Alpha Cephei (Alderamin)

α Cephei

Alpha Cephei is known as Alderamin, "The Right Shoulder" (of the king). The brightest star in Cepheus with a visual magnitude of 2.5, it has a distance of 49 light years.

Alderamin will become the Pole Star long in the future—in around 73,000 years.

Alderamin is easily located, particularly in the summer with the constellation high in the sky. We'll offer three ways to find the star.

First, from Cassiopeia, looking at the western arm (alpha-beta), extend this arm about four equal lengths. Don't stop short or you might be at zeta Cep, slightly south of our planned trajectory. If you've succeeded to find Alderamin, this should be your binocular view.

The second method is to start at alpha Cygni (Deneb) and move north nearly half the distance to the pole.

Thirdly, using the Big Dipper, move along the pointer stars (beta to alpha) to the Pole Star; you will 'bend' your trajectory slightly as you move toward the Pole Star. Now keep moving along this same curved trajectory about the same distance and you'll be very near Alderamin.


One binocular field northeast of alpha brings you to xi Cephei. This is a multiple system (Struve 2863) with a varying report on its colours:
      AB, two yellows (or perhaps two blues?): 4.5, 6.4; 275º, 8.0".
      AC: 4.5, 12.6; 206º, 109.7".

Back to alpha, now about a half binocular field south is nu and mu: binocular view.
      The bright star south of centre is mu Cephei, an irregular variable fluctuating between 3.4 and 5 magnitude. It was called by Herschel ‘The Garnet Star’ for its deep reddish colour; it's a pulsating red giant and is often compared with Betelgeuse in Orion.
     Mu Cephei is one of the largest stars visible to the naked eye; nearly a billion of our Suns could fit inside it. The star is a thousand times larger than the Sun's radius; its own radius would extend beyond the orbit of Jupiter.
     And yet the star's demise is only several million years away; it will 'soon' (in astronomical terms) explode as a supernova. Given the size of the star, a black hole could be the end result.

Just south of mu Cephei is a darkish nebula, very faint and extremely large. Inside this nebula (IC 1396) is the triple star system Struve 2816 with a double star neighbour. The primary of Struve 2816 is yellowish (or golden), its two components, on opposite sides of the primary, are white. Truly not to be missed.
      AC 5.7, 7.5; 120º, 11.8"
      AD: 5.7, 7.5; 338º, 19.8"

And Struve 2819 is in the same field, a fainter binary but nearly as attractive: 7.4, 8.6; 58º, 12.8".

Now move over to delta, one binocular field to the east. Click on delta Cephei on the map for its details.

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