'Oumuamua: The First Visitor From Another Star Still Defies Explanation
On the night of 19 October 2017, a robotic telescope on the summit of Haleakala, the dormant volcano that dominates the Hawaiian island of Maui, logged one more faint smudge among the thousands it records on a clear night. When the astronomer Robert Weryk sat down to inspect the Pan-STARRS1 images, the dot refused to make sense. It was moving too fast, and along a path that could not be bent into any orbit closing back on the Sun.
Weryk checked, checked again, then called colleagues. Within days the measurement was confirmed: the object had not come from our solar system. It had fallen in from interstellar space, rounded the Sun around 9 September at roughly 87 kilometres per second, and was already climbing back out, on a trajectory that would never bring it back. Astronomers had expected such visitors for decades, because every young planetary system should throw debris into the galaxy, but until that week not one had ever been caught.
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