Halcyonic System

Any solar system orbiting an object that was once a main sequence star, but isn't anymore (i.e. black holes, white dwarves, red giants, magnetars, pulsars, etc.).

The solar system will become a halcyonic system as the Sun dies.

Halcyonic Planet

Any planet in a halcyonic system (i.e. KMT-2020-BLG-0414L b, WD1054–226 b, WD 1856 b, etc.)

There are also halcyonic dwarf planets, the only example of which is WD 1145+017 b.

In 2020, we discovered the first halcyonic planet around a white dwarf.