Even the most inveterate pragmatist cannot remain indifferent when night, quiet and starry, falls to the ground. The constellation map of the northern hemisphere contains several expressive celestial drawings. However, all their beauty can be appreciated only by looking at the sky on such a night. Ursa Major and Ursa Minor, Bootes, Cassiopeia, Cepheus and others fascinate and force them to freeze in place, admiring the beauties of the vast expanse of space available for observation with the naked eye.
Today the focus of our attention is the constellation Cepheus (photo below), perhaps not the most vivid and impressive, but worthy of detailed study.
Location
With Cepheus in the sky, Ursa Minor and Cassiopeia are adjacent. Finding constellations like them is usually very simple: the stars of these celestial drawings are quite bright and noticeable. However, the Northern Cross asterism, located south of Cepheus in the constellation Cygnus, is the most significant reference point for the search.
On the whole territory of our country, Cepheus is an undisturbed constellation. The best time to observe it is from July to September. Part of the constellation is located on the Milky Way.
Proximity to the North Pole
The constellation Cepheus, the scheme of which includes about 150 stars, distinguishable in clear weather without the use of any equipment, its shape resembles an irregular pentagon. Interestingly, the closest neighbor of Cepheus, Ursa Minor, will not always contain a polar star. As a result of the precession, the stars from the constellation Cepheus will consistently take the place of today's Polar: Alfirk (beta), Alrai (gamma) and Alderamin (alpha). The first of these will take pride of place around the year 3100. It is these stars, together with Zeta and Iota Cepheus, that make up the formative asterism of the heavenly pattern.
Cepheus constellation: legend
Scientists believe that the considered group of luminaries appeared simultaneously with the neighboring Cassiopeia, Perseus, Pegasus and Andromeda. Myths about the constellations also speak of their common origin. Involuntarily, you will think about the possible knowledge of the ancients.
Cepheus, according to Greek mythology, was king of Ethiopia. Among other virtues and riches, he was most famous for the beauty of his wife Cassiopeia and daughter Andromeda. One version of the legend describes the queen as a wayward and obstinate woman. Cassiopeia inadvertently compared the beauty of her daughter with the impeccable appearance of the gods of Olympus, for which they were angry and wanted to punish both women.
Another option is that the jealous gods did not have to wait for the careless words of Cassiopeia: they themselves noticed the radiant beauty of Andromeda and decided to put an end to such disrespect. Be that as it may, a huge whale appeared off the coast of Ethiopia, every day getting out to land and devouring the inhabitants of the country. Cepheus tried to save the kingdom. Kit agreed not to ruin the villages, in return they had to give him the most beautiful girl every day.
Wonderful salvation
Sooner or later, the queue reached Andromeda. The grief of the parents knew no bounds, as well as the joyful anticipation of the envious gods. The girl was tied to a rock. The whale was already approaching the victim, when Perseus flew astride Pegasus and rescued the royal daughter.
The monster was defeated, and the beauty was saved. After a while, each hero was turned into a constellation: Cepheus, Cassiopeia, Andromeda, Perseus, Pegasus and even Keith.
Dim but significant
All of these heavenly drawings are located close enough to each other in the sky. The constellation Cepheus, like its royal prototype, is inferior to Cassiopeia in beauty. However, the monarch of the times of Antiquity and his heavenly image have much to be proud of. The stars that make up Cepheus have a certain appeal to scientists. Among them there are binary systems, and luminaries, huge even by the standards of the Universe, and the star, which gave the name to a whole type of similar cosmic objects.
Two cows
The brightest star that the constellation Cepheus boasts (the diagram gives an idea of the differences in the magnitudes of the elements) is Alderamin (alpha). The name in the translation means "right hand". It is located on the elbow of the royal figure. The magnitude of the star is 2.45. The distance that must be overcome from us to Alderamin is estimated at 49 light years. Alpha Cephei is a white subgiant belonging to the spectral class A. A star feature is a very fast rotation. Alderamin takes only 12 hours to complete one revolution, while for the Sun, for example, the same action takes about a month. Scientists have shown that alpha Cepheus is now at the stage of transformation into a red giant.
Beta Cepheus has the historical name Alfirk ("flock of sheep"). This is a variable star, the name of which designates a separate class of similar cosmic bodies. Variables such as beta Cepheus are characterized by a change in brightness within 0.01-0.3 magnitude. For Alfirk, the range extends from +3.15 to +3.21. The change period is 0.19 days.
In the Arab countries, ancient scholars united Alderamin and Alfirk in the asterism "Two Cows." By association with him, the name and scale of Cepheus - Alrai ("shepherd") was given.
Dual system
The constellation Cepheus has several stellar "coalitions." Alrai is interesting in that it is the first close couple, in one of the companions of which an exoplanet was discovered. The Cepheus A gamma is an orange subgiant, 1.6 times superior in mass to the Sun, and 8.2 times more in luminosity. A red dwarf revolves around him. The period for which the Cepheus B gamma makes one revolution is 74 years. The Alrai system is 45 light-years distant from the Sun.
