Exciting Times at Gemini
Is there no end to the excitement at Gemini?
In the previous issue of GeminiFocus we reported on the three-week-long efforts to follow
up on GW170817 — the gravitational wave triggered by two neutron stars spiralling closer
to each other and finally merging — whose signal rattled the LIGO and Virgo detectors for
almost two minutes on August 17th.
Two months later we witnessed yet another exceptional event: on October 19th, the
Pan-STARRS survey detected a small, high-velocity asteroid, A/2017 U1, moving away
from Earth. Nothing unusual, if it weren’t for the fact that the trajectory traced by the
tiny dot did not belong to the familiar family of elliptical orbits that bond all objects
(planets, comets, asteroids) in our Solar System. The orbit, rather, was highly hyperbolic:
A/2017 U1 has never been, and never will be, bound to the Solar System. For the first
time we had a glimpse at a visitor from interstellar space, earning A/2017 U1 the Hawai-
ian name of ‘Oumuamua (meaning “Scout”); this small asteroid was kicked out from its
parent planetary system, and is now crossing ours — as countless numbers have surely
done, undetected, before.
At Gemini, we received three Director’s Discretionary requests to observe ‘Oumuamua,
which, unlike GW170817, could be reached from both Cerro Pachón and Maunakea. For
three days — that’s all the time we had before ‘Oumuamua faded from view — both tele-
scopes stood on high alert. Observations began at Gemini South on October 25th and
continued at Gemini North on October 26th and 27th. The Very Large Telescope, Keck,
Canada-France-Hawai‘i Telescope, and the United Kingdom Infrared Telescope, joined
Gemini in the effort, and the collective data revealed ‘Oumuamua’s unique nature.