ʻOumuamua Hawaiian: [ʔowˌmuwəˈmuwə] is the only interstellar object detected passing through the Solar System. Formally designated 1I/2017 U1, it was discovered by Robert Weryk using the Pan-STARRS telescope at Haleakala Observatory, Hawaii, on 19 October 2017, 40 days after it passed its closest point to the Sun. When it was first observed, it was about 33,000,000 km (21,000,000 mi; 0.22 AU) from Earth (about 85 times as far away as the Moon), and already heading away from the Sun. ʻOumuamua is a small object, estimated to be between 100 and 1,000 meters long, with its width and thickness both estimated to range between 35 and 167 meters (328–3,280 ft × 115–548 ft × 115–548 ft).[11] It has a dark red color, similar to objects in the outer Solar System. ʻOumuamua showed no signs of a comet coma (atmosphere) despite its close approach to the Sun, but underwent non-gravitational acceleration. This effect is seen in many icy comets, although other reasons have been suggested.
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