Photometric colors of the brightest members of the Jupiter L5 Trojan cloud

Abstract

The L5 Jupiter Trojan asteroids are minor bodies that orbit 60 degrees behind Jupiter. Because these orbits are stable over the lifetime of the Solar System, the properties of these objects may inform us about the conditions under which the Solar System formed. We present BV R KC I KC photometry for the 42 intrinsically brightest and presumably largest members of the L5 Jupiter Trojans. We define a new principal color component a * T that is indicative of taxonomic types relevant to the Jupiter Trojan asteroids. We find that 76% of the largest L5 Jupiter Trojans are consistent with a D-type classification, while 24% show shallower slopes more consistent with X-type and C-Type classifications. Such a breakdown is consistent with other surveys and will help to place the Trojans in the larger context of the Solar System.

The Trojan Color Conundrum

“…Fortunately, available measurements of the phase reddening coefficient are consistent with zero (Chatelain et al 2016) and so we believe that this effect is also negligible. To explore these similarities and differences, we compare the cumulative color distributions in Figure (3).…”

“…This might affect the Jovian Trojans systematically, because they attain larger phase angles (up to ∼12 • ) than do the more distant bodies of the outer solar system in Table (3). Fortunately, available measurements of the phase reddening coefficient are consistent with zero (Chatelain et al 2016) and so we believe that this effect is also negligible.…”

“…The optical color distribution of the Jovian Trojans is weakly bimodal (Szabo et al 2007) but, while they are red compared to most other objects in the asteroid belt (Grav et al 2012, Chatelain et al 2016, the Trojans are completely lacking in the ultrared surfaces (B-R > 1.6) that are a distinctive feature of the Kuiper belt and Centaur populations (Jewitt 2002, Lacerda et al 2014.…”

The astorb database at Lowell Observatory

“…The PDS was our primary source of colors with the following data sets added: the 2 Micron All-Sky Survey (2MASS, Sykes et al, 2010), photometry from the Deep European Near-Infrared Southern Sky Survey (DENIS, Baudrand et al, 2007), the SDSS Moving Object Catalog v3.0 (Ivezic et al, 2010), colors of TNOs and Centaurs (Neese, 2014), photometry of Jupiter Trojans (Fornasier et al, 2008), and a compilation of UBV asteroid colors (Tedesco, 2005). One data set outside of the PDS was ingested with BVRI colors of Trojan asteroids (Chatelain et al, 2016).…”