The two stories of comet 3I-Atlas

By now, I think everyone that follows space-related news has heard about the comet that's sucking up every moment of news that's available.  The 3I in the name means it's the third object that we've positively identified as coming from another star system, - the I is short for Interstellar - although I've never seen a specific star system named that would explain where it came from. 

I paid attention to the passage of the other two comets that were named as coming from other star systems, 1I-Oumuamua, Hawaiian word for "a messenger from afar arriving first", in 2017 and 2I-Borisov in 2019. Oumuamua wasn't a comet; it was a rockier body with few properties that comets have; Borisov was the first comet from outside our solar system. Not one of the three extrasolar visitors have had their home star systems identified.

I consider it not at all surprising that a comet from another star system may have different chemical composition and therefore behave differently than what we regard as normal for comets we've seen down through history. I wouldn't be at all surprised to find out (if it was possible to do so) that other Interstellar comets have come through our solar system and we just couldn't tell they "weren't from around here." 

My reference to the "two stories" is that this comet gets talked about completely differently on space-related news sites versus sites more aimed at the general population, most notoriously like YouTube. Sites like Space.com (example article here) lately have been including prominent disclaimers like this one's, "a newly found interstellar comet poses absolutely no threat to Earth..." On YouTube, everyone from people I don't particularly disrespect but rarely ever looked at their channels, such as Michio Kaku, Avi Loeb, or Neil DeGrasse Tyson and over to channels I've never heard of, are railing about how dangerous it is and (apparently) making up news to back up their fear. 

Pardon my skepticism, but with none of the "serious" news sources citing these things, I have to ask why. Unfortunately "click bait" is an adequate answer. YouTube channels are overloaded with statements about the comet having done various shocking things, and while I haven't spent hours looking for them, I have yet to see more than one video on any of these allegations.

A view of comet 3I/ATLAS taken by the Gemini South Telescope (Image credit: International Gemini Observatory/NOIRLab/NSF/AURA/Shadow the Scientist Image Processing: J. Miller & M. Rodriguez (International Gemini Observatory/NSF NOIRLab), T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), M. Zamani (NSF NOIRLab))

Here on the blog, we've had little discussion about this, but I have a rough draft of something I wrote in a comment within the last month, that I'll add here:

Why do I think it's basically just another rock? Because it's acting like a rock. It's on a purely ballistic trajectory. It's moving fast compared to things we're used to observing - which is, after all, the last few years of human history - but it's not moving fast compared to the speeds required for living beings to cover the distances it has come. Good old Wikipedia says it's moving at 58km/sec or 0.000193c. We don't know where it came from, but even if it came from the closest stars at 4 light years away, that means more than 20,000 years to get here. Who's going to launch a system that slow, and why? What kind of system could work over 20,000 years without failing? If they wanted to take over our solar system or take our planet, if they have lifespans similar to ours, 20,000 years makes coming here to take over pretty much impossible.