Interstellar objects can provide scientists with a better understanding about the chemistry of star systems many light-years away.
Zitat James Webb Space Telescope takes 1st look at interstellar comet 3I/ATLAS with unexpected results
By Robert Lea published 6 hours ago
NASA's $10 billion space telescope studied the third interstellar object to enter the solar system, measuring the chemical contents of its halo.
The James Webb Space Telescope (JWST) has observed the interstellar visitor 3I/ATLAS for the first time. The powerful space telescope trained its infrared vision and its Near-Infrared Spectrograph instrument (NIRspec) on the comet on Aug. 6, 2025.
In a preprint paper describing their investigation of 3I/ATLAS, a team of astronomers that observed the comet with the JWST explains that studying comets like this from other star systems helps to study what conditions were like in those systems as they were forming. Those results can then be compared to what scientists have learned about the conditions around the sun 4.6 billion years ago, when the planets, asteroids, and comets of the solar system were forming.
As expected, 3I/ATLAS is outgassing as it approaches the sun, and astronomers have used the JWST and its NIRSpec instrument to identify carbon dioxide, water, water ice, carbon monoxide, and the smelly gas carbonyl sulfide in its coma.
What wasn't expected, however, was the highest ratio of carbon dioxide to water ever observed in a comet. This could reveal more about the conditions in which 3I/ATLAS formed.
The abundance of carbon dioxide in the coma of 3I/ATLAS could indicate that the interstellar comet has a heart that is intrinsically rich in carbon dioxide. This could imply that the comet contains ices that were exposed to much higher levels of radiation than comets in the solar system have been exposed to.
Alternatively, the team suggests this high carbon dioxide content could indicate that 3I/ATLAS may have formed in a specific site called the "carbon dioxide ice line" within the swirling cloud of matter, or "protoplanetary disk," that surrounded its stellar parent. This is defined as the point at which the temperature around an infant star or "protostar" falls low enough to allow carbon dioxide to change from a gas to a solid.
Furthermore, the low abundance of water vapor in the coma of 3I/ATLAS could indicate that there is something within the comet that is inhibiting heat from penetrating the icy core of the comet. This would hinder the amount of water transforming from ice into gas relative to the transformation rate of carbon dioxide and carbon monoxide.
Zitat In astronomy or planetary science, the frost line, also known as the snow line or ice line, is the minimum distance from the central protostar of a solar nebula where the temperature is low enough for volatile compounds such as water, ammonia, methane, carbon dioxide and carbon monoxide to condense into solid grains, which will allow their accretion into planetesimals. Beyond the line, otherwise gaseous compounds (which are much more abundant) can be quite easily condensed to allow formation of gas and ice giants; while within it, only heavier compounds can be accreted to form the typically much smaller rocky planets.
The term itself is borrowed from the notion of "frost line" in soil science, which describes the maximum depth from the surface that groundwater can freeze.
Each volatile substance has its own frost line (e.g. carbon monoxide,[1] nitrogen,[2] and argon[3]), so it is important to always specify which material's frost line is referred to, though omission is common, especially for the water frost line. A tracer gas may be used for materials that are otherwise difficult to detect; for example diazenylium for carbon monoxide.
Location Different volatile compounds have different condensation temperatures at different partial pressures (thus different densities) in the protostar nebula, so their respective frost lines will differ. The actual temperature and distance for the snow line of water ice depend on the physical model used to calculate it and on the theoretical solar nebula model:
170 K at 2.7 AU (Hayashi, 1981)[4] 143 K at 3.2 AU to 150 K at 3 AU (Podolak and Zucker, 2010)[5] 3.1 AU (Martin and Livio, 2012)[6] ≈150 K for μm-size grains and ≈200 K for km-size bodies (D'Angelo and Podolak, 2015)[7] The location of the frost line changes over time, potentially reaching a maximum radius of 17.4 AU for a solar-mass star before decreasing thereafter.[8] ... Observations of the asteroid belt, located between Mars and Jupiter, suggest that the water snow line during formation of the Solar System was located within this region. The outer asteroids are icy C-class objects (e.g. Abe et al. 2000; Morbidelli et al. 2000) whereas the inner asteroid belt is largely devoid of water. This implies that when planetesimal formation occurred the snow line was located at around 2.7 AU from the Sun.
