Something strange is happening at the edge of our solar system. An interstellar visitor, comet 3I/ATLAS, has just reappeared from behind the sun, and it is not behaving like any comet scientists have seen before. It has emerged with an unexpected glow that has left researchers stunned and scrambling for answers.
Unlike the comets born in our own system, 3I/ATLAS does not orbit our sun; it is a true interstellar traveller just passing through. The object made its closest approach to the sun on Wednesday, observed by three NASA spacecraft after being hidden from Earth's view since 21 October. What those spacecraft saw was baffling.
