Pushing the limits: K2 observations of the trans-Neptunian objects 2002 GV31 and (278361) 2007 JJ43

TL;DR

This study demonstrates the first use of the Kepler space telescope to observe trans-Neptunian objects, measuring their rotational periods and amplitudes, and highlights the potential for future space missions to study faint solar system bodies.

Contribution

It introduces a novel observational technique with Kepler for faint TNOs and provides initial rotational data for two objects, expanding capabilities beyond traditional ground-based methods.

Findings

Measured rotational periods: 12.097 h and 29.2 h.

Detected amplitudes of 0.10 and 0.35 mag.

Proposed inclusion of TNOs in future space missions for unbiased data.

Abstract

We present the first photometric observations of trans-Neptunian objects (TNOs) taken with the Kepler space telescope, obtained in the course of the K2 ecliptic survey. Two faint objects have been monitored in specifically designed pixel masks that were centered on the stationary points of the objects, when their daily motion was the slowest. In the design of the experiment, only the apparent path of these objects were retrieved from the detectors, i.e. the costs in terms of Kepler pixels were minimized. Because of the faintness of the targets we employ specific reduction techniques and co-added images. We measure rotational periods and amplitudes in the unfiltered Kepler band as follows: for (278361) 2007 JJ43 and 2002 GV31 we get P_rot=12.097 h and P_rot=29.2 h while 0.10 and 0.35 mag for the total amplitudes, respectively. Future space missions, like TESS and PLATO are not well suited to this kind of observations. Therefore, we encourage to include the brightest TNOs around their stationary points in each observing campaign to exploit this unique capability of the K2 Mission -- and therefore to provide unbiased rotational, shape and albedo characteristics of many objects.