GeminiFocus July 2017 | Page 5

Wes Fraser Figure 1. Blue Binaries Suggest a Smooth Migration for Young Neptune A Large and Long program using simultaneous ultraviolet and near-infrared data from Gemini North and the Canada- France-Hawai‘i Telescope lead to the discovery of a peculiar population of blue-colored, tenuously bound binaries residing among the otherwise unanimously red “cold classical” Kuiper Belt objects. These widely separated binary objects could have survived perturbing forces during the early phases of Neptune’s migration, helping us to better understand the planet’s accretion history in the outer Solar System. A Brief History of the Kuiper Belt Rendering of the outer Solar System. Small points correspond to the >1700 known and tracked objects. Colours correspond to different dynamical classes - the cold classicals are in red, the resonant plutino and two-tino objects are in purple and yellow, the transitory centaurs are in white, and the non-resonant excited objects are in light blue. A handful of the orbits of this class are shown by the dotted blue lines. The gas-giant planets are the larger circles, and the largest 10 dwarf planets are identified with white circles. Distances at 30, 50, and 100 AU are shown by the dashed white circles. The Kuiper Belt is complicated, and weird. Consider its shape (see Figure 1). First a disclaimer: the community uses the term belt pretty loosely. Imagine instead a broad torus hundreds of astronomical units (AU) thick and tens of AU tall, with a 30 AU radius hole cut out of the middle. That’s the true shape of the Kuiper Belt. Beyond its poorly named shape, what really catches a scientist’s eye is the Belt’s layered dynamical structure. The first Kuiper Belt Object (KBO) discovered, 1992 QB1, belongs to the so-called cold classical population, named for what may have been ex- pected to reside beyond Neptune: a population of planetesi- mals on circular, low inclination orbits, in a ring (or belt). Unlike the asteroid belt, whose empty Kirkwood gaps can clear- ly be attributed to the clearing effects of mean-motion reso- July 2017 GeminiFocus 3