Cepheus
Cepheus, shaped like a five-sided house with a steep roof. Here lies the original of the "Cepheid" variable stars that became the measuring rod for cosmic distances.
Science
The scienceCepheus is shaped like a five-sided "house" topped with a steep roof, a circumpolar constellation that wheels near the North Star all year round. Its Delta star (Delta Cephei) is a star that changed all of astronomy. It is a "pulsating variable" whose brightness rises and falls in a regular cycle of 5.4 days, and when Henrietta Leavitt discovered early in the 20th century the law that "the longer such a star's cycle, the truly brighter it is," Cepheids became the "standard candles" for measuring distances to galaxies. It was thanks to these very Cepheid variables that Hubble proved Andromeda to be another galaxy beyond our own Milky Way.
Mythology
How it became a constellationCepheus was the king of ancient Ethiopia, husband of Queen Cassiopeia and father of Princess Andromeda. When the queen's boast that her daughter's beauty outshone the sea nymphs brought a sea monster's threat upon the kingdom, an oracle made the cruel demand that Andromeda be offered as a sacrifice. The king who loved his daughter fell into despair, but to save his kingdom he had at last to bind her to a seaside rock. Later, when the hero Perseus rescued Andromeda, Cepheus and his whole family became constellations set side by side in the autumn sky.
Observing Guide
how to observe🔭 How to find it
A constellation that circles near Polaris: from the "W" of Cassiopeia, move a little to the side opposite Polaris and you'll see the shape of a "house" — a pentagon topped with a pointed roof — which is Cepheus. The pointed peak of the house faces toward Polaris, making it easy to gauge direction. Since it doesn't have many bright stars, the trick is to memorize the whole pentagonal outline as one shape.
✨ What to look for
Cepheus is rich in sights. Delta Cephei (δ Cep), the prototype pulsating variable that became a cosmic yardstick, changes brightness enough to follow with the naked eye, and nearby is the "Garnet Star" (μ Cephei) — a huge red supergiant reckoned among the reddest stars in the sky. There's also the large emission nebula IC 1396 (the Elephant's Trunk Nebula) and the spiral galaxy NGC 6946 (the Fireworks Galaxy), both popular astrophotography targets.
📍 Where to see it (US · Canada · UK · Australia)
Perched at high northern declinations (+58° to +78°), Cepheus is circumpolar from the US, Canada, and the UK — it never sets and is on view all year, climbing highest overhead on autumn evenings and sitting lower in the north come spring. From Australia the King never rises above the horizon and cannot be seen.