The Search for Planet X: Testing Inferences from the Kuiper Cliff

The goal of this project was to search a large archive of astronomical CCD imagery to test the validity of arguments regarding the existence of a hypothetical Planet X. As proposed by Brunini and Melita 2002 this object would be a low inclination Mars-sized body residing in the Kuiper belt between 55 and 75 astronomical units from the Sun. Resonances with this hypothetical planet form a convenient explanation of the Edgeworth-Kuiper Cliff, the observation that no low eccentricity Kuiper Belt objects are found more than 47 AU from the Sun despite numerous searches. Although the proposed Planet X is relatively bright its distance means that it could easily have been mistaken for a stationary object by previous searches. This project utilized the image archives of the University of Arizonas Spacewatch Project a near-Earth asteroid survey based at Kitt Peak National Observatory including data from May of 2003 to April of 2006. The survey images were taken with a CCD mosaic camera on a 0.9 meter telescope with a 2.7 square degree field of view at 1 resolution to a limiting magnitude of 21.7. A unique feature of this survey was its reimaging of the same sky area every 3 to 7 nights. The surveys rate sensitivity was 20-60 times greater than existing surveys. The final search covered approximately 10,600 square degrees of sky within 10 degrees of the ecliptic. An automated motion detection program was modified for this multinight search and processed approximately 3 terabytes of imagery. Nonetheless visual validation of the candidates was still required. The efficiencies of the software and of the human reviewer were measured as functions of rate field clutter and signal-to-noise. Quality control on the data was performed and methodologies were developed to aid in determining the unique coverage of the search and the probability of detecting the planetary candidate.