Program: GS-2022B-FT-109

Trans-Neptunian objects have a red and very-red color bimodality. The heliocentric distance of the transition zone from red to very-red in the original trans-Neptunian disk is not precisely known. As Neptunian Trojans were captured from the original trans-Neptunian disk into co-orbital resonances with Neptune during its outward migration, their colors could identify the aforementioned transition zone. Unfortunately, the current statistics of stable Neptunian Trojans with known visible colors are poor. We aim to double the number of Neptunian Trojans with measured colors, thus much more precisely determining the Neptunian Trojan color ratio and the transition zone location. We propose to use Gemini-N/GMOS-N in combination with other facilities to obtain visible color photometry of ~10 additional Neptunian Trojans. Of these ~10, we ask for ~2.6 h of Fast Turnaround time to observe the 4 faintest and more accessible targets from Gemini-N. The remaining ~5 objects will be observed during already approved programs using facilities at Palomar Observatory.