Gestern war ja die größte Annäherung von 3I/ATLAS an den Mars: 28,97 Mio. km. Aus diesem Anlaß:
Zitat Asteroid Explorers Marshall Eubanks · Admin Mars Perseverance has been photographing the Martian night sky the last two nights looking for our interstellar visitor, 3I/ATLAS. Simeon Schmauß reports that,
Zitat Simeon Schmauß @stim3on.bsky.social I think Perseverance may have spotted interstellar comet 3I/Atlas last night from Mars! After stacking 20 images from Mastcam-Z, I found a faint smudge of light in the constellation Corona Borealis close to the location where the comet was expected. The image can be seen here https://bsky.app/.../stim3on.bsky.social/post/3m2cd3hznus2h
Congratulations to the Perseverance team and all involved.
Zitat ESA’s ExoMars and Mars Express observe comet 3I/ATLAS
The two Mars orbiters had the closest view of the comet of all ESA spacecraft. During its closest approach to the Red Planet on 3 October, the interstellar interloper was 30 million km away from them.
Each spacecraft used its dedicated camera to watch the comet pass. Both cameras are designed to photograph the bright surface of Mars just a few hundred to a few thousand km below. Scientists were unsure what to expect from observations of a relatively dim target so far away.
ExoMars TGO captured the series of images shown in the GIF below with its Colour and Stereo Surface Imaging System (CaSSIS). Comet 3I/ATLAS is the slightly fuzzy white dot moving downwards near the centre of the image. This dot is the centre of the comet, comprising its icy-rocky nucleus and its surrounding coma.
CaSSIS could not distinguish the nucleus from the coma, because 3I/ATLAS was too far away. Imaging this kilometre-wide nucleus would have been as impossible as seeing a mobile phone on the Moon from Earth.
But the coma, measuring a few thousand kilometres across, is clearly visible. The coma is created as 3I/ATLAS approaches the Sun. The Sun’s heat and radiation is bringing the comet to life, causing it to release gas and dust, which collects as this halo surrounding the nucleus.
The full size of the coma could not be measured by CaSSIS because the brightness of the dust decreases quickly with distance from the nucleus. This means that the coma fades into the noise in the image.
Typically, material from the coma is swept into a long tail, which can grow up to millions of kilometres long as the comet moves closer to the Sun. The tail is much dimmer than the coma. We can’t see the tail in the CaSSIS images, but it may become more visible in future observations as the comet continues to heat up and release more ice.
Nick Thomas, Principal Investigator of the CaSSIS camera explains, “This was a very challenging observation for the instrument. The comet is around 10 000 to 100 000 times fainter than our usual target.”
3I/ATLAS has not yet revealed itself in the Mars Express images, partly because these were taken with an exposure time of just 0.5 seconds (the maximum limit for Mars Express) compared to five seconds for ExoMars TGO.
Scientists will continue to analyse the data from both orbiters, including adding together several images from Mars Express to see if they can spot the faint comet.
They also tried to measure the spectrum of light from comet 3I/ATLAS using Mars Express’s OMEGA and SPICAM spectrometers, and ExoMars TGO’s NOMAD spectrometer. At this point, it is uncertain whether the coma and tail were bright enough for a spectral characterisation.
Zitat Asteroid Explorers Marshall Eubanks ·Admin The inner solar system today showing our interstellar visitor, 3I/ATLAS. Its closeness to the Sun in the sky of the Earth (as illustrated by the blue lines) shows why optical observations from the surface of the Earth are now impossible. At the present, only PUNCH is providing regular 3I monitoring. The "superior conjunction" (the smallest elongation) of 3I as seen from Earth will be on 2025-Oct-21 at 05:00 UTC, while its perihelion will be on 2025-Oct-29 at 11:33 UTC.
Zitat Rohan Rahatgaonkar is a Ph.D. student at the Instituto de Astrofísica-Pontificia Universidad Católica de Chile. Darryl Z. Seligman is an Assistant Professor of Physics and Astronomy at Michigan State University.
In a surprising discovery, our team has detected glowing nickel vapor in the gas surrounding the incoming interstellar comet 3I/ATLAS at an extraordinary distance from the sun, where temperatures remain far too cold for metals to normally vaporize. This unexpected finding provides new insights into the chemistry of materials from beyond our solar system.
