Did We Detect An Alien Spacecraft? - Oumuamua

According to abundant geological evidence, an asteroid roughly 6 miles in width, hit Earth about 65 million years ago. Debris from the explosion was thrown into the atmosphere, severely altering the climate, causing a mass extinction event, leading to the extinction of roughly three quarters of species that existed at that time.

On the 19th of October 2017, an astronomer by the name Robert Weryk, detected a small object of about 300 to 3000 feet long and 115 to 548 feet in both width and thickness.

First observed, it was about 0.22 Astronomical Units away from Earth about 85 times as far away as the Moon, formally designated 1I/2017 U1, Oumuamua is the first interstellar object detected passing through our Solar System and appears to have come from roughly the direction of Vega in the constellation Lyra.

On the 27th of June 2018, astronomers reported a non-gravitational acceleration to Oumuamua's trajectory, potentially consistent with a push from solar radiation pressure or solar wind. The resulting change in velocity during the period when it was near its closest approach to the sun summed to about 17 meters per second.

Many theories have been proposed to explain Oumuamua’s behaviour.

The confusion of a non-gravitational acceleration to Oumuamua’s trajectory led public speculation to believe the object was of alien nature and potentially an alien spacecraft. In addition, this speculation was aided by a small number of astronomers having suggested that Oumuamua could be a product of alien technology, but there is insufficient evidence in support of this hypothesis despite all its strangeness.

On the 26th of October 2018, Loeb and his postdoc Shmuel Bialy submitted a paper exploring the possibility of Oumuamua being an artificial thin solar sail accelerated by solar radiation pressure, in an effort to help explain the object's comet-like non-gravitational acceleration. Other scientists have stated that the available evidence is insufficient to consider such a premise, and that a tumbling solar sail would not be able to accelerate. In response, Loeb wrote an article detailing six anomalous properties of Oumuamua that make it unusual, unlike any comets or asteroids seen before. A subsequent report on observations by the Spitzer Space Telescope set a tight limit on cometary outgassing of any carbon-based molecules and indicated that Oumuamua is at least ten times more shiny than a typical comet. The solar sail technosignature hypothesis is considered unlikely by many experts owing to available simpler explanations that align with the expected characteristics of interstellar asteroids and comets.

Outgassing of nitrogen ice could explain why no outgassing was detected. Nitrogen ice the size of Oumuamua could survive for 500 million years in the interstellar medium and would reflect two-thirds of the Sun's light. This explanation has been further supported in March 2021 when scientists presented a theory based on nitrogen ice, and further concluded that Oumuamua may be a piece of an exoplanet similar to the dwarf planet Pluto, an exo-Pluto as noted, from beyond our solar system. This theory has been criticized by Loeb. In November 2021, theoretical studies by Siraj and Loeb hypothesized that 'Oumuamua was not a nitrogen iceberg.

It has been proposed that Oumuamua contains a significant amount of hydrogen ice. This would point to it originating from the core of an interstellar molecular cloud, where conditions for the formation of this material might exist. The Sun's heat would cause the hydrogen to sublimate, which would in turn propel the body. The hydrogen coma formed by this process would be difficult to detect from Earth-based telescopes, as the atmosphere blocks those wavelengths. Regular water-ice comets undergo this as well, however to a much lesser extent and with a visible coma. This may explain the significant non-gravitational acceleration that Oumuamua underwent without showing signs of coma formation. Significant mass loss caused by the sublimation would also explain the unusual cigar-like shape, comparable to how a bar of soap becomes more elongated as it is used up.

However, it was later shown that hydrogen icebergs cannot form out of small grains and that, to not evaporate during their journey in interstellar space, they would had to be formed about 40 million years ago, in the close neighbourhood of the solar system.

Oumuamua would be remarkable for extrasolar origin, high obliqueness, and observed acceleration without an apparent coma. By July 2019, most astronomers concluded that Oumuamua is a natural object, but its exact characterization is contentious given the limited observation window. 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 a relatively low density. Proposed explanations include the remnant of a disintegrated rogue comet or a piece of an exoplanet rich in nitrogen ice, similar to Pluto. In January 2022, researchers proposed Project Lyra, which presented the notion that a spacecraft launched from Earth could catch up to 'Oumuamua in 26 years for further close-up studies.