Alien spaceship? Latest 3I/ATLAS image shows lack of tail; Harvard astronomer Avi Loeb questions comet theory

The buzz around interstellar object 3I/ATLAS—hypothesized by some to be anything from an exotic comet to a piece of alien technology—is likely to take another unpredictable turn, with a new image taken post-perihelion showing that the object lacks a prominent cometary tail, something that should have been visible following its recent trip around the sun.

Since its discovery, the true nature 3I/ATLAS, the third known interstellar visitor to our Solar System, has been a topic of immense speculation.

Despite assurances from NASA and other space agencies that 3I/ATLAS was a mere comet visiting from another star system, many weren't convinced, in part due to the object behaving in a manner that defied conventional cometary models.

Theories about 3I/ATLAS and speculation about its true nature were also fuelled by Harvard astrophysicist Avi Loeb, who made several claims that it could be an advanced alien probe.

As speculation continued to mount amid high-profile media coverage, scientists had hoped to lay the buzz to rest with images from 3I/ATLAS' trip around the sun.

That, however, is unlikely to allay concerns, with the freshly released image fuelling further confusion.

If 3I/ATLAS were indeed a comet, its trip around the Sun in late October and the consequent solar heating should have triggered significant sublimation, turning ice to gas to create a massive, luminous cloud of gas and dust or a 'tail', which are typical for comets.

Had there been visual confirmation of said tail, it would probably have laid to rest a large chunk of the speculation.

However, now, with the image showing the lack of a prominent tail, speculation about 3I/ATLAS being an alien spacecraft have picked up again.

Pointing out that earlier data had showed 3I/ATLAS was experiencing non-gravitational acceleration (that is, its movement was being influenced by some force other than the Sun's gravity), Loeb pointed out that this should have been explained by a prominent tail.

Typically, non-gravitational acceleration in celestial bodies like comets is attributed to the 'rocket effect' of outgassing, wherein in a comet's ice vaporizes from solar heat, and creates a jet of gas that pushes the nucleus of the comet like small engine.

If this were indeed the reason behind 3I/ATLAS' non-gravitational acceleration, then it should have been visible in a prominent tail, Loeb claimed, explaining that 3I/ATLAS would have needed to shed at least 13% of its mass in vaporized material to explain the data, which, in turn, would have resulted in a prominent, visible tail.

With that tail now evidently absent, Loeb added it to the list of 'anomalies' that have thus far been observed.

Loeb noted that not only was 3I/ATLAS gigantically massive—far bigger than earlier interstellar visitors like 'Oumuamua and Comet Borisov—but was travelling at speeds far exceeding those of earlier interstellar visitors.

He also noted that 3I/ATLAS' trajectory appeared to be fine-tuned to bring it close to multiple planets, while obscuring it from Earth's view during perihelion.

He also added that 3I/ATLAS' vapour plume, instead of being made mostly of water ice, was observed to be dominated by exotic materials, with its nickel-to-iron ratio being resembling industrial alloys more than space debris.

So, is 3I/ATLAS a comet, an alien spacecraft, or something else beyond our current comprehension? The jury is still out.