Seeing Double!  Binaries in the Kuiper Belt

Dr. Denise Stephens
Department of Physics and Astronomy
Brigham Young University


The first binary kuiper belt object (KBO) was found in 1978 by James Christy of the U.S. Naval Observatory in Flagstaff, Arizona.  He was working with images of Pluto when he noticed a bump that was always oriented approximately north-south.  Searching past images, he found other instances of the "bump" and soon realized that he had found a moon around Pluto, now known as Charon.  It would be another 23 years before the second KBO binary system would be discovered in 2001.  Since then we've been using the unprecedented resolution and stability of the Hubble Space Telescope (HST) to image KBOs and have discovered over 50 confirmed binary systems.

In this presentation I'll define the nature of a KBO and why we prefer to call these objects TNOs.  I'll talk about how these objects formed and give a brief background into their orbits and dynamics.  I'll highlight how we use the structure and dynamics of these objects to contrain models of solar system formation.  After laying this foundation, we'll go into the recent discoveries of binary systems and how we use these objects to determine system mass and density.  I'll discuss the observational techniques we use and the programs we've written to find both resolved and unresolved (according to the Rayleigh criteria) binary systems in our HST observations.  Finally, I'll highlight a few examples of binary pairs whose orbits we've calculated and the typical values for density that we are finding.