Subaru, Keck I and II, and the IRTF at sunset, as seen from Gemini North | © Alex Parker | Astronomy Department, University of Victoria

New Horizons' post-Pluto Mission

Since my PhD in 2011, I have been engaged in the search for a Kuiper Belt object to send NASA's New Horizons spacecraft to after its Pluto encounter in 2015. This post-Pluto mission through the Kuiper Belt will be the only in-situ exploration of this region of the outer Solar System in the foreseeable future.

Our search targets the area of sky where Kuiper Belt objects that will eventually pass New Horizons currently reside. Unfortunately, this area of sky is deep in the galactic plane, and the background is packed with stars. I apply advanced difference-imaging techniques to suppress the starlight while leaving behind the slowly-moving Kuiper Belt objects of interest.

New Horizons Mission: Kuiper Belt Fly-Through from Alex Parker on Vimeo.

We have discovered dozens of new icy bodies in the outer solar system, many of which pass close enough to New Horizons for the spacecraft to image them at resolutions exceeding ten times that of the Hubble Space Telescope. The search continues for a close flyby candidate.

Main Belt Asteroid Families in Color

Main Belt Asteroid Families as seen by SDSS This figure from Parker et al. (2008) was chosen as the cover illustration for the journal Icarus' November 2008 edition.

It illustrates the orbital properties of the asteroids seen by the Sloan Digital Sky Survey: specifically, their inclination vs. their eccentricity. Vertically, the three sets of plots show different subsets in semi-major axis (or mean distance from the Sun).

The colors of the points are a representation of the photometric colors measured by the Sloan camera, and are indicative of the surface properties and compositions of each individual asteroid.

The left panels show the entire population, while the right panels illustrate collisional families identified in Parker et al. (2008). These families were created by the destruction of a large parent object through a catastrophic collision. All of the fragments therefore share chemical composition and similar orbits, and so appear as clusters of objects in their orbital parameters, and these clusters share common colors. Note the dominance of blue (C-type) families in the outer belt, and the dominance of red families (S-type) in the inner belt.

Wide Binaries in the Kuiper Belt

Comparison of the angular size of the Moon as seen from Earth to the angular size of L5c02b when seen from the surface of L5c02a Wide binaries in the Kuiper Belt are extremely sensitive probes of the conditions in the outer Solar System. Because even very slight perturbations could dislodge them from orbit around each other, we can use them to test whether or not average Kuiper Belt Objects are frequently subjected to impacts or if they ever interacted with giant planets.

The origin of the Kuiper Belt is a debated subject, and one theory holds that interactions with Neptune transported the Kuiper Belt to its present location from originally much closer to the Sun. However, Parker and Kavelaars (2010c) show that such interactions would have destroyed the wide binaries in the Kuiper Belt, through the process illustrated here.

Neptune and a binary Kuiper Belt Object during a close encounter. This animation of a single close encounter between a binary and Neptune shows one view centered on the binary and another centered on Neptune. Significant modification (though not disruption, in this case) of the binary orbit is seen during the closest approach.

These wide binaries (like 2001 QW322) have only been found in the Cold Classical Kuiper Belt, indicating that this region of the Kuiper Belt was likely never subjected to interactions with Neptune, and may have formed near its present location. Read more at Nature News.

In my PhD research, I demonstrated that the widest Kuiper Belt binaries have orbits inconsistent with the predictions of classical theories of binary formation. A novel mechanism for binary production is needed; recently it has been shown that binary objects may be a side-effect of gravitational collapse-driven planetesimal formation, and binaries formed through this process may have properties more in-line with those observed.

In addition to being valuable testbeds for astrophysics, these binaries are interesting places in their own right. This animation compares the angular size of the Moon as seen from Earth to the angular size of the satellite of L5c02 (a wide binary discovered by the CFEPS survey) seen from its surface over one orbital period. In other words, if you were standing on the surface of this object and looking up toward its companion, this is roughly what you would see (compared to how we see our own Moon).