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The first known interstellar visitor to our solar system is neither a comet nor an asteroid as was first suspected and does not look like a cigar in any way. A new study indicates that the mystery object is likely a remnant of a Pluto-like, cookie-shaped world.
Arizona State University astronomers report that the bizarre 45-meter (148-foot) object appears to be made of frozen nitrogen, just like the surface of Pluto and Neptune’s largest moon, Triton.
Study authors Alan Jackson and Steven Desch believe that an impact knocked over a piece of an icy nitrogen-covered planet 500m years ago and sent the piece falling from its own star system to the our. The reddish remnant is thought to be a fragment of its original self, its outer layers evaporated by cosmic radiation and, more recently, by the sun.
It is named Oumuamua, Hawaiian for scout, in honor of the Hawaii Observatory which discovered it in 2017.
Visible only as a point of light millions of miles away, it was determined to originate beyond our solar system because its speed and trajectory suggested it was not orbiting the sun. or whatever.
The only other object confirmed to have deviated from another star system in ours is Comet 21 / Borisov, discovered in 2019.
Oumuamua looked like an asteroid but sped like a comet. Unlike a comet, it did not have a visible tail. Speculation has swung between comet and asteroid – and it has even been suggested that it could be an alien artifact.
“Everyone is interested in aliens, and it was inevitable that this first object outside the solar system would make you think of aliens,” Desch said. “But it is important in science not to jump to conclusions.”
Using his sheen, size and shape – and that he was propelled by leaking substances that didn’t produce a visible tail – Jackson and Desch designed computer models that helped them determine that Oumuamua was very probably a piece of gradually eroded nitrogenous ice.
Both of their papers were published by the American Geophysical Union and also featured at this year’s Lunar and Planetary Science Virtual Conference.
Not all scientists accept the new explanation. Harvard University’s Avi Loeb disputes the results and supports his hypothesis that the object appears to be more man-made than natural – in other words, something from an alien civilization, perhaps a light sail. His recent book Extraterrestrial: The First Sign of Intelligent Life Beyond Earth addresses the subject.
Given that Oumuamua is different from comets and asteroids – and something never seen before – “we cannot assume that things are going as usual, as many scientists argue,” Loeb wrote in a email Wednesday. “If we are considering something that we have not seen before, we must leave the hypothesis of artificial origin on the table and collect more evidence on objects of the same class.”
When Oumuamua was at its closest approach to Earth, it appeared to be six times as wide as its thickness. These are the approximate proportions of a slice of an Oreo cookie, Desch noted.
It is now long gone, beyond the orbit of Uranus, over 2 billion miles away and far too small to be seen even by the Hubble Space Telescope. As a result, astronomers should build on the original observations and hopefully continue to refine their analyzes, Jackson said.
By the time the object begins to leave our solar system around 2040, the width-to-thickness ratio will have dropped to 10: 1, according to Desch. “So maybe Oumuamua was compatible with a cookie when we saw it, but will soon be literally as flat as a pancake soon.”
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