|
Translate this page into:
         
|
CEPHEUS
The King
Cepheus - Alexander Jamieson - 1822
|
|
Translate this page into:
|
Cepheus was the fabled Ethiopian king who was married to the boastful queen Cassiopeia. He is one of the six characters placed in the sky to commemorate the Andromeda story, a grand and famous tale of high adventure and romance, complete with gods and goddesses, heroes and monsters, and lessons concerning mortal humility.
Being very close to the north celestial pole, Cepheus is visible all night long from most northerly latitudes, forever circling the north star, Polaris. Unfortunately, it is an indistinct constellation, whose brightest stars seem to form the shape of a steeply pitched roof house, rather than a monarch on a throne. But for all its superficial ambiguity, Cepheus does contain some objects of great interest.
The alpha star in the constellation is Alderamin, from the Arabic for right shoulder, as it indeed represents the right shoulder of the king. It is an A7 white star, with a magnitude of 2.5, 49 light years away. Due to precession - the gradual shifting of the stars caused by the gyroscopic wobble of Earth's axis - Alderamin will be our north star or pole star in the year 7500, the position now occupied by the star Polaris.
The other three named stars in Cepheus have Arabic origins that have nothing to do with a king, and suggest that ancient Arabs saw much different figures in this part of the sky. Beta Cephei is named Alfirk, meaning the herd. It is a B2 blue giant, with a magnitude of 3.1, 690 light years away.
Gamma Cephei has the name Alrai, Arabic for the shepherd. It is a K1 orange star, with a magnitude of 3.2, 49 light years away. Precession will move Alrai closer to the north celestial pole than Polaris by the year 3000, making it our next north star. Most exciting of all is that in 2002, a Jupiter sized planet was discovered in orbit around Alrai. It is the only known planetary system in the constellation.
In the center of the constellation is the star Alkurhah. With a magnitude of 4.29, it is not particularly bright and is not part of the figure of the king. The name is translated from the ancient Arabic to mean the white blaze on the forehead of a horse.
Also not part of the figure is the Garnet Star, so named by the famous 18th century astronomer William Herschel who discovered the planet Uranus. The Garnet Star is an M2 red supergiant, that rivals the mammoth Betelgeuse in the constellation Orion. It is not only one of the reddest stars ever discovered, it is one of the five largest known stars in the entire Milky Way galaxy, with a diameter estimated at 850 million miles, compared to our Sun, with a diameter less than one million miles. Fortunately for us, this monster star is very far away, out at a safe distance of approximately 2,000 light years.
Coincidentally, Cepheus harbors another red supergiant that is thought to be even larger than the Garnet Star. At a distance of 2,400 light years, it appears as a relatively dim 4.9 magnitude star, named VV Cephei. Its true brightness could be as much as 500,000 times greater than our Sun. It is currently considered the second or third largest star in the galaxy.
Last, but far from least is probably the most famous star in the constellation, the little unnamed star, Delta Cephei, one of a group of three indistinct little stars marking the king's head. It is a very special type of variable star, whose variations in color and brightness are regular and predictable, no matter where it is in the universe, allowing astronomers to use it as a benchmark for measuring distances in space. Delta Cephei was the first of these stars to be discovered, and all subsequent stars of this type are now classified as Cepheid variables. It was a Cepheid variable in the Andromeda Galaxy that allowed Edwin Hubble to determine its true distance, and discover the fact that our Milky Way galaxy was only one of countless galaxies in a Universe too vast to even imagine. It was a Cepheid variable that completely changed our picture of the Universe.
|
|
|
|