Paper: Is the Interstellar Object 3I/ATLAS Alien Technology?

[thorbiorn]

My only comment is , what a joke NASA is.

NASA is probably like the CDC in some respects. Maybe they have been asked to keep people a bit more in the dark, or continue to do so. They can't afford to get too far ahead of themselves compared to the drone investigations, blurry UPA pictures, Charlie Kirk murder, the Epstein files, Ukraine project, Gaza support, and who knows comet cluster and Sun twin.

I found a Russian channel, Astro Channel, auto dubbed into English, with an amateur who went out to take his own pictures in some mountains 1700 m above sea level.

When comparing Nov 11 with Nov 18 he proposes that the comet has broken up. Whether that is true or it is just an optical effect due to a jet from one part, I don't know, but you can see the image here, and zoom in if you like.

 

[Gaby]

When comparing Nov 11 with Nov 18 he proposes that the comet has broken up. Whether that is true or it is just an optical effect due to a jet from one part, I don't know, but you can see the image here, and zoom in if you like.

Very unlikely. It looks like a star behind it. I think the Cs are right, the comet nucleus is greater than what they say, more like 8 km and possibly growing. Otherwise, it would have disintegrated as a result of the various X flares it discharged from the sun and which hit the comet directly.

And there are spectroscopic results from that time period. They were done in the Physical Research Laboratory in Mt Abu Observatory. Here are the results:

ATel #17502: Comet 3I/ATLAS: Post-perihelion spectroscopic results from PRL Mt Abu Observatory

www.astronomerstelegram.org

Comet 3I/ATLAS: Post-perihelion spectroscopic results from PRL Mt Abu Observatory

Shashikiran Ganesh (PRL), Goldy Ahuja (PRL), Arvind B.(PRL,), Anil Bhardwaj(PRL)

on 19 Nov 2025; 16:03 UT

Observations of the comet 3I/ATLAS, also known as C/2025 N1 (ATLAS), were obtained using the instruments on PRL's 1.2m telescope at the Mount Abu Observatory during November 12 to 17 in the late hours of the night, just before dawn. Initially, when the comet was visible for only a short time, observations were carried out using an imager in the R filter (see false colour image in the online link below).

On the later nights, we carried out spectroscopic observations on the PRL 1.2m telescope. The observations were conducted using the LISA instrument, which provides spectral coverage from 3800 to 6800 Å. At the time of observation, the comet was at a heliocentric distance of around 1.51-1.53 AU and a geocentric distance of 2.08 - 2.05 AU. The slit was placed on the photocenter of the coma of the rare interstellar object, and exposures of 15 minutes were obtained with the telescope following the fast-moving object in non-sidereal tracking mode. The spectrum was extracted using a rectangular aperture of 32.60 × 1.76 arcseconds, corresponding to approximately 48707 km × 2617 km on the coma. The spectrum was flux-calibrated and solar continuum corrected to remove the dust contribution. The spectra show typical emission lines and bands from CN, C2 and C3, as are also usually seen in Solar system comets. The spectra are available in the link below.

To our knowledge, these are the first post-perihelion spectra of Comet 3I/ATLAS. The spectra show it to be a comet similar to those belonging to the Solar System. Our value for the log(C2 / CN) production rate ratio is approximately -0.73 (observation of November 16, 2025), which indicates the comet to be similar to the depleted class of comets of the solar system in terms of carbon composition. Observations with longer exposure times will help confirm the production rates and ratios.

We are conducting further observations with PRL's Mount Abu telescopes and encourage continued monitoring of 3I in the days to come.

Work at the Physical Research Laboratory is supported by the Department of Space, Govt. of India.

C/2025 N1 or 3I/ATLAS ATel

Figures to accompany the ATel on Comet 3I/ATLAS - observations from 1.2m telescope at PRL Mt Abu Observatory False colour representation of an R band image of Comet 3I/ATLAS using PRL Imager on 1.2m Mt Abu Telescope - November 12, 2025 LISA spectrum of 3I/ATLAS on November ...

docs.google.com

 

[Gaby]

I think the Cs are right, the comet nucleus is greater than what they say, more like 8 km and possibly growing.

Ok, might be the reason none of the big telescopes wants to take a high definition picture of it.

From xras

Photograph: Julien de Winter, November 25, 2025 (https://app.astrobin.com/i/jtmq82 ).

