Back in July, scientists operating a planetary defense facility designed to detect potentially hazardous asteroids spotted a visitor from another star: an interstellar object, and the third of its kind ever discovered. The voyager, known as 3I/ATLAS, was only visible as a white pixelated splodge 420 million miles from Earth. At the time, very little was known about the object except that it was some sort of comet.

But over the summer, 3I/ATLAS plunged toward the inner solar system—and the fireworks show began in earnest. When comets get close to the sun, they develop a sparkly tail and a blooming coma, the halo around the comet’s icy nucleus that appears when it begins to vaporize. Around October 30, 3I/ATLAS got as close as it will get to the sun, and on November 10, it emerged from th

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