What makes interstellar objects so scientifically valuable is that they carry chemical and physical information from the star systems where they formed, potentially billions of years ago. They're like cosmic time capsules, delivering samples from distant exoplanetary systems we could never otherwise visit and study directly. The discovery of 3I/ATLAS opens the door to a completely new branch of study in astrophysics. ... As 3I/ATLAS journeys toward the sun, we've witnessed a fascinating sequence of chemical activation. Our first significant detection came on July 20, when our spectrographs recorded spectral lines consistent with atomic nickel vapor in the comet's tenuous atmosphere at a distance of 3.88 astronomical units (AU) from the sun, nearly four times Earth's distance from the sun.
This nickel detection was unexpected at such large distances, where temperatures remain extremely cold. As the comet continued its approach, we observed that the amount of nickel vapor coming off of the comet was strengthening significantly. Our measurements indicated that there was a substantial increase in the amount of nickel atoms coming off of the comet as it approached the sun.
About three weeks later, by mid-August, when 3I/ATLAS had reached about 3.07 AU from the sun, we detected the spectral signature of cyanogen (CN) gas, a common molecular emission in solar system comets.
What makes these observations particularly intriguing and puzzling is the detection of nickel without concurrent detection of iron above our instrumental limits. This unusual chemical signature suggests the nickel is potentially being released through processes that work at much lower temperatures, rather than through the direct transformation of solid metal directly into gas (a process called sublimation), which would normally require much higher temperatures.
The evidence points to the possibility that nickel atoms might be bound within special types of molecules that break apart easily when exposed to sunlight. These could include molecules where nickel is attached to carbon monoxide or other organic compounds, which can release nickel atoms at much lower temperatures than would be needed for metal to vaporize directly.
These findings, when considered alongside observations from the James Webb Space Telescope (JWST), provide complementary evidence for understanding this comet's unusual chemistry. JWST observations revealed that the cloud of gas surrounding the comet, called the coma, contains much more carbon dioxide (the same gas that makes soda fizzy) than water, a ratio that is unusual compared with most solar system comets. JWST also detected water ice particles and carbon monoxide gas in the comet's coma, suggesting a complex mix of frozen materials that are warming up and creating the activity we observe.
Such observations suggest the nickel may be bound in molecules that break apart under solar radiation, releasing both metals and gases in chemical reactions. But the detailed balance of carriers, their release mechanisms, and how iron and other metals fit into the picture remain active areas of analysis.
ABSTRACT Interstellar comet 3I/ATLAS has been approaching its 2025 October 29 perihelion while opposite the Sun from Earth, hindering ground-based optical observations over the preceding month. However, this geometry placed the comet within the fields of view of several space-based solar coronagraphs and heliospheric imagers, enabling its continued observation during its final approach toward perihelion. We report photometry from STEREO-A’s SECCHI HI1 and COR2, SOHO’s LASCO C3, and GOES-19’s CCOR-1 instruments in 2025 September–October, which show a rapid rise in the comet’s brightness scaling with heliocentric distance r as r−7.5±1.0. CCOR-1 also resolves the comet as an extended source with an apparent coma ∼4′ in diameter. Furthermore, LASCO/CCOR-1 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.
Fast hatte ich vermutet, dass Sie, werter Herr Elkmann, auch versuchen werden, uns entsprechende Information vorzuenthalten. Aber gerade noch rechtzeitig hatten Sie die entsprechende Daten zum brisanten Mutterschiff geliefert.
Gruß Morn <>< ______________________________________ Socialism in general has a record of failure so blatant that only an intellectual could ignore or evade it. Thomas Sowell
Zitat The interstellar invader Comet 3I/ATLAS is continuing to surprise scientists, this time by brightening at an unexpectedly rapid pace as it made its closest approach to the sun. Experts studying the object don't yet know why that happened.
"The reason for 3I’s rapid brightening, which far exceeds the brightening rate of most Oort cloud comets at similar r [radial distance], remains unclear," the scientists behind the research, Qicheng Zhang of Lowell Observatory in Flagstaff, Arizona, and Karl Battams, an astrophysicist at the Naval Research Laboratory (NRL) in Washington DC, write in a paper discussing the observation published on the research repository site arXiv.
