Sorry, but interstellar visitor 3I/ATLAS really is a comet, not aliens

Interstellar object 3I/ATLAS doing something strange again. This interloper from another star is currently hidden from view behind the Sun, leading some people to wonder what it might be hiding. There can only be one explanation, they whisper: it’s an alien spaceship.

But this, of course, is complete nonsense. It makes no sense for a spacecraft to darken itself for just a few days when it was previously clearly visible and will be visible again. If this is truly an alien ship hoping to remain incognito, then either the aliens piloting it are extremely stupid, or they think we are.

How can I be so sure? Well, to paraphrase what an astronomer recently told me: if this really is a spaceship, it's done a damn good job of camouflaging itself as a comet. That's what the clickbait discourse about 3I/ATLAS (named after the eagle-eyed planetary defense apparatus who spotted this in July) is both frustrating and unintentionally hilarious. It is quite obvious that this is a comet.

Let's note the reasons. He is surrounded by a coma, a shell of evaporated ice. He has a shiny tail. It is moving on a trajectory that can best be explained as an ice projectile entering the solar system from somewhere else. Oh, and why is it “hiding” behind the sun? That's because it has just reached perihelion, the closest point to our home star during its journey around our planet. All space travelers – from planets and comets to asteroids – have perihelions; From Earth's point of view, 3I/ATLAS is closest to the Sun, although it is behind it.

Of course, there are some strange things about 3I/ATLAS that astronomers are concerned about. First of all, he has much more the ice in it is made of carbon dioxide than water ice. But that still makes it a comet, not a space probe. It also has both nickel and iron in it, which – wait, these are metals! Spaceships are made of metals! Does this mean that 3I/ATLAS is actually a spacecraft? No – we constantly see metals inside the rocky-icy mud cores of comets. In fact, the comets of our solar system come in many different types, and some of them are enough strange.

The fact that 3I/ATLAS at one point had a dusty tail pointing towards the sun rather than away from it was also a bit unusual. Some suggested that it was not a tail at all, but rather the plume of a spacecraft engine trying to slow down. The problem is that 3I/ATLAS's trajectory is that of an interstellar comet, not someone hitting the brakes on their interstellar spacecraft. The peculiar direction of the tail was determined by the type of ice-dust particles. flew off its surface. These ephemerals are normally pushed away from the Sun by the pressure of solar radiation, but some of this cometary dandruff was so heavy that it could not be pushed back and instead fell towards the Sun.

3I/ATLAS is only the third interstellar object ever observed, so we can expect to find some anomalous features when studying such a small population. The first known interstellar object, 'Oumuamua, was much stranger: it was likely cigar-shaped and accelerated rapidly as it left the solar system. Although this is strange, it is nevertheless quite understandable. bright object similar to a comet. Both 2I/Borisov and 3I/ATLAS, the next two interstellar objects, also have their own interesting features. But suggesting that these are spaceships rather than comets is like calling the ice cubes in the freezer pineapples. You can do it, but you'll have to provide a lot more evidence if you want to convince me.

Many of us, myself included, are looking forward to the day when we discover that we are not alone in the Universe, so I don't find it surprising that people have latched on to the (baseless) idea that 3I/ATLAS might be a sign that that day has finally arrived. But in an era filled with misinformation, suggesting that this comet could be aliens, despite all the evidence, is not just stupid – it is deeply irresponsible.