Oumuamua, formally designated as 1I/2017 U1, is the first known interstellar object to visit our solar system. It was discovered on October 19, 2017, by the University of Hawaii’s Pan-STARRS1 telescope, which is funded by NASA’s Near-Earth Object Observations (NEOO) Program. The discovery was made approximately 40 days after Oumuamua passed its closest point to the Sun on September 9 of the same year.
Oumuamua is estimated to be between 100 and 1,000 meters long, with a width and thickness estimated between 35 and 167 meters. It has an elongated, cigar-like shape and a red color similar to objects found in the outer Solar System. Despite its close approach to the Sun, Oumuamua showed no signs of having a coma, which is a gaseous “head” around a comet’s icy nucleus. It exhibited non-gravitational acceleration, possibly due to outgassing or the push from solar radiation pressure.
The object has a rotation rate similar to that of Solar System asteroids, but its light curve suggests that it is tumbling rather than spinning. It is moving at a fast pace relative to the Sun, indicating it is likely of extrasolar origin. Its path cannot be captured into a solar orbit, so it will eventually leave the Solar System.
Astronomers had long theorized the existence of interstellar objects, but Oumuamua was the first confirmed detection in our solar system. It provided direct evidence that such objects exist beyond our planetary system. It has sparked widespread interest and speculation due to its unusual characteristics.
One of the leading theories to explain Oumuamua’s behavior involves the sublimation of either nitrogen or hydrogen ice. While it has been the subject of speculation about being an alien spaceship, there is currently no evidence to support this hypothesis. Oumuamua’s behavior and composition align more closely with that of a comet, albeit an unusual one.
In August 2019, a second interstellar object, named 2I/Borisov, was discovered in the solar system. Unlike Oumuamua, Borisov exhibited more typical comet characteristics, such as a coma and a tail.
Research conducted by Jennifer Bergner and her team at the University of California, Berkeley, published in Nature, proposes a model that explains some of the strange behavior of Oumuamua. According to their study, Oumuamua was indeed a comet, but with an uncommon composition.
Overall, Oumuamua has provided scientists with valuable insights into interstellar objects and their behavior within our solar system. Further studies and observations will continue to shed light on the mysteries surrounding these fascinating visitors from afar.