Free Astronomy Magazine January-February 2018

dramatically changed its trajectory (there are 357 stars within 10 parsecs of the Sun). If in the future an in- habitant of a distant exoplanet should see Oumuamua (it is head- ing towards the Pegasus constellation), it would appear to be coming from the direction of the Sun, but it only made a brief appear- ance here − though it will take it several years to permanently exit the solar system. Although Oumuamua's origins will remain a mystery, we know for sure that in astro- nomical terms it has passed extremely close to the Sun, so much so that no one would ever have expected such an event. The most optimistic predictions indicated that, depending on the power of the telescopes used, the first object of that type would probably be discovered at a distance from the Sun of 10 to 30 astronomical units, thus in a much larger volume of space. Having found it so close to the Sun and the Earth could mean either that there are more of such visitors than expected or that we were very lucky this time. 13 JANUARY-FEBRUARY 2018 SOLAR SYSTEM Undoubtedly, the discovery of Oumuamua opens a new research path that will have significant repercussions on theories on the formation and evolution of planetary sys- tems, as well as on our knowledge of the matter they disperse within our galaxy. It is easy to forecast that in the coming years, with the most powerful photographic telescopes in the world, such as PanSTARRS 1, its recent twin PanSTARRS 2, the Catalina Sky Survey (0.5- to 1.5-meter telescopes), the Visible and Infrared Survey Telescope for Astronomy (VISTA, 4.1 meters) and the Large Synoptic Survey Telescope (LSST, 8.4 meters, beginning operation in 2021), as- tronomers will be able to discover a grow- ing number of interstellar visitors. It is expected that the LSST will allow us to find, on average, one new object per year. When a statistically significant number have been discovered, we will know whether there are more asteroids or more comets among them. Since the giant planets are mainly respon- sible for expelling those objects from plan- etary systems, a predominance of rocky and iron-bearing asteroids will mean that systems with giant planets very close to their stars are more common; on the other hand, a prevalence of icy cometary nuclei could tell us that the maximum expulsion of objects occurs at great distances from the stars, where cold volatiles are much more abundant and persistent. ! A t the top right, an animation showing the path of Oumuamua through the solar system. Observations made with the ESO VLT and other telescopes have shown that this single object is dark, reddish and very elongated. [ESO, M. Korn- messer, L.Calcada. Music: Azul Cobalto]