3I/Atlas has been looked at by NASA's SPHEREx telescope which was sent into orbit earlier this year to help map the Universe , data from SPHEREx suggests Atlas is a very big boy with a diameter of 46 kilometers making it too big and too bright to be your traditional comet and there's still no tail visible , I'm with Avi Loeb and hope it's just an anomaly that will sail on through.
Hopefully the Webb data will be released soon and we can get a better picture of what we are looking at .... unless there's a "problem with the data" of course.
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-...fe3a31b3e5
Hopefully the Webb data will be released soon and we can get a better picture of what we are looking at .... unless there's a "problem with the data" of course.