Our old pal, Comet 3I/ATLAS, is back in the news. The comet we breathlessly covered last year as scientists were mystified by this interstellar traveler, some of whom entertained the idea that it might be some kind of alien artifact. It’s become big enough that, like our modern Hollywood franchises, we’ve run out of stories to tell about its present and future, so now we’ve reverted all the way to its past. A team of researchers from the University of Michigan thinks they figured out where it came from, in essence, providing our coverage of its drift through our solar system with a prequel, its own superhero origin story. According to a study published in Nature Astronomy , Comet 3I/ATLAS likely formed in an extremely cold, isolated part of the galaxy, outside of our solar system, and a neck of the woods that never quite formed into a fully functioning solar neighborhood like ours. The scientists figured this out after detecting unusually high levels of deuterium in the water it contained.…