https://zettelsraum.blogspot.com/2025/07...uncan.html#more

Mit einem kleinen Literaturverzeichnis.

Oha. Preprint auf arXiv vom 17. Juli.

[Submitted on 17 Jul 2025] "NSF-DOE Vera C. Rubin Observatory Observations of Interstellar Comet 3I/ATLAS (C/2025 N1)"


Abstract:

Zitat

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We report on the observation and measurement of astrometry, photometry, morphology, and activity of the interstellar object 3I/ATLAS, also designated C/2025 N1 (ATLAS), with the NSF-DOE Vera C. Rubin Observatory. The third interstellar object, comet 3I/ATLAS, was first discovered on UT 2025 July 1. Serendipitously, the Rubin Observatory collected imaging in the area of the sky inhabited by the object during regular commissioning activities. We successfully recovered object detections from Rubin visits spanning UT 2025 June 21 (10 days before discovery) to UT 2025 July 7. Facilitated by Rubin's high resolution and large aperture, we report on the detection of cometary activity as early as June 21st, and observe it throughout. We measure the location and magnitude of the object on 37 Rubin images in r, i, and z bands, with typical precision of about 20 mas (100 mas, systematic) and about 10 mmag, respectively. We use these to derive improved orbit solutions, and to show there is no detectable photometric variability on hourly timescales. We derive a V-band absolute magnitude of H_V = (13.7 +/- 0.2) mag, and an equivalent effective nucleus radius of around (5.6 +/- 0.7) km. These data represent the earliest observations of this object by a large (8-meter class) telescope reported to date, and illustrate the type of measurements (and discoveries) Rubin's Legacy Survey of Space and Time (LSST) will begin to provide once operational later this year.

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36 pages, 16 figures, 4 tables; collaboration between the NSF-DOE Vera C. Rubin Observatory and the LSST Solar System Science Collaboration (SSSC)

https://arxiv.org/html/2507.13409v1

Aber worauf ich hinaus will: für diese 36 Seiten werden insgesamt 114 Autoren aufgelistet.

Zitat

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As noted by several observers (Jewitt & Luu, 2025; Alarcon et al., 2025; Seligman et al., 2025; Opitom et al., 2025; Bolin et al., 2025), 3I/ATLAS is observed to exhibit a short sunward-pointing tail in imaging data obtained since its discovery. While such a morphology is certainly unusual—given that dust tails are typically directed antisolar due to radiation pressure acting on dust grains—it is not without precedent among distant active bodies. Notably, Farnham et al. (2021) reported a similar sunward enhancement in comet C/2014 UN271 (Bernardinelli–Bernstein), which they interpreted as the result of the slow ejection of relatively large dust particles predominantly from the sunlit hemisphere.

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Stichwort Duncan Lunan.

Zitat

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It will never be hidden by Mars on its current path, let alone pass behind Venus. And its closest approach to Mars on September 24th will still be at a distance of 0.2 AU, 1,860,000 miles. There is a remote chance that it might be captured by the cameras on the Mars Reconnaissance Orbiter and others orbiting Mars (David Dickinson, ‘Inbound: Astronomers Discover Third Interstellar Object’, Universe Today, online, July 2nd, 2025.) But I’m not holding my breath, because when Comet Siding Spring (aka Comet McNaught) passed Mars at 80,000 miles in October 2014 (Fig. 11), most satellites saw nothing. Mars Orbiter Mission (MOM) saw it as a faint dot (Fig. 12), and the Curiosity rover (which has just completed 13 years on Mars) captured it as a streak on a time exposure (Fig. 13). It should also be noted that MAVEN and Mars Odyssey are scheduled for early shut-down among cuts to NASA’s science budget by the Trump administration, and may not be operational by the end of September.
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Also, for the record, an ‘Oberth manoeuvre’ is most effective when performed very close to the object being flown past. The term is normally used for a velocity change, and Fig. 2 shows that to achieve an encounter with the Earth, by a retrofire beyond the Sun, 31/ATLAS would have to shed a lot of its 60 kps current velocity. It made me wonder if Prof. Loeb was thinking of putting it into a Hohmann transfer (a 180-degree turn around the Sun, changing from one planetary orbit to another, Fig. 14), which was first publicised in the 1924 book Die Rakete by Hermann Oberth (see ‘Oscar Schwiglhofer’, ON, 27th July 2025).

Fig. 15 shows a Mars-Earth transfer as a dotted line. But a Hohmann transfer between Mars and Earth would take 6-9 months, depending on the position of Mars in its elliptical orbit, so a retrofire in late October couldn’t threaten Earth in November, as per the headline. Accelerating at perihelion would straighten the path and miss the Earth by still more than at present, so that’s not the answer unless it could tighten the curve, using still more fuel by introducing a new velocity vector, directed towards the Sun (Figs. 2 & 15), and it would have to be very large, possibly another 60 kps.

Decelerating the supposed spacecraft would also reduce the damage it could cause (assuming an impact is intended), because the energy release is proportional to the square of the impact velocity. Conversely, accelerating into a new hyperbolic path would increase it, enough perhaps for even a 0.2-km objec
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Even more so, if you’re going to such trouble to devastate Earth with 31/ATLAS, why not just launch it straight at the Earth and have done?

Again, the answer could be deniability, but given that everything from the Vera Zubrin Telescope downwards will be searching for 31/ATLAS when it comes out from the Sun, the objective wouldn’t be to conceal it from us – not that we could do anything about it, at such short notice. Rather encouragingly, it would suggest that there is some higher authority like a Galactic Federation, from whom the attackers have to hide their wicked plans, and who might detect and forestall them.

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https://theorkneynews.scot/2025/08/10/interstellar-comet/