Thread by @ExploreCosmos_

In October 2017, astronomers made a startling discovery that captivated the world's imagination: an object hurtling through our Solar System at an incredible speed, seemingly originating from interstellar space. Named 'Oumuamua which loosely translates to "scout" ... 1/

... or "messenger" in Hawaiian, this enigmatic visitor has sparked intense scientific interest & speculation ever since.

First detected by the Pan-STARRS1 telescope in Hawaii, Oumuamua's unique trajectory & speed immediately distinguished it from any known celestial object. 2/

The origin of Oumuamua remains one of its most perplexing aspects. Traditional comets and asteroids from within our solar system are relatively easy to categorize based on their composition and behavior. However, Oumuamua defied easy classification. 3/

Its unusual shape, lack of a discernible coma or tail, and rapid non-gravitational acceleration puzzled researchers.
Scientists have proposed various theories to explain Oumuamua's peculiar characteristics and its journey across the cosmic expanse. 4/

Here are some of the most prominent hypotheses, including a speculative theory that has circulated in some circles:

--Natural Object: One prevailing theory suggests that Oumuamua is a natural object, possibly a loosely bound agglomeration of ice & rock, similar to a comet .. 5/

... or asteroid. Its elongated shape could be the result of a collision or gravitational forces during its formation. However, this theory struggles to fully account for its unusual acceleration. 6/

--Fragment of a Destroyed Planet: Another hypothesis speculates that Oumuamua could be a fragment of a destroyed planet or exoplanetary system, ejected into interstellar space by a catastrophic event. 7/

This theory would explain its odd shape and unusual trajectory, as well as its lack of a coma or tail.

--Interstellar Spacecraft: Perhaps the most tantalizing possibility is that Oumuamua is an artificial object, an alien spacecraft or probe sent from another civilization. 8/

Proponents of this theory point to its acceleration, which could be attributed to solar radiation pressure or even deliberate propulsion systems. But the lack of any definitive evidence or communication from an extraterrestrial origin makes this theory highly speculative. 9/

--Origin from the Pleiades: In some speculative discussions, there have been suggestions that Oumuamua originated from the Pleiades star cluster. While the Pleiades is a well-known & beautiful cluster of stars, located ~ 444 light-years away in the constellation of Taurus, ..10/

... there is currently no scientific evidence supporting this theory. It remains an intriguing but unproven idea in the realm of speculation.

Astronomers haven't definitively detected any fully formed planets orbiting stars in the Pleiades yet. 11/

But there is evidence that suggests planets are forming or have recently formed there.

In 2007, researchers found evidence of dust clouds around a young star in the Pleiades called HD 23514. These dust clouds are thought to be the result of collisions between ... 12/

... planet embryos, which are early stages of planets. This suggests that rocky planets, similar to those in our solar system, may be forming in the Pleiades. 13/

👉 gemini.edu/node/259

Despite the wealth of theories put forth by scientists, Oumuamua continues to elude easy categorization. To unravel its mysteries, astronomers are eager to detect and study more interstellar visitors in the future. Telescopes, such as the #JWST, .. 14/

... promise to enhance our ability to observe & analyze objects like Oumuamua with greater precision. 15/

Some details about our "visitor":

*Size: Oumuamua is estimated to be between 100 and 800 meters (330 to 2,600 feet) in length. Its elongated shape and lack of discernible features make precise measurements challenging, but it is significantly longer than it is wide. 16/

*Shape: Oumuamua has an elongated, cigar-like shape, with its length estimated to be at least five to ten times its width. This unusual shape distinguishes it from typical asteroids and comets observed within our solar system. 17/

*Speed: Oumuamua entered the SS at an extremely high speed, traveling at ~ 315,000 km/h (196,000 miles per hour) relative to the Sun. Its hyperbolic trajectory indicated that it originated from outside the solar system & was passing through on a one-time journey. 18/

*Rotation: Oumuamua rotates on its axis with a period of about 7.3 hours. This relatively rapid rotation was inferred from variations in its brightness observed as it tumbled through space. 19/

*Non-gravitational Acceleration: One of the most intriguing aspects of Oumuamua is its observed acceleration that cannot be solely explained by gravitational forces. This non-gravitational acceleration, observed as a deviation from its expected trajectory, ... 20/

... suggests that Oumuamua experienced some form of propulsion or outgassing, although the exact mechanism remains uncertain.

*Composition: Oumuamua's composition is still a subject of debate among astronomers. Without close-up observations, it is challenging to determine... 21/

... its exact makeup. Some theories suggest it could be composed of rock and metal, while others propose a more icy or carbon-rich composition. 22/

*Closest Approach: Oumuamua made its closest approach to the Sun on Sep 9, 2017, at a distance of ~ 0.25 AU, ~37.6 million km (23.4 million miles) from the Sun. After its encounter with the Sun, it began its journey back into interstellar space. 23/23

📸 ESO/K. Meech et al.

24/24

Non-Gravitational Acceleration in the Trajectory of 1I/2017 U1 (ʻOumuamua).

👉 eso.org/public/archive…