3I/ATLAS before closest approach to earth

 

What a weird comet, eh? Here's my shot, taken this morning at around 5 o'clock. Close inspection of the image reveals somewhat of a tail pointing upward, and somewhat of another tail pointing downward. Tail and anti-tail? Perhaps. But keep in mind that we're viewing the comet such that its tails may be pointing away from us, regardless of which side of the comet they appear to be on from our perspective. 

Of course, the odd shape of Comet 3I/ATLAS is just one more of several alleged anomalies that conspiracy theorists have pointed to in an effort to persuade us that it's not a comet at all, but rather a space probe sent by aliens from a distant star system to gather information about us or to attack us. 

Whatever!

I don't believe there's anything artificial about 3I/ATLAS. For one thing, it's come a long way and has to have traveled a very long time across the galaxy. It is likely older than our solar system, meaning that if it was launched by aliens, they sent it off before our sun and its family of planets existed. But no one can deny that its appearance is comet-like. It is traveling fast enough that we know that it's passing through our solar system on a journey that originated deep in interstellar space. So, while it may not look and behave like comets that we're familiar with, that doesn't mean that it's not a natural celestial body. 

Consider the Voyager 1 and Voyager 2 space probes we launched for a Grand Tour of our solar system back in 1977. These two spacecraft are very tiny compared to 3I/ATLAS. With gravitational assists from several planets, they escaped the sun's gravity, but after 48 years of travel they still haven't exited our solar system. Voyager 1 is traveling at a velocity of 17 km/s, a speed that would take 75,651 years to reach the nearest star, Proxima Centauri (at a distance of 4.25 light years from our sun). Unfortunately, the transmitters on Voyager 1 aren't powerful enough for us to continue receiving signals much longer. NASA estimates that we will lose communication with Voyager 1 sometime over the next 5 years. 

When it entered our solar system, Comet 3I/ATLAS was traveling about 3.6 times faster (61 km/s) than Voyager I. At that speed, it would have taken it 20,736 years to reach us, if it had been launched from Proxima Centauri (which, it wasn't). Even if it had some kind of nuclear power source, do you really believe any of its onboard electronic components would still function after a trip of 20,736 years? 

And let's not forget that our solar system is a moving target. We've moved through the galaxy quite a ways in the past 20,736 years! Do you have any confidence that some very distant aliens could have adjusted their sights to aim at an intercept point such that their spacecraft, after many tens of thousands of years, would enter our solar system on this lucky Grand Tour path that would get close fly-bys of Mars, Venus, Earth, and Jupiter? That would be pretty remarkable indeed! 

Not only that, but do you think these aliens are still alive 20,736 years later, so as to receive the data back from their probe? And that would be quite a powerful transmitter on 3I/ATLAS, to send back the data in a reasonable time frame! You'll recall that it took New Horizons 15 months to complete the transmission (at 1 kilobyte/s) of all the data it collected at Pluto. And that was from a distance of only 3 billion miles. What if New Horizons had to send that data back to us from 10 or 20 light years away (one light year = 5.88 trillion miles)?

Oh, but surely the advanced civilization behind 3I/ATLAS had the technology to get around all the limitations we have yet to overcome. 

Well, the more advanced we allow them to be in our imaginations, the more you have to wonder why we're still alive! If they were "coming for us," don't you think that all of their sophisticated technology would have "gotten us" by now?

Yes, it takes some very wild speculation to convert 3I/ATLAS from "natural object" to "alien spacecraft"! Oh, and one last thought about the Voyagers. When they arrive at some nearby star many thousands of years hence, they will not look like comets, if any aliens are able to see them at all! The Voyagers' slim, artificially manufactured bodies will not outgas and form bright, million-mile tails visible for hundreds of millions of miles across some hypothetical distant solar system. And really. How much arrogance does it take in order for us to believe that aliens living many lightyears away from earth are so darned curious about us that they would build a spacecraft of preposterous size and launch it on such an impossible mission?

I'd say that one of the things that makes 3I/ATLAS look a little odd to us at the moment is the fact that its trajectory didn't bring it close enough to the sun to get really interesting. Spectacular comets usually cross the orbits of Venus or Mercury. When comets get that close to the sun, they really break up and create spectacular tails. But 3I/ATLAS didn't even come as close to the sun as the earth. It passed just inside of Mars' orbit. While that's close enough to break things up a wee bit, it didn't get anywhere near close enough to the sun so as to become a glorious sight from earth. 

Right now, Comet 3I/ATLAS has already passed perihelion (its closest approach to the sun) and is heading outbound toward the opposite side of the solar system from where it entered. As the comet heads outward, earth is finally coming around in its solar orbit to reach its closest point to the comet. But it's probably not at all how you're imagining "close approach" if you haven't paid a visit to JPL's Small-Body Database website. Spoiler alert: 3I/ATLAS isn't approaching earth! It's heading away from us! Instead, earth is sneaking up behind 3I/ATLAS, but it will soon curve away as we continue our more circular orbit around the sun. Below is a screen capture I made for December 20, 2025, when earth will come as close to 3I/ATLAS as we can possibly get.

JPL Small Body Database Lookup Orbital Viewer

That's right! For all the internet hype you're reading about 3I/ATLAS and its closest approach to earth ("Launch the probes!"), the above image from JPL's orbital viewer reveals all! See those numbers in the lower lefthand corner? "Earth distance: 1.798 au." One "au" (astronomical unit) is the distance from earth to the sun (on average, 93,000,000 miles.) Yeah, so the comet is only getting as close to us as about 167,000,000 miles. With only a weak heating from the sun at closest approach and shrinking now as it retreats to the outer solar system, don't expect images of 3I/ATLAS to improve much between now and December 20. Note that in the JPL graphic above, the direction of travel for the comet is from bottom to top, whereas the direction of earth's motion is counterclockwise in its orbit. 

People love to be part of a conspiracy theory, I suppose. And sure. Why not? It's much more fun to imagine that 3I/ATLAS was sent here by aliens, than it is to believe that it was just a rock that got kicked out of its own solar system tens or hundreds of thousands of years ago and is just randomly passing by our sun on its accidental journey through the galaxy. 

So, if you wanna believe Harvard astronomer Avi Loeb's wild theory that 3I/ATLAS is a space probe, go ahead. Enjoy your speculation! Who knows for certain what this thing was? But as it leaves our solar system and continues on its slightly altered path (from our sun's gravitational assist) through the galaxy, my own opinion is that it's just an accidental and very natural celestial rock that's behaving like a comet. You know the drill... "If it looks like a duck, walks like a duck, and quacks like a duck, then why in the world shouldn't we just call it a darned duck?"


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