Not that long ago, we could only speculate about what sorts of things were adrift in the interstellar darkness way out past the boundaries of our familiar solar system. Today, however, we know of three visitors from the great beyond that have passed close by the sun: 1I/'Oumuamua (from 2017), 2I/Borisov (from 2019), and now 3I/Atlas (from July 1, just two days ago!).
After millennia of detecting nothing of the sort, finding three confirmed interstellar objects in less than ten years' time may seem impressive. But, let me tell ya, you ain't seen nothin' yet. That's because the premier telescope to find more of these things, the Vera C. Rubin Observatory, is only now just coming online. As Rubin gets up to speed in its planned 10-year survey of the entire overhead sky, it should uncover many, many more of these mysterious emissaries from other stars.
But, ahem, I'm getting ahead of myself. Let's get back to the latest arrival, 3I/Atlas. One reason this particular object is so interesting is that it could serve as a bit of a statistical tiebreaker for interpreting its predecessors, 1I/'Oumuamua and 2I/Borisov. 'Oumuamua was deeply weird, but being the very first interstellar visitor known to science, no one could say whether its seemingly strange characteristics were really odd in a cosmic sense. Borisov, by contrast, basically seemed to be a run-of-the-mill comet, albeit one from an alien star. Having even one additional object for comparison between these two extremes would thus be very useful—and now, of course, we do!
But this is all still so fresh that we can't yet say where 3I/Atlas falls in the spectrum of small-number statistics. As our top story notes, brightness-based estimates of this object's size generally range anywhere from 5 to 50 kilometers. Presently passing between the orbit of Jupiter and the asteroid belt, 3I/Atlas is bound for a closest approach to the sun on October 30. In the intervening months, you can bet that astronomers across the globe will be lavishing it with observational attention from many of the world's best telescopes. So stay tuned for more exciting science!
Thoughts? Questions? Let me know via e-mail (lbillings@sciam.com), Twitter or Bluesky.
Thanks for reading, and I'll see you next time.
—Lee Billings
