Small Jupiter Trojans Break Color Pattern, Subaru Finds
Get the Health newsletter
Daily health & science — research, biotech, public health, the studies worth knowing. Free.
- Subaru Telescope's Suprime-Cam observations revealed that small Jupiter Trojans display a continuous color distribution, in contrast to the clear bimodal red vs. less-red split long established for larger Trojans, with less-red objects dominating the small population.
- Fumi Yoshida of the University of Occupational and Environmental Health, working with the National Astronomical Observatory of Japan and Kobe University, led the team that detected 120 Jupiter Trojans roughly 60 degrees ahead of Jupiter and analyzed their colors at kilometer scales.
- The data were collected in May 2017 on Suprime-Cam's final scheduled night on the telescope, before it was retired in favor of the Hyper Suprime-Cam, whose larger size requires more time to swap filters and made it unsuitable for rapid multicolor photometry of rotating asteroids.
- The study found no meaningful difference in size distribution between red and less-red small Trojans, undercutting the hypothesis that red asteroids fragment into less-red ones and pointing instead to similar collisional histories for both populations.
- Because small asteroids are thought to be fragments of larger parent bodies, their colors likely preserve the interiors of those parents, whereas the surfaces of large Trojans have been reworked by long exposure to the space environment.
- NASA's Lucy mission, which will conduct the first flybys of Jupiter Trojans, and the European Space Agency's JUICE mission, currently exploring the Jovian system, are positioned to test these findings with close-up spacecraft data.
Why it matters: The 120-asteroid catalog and its continuous-color finding give planetary scientists a sharper constraint on where Jupiter Trojans came from: if small fragments don't preserve the red/less-red split, the 'fossils of the solar system' are telling a more uniform story about planetesimal interiors than the bimodal framing implied. Paired with incoming Lucy flyby data, the Subaru result will help modelers test whether the two Trojan populations truly formed at different solar distances or were homogenized by collisions.
