Cepheus

 

Meaning: The King of Ethiopia

Cepheus Outline

Print out the star map from Sky and Telescope

Things to look for:
Herschel’s Garnet Star, μ Cep

Messier objects:
None

Note: [x.x] indicates visual magnitude

Pronunciation: see’ fee us
Associated Asterisms: None
% of the sky: 1.43%
Visible Stars: 57 stars brighter than magnitude 5.5

Cepheus Stars

Cepheus Chart

Cepheus is a medium sized constellation with a few surprises and is mostly overlooked. It is true it lacks any Messier objects but as it reaches up around, cupping Polaris and contains δ Cep, the original Cepheid variable that gave us the yardstick to measure the Universe, its odd it doesn’t get more press. It isn’t a bright constellation with Alderamin, α Cep only 85th in the list of the skies brightest stars. The other named stars are Alfirk β Cep, Erakis μ Cep, Alrai/Er Rai γ Cep and Kurhah ξ Cep. The shape of the constellation should be one of the most recognised as it is the spitting image of a child’s house.

δ Cep was identified as special by John Goodricke in 1784 when he detected its periodic change in brightness. Later theorists worked out the change in luminosity was due to changes in the radius of the star caused by a pulsating in its outer atmosphere. More Cepheid variable stars were discovered and between 1908 and 1912, Henrietta Levitt determined that the period of the pulsations was related to how luminous the star was. Given very accurate measurement of distance to nearby Cepheids it meant it was possible to use more distant Cepheids as a yardstick for distances across the Milky Way and to other galaxies.

μ Cep is also called The Garnet Star as it is one of the reddest stars visible in the night sky. It is a variable star oscillating between magnitude 3.6 to 5.1 but lacks a regular period.

Cepheus contains the Guitar Nebula which although out of the reach of amateur telescopes is notable for the high speed neutron star causing the shock wave and wake in interstellar gas behind it. It has been imaged many times since its discovery in 1993 giving a series of images of the progression of the wake.

Locating Cepheus

Cepheus mythology

Cepheus sits behind Ursa Minor bordered by Lacerta, Camelopardis, Cassiopeia, Cygnus and Draconis. Alderamin and Alfirk point towards Polaris. The pointy roof of the ‘house’ is up towards Polaris and is approximately between Polaris and Caph in Cassiopeia.