At www.sciencemag.org/news/2018/06/mysterious-interstellar-visitor-comet-fl… … Oumuamua, the so called interstellar visitor claimed to be passing through our solar systme, a cigar shaped space rock, is being re-classified as a comet rather than an asteroid – as tell tale gas emissions have been detected (or theorised). Scientists have continued to watch Oumuamua as it passes towards the edge of the solar system and they have been able to refine its trajectroy. It appears to be moving too fast for gravity alone and something else is helping to propel it. The most convincing explanation, they say, was water and gases ejected from Oumuamua (see the article in Nature journal).
The same story is at https://phys.org/print449324675.html … the so called visitor from another solar system, a cigar shaped object, Oumuamua, has now been identified as a comet. One reason for this change is that many space rocks are ejected during the formation of planetary systems and most of these are comets (it is alleged). If it was an asteroid, we are told, it would have underscored scientists understanding of our solar system – so is it a comet or not (as is it convenient to call it a comet).