Nola Taylor Redd reports that in late 2017, a cucumber-shaped visitor zoomed through the inner solar system. Known as 1I/2017 U1 'Oumuamua, the unusual object sped around the sun before disappearing to the outskirts of the solar system, on its way back to interstellar space. New research reveals that it wasn't smooth sailing for the interstellar interloper. Instead, it looks like 'Oumuamua didn't glide through the solar system but rather tumbled along its path, flipping as it journeyed on.
"Any time you look at 'Oumuamua, a random side of it would be facing you," Wesley Fraser, of Queen's University Belfast in the United Kingdom, told Space.com. Working with several other researchers, Fraser examined observations made by astronomers around the world to conclude that the object is tumbling through space. Fraser thinks it's likely that a collision sent the rock tumbling while it still orbited its parent star, before gravitational interaction with a planet flung the object out of its natal system. "I think 'Oumuamua was first sent tumbling and then punted out of its home," Fraser said.
Last fall, a cucumber-shaped visitor zoomed through the inner solar system. Known as 1I/2017 U1 'Oumuamua, the unusual object sped around the sun before disappearing to the outskirts of the solar system, on its way back to interstellar space. But new research reveals that it wasn't smooth sailing for the interstellar interloper. Instead, it looks like 'Oumuamua didn't glide through the solar system but rather tumbled, flipping as it journeyed on. "Any time you look at 'Oumuamua, a random side of it would be facing you," Wesley Fraser, of Queen's University Belfast in the United Kingdom, told Space.com by email. ['Oumuamua: Our 1st Interstellar Visitor Explained in Photos]
Working with several other researchers, Fraser examined observations made by astronomers around the world to conclude that the object is tumbling through space. Fraser thinks it's likely that a collision sent the rock tumbling while it still orbited its parent star, before gravitational interaction with a planet flung the object out of its natal system. "I think 'Oumuamua was first sent tumbling and then punted out of its home," Fraser said.
'Oumuamua first caught astronomers' eyes on Oct. 19, 2017. Calculations revealed that the unusual object was moving at about 85,700 mph (137,900 km/h) relative to the sun, a speed that meant it was just passing through the solar system and not remaining a permanent member. Telescopes around the world turned to the object, trying to collect as much information as possible before it left the solar system forever. The interstellar asteroid was named 'Oumuamua, Hawaiian for "a messenger from afar arriving first."
Some characteristics were easy to pin down. Scientists determined that the rocky object is about 1,300 feet (400 meters) long, and quite thin — perhaps just 130 feet (40 m) wide. It showed no sign of any activity suggestive of ice, like a comet might display, but instead looked to be made of solid rock. Its surface was reddened by cosmic rays over hundreds of millions of years, most likely as it traveled through interstellar space. But not everything was so easy to determine. Astronomers were having a hard time figuring out how the object rotated. As more and more papers were published on the topic, each estimated a different rotational period.
"Normally in a situation like this, as more data becomes available, the published rotation periods get more refined, and the values begin to converge on the correct value," Fraser said. "So it was surprising to see this wasn't the case with 1l ['Oumuamua]." "It seemed no one could agree … and the more data added, the worse the discrepancies got," Fraser said. He decided to pull all of the information gathered by astronomers around the world into a single coherent set, and measure the rotation period for himself.
Normally, when a rocky body such as an asteroid rotates, it produces a regular pattern of brightness variations that astronomers measure. That's because the object continues to show the same face to the observer. But this wasn't the case for 'Oumuamua; the brightness variations were unpredictable, Fraser said.
Similar measurements can come from active comets, he said. Dust and gas around comets can obscure their light, creating a variable signature. But 'Oumuamua showed no sign of comet-like activity. "The only other option we could come up with was [that it was] tumbling," Fraser said.
He compared the object to a spinning tennis racket thrown into the air, with its flat side facing up. The shape of the racket leads to a random tumbling motion. [see Asteroid Basics: A Space Rock Quiz]
Study co-author Petr Pravec, an astronomer at the Academy of Sciences of the Czech Republic, modeled the data and quickly found a tumbling model that worked. "Voilà! We had our answer," Fraser said. "We knew it must be true, but Petr really showed that our expectation did match reality." The research was published online earlier this month in the journal Nature Astronomy (more).
But this is not the end of the story. Read the rest of the article.
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