An efficient observational strategy for the detection of the Oort cloud

TL;DR

This paper proposes an observational strategy using small telescopes near the quadrature direction to detect Oort cloud objects via occultations, potentially revealing details about the Solar System's outer regions.

Contribution

It introduces a method leveraging longer occultation durations at quadrature to increase detection rates with small telescopes, enhancing the feasibility of Oort cloud detection.

Findings

Detection rate increases by 1-3 orders of magnitude with small telescopes.

Occultations are more detectable near quadrature due to longer durations.

Method can distinguish Oort cloud objects from Kuiper belt objects.

Abstract

The Oort cloud is presumably a pristine relic of the Solar System formation. Detection of the Oort cloud may provide information regarding the stellar environment in which the Sun was born and on the planetesimal population during the outer planets' formation phase. The best suggested approach for detecting Oort cloud objects in situ, is by searching for sub-second occultations of distant stars by these objects. Following Brown & Webster, we discuss the possibility of detecting Oort cloud objects by observing near the quadrature direction. Due to the Earth's projected velocity, the occultations are longer near the quadrature direction and are therefore easier to detect, but have lower rate. We show that, for <1-m size telescopes, the increased exposure time will result in about one to three orders of magnitude increase in the number of detectable stars that have an angular size smaller than the Fresnel scale and are therefore suitable for an occultation search. We discuss the ability of this method to detect Oort cloud objects using existing survey telescopes, and we estimate the detection rate as a function of the power-law index of the size distribution of the Oort cloud objects and their distance from the Sun. We show that occultations detected using ~1-s integration by <1-m telescopes at the optimal region near the quadrature points will be marginally dominated by Oort cloud objects rather than Kuiper belt objects.