Gamma Cepheus A has an exoplanet, theoretically discovered in 1988. In 2003, its existence was confirmed. A planet makes one revolution around a star in 2.5 years. Its mass, according to scientists, should exceed the mass of Jupiter by 1.59 times.
Delta
Another binary system is Alredif or Cepheus delta. However, it is not known because of its components. Alredif is a star who gave the name to a class of variable stars, Cepheids.
Cepheus Delta changes its brilliance with a period of more than five days. In this case, the increase occurs faster than its decrease. The star’s peculiarity is that a change in a number of characteristics is also associated with a change in brightness: the luminary in different periods can be attributed to different spectral classes. With a minimum magnitude of brightness, Delta Cephei becomes a representative of type G2, to which the Sun belongs, and at maximum - F5. These features, atypical for stars, remained without explanation for some time.
The answer, however, was found. It was found that the star pulsates, that is, changes its diameter. On average, this parameter of the Cepheus delta is equal to 40 diameters of our luminary. During the ripple, it changes by 4 corresponding values, which amounts to several million kilometers. During the compression period, the Alredif surface warms up, its brilliance grows. The expansion is characterized by some cooling and a decrease in gloss. Similar changes are characteristic of the entire class of Cepheids.
Red supergiants
The constellation Cepheus is famous for the presence in its composition of three huge stars, the sizes of which stand out among all the known objects of the Universe. These are red supergiants. The first of them is mu Cepheus. A star is 350,000 times greater than the Sun in full luminosity. The second name of the giant is Herschel's Pomegranate Star. It was William Herschel who first noticed the beautiful shade of the star. The largest mu Cepheus is 1650 times larger than the Sun. Scientists disagree on how far from this star this red supergiant is. Recently, the most accurate figure is 5200 light years. Now mu Cepheus is at the stage of dying. In the next few million years, an explosion awaits her, after which the collapsed core of the star will most likely turn into a black hole.
Mu Cephei also has a triple star system. The main pair of it is made up of less impressive components B and C.
The second red giant is VV Cepheus, a double eclipsing star 5,000 light-years distant from the Sun. Component A of the system is a huge luminary, the third largest among all known ones and the second largest in this parameter in the Milky Way galaxy. Its diameter is more than 2.5 billion kilometers, which exceeds the similar characteristic of the Sun by about 1,700 times. VV Cepheus A shines brighter than our star in 275-575 thousand times. The second component of the system revolves around the first with a period of 20 years. In size, it exceeds the Sun by 10 times.
The third red super giant is HR 8164. The luminary does not have its own name. Its magnitude is approximately 5.6.
Close neighbor
All these objects are at a decent distance from the Earth. However, Cepheus also has one star, located just 13 light years from us. This is Kruger 60, a double star system. Both of its components are red dwarfs, significantly inferior to the Sun in their dimensions. Kruger 60 A is almost four times less in mass; its radius is 35% of the radius of the Sun. Component B is even more “modest”: it is inferior in mass to our luminary by about 5.5 times. The Kruger diameter of 60 V is 24% of the corresponding parameter of the Sun. The second companion refers to flashing stars. Every eight minutes, its luminosity doubles, and then returns to its original value. System components revolve around one center of mass with a period of 44.6 years.
Fireworks and trunk
Not only interesting stars, but also nebulae, the constellation Cepheus boasts. A photo of one of them resembles an image of a firework. The nebula is NGC 6946 and the name has a corresponding. It is interesting because nine supernova stars are already discovered within its limits. So far no other nebula can boast of such a number. Fireworks are located on the border with the constellation Cygnus.
One more similar cosmic formation is connected with Cepheus. IC 1396 is an emission nebula famous for having the Elephant Trunk, a dark cloud of interstellar dust on its territory. It got its name due to visual resemblance to the corresponding part of a huge animal.
Open cluster
The constellation Cepheus in its "territory" also stores one of the most ancient formations of the cosmos, discovered so far. This is an open cluster of NGC 188. It includes 120 stars formed at about the same time from a common molecular cloud. Herschel discovered it in 1831. The very first calculation of the age of the cluster estimated its lifetime at 24 billion years. Subsequent calculations reduced this figure. Today it is believed that NGC 188 is 5 billion years old.
The description of the constellations, even the most detailed, will not help to understand the beauty of heavenly drawings. The exact coordinates of the stars, a description of their characteristics do not give that sensation of the infinity of the Universe that appears when you peer into the night sky. Myths about the constellations partially and in their own way convey the interconnectedness of the terrestrial and cosmic, however, they will not replace direct observation. On the other hand, data on objects included in the heavenly pattern help to understand what is hidden even behind the most seemingly inconspicuous stars. A striking example of this is Cepheus, the constellation is not the most noticeable, but containing a lot of interesting elements and telling the curious about them.