Another Unusual Planet

In Poul Anderson's "Starfog," a subjovian planet had had:

a cloudy hydrohelium and methane atmosphere;
a core surrounded by ice and frozen gases;
an orbit a billion and a half kilometers from its primary, which:

received an abnormal infall of matter;
swelled and cooled;
consumed its inner planets;
blew away atmospheres, boiled oceans, melted ice and unleashed tectonic forces on the outer planets.

Consequently, the former subjovian is now an Earth-sized ball of metal and rock with mountains, cratered plains and an immense blue-red sun. However, a newly formed star, as bright as a thousand Sols, passes close while at the same time the glowing cluster of red, golden, emerald and sapphire stars rises behind the expanded sun.

Events on uninhabited planets become as fascinating as activities on inhabited planets.