The asteroid 1999 JU3, a target of the Asteroid Explorer "Hayabusa2," was named "Ryugu".
In the Japanese ancient story "Urashima Taro", the main character, Taro Urashima, brought back a casket from the Dragon's palace, or the "Ryugu" Castle, at the bottom of ocean. The Hayabusa2 will also bring back a capsule with samples, thus the theme of "bringing back a treasure" is common.
Rocks containing water are expected to exist on asteroid 1999 JU3. The name "Ryugu" also reminds us of water, as "Ryugu Castle" is under the ocean.
According to the naming rule stipulated by the International Asteroid Union (IAU), the name "is preferably from mythology" and the "Ryugu" fits that rule. Also, there is little concern of infringing the Trademark Law or any other third party trademarks.
Total number of entries was 7,336. Among them, 30 were for "Ryugu". Some similar ones are "Ryugujyo (meaning Ryugu Castle)" (5 entries), "RyuuGuu" (5), "Ryuguu" "Ryugujyo" and "Ryugujou" (one entry each).
The naming of an asteroid usually takes about three months to review. The review process for the "Ryugu" this time was unprecedentedly quick, and the name was published on September 2015 issue of the Minor Planet Circular by Minor Planet Center, which manages the names of asteroids in the solar system.
Let’s name the asteroid "1999 JU3", the destination of the “Hayabusa2”!