The rapid brightening of 3I/ATLAS was observed by STEREO-A and STEREO-B, the twin spacecraft that make up Solar Terrestrial Relations Observatory (STEREO), by the sun observing Solar and Heliospheric Observatory (SOHO), and the weather satellite GOES-19. The space-based observations were necessary because ground-based instruments won't be able to observe the interstellar comet again until it passes out from the other side of the sun into its "postperihelion" phase, escaping the glare of starlight in mid- to late-November 2025.
The team proposes a few different mechanisms that could account for the unexpectedly rapid brightening of this comet from beyond the solar system. It could be the result of the speed at which 3I/ATLAS is approaching the sun; alternatively, it could tell scientists something about the comet itself. That is exciting because if the internal composition of 3I/ATLAS is different from that of the nuclei of Oort cloud comets, it could mean that the planetary system from which it originates also has a different chemical makeup.
"Oddities in nucleus properties like composition, shape, or structure — which might have been acquired from its host system or over its long interstellar journey — may likewise contribute [to the rapid brightening]," Zhan and Battams continued. "Without an established physical explanation, the outlook for 3I's postperihelion behavior remains uncertain, and a plateau in brightness — or even a brief continuation of its preperihelion brightening — appears as plausible as rapid fading past perihelion."
Zitat Skywatch Signal@UAPWatchers·3h 🚨 BREAKING: First Radio Signal Detected from 3I/ATLAS
At 04:10 UT, Oct 24 2025, South Africa’s MeerKAT Radio Telescope captured the first confirmed radio absorption lines from the interstellar object 3I/ATLAS marking the object’s official radio detection milestone.
According to a report by D.J. Pisano et al., MeerKAT identified hydroxyl (OH) radicals at 1.665 GHz and 1.667 GHz, showing narrow absorption at Doppler shifts around -15.6 km/s.
In other words molecules tied to water breakdown, the fingerprints of active chemistry are now confirmed around an object that originated beyond our Solar System.
These OH lines align with thermal broadening consistent with 230 K surface temps. The detection came just days after solar conjunction, when 3I/ATLAS was nearly aligned with the Sun. Avi Loeb notes the object’s trajectory sits within 9° of the 1977 Wow! Signal direction.
This isn’t alien contact. But it’s the first radio whisper from an interstellar visitor and it came from one of the most sensitive arrays on Earth. NASA’s Juno spacecraft will attempt a follow up scan in March 2026 as 3I/ATLAS swings near Jupiter. History just added a new data point.
Zitat Detection of 1665/1667 MHz OH absorption in 3I/ATLAS
ATel #17473; D. J. Pisano (University of Cape Town), Oleg M. Smirnov (Rhodes University & SARAO), Mykola Ivchenko (KTH), Lorenz Roth (KTH), Sarah Buchner (SARAO) on 4 Nov 2025; 10:28 UT Credential Certification: Oleg Smirnov (o.smirnov@ru.ac.za)
Subjects: Radio, Comet
We observed 3I/ATLAS with MeerKAT on 24 October 2025 from UTC 05:17:16-08:29:37, using the L-band receivers and the NE54M (1.633 kHz channel width) correlator mode, reaching an rms sensitivity of 1.5 mJy/beam in a 0.3 km/s channel with a beam size of 40â€. Angular separation from the Sun at time of observation was 3.76 degrees. OH absorption was detected in both the 1665 MHz and 1667 MHz lines. Gaussian fits to the two lines yielded peak fluxes of -8.4+/-3.1 mJy and -14.2+/-3.4 mJy at -15.59+/-0.16 km/s and -15.65+/-0.17 km/s for the two lines, respectively. The FWHMs were 0.88+/-0.37 km/s and 1.26+/-0.40 km/s. The integrated fluxes over the two lines are -7.9+/-2.9 mJy km/s and -19.1+/-5.2 mJy km/s. The absorption features are consistent with the expected OH level population due to the heliocentric velocity of the comet. The detection of OH on 24 October 2025 contrasts with the MeerKAT non-detection of these lines on 20 September 2025 from 14:36:54-15:39:25 UTC (rms noise of 3 mJy/beam) and 28 September 2025 from 10:00:26-16:55:53 UTC (rms noise of 1 mJy/beam). The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science, Technology and Innovation. DJP and OS greatly acknowledge support from the South African Research Chairs Initiative of the Department of Science, Technology and Innovation and the National Research Foundation.
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