GeminiFocus January 2018 - Page 9

ous observations at Gemini, we found that the light curve does not repeat itself — there are small differences from one rotation to the next,” explained Siyi Xu, an astronomer at Gemini Observatory and a coauthor on the study. “The most likely explanation is that this object is ‘tumbling’ — its rotation axis is not aligned with its principal axis.” These results have been submitted for publi- cation, and a preprint is available online. Catastrophic Remains The “tumbling” motion of ‘Oumuamua as it travels through space suggests that it may have experienced a catastrophic collision in the distant past, perhaps the event that sent it, and likely myriad compatriots, careening across the cosmos. However, another pre- print by Bannister’s team points out that tidal torquing during close encounters and out- gassing events can also set a body tumbling. It is unlikely that ‘Oumuamua is unique. The Large Synoptic Survey Telescope, now under construction near the Gemini South tele- scope in Chile, will begin operations in a few years and is expected to find many more of these interstellar wanderers. What will be their shapes, colors, and trajectories? The Gemini telescopes will be ready to charac- terize these new discoveries as well. Notably, the forthcoming OCTOCAM instrument on Gemini South will enable high-cadence ob- servations in eight wavelength bands simul- taneously, a truly revolutionary innovation for such follow-up studies. Predictably, science fiction allusions abound- ed in the wake of ‘Oumuamua’s passage through our neighborhood. Most common- ly, the reference was to the Arthur C. Clarke novel in which an enormous cylindrical ob- ject, dubbed Rama, arrives in our Solar Sys- tem on a hyperbolic orbit and executes a gravitational “slingshot” maneuver during a close passage to the Sun. However, at 50 kilo- January 2018 meters across, the fictional Rama was about 100 times larger than ‘Oumuamua and was spinning on its symmetry axis, rather than tumbling headlong. Another comparison, inspired by the name ‘Oumuamau, can be made to Carl Sagan’s novel Contact, in which a message is detect- ed from the direction of the star Vega in the constellation Lyra. Tracing back the trajec- tory of ‘Oumuamua, one finds that it likewise points to Lyra, very near the position of Vega. It is tempting to imagine that this messenger has come to us from the debris disk known to encircle that brilliant star that stands almost directly overhead, beckoning us from amidst the stream of the Milky Way on midsummer nights in the Northern Hemisphere. Alas, the Milky Way is dynamic, and one mil- lion years ago, roughly when ‘Oumuamua would have been at the distance of Vega, the star itself was in a very different place. Neither the signal in Sagan’s novel, nor our recent interstellar visitor, truly originated in the Vega system. However, both emissar- ies carried the same message, and it is one worth pondering in our turbulent times. The meaning is most succinctly encapsulated in the final two lines of a very different piece of literature, a poem by the great Argentine writer Jorge Luis Borges: “Más allá de este afán y de este verso Me aguarda inagotable el universo.” A popular, though loose, English translation of the work puts it as follows: “Beyond these efforts and beyond this writing The universe awaits, inexhaustible, inviting.” John Blakeslee is the Chief Scientist at Gemini Observatory, located at Gemini South in Chile. He can be reached at: GeminiFocus 7