Figure 1 . The trajectory of ‘ Oumuamua , previously known as A / 2017 U1 , through our Solar System . Orbits of the eight major planets and a Halley-type comet are also shown . Credit : Brooks Bays , SOEST Publication
Services , UH Institute for Astronomy
on a hyperbolic path passing through our region of space , rather than a closed elliptical ( or borderline parabolic ) orbit like the Earth and all other planets , asteroids , and comets ever encountered within the Solar System . This meant that it must have originated from some other star system , the first definitively detected emissary from the stars .
The object ’ s discovery was officially announced by the Minor Planet Center ( MPC ) on October 25th and given the provisional cometary designation C / 2017 U1 . Gemini received a Director ’ s Discretionary Time ( DDT ) proposal from the discovery team for multiband imaging with the Gemini Multi-Object Spectrograph ( GMOS ) at Gemini South and obtained the requested observations on the evenings of October 25th and 26th . Although the target was accessible from both Cerro Pachón and Maunakea , weather conditions in the North were poor on the first night , and therefore the two widely separately sites proved once again a major advantage .
Two additional teams submitted DDT proposals for GMOS and Near-InfraRed Imager and spectrometer ( NIRI ) imaging at Gemini North and obtained data over three nights beginning on October 26th ( UT October
27th ). During the course of this campaign , the object ’ s provisional designation was changed to A / 2017 U1 because no cometary tail was detectable in very long exposures . Thus , excluding sci-fi explanations , its surface must be rocky like an asteroid , rather than icy like a comet . The change with respect to the designation specified in the DDT programs initially caused the observing software not to find the target coordinates from the online NASA database , but the issue was quickly solved by alert Gemini staff . All three DDT programs were successfully completed in October and have produced publications .
Before the interstellar visitor sailed away from our shores forever , it was renamed once more . The naming convention for minor planets ( such as comets and asteroids ) prescribed by the International Astronomical Union ( IAU ) did not allow a formal name to be assigned based on the too-brief arc of observation . However , as explained in an MPC Circular issued on the 7th of November , “ Due to the unique nature of this object , there is pressure to assign a name .” The will of the people was heard , and the IAU introduced a new designation scheme for interstellar objects . The asteroid formerly known as A / 2017 U1 received the permanent designation 1I ( to indicate its status as the first interstellar object ) and the name ‘ Oumuamua . The name is of Hawaiian origin and connotes the idea of an advance scout , or a messenger “ reaching out ” to us .
Science Returns
The scientific developments resulting from ‘ Oumuamua ’ s passage through our Solar System are even more remarkable than those related to nomenclature . The observations from Gemini and other observatories imply
4 GeminiFocus January 2018 / 2017 Year in Review