Interstellar visitor 'Oumuamua's trajectory suggests it's not an asteroid after all By Michael Irving June 29, 2018 A new artist's impression of the interstellar object 'Oumuamua, which is now believed to be a very mildly-active comet ESA/Hubble, NASA, ESO, M. Kornmesser VIEW 2 IMAGES 'Oumuamua is one fascinating rock. The 400-meter-long (1,300-ft) cigar-shaped object is the first interstellar visitor ever detected passing through our Solar System, and while it was originally classed as an asteroid after its discovery, astronomers have now updated the label. 'Oumuamua, it turns out, is a comet after all, but it's unlike any other known comet 'Oumuamua (then known as A/2017 U1) was first spotted on October 19, 2017 by the Pan-STARRS 1 telescope in Hawaii, and it was initially assumed to be a run-of-the-mill asteroid. It wasn't until its trajectory was plotted that astronomers realized it was on a hyperbolic path, meaning it was just popping in for a single lap around the Sun before slingshotting back out of our neighborhood forever.