(08-08-2025, 04:23 PM)gortex Wrote: If it is our Alien Overlords I do hope it's a case of "we come in peace" and not "Mmmm you look tasty"

Quote:It is quite clear that a mission launched from Earth to 3I is completely infeasible, given how little warning we had of its arrival in the Solar System. Furthermore, it would not be within the performance envelope of the proposed ESA Comet Interceptor mission, so in other words, even if a spacecraft had been waiting at the Sun/Earth L2 point. Now, 3I coincidently comes quite close to Mars, Jupiter, and Venus, which is in itself a strange happenstance and will be unlikely to recur with any future ISO.

It seems reasonable, therefore, given the above serendipities and the impossibility of a dedicated probe being launched to encounter it in time, to enquire whether any existing spacecraft orbiting around Mars or Jupiter could be exploited for an intercept or a close approach. It is thus in this context that the work is worthwhile, and such analysis will only apply to ISOs that happen to have close encounters with the planets, which, as I have articulated, will be very rare indeed.

If doable, this exciting new goal will rejuvenate Juno's mission and extend its scientific lifespan beyond March 14th, 2026. So far, we have examined a zero-distance intercept of Juno with 3I/ATLAS. The optimal option involves a Jupiter Oberth Maneuver, which requires an application of ∆V on September 9th, 2025, only 8 days prior to the originally intended termination date for Juno's plunge into the atmosphere of Jupiter. Having delivered this thrust to diminish Juno's altitude, a further ∆V is subsequently delivered, constituting a Jupiter Oberth Maneuver and resulting in an eventual intercept of the target 3I/ATLAS on March 14th, 2026.
https://www.sciencealert.com/nasa-probe-could-intercept-interstellar-comet-scientists-say

Quote:Over the past day, new figures were added to the latest paper I wrote a week ago with Adam Hibberd and Adam Crowl, which suggested to probe 3I/ATLAS with the Juno spacecraft when it passes within a distance of 54 million kilometers from Jupiter on March 16, 2026. The new figures show that two impulses of thrust can bring Juno to within 25 million kilometers from the path of 3I/ATLAS, using merely 60 kilograms of propellant, only 3% of the initial fuel that Juno had at its disposal. Here’s hoping that NASA will follow up on our proposal for the benefit of interstellar space archaeology. The scientific exploration of our cosmic neighborhood is young and we still have a lot to learn.
https://avi-loeb.medium.com/3i-atlas-has-no-visible-tail-or-spectral-fingerprints-of-gas-around-it-cfd5d2cb0a86

(08-17-2025, 10:20 AM)gortex Wrote: Prof. Avi Loeb has written a new paper suggesting that as we can't send a probe to intercept 3I/Atlas we could perhaps use the Juno spacecraft which is currently orbiting Jupiter to take a look at 3I/Atlas as it passes the planet on on March 14th 2026 6rather than than crash the probe into Jupiter as currently planned. 

Quote:It is quite clear that a mission launched from Earth to 3I is completely infeasible, given how little warning we had of its arrival in the Solar System. Furthermore, it would not be within the performance envelope of the proposed ESA Comet Interceptor mission, so in other words, even if a spacecraft had been waiting at the Sun/Earth L2 point. Now, 3I coincidently comes quite close to Mars, Jupiter, and Venus, which is in itself a strange happenstance and will be unlikely to recur with any future ISO.

It seems reasonable, therefore, given the above serendipities and the impossibility of a dedicated probe being launched to encounter it in time, to enquire whether any existing spacecraft orbiting around Mars or Jupiter could be exploited for an intercept or a close approach. It is thus in this context that the work is worthwhile, and such analysis will only apply to ISOs that happen to have close encounters with the planets, which, as I have articulated, will be very rare indeed.

