![]() The first character diacritic is a Hawaiian ʻokina, not an apostrophe, and is pronounced as a glottal stop the Pan-STARRS team chose the name in consultation with Ka‘iu Kimura and Larry Kimura of the University of Hawaiʻi at Hilo. It roughly translates to 'first distant messenger'. The name comes from Hawaiian ʻoumuamua 'scout' (from ʻou 'reach out for', and mua, reduplicated for emphasis 'first, in advance of' ), and reflects the way the object is like a scout or messenger sent from the distant past to reach out to humanity. The object may be called 1I 1I/2017 U1 1I/ʻOumuamua or 1I/2017 U1 (ʻOumuamua). As the first object so identified, ʻOumuamua was designated 1I, with rules for the eligibility of objects for I-numbers and the names to be assigned to these interstellar objects yet to be codified. Once it was unambiguously identified as coming from outside the Solar System, a new designation was created: I, for Interstellar object. ![]() Originally classified as comet C/2017 U1, it was later reclassified as asteroid A/2017 U1 due to the absence of a coma. Hyperbolic trajectory of ʻOumuamua through the inner Solar System with the Sun at the focus ( animation)Īs the first known object of its type, ʻOumuamua presented a unique case for the International Astronomical Union, which assigns designations for astronomical objects. In January 2022, researchers proposed Project Lyra, where a spacecraft launched from Earth could catch up to 'Oumuamua in 26 years for closer studies. On 22 March 2023, astronomers proposed the observed acceleration was "due to the release of entrapped molecular hydrogen that formed through energetic processing of an H 2O-rich icy body", consistent with 'Oumuamua being an interstellar comet, "originating as a planetesimal relic broadly similar to solar system comets." Ī number of astronomers have suggested that it could be a product of extraterrestrial technology however, there is insufficient evidence to support any hypotheses, "despite all strangeness". Proposed explanations of its origin include the remnant of a disintegrated rogue comet, or a piece of an exoplanet rich in nitrogen ice, similar to Pluto. While an unconsolidated object (rubble pile) would require ʻOumuamua to be of a density similar to rocky asteroids, a small amount of internal strength similar to icy comets would allow it to have a relatively low density. By July 2019, most astronomers concluded that it was a natural object, but its exact characterization is contentious given the limited observation window. ![]() ʻOumuamua would be remarkable for its extrasolar origin, high obliqueness, and observed acceleration without an apparent coma. Its planetary system of origin and age are unknown. Extrapolated and without further deceleration, its path cannot be captured into a solar orbit, so it will eventually leave the Solar System and continue into interstellar space. Its light curve, assuming little systematic error, presents its motion as " tumbling" rather than "spinning", and moving sufficiently fast relative to the Sun that it is likely of an extrasolar origin. It has a rotation rate similar to that of Solar System asteroids, but many valid models permit it to be more elongated than all but a few other natural bodies. It has exhibited non‑gravitational acceleration, potentially due to outgassing or a push from solar radiation pressure. Despite its close approach to the Sun, it showed no signs of having a coma. It has a red color, similar to objects in the outer Solar System. ʻOumuamua is a small object estimated to be between 100 and 1,000 metres (300 and 3,000 ft) long, with its width and thickness both estimated between 35 and 167 metres (115 and 548 ft). When it was first observed, it was about 33 million km (21 million mi 0.22 AU) from Earth (about 85 times as far away as the Moon) and already heading away from the Sun. Formally designated 1I/2017 U1, it was discovered by Robert Weryk using the Pan-STARRS telescope at Haleakalā Observatory, Hawaii, on 19 October 2017, approximately 40 days after it passed its closest point to the Sun on 9 September. ʻOumuamua is the first interstellar object detected passing through the Solar System. ![]()
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