Cepheus, the King, is a faint house-shaped constellation near the north celestial pole, holding Delta Cephei, the star that gave its name to the Cepheid variables.
At a glance
| stars in the figure | 10 |
|---|---|
| not placed by measurement | Mu Cephei (no usable parallax; left out of the depth below) |
| nearest star of the figure | Errai, 46 light-years (14.1 pc) |
| farthest star of the figure | Delta Cephei, 865 light-years (265 pc) |
| depth | the farthest is 19 × farther than the nearest |
Read off the piece’s own catalogue, the same values it draws with.
About Cepheus
Cepheus was the king of Ethiopia in Greek myth, husband of Cassiopeia and father of Andromeda. His figure looks like a simple house with a pointed roof, lying on the Milky Way beside Cassiopeia. Alderamin is the brightest star. Errai, at the roof’s peak, has a planet, and the slow wobble of Earth’s axis will in time make both Errai and Alderamin the northern pole star.
Delta Cephei pulses in a steady rhythm, and stars like it, the Cepheids, follow a law tying the rhythm to their true power: that law turned them into distance markers to other galaxies. Mu Cephei, the Garnet Star, is a deep red supergiant among the largest stars known. From mid-northern latitudes Cepheus never sets.
What you see in the piece
Flown out to, the little house comes apart: Errai is a near neighbour and Delta Cephei lies far behind it. Mu Cephei, deep red from Earth, sits at a stand-in distance, because its own is not measured.
Measured or modelled
Mu Cephei has no usable parallax, so its distance is not measured: the piece pins it at a stand-in distance only so its line can still draw, and the card leaves it out of the nearest, farthest and depth.
Questions
What is a Cepheid variable?
A pulsating star like Delta Cephei, whose rhythm of brightening and fading reveals its true power, so comparing that with how bright it looks gives its distance.
How far away are the stars of Cepheus?
Of the stars with a measured distance, they range from Errai, 46 light-years (14.1 pc), to Delta Cephei, 865 light-years (265 pc): the farthest is 19 × farther than the nearest. Mu Cephei has no usable parallax, so its distance is not measured.