Cosmic interloper Oumuamua may not have been aliens, but a strange ice cube

It’s been over two and a half years since astronomers first discovered Oumuamua, a strange elongated object beyond our solar system that crosses through our cosmic neighborhood. Its shape and sudden acceleration from our planet made some scientists suspect it could be a bizarre asteroid or an alien ship.

Now another explanation could be responsible for the oddity of Oumuamua: astronomers from the University of Chicago and Yale believe that it was the cleanest and pristine ice cube ever.

“It’s a frozen iceberg made of molecular hydrogen” Darryl Seligman, a postdoc at the University of Chicago, said in a publication. “This explains every mysterious property about it. And if it’s true, it is likely that the galaxy is full of similar objects.”

Seligman wrote a paper Accepted for publication in a future issue of the Astrophysical Journal Letters, which sets out the theory.

One of the most intriguing properties of Oumuamua was that it seemed to accelerate like a comet powered by ice that is burned by the sun, but had no tail that was made up of the resulting gases like a comet does.

But it could be that Oumuamua’s tail was just invisible to the telescopes watching him. Seligman and his colleagues found that molecular hydrogen ice is the only substance that can explain all of the craziness. It does not produce or reflect light when it burns, which would explain why Oumuamua did not have an observable tail. The scientists also calculated that it might have given the object the speed boost seen when it flew back into space.

Molecular hydrogen freezes a little above absolute zero and this only happens at odd places in the Milky Way, like a giant molecular cloud of freezing hydrogen and helium.

“It would be the most original primordial matter in the galaxy,” said Seligman. “It’s like the galaxy did it and FedEx told us directly.”

He adds that the interaction between energetic particles in space and the frozen hydrogen could also explain Oumuamua’s unique shape.

“Imagine what happens to a bar of soap,” he said. “It starts out as a pretty normal rectangle, but as you use it, it gets smaller and thinner over time.”

Seligman believes that it was particles of our own sun that probably had the greatest impact on the transformation of Oumuamua. That said, if astronomers catch an incoming hydrogen iceberg in the future, it may be possible to observe how it is cut off and prove the theory.

Unless, of course, the real explanation is that a distant alien civilization is using molecular hydrogen as the rocket fuel.