When Oumuamua first flew into view, we thought it looked like a cigar.
But now, thanks to a new study, the mystery object appears to be a shard of a “Pluto-like world” and shaped like a space-steak.
The Pan-STARRS telescope in Hawaii found it in 2017, so the object's name is derived from the Hawaiian word for ‘scout’.
Pan-STARRS PS1 Observatory atop Haleakala, Maui discovered Ouamuamua in 2017.
Astronomers at Arizona State University reported this week that the 45-metre-wide object’s makeup resembled Pluto and Neptune's largest moon, Triton, since it seems to be made of frozen nitrogen.
A rocky nitrogen planet limped into our solar system 500 million years ago after an impact knocked a chunk off, leaving a piece of it tumbling into ours. Or so it’s hypothesised by study authors Alan Jackson and Steven Desch.
Optical measurements indicate that the reddish remnant is a sliver of the planet's original self, its outer layers evaporated by cosmic radiation and, more recently, the sun.
When viewed from millions of miles away, it was determined to be an extrasolar object since its speed and path indicated it wasn't orbiting the sun or anything else.
What is Oumuamua?
An artist's rendition of the first interstellar object ever detected in our solar system, named Oumuamua.
Only one other object has been confirmed to have crossed into our solar system from another star system, the comet 21/Borisov, discovered in 2019.
Nevertheless, it’s difficult to categorize Oumuamua, as it doesn't seem to fit in any existing categories. It looks like an asteroid but travels at the speed of a comet.
Unlike a comet, however, it lacked a tail. It has been categorized as an asteroid and comet and even suggested by some as an alien relic.
"Everybody is interested in aliens, and it was inevitable that this first object outside the solar system would make people think of aliens," said Professor Desch.
"But it's important in science not to jump to conclusions."
Using its shininess, size and shape — and that it was propelled by escaping substances that didn't produce a visible tail —
They observed the reflection of light, shape, and size of the object - which was propelled by escaping substances that didn't produce a tail - to determine that Oumuamua was most likely a disintegrating shard of nitrogen ice.
In addition to their two papers published in the American Geophysical Union, they presented them at the Lunar and Planetary Science Conference earlier this year.
Not all scientists agree.
Oumuamua has characteristics that some believe is part of alien technology.
The chairman of Harvard University's astronomy department, Avi Loeb, disputes the findings and maintains that the object looks artificial rather than natural when viewed in three dimensions — in other words, an alien craft or craft from space, perhaps a light sail.
Given that Oumuamua is unlike comets and asteroids — and something not seen before — "we cannot assume ‘business as usual,' as many scientists argue," Professor Loeb said. "If we contemplate ‘something that we had not seen before,' we must leave the artificial origin hypothesis on the table and collect more evidence on objects from the same class."
According to Professor Desch, when Oumuamua was at its closest approach to Earth, its width was six times larger than its thickness. But now it’s gone, beyond Uranus over 3.2 billion kilometres away and much too far to be seen even by our Hubble Telescope.
Because of this, astronomers will be forced to use their original observations and, hopefully, refine their analyses in the future, Mr Jackson said. And as a result, we may never know the true nature of Oumuamua.
By the time the object starts leaving our solar system around 2040, the width-to-thickness ratio will have dropped to 10-to-1, according to Professor Desch.
"So maybe Oumuamua was consistent with a cookie when we saw it, but will soon be literally as flat as a pancake," he said.
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