Copyright ©2025
by Ralph F. Couey
One of the things that has been learned about the universe is that it is neither quiet nor static. Somewhere out there, stars explode, black holes form and merge, asteroids and comets streak through the void. The more that is discovered, the more we realize what a busy place it is.
Up until 2017, what we saw in the sky, other than stars, was assumed to originate locally, that is, from our own solar system. But that year, a new object was discovered, one that, when its trajectory and speed were analyzed, wasn't local in origin. It had originated from outside our solar system, the first such object discovered. Because it was found by one of the telescopes on top of a volcano in Hawai'i, it was named "'1I/Oumuamua," Hawai'ian for "messenger from afar arriving first." The 1I marked it as the first object known to come from interstellar space. It got a lot of attention, not only because it was the first extrasolar visitor, but because of its elongated shape. Some people believed, and still do, that it was actually a ship from some distant civilization on a voyage of discovery. After a lot of observation and study, it was suggested that 'Oumuamua was neither an asteroid nor a comet, but perhaps a piece of a destroyed exoplanet similar to Pluto.
It was thought that this was a once-in-a-lifetime event. But two years later, another object came streaking in from the outer darkness. This one was given the less poetic name "2I/Borisov," 2I being the second interstellar object found. This one was absolutely a comet, with the requisite coma and tail. Now, a third interstellar object, "3I/Atlas," has been discovered. Its trajectory suggests its point of origin was the crowded center of the Milky Way galaxy, and could be as much as 14.6 billion years old. That's astonishing, because it dates this comet back to the very beginning of the Milky Way's formation, and perhaps close to the beginning of the universe itself.
Another surprise was Atlas' apparent size, initially thought to be about 6.5 miles wide, roughly the same size as the Chicxulub impactor that exterminated the dinosaurs. Recent data reduces it to about 3.5 miles wide, although this is still sufficiently large to wreak life-altering damage to Earth. That there are objects out there about that same size that we don't yet know about, at least gives me pause.
