Free Astronomy Magazine January-February 2018

12 JANUARY-FEBRUARY 2018 SOLAR SYSTEM such as the 5-meter telescope on Mount Palomar (the Hale Telescope) and the 4.2- meter telescope on Roque de los Mucha- chos, Canary Islands (the William Herschel Telescope). It is interesting to note that Oumuamua entered our solar system from a point in space just 6° from what is called the solar apex, i.e., the apparent direction in which the Sun and its system are moving (at about 250 km/s). It is statistically more like- ly that an extrasolar object would arrive from that direction and, if it originated with and was expelled by a relatively close star, it is equally likely it would travel at a speed of 20 to 30 km/s. Since Oumuamua's arrival speed is almost centred in that range, some researchers have pointed to some possible asteroid parent stars, all of which are relatively close star associations, such as the Scorpius-Centaurus association, the Carina association, the Columba asso- ciation and the Tucana-Horologium associ- ation. It is actually impossible to establish from which planetary system Oumuamua was initially expelled because, before com- ing to us, it may have had previous close transits with other stars, which would have A rtist’s impres- sion of Ou- muamua. Observa- tions from ESO’s VLT and other tele- scopes around the world show that this unique object was travelling through space for millions of years before its chance encounter with our star system. [ESO/ M. Kornmesser]