Last week, the first comet or asteroid to come to our solar system form somewhere else was discovered. At first, astronomers were wary, but now the evidence is shaping up that this flying rock really was hurtled at us from somewhere else. But where did it come from and what can it teach us?
The object, currently with the catchy name A/2017 U1, was spotted on October 18 when it was already heading away from us. It had been closer to the Sun in September and passed within 15 million miles of Earth on October 15.
Astronomers have jumped at the chance to study the rock in the days since then, and captured some fascinating details that hint at its origins. Its movements have been enough to build up a decent picture of the places it visited before we spotted it, and it tells an interesting story.
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Abigail Beall 