After ruling out solar-radiation pressure, drag- and friction-like forces, interaction with solar wind for a highly magnetized object, and geometric effects originating from 'Oumuamua potentially being composed of several spatially separated bodies or having a pronounced offset between its photocentre and centre of mass, we find comet-like outgassing to be a physically viable explanation, provided that 'Oumuamua has thermal properties similar to comets. https://pubmed.ncbi.nlm.nih.gov/29950718/
PDF: https://csnbiology.org/rw_common/plugins/stacks/armadillo/me...
PS: At to extreme velocity, something large traveling 0.1+ c or even 0.01c is very likely to be aliens. This was fast, but a long way from those kind of speeds.
The model predictions for the magnitude and temporal evolution of the non-gravitational acceleration are within a factor of about 2–3 of the observations (see Methods) for a water production rate of QH2O = 4.9 × 1025 molecules s−1 (or 1.5 kg s−1) near 1.4 au and an addi- tional contribution from QCO = 4.5 × 1025 molecules s−1 (or 2.1 kg s−1). Outgassing at this level does not conflict with the absence of spectro- scopic detections for outgassing of OH, because the values quoted are well below the spectroscopic limits on production rates16. However, the inferred upper limits for water production at 1.4 au, which are based on the non-detection of CN7 and assumed Solar System abundances for QCN/QOH17, show that ‘Oumuamua would need to be substantially depleted in CN (by a factor of more than about 15) relative to water.
And:
However, if the grains are predominantly larger than a few hundred micrometres to millimetres, they would not have been detected at optical wavelengths (see Methods). In the Solar System, comet 2P/Encke is noteworthy for its lack of small dust near perihelion18. Cometary behaviour implies that ‘Oumuamua must have some internal strength, at least comparable to Solar System comets19, because asteroid-like densities are ruled out (see Methods).
It’s an interesting read, suggesting interstellar space as being significantly different than what you see inside solar systems.
The big unknown for me about the object is that we don’t actually have a good idea about its shape. Drawings show it has a cigar shaped rock, which is only one possible configuration compatible with the radio reflections. If only we could have actually seen the object, a lot of this uncertainty would have been eliminated.