Right now, our solar system is hosting a friendly (it is friendly, right?) visitor from far, far away. But it turns out, it’s also visiting from long, long ago, and that makes our friend (it is a friend, definitely) even more exciting for scientists to study. In terms of what we can learn from it, this is not merely a star voyager — it’s a time traveler.
As Universe Today reports, scientists have worked back the trajectory of the comet, known as 3I/ATLAS, back to what they believe to be its origin point, the galactic thick disk. 85% of the galaxy’s stars are in this region, but what’s more, it’s where the oldest ones live. These elder stars can get up to 10 billion years old, meaning that they formed much closer to the birth of the whole universe than to the modern day. This period of history, known as “cosmic noon,” is when about half of all stars in the entire universe formed. It was the adolescence of existence.
Scientists would really like to study this period, but it’s a little hard to fly a probe way out into the furthest reaches of our galaxy. It sure would be nice if the thick disk were to send out something our way instead — hey, wait! In fact, scientists think our friend specifically came from an 8-billion-year-old star cluster. National Geographic quotes astrochemist Martin Cordiner as saying that 3I/ATLAS “could be one of the oldest objects in the galaxy.”
Pretty exciting. This is a first-ever opportunity to gain some insights into how the Milky Way first formed and learn a little more about cosmic noon. So far, the answers are looking… really weird.
Exotic comet
You might think that “interstellar visitor from the oldest part of the galaxy” would be remarkable enough, but 3I/ATLAS took that as a challenge. As it approached our Sun, the heat evaporated the surface into a large coma and tail, like with any other comet. Within that 35,000 mile-long train, scientists have detected cyanide. Yes, that kind of cyanide. Apparently that’s normal for comets, which makes me much less likely to visit one personally.
So, the cyanide’s not weird. But the carbon dioxide is. While comets do normally have some CO2 in its mix, the sheer amount of it in 3I/ATLAS is novel; it has more of it in its coma than even water, which is generally what icy comets have the most of. Scientists can’t currently explain why that is, which is how all friendly encounters begin, surely.
Don’t worry, it gets stranger. Somehow, the coma is also showing signs of nickel. Metals like nickel are unusual, though not unheard of, in comets. The spooky part is that nickel normally wouldn’t evaporate at the visitor’s current distance from the Sun. What’s going on there? Unclear! At least it’s not doing anything truly bizarre, like also showing signs of iron. Oh wait. There’s that too.
Waving hello, waving goodbye
Obviously, there’s a lot for scientists to figure out here. How, exactly, did this thing form? What precisely is it made of? What has it seen on its long travels across space and time, and what will it tell us? At the moment, we don’t even know how big it is. And we don’t have much time to find out.
Only the third interstellar object ever spotted in our part of the universe, 3I/ATLAS is just transiting through our neighborhood. Arcing in the Sun’s gravity right between Earth and Mars, it will simply wave hello and goodbye before exiting the system and diving back out into the rest of the galaxy. It will reach perihelion, the closest it gets to the Sun, on October 30. Bad luck means that the Earth will be on the other side of our star on that date, so we won’t get to observe what happens to the comet when the heat is most intense.
We humans only first started noticing foreign visitors in our neighborhood in 2017, and fantastic new telescopes like the Rubin Observatory will only make us more able to spot them. Rubin hopes to gather more space data in its first year of operation than all other optical observatories in history combined. So whatever questions 3I/ATLAS leaves unanswered, we may be able to ask the next friend to come along.