Notice how the tail is less spectacular, but the body is pretty intense, with a sunward spike. That can be expected from a very fast moving comet with a highly eccentric orbit.

xras

3I/ATLAS lowers brightness despite getting closer to Earth

The brightness of the 3I/ATLAS object has decreased quite noticeably over the past few days, by more than a third, when observed from Earth, despite the fact that the celestial body continues to rapidly approach the planet. The magnitude (the main characteristic of the brightness of celestial bodies), which was 10.1 at the beginning of the week, has increased, based on recent observations, to 10.6, which means that the brightness of the body is now about 63% of what it was 6 days ago. Since the distance between the object and the Earth has decreased by 10 million kilometers during this time, the main reason for the decrease in brightness is probably the continued distance of the body from the Sun. Since an object classified as a comet should shine with the reflected light of the Sun, as the distance from the latter increases, the brightness of the body should also decrease. At least, this explanation looks quite natural.

However, it is possible that the decrease in brightness is also influenced by internal causes, for example, changes in the characteristics of the central body that are hidden from observation and affect its albedo. Despite the decrease in brightness, 3I/ATLAS continues to occupy a fairly high, 4th place in brightness, among almost 100 comets currently in the Earth's sky and available for observation. At the same time, comet C/2025 A6 (Lemmon), which has already been partially forgotten and dropped out of the news, continues to be in the first place, the luminosity of which has decreased by almost 10 times over the past month, but still remains at a high level. As for 3I/ATLAS, its current brightness values keep it accessible not only to scientific, but also to semi-professional instruments.

The incoming images (one of which is attached to the message) show, in particular, a very unusual "ragged" structure and dynamics of the tail of the object at the moment. One of the main intrigues at the moment is whether NASA will decide to turn its two most powerful instruments, the Hubble and James Webb telescopes, to 3I/ATLAS. Both devices have already captured the object, but several months ago and at a noticeably greater distance from the Sun than it is passing now. Technically, such an opportunity should be provided in the next 2-3 weeks: the distance of the object from the Sun will be large enough so that its images can be taken without the risk of damage to the most expensive space instruments in the history of mankind. So far, however, NASA has not given any clear comments on this matter.

 

[thorbiorn]

Comet 3I/ATLAS: Post-perihelion spectroscopic results from PRL Mt Abu Observatory

The Mount Abu InfraRed Observatory (MIRO) is located near the town Mount Abu in the state of Rajasthan, India. The observatory is at an altitude of 1680 metres and is adjacent to Guru Shikhar, highest peak of the Aravalli Range. The 1.2 m infrared telescope at It is the first major facility in India specifically designed for ground-based, infrared observations of celestial objects. Further the low amount of precipitable water vapour (1–2 mm during winter) at Guru Shikhar makes it a good site for the infrared telescope observations. The site has been found to be good (about 150 cloud free nights per year) for astronomical observations.

India can do what NASA can't or won't.

Ok, might be the reason none of the big telescopes wants to take a high definition picture of it.

The telescopes might be busy, I imagine they are booked long in advance by researchers busy writing the papers they have to write to keep their jobs, or some trying to do their ph.D. Maybe some are looking into black holes or trying to find out what came before the big bang?

Going through the lists, there have been several larger ones comets among those that have been calculated:
From List of periodic comets
Before 2000 there is one with 9.1 km
2000s, there is one about 10 km
2010s there is one about 21 km
2020s there is one with 0.31-0.50 km
For many of the comets there are no estimates.
From List of long-period comets
19th century, one of 29.65 km, one of 24.75 km
20th century, one of 13.7 km
21st century, one of 27.55 km, one of 12.8 km
From List of near-parabolic comets
Many are listed, but not many with size estimates, in the 1970, there is one with 5-10 km
1990s Hale-Bob 30 km, C/1999 F2 Dalcanton 18.18 km
2000 12.36 km
2002 Several large comets, 11 km, 58.9 km 30.7 km, 40.7 km, 12.3 km - or was it just that someone cared to calculate?
2004 C/2004 X2 LINEAR 10.5
2005 C/2005 G1 LINEAR 18.9 km
2006 C/2006 M1 LINEAR 16.3 km
C/2006 W3 Christensen 13 km
C/2014 UN271 Bernardinelli–Bernstein was 68.5 km
C/2014 N3 NEOWISE 15 km

Since 2014 there has been few calculation and none exceeds, C/2020 T2 Palomar with its 5.525 km. The reference is:

G. I. Kokhirova; A. M. Buriev; N. T. Sharipova; S. N. Safarov (11–15 March 2024). Long-Period Comet C/2020 T2 (Palomar) and Its Characteristics Based on Observations at the Hissar Astronomical Observatory (PDF). 55th Lunar and Planetary Science Conference. Vol. 3040. The Woodlands, Texas, USA. Bibcode: 2024LPICo3040.1803K.

Even if 3l/ATLAS should show up as something more substantial, there has been many bigger ones before and there was no issue. The above paper however came out only about three years after its passage of the Sun, so perhaps some calculations of more recent comets will be done.