(JSEE NOT FULL LORE)
More than 5 billion years ago, a extremely luminous WN5h star named Rhea exploded in a hypernova during a certain encounter of the URADEG and the SimpleGalaxy. This formed Juno, the LJC and other stars and millions of years later, Juno formed its own protoplanetary disk.
All of the 8 planets and the 2 dwarf planets, and the 5 hypothetical objects, we see in Juno System: Enhanced Edition were formed from this disk.
Tydos and Jairn started accreting gas from the disk, which formed their circumplanetary disks, which formed the moons of Tydos and Jairn, While the same cannot be said for Nontone, Urados was somehow able to form a circumplanetary disk, which formed its moons.
Giant V and VI were once planets ended up being ejected from the system shortly after Droadean Eon ended.
Vulco was also formed from Juno's protoplanetary disk.
(The significant expansion of the Local Juno Cloud over time was caused by strong winds from young stars, and other supernovae and plus the formation of other stars in the cloud.)
(Over 16 million years ago, thousands of stars, 75-1000 Juno light years, all exploded at once, forming the Local Juno Bubble(my Analogue of the Local bubble?) Like the LJC, other supernovae expand the bubble's radius, which is now 1252 Jly)