Not very dramatic news, but worth a post. An observer claims Color Indices of 3I/ATLAS, and a possible Type Identification:
Astrophysics > Earth and Planetary Astrophysics arxiv.org/abs/2508.08829
Beniyama, J. Simultaneous visible spectrophotometry of interstellar object 3I/ATLAS with Seimei/TriCCS
Using the Seimei telescope in Japan, Beniyama has published (well, a preprint…) initial color data for the interstellar object. The comet was imaged in four medium bands- three in the visible, and one extending into the near-infrared (as many instruments can do). The results show an obvious “red” appearance, at least in astronomical terms; to spectrophotometry specialists, ‘redder’ and ‘bluer’ are relative terms, compared to each other and to ‘grey’ (a flat color spectrum). It doesn’t mean ATLAS looks red like a stop sign. It would be more precise to say it looks clearly non-blue, and not grey either.
Furthermore, based on those color indices (the brightness differences between the redder bands, and the bluer bands), Beniyama assigns the comet to a ‘D-type’ classification. This is not a bold statement. There are lots of comets that fall into D type. Still, the TriCCS instrument that Beniyama used only ranges through these four color bands. A more definitive type identification should extend further into the infrared, and with preferably finer spectral resolution than these bands.
Again (and again, and again), I’ll caution that arXiv.org is no rigorous, definitive source of information. In this case, the site explicitly states that Beniyama’s paper is a preprint, accepted for publication in a peer-reviewed science journal but still in need of copyediting. In other words, the general concept is pretty good, but don’t quote them on it… the paper may still change for the final, published edition.
There’s an unspoken benefit, I’ll say. Here, we have- in open, accessible media- follow-up and study by a Japanese telescope, on Japanese soil, with a Japanese instrument, by a Japanese scientist. Let there be no conspiracy cries of “NASA’s hiding the killer asteroid! NASA’s hiding the killer asteroid!” 3I/ATLAS is readily seen with numerous telescopes around the world; there are even posts of amateurs (with significant telescopes, admittedly) detecting and tracking the comet. You can’t hide the sky.