Free Astronomy Magazine January-February 2018

11 JANUARY-FEBRUARY 2018 SOLAR SYSTEM 3.5-meter WIYN Telescope at the Kitt Peak National Observatory and the 2.5-meter Nordic Optical Telescope in La Palma, Ca- nary Islands, revealed an 8-hour rotation period and a ratio of 6:1 between the axes, for a real dimension of about 180x30x30 meters. Even more extreme is the ratio be- tween the axes obtained by a team of as- tronomers led by Karen Meech (IfA). Combining images taken by the VLT's FORS (FOcal Reducer and low dispersion Spectro- graph) with data produced by other obser- vatories, they concluded that Oumuamua is at least 400 meters long and only one- tenth as wide, that it turns on its axis in 7.3 hours and that it has a very dark red sur- face. This peculiarity is compatible with a long stay in interstellar space (perhaps bil- lions of years) and is virtually the only in- formation provided by spectroscopic ob- servations, despite the spectra being ac- quired by other big telescopes as well, A brief over- view of the discovery of the first interstellar asteroid. [ESO]