Program: GN-2024B-Q-220

The Kuiper Belt, residing beyond Neptune, hosts remnants of failed planet formation in the form of numerous small planetesimals. Trans-Neptunian Objects (TNOs) are often nonspherical or part of binary systems. Spectral variability, identified in a limited number of TNOs, holds potential for unveiling crucial information about their history, composition, and broader solar system formation. Among these TNOs we have found 2015 RB281, a TNO displaying significant colour variation between two epochs, belonging to the cold classical TNOs—presumed undisturbed remnants formed at their current distances. This TNO shows >5sigma variation in surface colour, potentially challenging prevailing theories of TNO formation that propose distinct surfaces forming at different solar distances. The proposed observations target 2015 RB281 employ g and r bands to evaluate photometric variability and validate optical color variations. These observations aim to decipher whether the observed colour variation results from compositional variations or uncharted lightcurve amplitudes, potentially indicating an undetected contact binary nature. Exploration of the TNO's lightcurve is crucial for investigating the TNO's formation mechanism. Streaming instability, pivotal in forming planetesimals, is tied to differential motion between solid particles and gas, fostering gravitational instability and denser region formation. Confirming 2015 RB281 as a contact binary with distinct compositions could challenge streaming instability or necessitate novel formation processes. In conclusion, this low-risk, high-reward observation campaign targets a unique TNO, promising intriguing insights into Kuiper Belt object histories. With a focus on 2015 RB281, the study encompasses colour variation, photometric variability, and potential contact binary identification, presenting a comprehensive exploration of this enigmatic object.