Looking for slow objects in the outer solar system

We present a study focused on the detection of large, distant objects in the Solar System, specifically those of planetary size located beyond 100 AU. This search is motivated by models of the primordial planetesimal disk, which suggest that the early Solar System may have hosted hundreds to thousands of Pluto-sized bodies, and potentially a few Mars-sized or larger objects. These predictions, consistent with both dynamical simulations and accretion models, raise the possibility that some of these distant bodies may still exist but remain undetected.

To explore this, we analyze deep-sky images collected over the past four years by the 0.68-m Schmidt telescope at Mt. Bigelow and the 1.5-m Cass telescope at Mt. Lemmon, both part of the Catalina Sky Survey. Our approach involves co-adding wide-field unfiltered images from different nights to increase the sensitivity and reveal faint, slowly moving sources. Image alignment is performed using the Tycho Tracker software, and source detection is carried out via Python codes based on the Astropy library and a matched-filter technique. This stacking method allows us to reach a limiting magnitude of V ≈ 21.5, sufficient to detect distant objects in the trans-Neptunian region. We then compare source positions across different epochs to identify candidate moving objects. For those showing consistent motion, we determine preliminary orbits using the software Find Orb, which enables orbital fitting even with sparse and low-cadence data sets. This step is essential for distinguishing real distant Solar System bodies from false positives or artifacts.

The methodology described here offers a robust and scalable framework that can be applied to other panoramic multi-epoch surveys, improving our ability to uncover faint and distant members of the Solar System population.

.Keywords: Surveys, co-added images, match filter.