Orion is a stellified hunter.
An alternative way to stellify the planet may be to not collapse Jupiter, but instead to introduce a collapsed object into its core.
By the 'hissing snake' Spenser presumably means the scorpion sent by Diana that killed Orion. Like Orion it, too, was stellified. But since, as Scorpio, it rises in the east as Orion's sign sets in the west, the two were regarded as being kept forever apart, Orion perpetually avoiding in the heavens his vanquisher on earth.