HFG 1

HFG 1 is an old planetary nebula in the constellation Cassiopeia. It was created by the binary system V664 Cassiopeiae and has a distinctive comet-like bow-shock and tail structure.

The central binary system V664 Cas is moving through interstellar gas, which compresses the nebular material into a bow shock. The motion also helps produce the extended tail behind the nebula.

Many planetary nebulae appear as shells or rings, but HFG 1 has a pronounced cometary shape. Its interaction with the surrounding interstellar medium makes the nebula look more like a moving wake.

V664 Cas is the binary central star system responsible for the nebula. Astronomers study its motion and binary evolution to understand why HFG 1 has a bow shock and long tail.