There is a new article about 'Oumuamua, the interstellar object observed last year passing through the solar system.

At the time, there was a lot of speculation about whether the object was natural or artificial. The object had a large regular variation in brightness, such regular variations are often due to seeing an object from different orientations as it spins, but the variations in brightness were more extreme than has been observed before from natural objects like asteroids. Some interpreted this as indicating the object had an elongated shape not normally seen in nature, bright when seen broadside and faint when seen edge-on or end-on. This was speculative, brightness variations can also be caused during rotation by a surface with bright or dark patches, and I'm not sure how certain we are that the brightness variations were actually as extreme as commonly reported. (If this report about brightness variations was inaccurate, it could easily match the typical properties of an asteroid-like object, so the "must be artificial" speculation seemed less certain to me.)

Speculation that 'Oumuamua was artificial often painted the object as an elongated metal spacecraft. But this new article takes the concept in a totally different direction.

'Oumuamua's trajectory had a slight deviation from what would be expected from gravity. This is not unusual, comets warming up near the sun vent ices producing a slight thrust, and asteroids are pushed lightly by the pressure of sunlight. Scientists calculated what the properties of the object would be if this deviation was due to the pressure of sunlight, and found that a lightsail with reasonable properties (size, thickness, etc) would match the observations. So if 'Oumuamua was artificial, it may have been a thin low-mass lightsail, not a large high-mass metallic ship.

A small note in the article, but particularly interesting, calculates the chance of a random interstellar object passing so close to the sun (0.25 AU, one-quarter of the Earth/Sun distance), and finds this somewhat unlikely by random chance - suggesting it may have been a targeted interstellar lightsail (reconnaissance probe?) instead of a discarded piece of space debris.

Sauce: "'Oumuamua, Thin Films and Lightsails"

https://www.centauri-dreams.org/2018/10/29/on-oumuamua-thin-films-and-lightsails/