If doable, this exciting new goal will rejuvenate Juno's mission and extend its scientific lifespan beyond March 14th, 2026. So far, we have examined a zero-distance intercept of Juno with 3I/ATLAS. The optimal option involves a Jupiter Oberth Maneuver, which requires an application of ∆V on September 9th, 2025, only 8 days prior to the originally intended termination date for Juno's plunge into the atmosphere of Jupiter. Having delivered this thrust to diminish Juno's altitude, a further ∆V is subsequently delivered, constituting a Jupiter Oberth Maneuver and resulting in an eventual intercept of the target 3I/ATLAS on March 14th, 2026.
https://www.sciencealert.com/nasa-probe-could-intercept-interstellar-comet-scientists-say

It also seems the slight tail and ovoid shape shown by the Hubble image of 3I/Atlas isn't a tail as it's on the leading edge of the object heading toward the Sun , spectral analysis of the object also shows no evidence of a Cometary tail ... yet.

Quote:Over the past day, new figures were added to the latest paper I wrote a week ago with Adam Hibberd and Adam Crowl, which suggested to probe 3I/ATLAS with the Juno spacecraft when it passes within a distance of 54 million kilometers from Jupiter on March 16, 2026. The new figures show that two impulses of thrust can bring Juno to within 25 million kilometers from the path of 3I/ATLAS, using merely 60 kilograms of propellant, only 3% of the initial fuel that Juno had at its disposal. Here’s hoping that NASA will follow up on our proposal for the benefit of interstellar space archaeology. The scientific exploration of our cosmic neighborhood is young and we still have a lot to learn.
https://avi-loeb.medium.com/3i-atlas-has-no-visible-tail-or-spectral-fingerprints-of-gas-around-it-cfd5d2cb0a86

Not sayin it's Aliens but if we don't use all the tools at our disposal to look with an open mind how will we know , assuming it's a Comet doesn't make it a Comet.

(08-18-2025, 07:06 PM)FCD Wrote: Kenzo, very interesting!!

I am constantly amazed these days at the levels of accuracy they are able to achieve with some of these photographs of space objects!  I mean, 3 Arc secs.??  Really??  WOW!!  This probably means they have classified capabilities well below even this!

I don't think there's a whole lot to be learned by crashing Juno into Jupiter as planned.  Maybe some atmospheric data on the way down, but once you're at a certain altitude on Jupiter the intense gravitational forces will crush just about any instrument invented by mankind.

Quote:Figure 3 of the analysis paper (accessible here) shows a steep surface brightness profile of the glow with a projected power-law slope of -3, which implies a three-dimensional emissivity profile with a radial power-law slope of -4. Such a slope is steeper than observed in solar system comets. Together with my brilliant colleague, Eric Keto, we realized that the observed slope of -4 is consistent with an alternative model in which the dust outflow around 3I/ATLAS is illuminated by a central source. This model naturally accounts for the steep brightness profile, since the outflow density slope of -2 is accompanied by the radial decline of the illuminating radiation flux with an additional declining slope of -2.

If 3I/ATLAS generates its own light, then it could be much smaller than expected from a model in which it reflects sunlight. The reflection model requires a diameter of up to 20 kilometers, which is untenable given that the limited reservoir of rocky material in interstellar space can only deliver such a giant rock once per 10,000 years or longer (see the calculation in my paper.

The simplest interpretation is that the nucleus of 3I/ATLAS produces most of the light. I calculated that the nucleus cannot be a thermal emitter with an effective surface temperature below 1000 degrees Kelvin or else its peak emission wavelength would have been longer than 3 micrometers with an exponential cutoff at shorter wavelengths, incompatible with the data. At higher effective temperatures, the required luminosity of 3I/ATLAS can be obtained from a source diameter smaller than 100 meters. A compact bright emitter would make 3I/ATLAS of comparable size to the previous interstellar objects 1I/`Oumuamua or 2I/Borisov, making more sense than the 20-kilometer size inferred in the model where it reflects sunlight.
https://avi-loeb.medium.com/does-3i-atlas-generate-its-own-light-e9775594afc5

(08-19-2025, 06:30 PM)F2d5thCav Wrote: Gortex,

  It is visible radiation emitted by the impulse drive 

  Voyager is returning home with much new data ...

