Red, double, variable stars, and more September brings us great views of red Mu ([mu]) Cephei (Herschel's Garnet Star
); Epsilon ([epsilon]) Lyrae (the Double Double) and Albireo; Delta ([delta]) Cephei.
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This is Mu Cephei, also known as Herschel's Garnet Star
. The color of this vast red supergiant is quite apparent in binoculars or a small telescope.
It is also home to two important variable stars; delta Cephei, prototype of the Cepheid variables, and mu Cephei, the semi-regular Garnet Star
named by Sir William Herschel and one of the reddest naked eye stars in the sky (although this is totally lost on the colour-blind Director).
Herschel's Garnet Star
(4th-magnitude Mu Cephei) is at top.
In my online article 'Realm of the Majestic Ruby Star in Taurus' (which I derived from my Red Star Catalogue, compiled back in the 1980s), I remarked that 119 Tauri was only superseded in the degree of its reddish colour intensity by Mu Cephei (the Garnet Star
) and that no one had prior to that time actively recorded the star in any red star listings anywhere, nor acknowledged it for its redness by drawing any comparisons to other red stars in the sky.
It was dubbed the Garnet Star
by 18th century English astronomer William Herschel.
I was sweeping through the constellation Cepheus, named for the legendary king of Ethiopia, when my eyes fell on Trumpler 37, a charming open cluster located just over 1[degrees] south-southwest of Mu ([mu]) Cephei, Herschel's Garnet Star
. The cluster truly is a binocular highlight--a rich concentration of suns that sprawls across almost 1 1/2[degrees].
The pole will be closest to Gamma Cephei (Errai) in about AD 4200, pass lovely double Xi ([xi]) Cephei (Kurhah) around the year 6700, come within a few degrees of Alpha Cephei (Alderamin) around 7500, and edge by Mu ([mu]) Cephei (Herschel's Garnet Star
) around 8000.
Mu ([mu]) Cephei, 6[degrees] to Delta's west, is William Herschel's "Garnet Star
"; a slow, semiregular variable that has ranged from magnitude 3.4 to 5.1 but spends most of its time around 4.
Several dark nebulae are silhouetted against the dim 3[degrees]-wide glow of the Cepheus emission nebula 1C 1396, if you keep the deep orange supergiant Mu (p) Cephei (popularly known as Herschel's Garnet Star
) out of the field of view.
So too does its lack of a popular name, unlike Herschel's Garnet Star
(Mu Cephei), Hind's Crimson Star (R Leporis), and La Superba (Y Canum Venaticorum).