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, as-
teroids, 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 Cen-
ter (MPC) on October 25th and given
the provisional cometary designa-
tion C/2017 U1. Gemini received a
Director’s Discretionary Time (DDT)
proposal from the discovery team for
multi-band 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 ac-
cessible from both Cerro Pachón and Mau-
nakea, 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 pro-
posals 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 sur-
face must be rocky like an asteroid, rather
than icy like a comet. The change with re-
spect to the designation specified in the DDT
programs initially caused the observing soft-
ware 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.
January 2018
Before the interstellar visitor sailed away
from our shores forever, it was renamed
once more. The naming convention for mi-
nor 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 ob-
servation. 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 ob-
jects. The asteroid formerly known as A/2017
U1 received the permanent designation 1I
(to indicate its status as the first interstel-
lar 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.
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
Science Returns
The scientific developments resulting from
‘Oumuamua’s passage through our Solar Sys-
tem are even more remarkable than those
related to nomenclature. The observations
from Gemini and other observatories imply
GeminiFocus
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