For starters, it was the first interstellar object ever detected inside our solar system. Judging from the object’s trajectory, astronomers concluded it was not bound by the sun’s gravity — which suggested it was just traveling through.
No crisp photos could be taken, but astronomers were able to train their telescopes on the object for 11 days, collecting reams of other data.
At first, scientists thought it was an ordinary comet. But Loeb said that assumption ran the risk of allowing “the familiar to define what we might discover.”
“What would happen if a caveman saw a cellphone?” he asked. “He’s seen rocks all his life, and he would have thought it was just a shiny rock.”
Loeb soon opened his mind to another possibility: It was not a comet but discarded tech from an alien civilization.
A number of unusual properties about the object helped Loeb make this conclusion.
First were ‘Oumuamua’s dimensions.
Astronomers looked at the way the object reflected sunlight. Its brightness varied tenfold every eight hours, suggesting that was the amount of time it took for it to complete a full rotation. –