An emissary from interstellar space
3I/ATLAS was discovered last week, and recently confirmed as an interstellar object.
K Ly/Deep Random Survey/CC-BY-4.0-SA
A recently discovered extraterrestrial "visitor" is hurtling toward the inner solar system at 130,000 miles per hour and has quickly captured the attention of astronomers and space enthusiasts around the world, including here at the University of Arizona.
Dubbed 3I/ATLAS, it is only the third object known to have crossed into the solar system from interstellar space. Carson Fuls is director of the Catalina Sky Survey, a NASA-funded project at the university's Lunar and Planetary Laboratory. University of Arizona News spoke with Fuls to learn more about the mysterious object traversing our solar system on its journey through interstellar space.
What is special about interstellar objects such as 3I/ATLAS visiting our solar system?
Zoom out and consider that our sun, every planet, asteroid, comet, even every shooting star that you've ever seen, was formed all together as part of our solar system. This object came from an entirely different solar system. We have no idea which one, or how long this thing has been traveling through the void, but it is an actual piece of another star system.
3I/ATLAS, imaged here by the European Southern Observatory's Very Large Telescope, is only the third visitor from outside the solar system ever found.
ESO/O. Hainaut
The nearest star is four light years away, so 3I/ATLAS has traveled light-years to get here. It's early, and we're still gathering data about it, but this object looks a lot like the comets from our solar system. This is exciting because if other star systems resemble our own, then perhaps there are Earth-like planets out there as well. For now, we don't really know.
Carson Fuls is director of the Catalina Sky Survey, a NASA-funded project at the university's Lunar and Planetary Laboratory.
Courtesy of Carson Fuls
What do we know about 3I/ATLAS? What might it look like?
The latest observations show this object has a coma (cloud of gas), so it is a comet. This is expected, as comets are thought to be routinely whipped out of their star systems by close approaches to planets.
Right now, 3I/ATLAS is estimated to be about 4.5 kilometers [2.8 miles] in diameter, although this is difficult to estimate because a comet's nucleus is obscured by the cloud of gas and dust around it. The shape is incredibly hard to determine right now, as we would need to peer underneath the coma. We may be able to get a better idea once the comet heads out and stops sublimating vapor, but for now, it's a mystery.
The University of Arizona-based Catalina Sky Survey, or CSS, has been surveying, discovering and tracking near-Earth asteroids for a quarter century and to date has discovered 16,900 near-Earth asteroids, accounting for about 44% of all known NEOs.
Catalina Sky Survey
Is 3I/ATLAS visible to amateur observers, or will it be at some point?
While this object will never be visible to the naked eye, it will be fairly bright this fall and visible to an average backyard telescope, most likely around Nov. 1.
How do we know 3I/ATLAS is an interstellar visitor and not just a comet of our own?
We know because of how fast this object travels. The rest of our solar system is trapped in a dance around the sun. Most comets that we discover head into the inner solar system and then back out to the outer solar system. Even if they get a little kick by passing by Jupiter on their way out and leave forever, they are not traveling that fast. This object is cruising. There is no possible way that our sun could pull it back into an orbit, and there is no way it ever was. It's not even close. It is simply traveling too fast to be a part of our solar system.
Are interstellar objects fundamentally different from solar system dwellers?
Not that we know of. So far, this object would appear to just be another comet discovery if it wasn't for its hyperbolic orbit.
What is known about the origin of this object? Is there a location in nearby space that is more likely to be their place of origin than others?
All we can do is guess at how common visitors like this are to our solar system. This one came from the direction of the galactic center, which makes sense, as it harbors a higher density of stars, but these objects could really come from any direction. This does show that we are getting better at discovering the small bodies in our solar system. With the new generation of surveys coming online, we expect the pace of these types of discoveries to pick up, but by how much, we can only guess.
How is the Catalina Sky Center involved in observing 3I/ATLAS?
As a planetary defense program, we got to work observing this object to see if it was coming close to Earth or not. Once it was determined that this object poses no threat to Earth, we moved on to observing other targets. While we are all excited by the prospect of a new interstellar visitor, we are laser-focused on our mission of discovering and tracking NEOs (near-Earth objects), so our work with 3I/ATLAS ended.
Do interstellar objects hold clues about the universe that we could not figure out otherwise?
Absolutely! Either way, we learn something. If we find an object with a composition that does not match the comets of our solar system, our models of solar system formation must account for that possibility in other star systems. However, at this point, this object does match what our comets look like, which means that we have evidence for a common formation mechanism of comets around other stars. Both are exciting!
