The first interstellar guest in our solar system was first observed from Hawaii in October 2017. The guest got the name 'Oumuamua which is Polynese for "guest" or "scout". Unlike everything else we observe in our solar system 'Oumuamua is not moving in closed circuits and returns in their cycle, on the contrary it will never return to our solar system when it leaves. And that is not the only thing that is special about it. Eirik Flekkøy and Renaud Toussaint recently published a new article together with astronomer Jane X. Luu about 'Oumuamua in Astrophysical Journal Letters. In the abstract they write the following:
The first known interstellar object, 1I/2017 U1 'Oumuamua, displayed such unusual properties that its origin remains a subject of much debate. We propose that 'Oumuamua's properties could be explained as those of a fractal dust aggregate (a "dust bunny") formed in the inner coma of a fragmenting exo-Oort cloud comet. Such fragments could serve as accretion sites by accumulating dust particles, resulting in the formation of a fractal aggregate. The fractal aggregate eventually breaks off from the fragment due to hydrodynamic stress. With their low density and tenuously bound orbits, most of these cometary fractal aggregates are then ejected into interstellar space by radiation pressure.
The full article can be read in Astrophysical Journal Letters. The authors have also published a popular-science article in Aftenposten Viten (in Norwegian).
Luu, J. X., Flekkøy, E. G., & Toussaint, R. (2020). ’Oumuamua as a Cometary Fractal Aggregate: The “Dust Bunny” Model. The Astrophysical Journal Letters, 900(2), L22.