Skywatchers at Nasa have discounted a Harvard astronomer’s hypothesis that a rare interstellar object hurtling through our solar system is a relic from a civilization in another celestial neighborhood, and “could potentially be dire for humanity”.
Avi Loeb, head of Harvard University’s Galileo Project, which searches for evidence of extraterrestrial intelligence, raised eyebrows by suggesting in a scientific paper in July that Comet 3I/Atlas, set for a close pass with Mars next month, could be artificially made.
It is only the third known object originating outside the solar system to pass through and was named for the Asteroid Terrestrial-Impact Last Alert System (Atlas) survey telescope in Río Hurtado, Chile, that discovered it on 1 July.
Loeb says observations of the object so far have not revealed gaseous tails of dust and plasma common to comets originating inside the solar system, and have shown it following an unorthodox trajectory, suggesting “a technological artifact” with “active intelligence”.
“[If] future data will indicate the absence of a cometary tail, we will be faced with the tantalizing possibility that it did not inherit a random velocity in interstellar space but instead was sent towards the inner solar system by design,” Loeb wrote in a blogpost.
Even more sinister, Loeb asserts in his paper, is the possibility of the object performing a clandestine deep space maneuver while it is hidden behind the sun in late October, then setting course for a “malign intent” rendezvous with Earth.
“The consequences, should the hypothesis turn out to be correct, could potentially be dire for humanity, and would possibly require defensive measures to be undertaken, though these might prove futile,” he wrote.
Loeb’s postulation, to which he admits he does not necessarily subscribe, but which he contends is at least worthy of analysis, failed to impress experts at Nasa. The space agency has been studying the object closely through ground and space telescopes since it was first spotted, and state categorically it poses no threat to Earth.
“It looks like a comet. It does comet things. It very, very strongly resembles, in just about every way, the comets that we know,” said Tom Statler, Nasa’s lead scientist for solar system small bodies.
“It has some interesting properties that are a little bit different from our solar system comets, but it behaves like a comet. And so the evidence is overwhelmingly pointing to this object being a natural body. It’s a comet.”
Imagery from the Hubble space telescope suggests it is up to 3.5 miles (5.6km) wide, and traveling at 130,000mph (209,000km/h), the highest velocity ever recorded for a visitor to the solar system.
Statler said all comets, not just those that are interstellar, exhibit some elements of anomaly.
“Comets are mixtures of dust and ice, they’re being heated by the sun, that heating is changing, and exactly how they respond to that is something that’s a bit unpredictable,” he said.
“So even in our solar system, comets can have a history of suddenly brightening if there’s, say, a particular pocket of ice that sublimates quickly and drives off a large amount of dust.
“It’s the sort of thing that our comet observers and experts are prepared for, and presents an opportunity to get more information.”
Statler said the object would not come closer to Earth than about 170m miles due to the positions of the planets over the next few months. It will make close passes with Mars, Jupiter and Venus.
“It’s special because we now have the ability to discover these interstellar comets,” he said.
“It’s not that they’re really anything new, but we’ve just recently had the ability to discover them, and we’ve discovered only three so far. This gives us a window we’ve never had before, directly into the composition of other solar systems.”
Loeb, meanwhile, acknowledged in his blogpost that “the simplest hypothesis is that 3I/ATLAS is a comet”, and that he was raising alternative possibilities as an exercise in challenging preconceived ideas.
“Let us instead maintain our childhood curiosity and seek evidence rather than pretend to be the adults in the room that know the answers in advance,” he wrote.
“The hypothesis is an interesting exercise in its own right, and is fun to pursue, irrespective of its likely validity.”
