The first known interstellar visitor to our solar system is not a comet or asteroid as previously suspected and looks nothing like a cigar. A new study says the mystery object is likely a relic of a Pluto-like world and shaped like a cookie.
Astronomers at Arizona State University report that the strange 45-meter (148-foot) object appears to be made of frozen nitrogen, as does Pluto’s surface and Neptune’s largest moon, Triton.
The authors of the study, Alan Jackson and Steven Desch, believe that an impact 500 m years ago smashed a chunk of a nitrogen-covered planet and tumbled the piece from its own star system to ours. The reddish remnant is believed to be part of its original self, the outer layers of which have been evaporated by cosmic rays and, more recently, the sun.
It’s called Oumuamua, Hawaiian for scout, in honor of the Hawaii observatory that discovered it in 2017.
Visible only as a pinpoint of light millions of miles away, it was determined to have originated outside of our solar system, as its speed and path suggested it was not orbiting the sun or anything else.
The only other object confirmed to have drifted from another galaxy to ours is Comet 21 / Borisov, discovered in 2019.
Oumuamua looked like an asteroid, but it flew like a comet. Unlike a comet, it did not have a visible tail. Speculation alternated between comet and asteroid – and it was even 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 people think of aliens,” Desch said. “But it’s important in science not to jump to conclusions.”
Using its brilliance, size, and shape – and that it was propelled by escapes that did not produce a visible tail – Jackson and Desch devised computer models that helped them determine that Oumuamua was most likely a lump of nitrogen ice that was gradually being eroded.
Their two papers have been published by the American Geophysical Union and also presented at this year’s virtual Lunar and Planetary Sciences conference.
Not all scientists accept the new statement. Avi Loeb of Harvard University disputes the findings, insisting that the object appears more artificial 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 topic.
Given that Oumuamua is unlike comets and asteroids – and something that hasn’t been seen before – “we can’t assume things are normal, as many scientists claim,” Loeb wrote in an email Wednesday. “When considering something that we had not seen before, we should leave the artificial origin hypothesis on the table and gather more evidence about objects of the same class.”
When Oumuamua was closest to Earth, it was found to have a width six times its thickness. Those are the raw proportions of one wafer of an Oreo cookie, Desch noted.
It is long gone now, beyond Uranus’ orbit, more than 2 billion miles away, and far too small to be seen, even with the Hubble Space Telescope. As a result, astronomers should rely on the original observations and hopefully continue to refine their analyzes, Jackson said.
By the time the object leaves our solar system around 2040, the width-to-thickness ratio will have dropped to 10: 1, according to Desch. are like a pancake. “