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: [email protected]
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