Quote:Most interestingly, the flux detected at a wavelength of 1 micrometer from 3I/ATLAS suggests a large nucleus with a diameter of 46 kilometers. If this represents a solid body, then the mass of 3I/ATLAS must be a million times bigger than the previous interstellar comet 2I/Borisov. This makes little sense since we should have found of order a million objects of the size of 2I/Borisov before discovering a 46-kilometer interstellar object. Moreover, as I noted in my first paper on 3I/ATLAS (accessible here), the amount of rocky material per unit volume in interstellar space is too small by a factor of ten thousand than the value needed to deliver into the inner Solar system one giant rock of this size over the ATLAS decade-long survey.
Alternatively, 3I/ATLAS may have targeted the inner solar system by technological design. This possibility is consistent with the alignment of its trajectory with the orbital plane of the planets around the Sun, a coincidence of a part in 500 for a random orientation — as observed for 2I/Borisov.
The lack of a cometary tail in the Hubble Space Telescope image is evidence that there is not much dust around 3I/ATLAS with particle size on the scale of the wavelength of sunlight (0.5 micrometers). In that case, the observed reddening in the spectrum of reflected sunlight should originate from the surface of the object, implying that the object is large and dominates the reflected sunlight rather than the dust cloud around it.

The CO2 mass loss amounts to the ablation of a millimeter thick layer from the surface of a 46-km rock over a period of 10 years. This means that a relatively thin outer layer is sufficient to maintain the observed cloud of CO2 gas and dust around 3I/ATLAS. What lies under this outer layer is still unknown. We are all waiting for the release of the first data from the Webb Space Telescope, when it observed 3I/ATLAS on August 6, 2025.

Here’s hoping that as the Sun turns on the heat on 3I/ATLAS in the coming months, it will reveal its true nature.

https://avi-loeb.medium.com/3i-atlas-is-large-and-emits-carbon-dioxide-co2-22fe3a31b3e5

Quote: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.


https://www.space.com/astronomy/james-webb-space-telescope-takes-1st-look-at-interstellar-comet-3i-atlas-with-unexpected-results

Quote:The CO2 mass loss amounts to the ablation of a millimeter thick layer from the surface of a 46-kilometer object over a period of a few years. In other words, a relatively thin outer layer is sufficient to maintain the observed cloud of CO2 gas around 3I/ATLAS. What lies under this outer skin remains unknown.

The high CO2 to H2O ratio is puzzling. There is only one previous comet with a similarly extreme CO2 to H2O ratio, named C/2016 R2, but its image shows a clear cometary tail that does not look anything like the plume around 3I/ATLAS. The Webb team conjectures that the anomalous composition of the gas plume surrounding 3I/ATLAS might be the result of high reflectance or reduced heat penetration through its surface. Increasing the albedo from 5% to the maximum value of 100% for a mirror, reduces the estimated diameter from 46 to 10 kilometers based on the SPHEREx data. This still poses an untenable demand on rocky material in interstellar space.

A way to resolve the discrepancy between the mass reservoir of rocks in interstellar space and the unexpected discovery of a large object, is that 3I/ATLAS was not drawn from a population of rocks on random trajectories but instead — its trajectory was designed to target the inner Solar system. This possibility is consistent with the alignment of this retrograde trajectory with the orbital plane of the planets around the Sun, a coincidence of 1 part in 500 for a random occurrence.
https://avi-loeb.medium.com/the-first-webb-telescope-observations-of-3i-atlas-8cd89e872870

(07-17-2025, 09:40 AM)F2d5thCav Wrote:

(07-16-2025, 11:26 AM)F2d5thCav Wrote: Detonation of all those atomic and nuclear weapons decades ago are now bearing wormy fruit.

Question for Gortex.

Which star is 80 light years distant and considered a candidate to have planets that could support life ?

80 years since Trinity Test.

Ω