What did Cepheus say?

Starting from the W-shaped Cassiopeia and heading west along the Milky Way in autumn, you can meet a "flat pentagon" half immersed in the Milky Way on the north side, which is a pattern composed of several main stars in Cepheus. Another part of Cepheus "rushed" to the north celestial pole and took a semi-enclosed posture towards the North Star. Cepheus is the closest to Polaris except its own constellation (Ursa minor).

Cepheus has 1 a very famous variable star called Cepheid I, which is 5? The period of No.37 is shrinking and expanding, and the brightness changes with it, so it is a typical "pulsating variable star" with brightness of 1. More than 600 variable stars like this have been found now, collectively known as Cepheid variable stars. Cepheid 1 is the fourth star of Cepheus, located at the tip of Cepheus. It is white at its brightest and yellow at its darkest. Cepheid-1 is 30 times larger in diameter than the sun, but only six-tenths as dense as the sun. In the process of each expansion and contraction, the diameter difference between the front and rear is 5 million kilometers.

From Cygnus to the north along the Milky Way, near Polaris, you can find Cepheus. It is composed of several stars that are not very bright, and it is not very prominent in the starry sky. On the star map, it is usually drawn as a slender and twisted pentagon. Cepheus occupies the sky area from 20: 00 to 0 1-8: 30 right ascension; The declination is 5 1 ~ 89, with an area of 588 square degrees. Every year at 8: 00 p.m. on October 7th, 65438/kloc-0, Cepheus rose to the sky.

Cepheus was divided into "Karim Abdel-Jabbar" and "Kitchen God" on the ancient map of China. Zhao Fu was a famous coachman in ancient times. Cepheus, the Latin name of Cepheus, is the name of the Ethiopian king in ancient Greek mythology. Its queen Cassiopeia boldly declared that her daughter was more beautiful than Poseidon's, which caused Poseidon's anger. He sent sea monsters to ravage the coast of the kingdom, forcing the unfortunate king to give his daughter to the sea monsters to feed. Because the Greek hero Passieux came to kill the sea monster and rescue the princess, Passieux became a promise of the ancient Ethiopian kingdom. Later, this family was put into the sky and became the famous fairy king, fairy queen, fairy and Perseus, collectively known as the royal constellation.

Cepheus has no bright stars, including 1 second-class star, 2 third-class stars, 18 fourth-class stars and1/8 visible stars. Cepheus, whose middle name is Tiangouwu, is called "citizen of Aldra" in Arabic, which means "right shoulder". The apparent magnitude of this star is 2? The absolute magnitude of A7 dwarf with a magnitude of 44 is 1? 5 and so on. The distance is 5 1 light-year. Due to the precession of the earth's rotation axis, it will become our Polaris in 5500 AD. Cepheus beta magnitude 3? B2 superstar with an absolute magnitude of -3? 6 and so on, 760 light-years away, belongs to the pulse variable Canis major, also known as the beta pulse variable Cepheus. The shape of this dimming curve is close to sine curve. When the light variation period is about 3 ~ 7, the light amplitude is generally less than 0? 1 etc. (See Canis Canis). The dimming period of Wang Xian γ is 4: 34: 18? Vast, the light amplitude is 0? 1 1 and so on (3? 16 and so on ~ 3? 27, etc). Some observers have determined that the distance is less than 300 light years, but others have determined that the distance is as high as 980 light years or even 1000 light years. Cepheus γ, called "Al Rai" in Arabic, means shepherd, or apparent magnitude 3? The sub-giant of K 1, such as 2 1, is light-years away from the blade and has an absolute magnitude of 2? 27 and so on.

The most famous of Cepheus is Cepheus δ, whose middle name makes father one. It is a typical variable star. The first person to confirm that it is a variable star is john goodricke, a deaf-mute young man in Britain who is less than 20 years old. 1784, john goodricke noticed that the brightness of Cepheus delta star changed periodically, that is, the brightness was 3? 48 and 4? 37, and so on for a week. In the same year, he also discovered the brightness change of Lyra β (gradual change stage II). John goodricke also explained the reason of Cepheid-1 brightness change, pointing out that Cepheid-1 is a real variable star, which is due to its own brightness change.

John goodricke was the first person (1782) to discover that the brightness of Perseus β (Daling V) changed, and correctly explained that the reason for the brightness change of Daling V was that two stars revolved around each other and blocked each other, which made the brightness change periodically. 1894, the Russian astronomer Belo Loppol first observed that the spectral line of Cepheus δ moved periodically, which was thought to be caused by Cepheus δ orbiting an invisible companion star. 19 14 years, American astronomer shapley further studied and found that the effective temperature and apparent velocity of Cepheus I also changed periodically. When the brightness of Zao Fu I is extremely high, the effective surface temperature increases, the apparent velocity of the star increases and the radius of the star decreases. This shows that the brightness change of Cepheid variable I can't be caused by the orbital motion of binary stars, but the pulsating change of Cepheid variable I's own expansion and contraction. That is to say, the star shrinks (the apparent velocity increases and the radius decreases) and the effective surface temperature increases, which makes the brightness of the star increase; The star expands (the radius becomes larger), the effective temperature decreases and the brightness of the star decreases. This variable star whose brightness changes periodically due to the pulsation of stars is represented by Cepheus delta, so it is called Cepheid variable star, or classical Cepheid variable star. Their light variation period is mostly 5 ~ 10 days, and the light variation amplitude is generally around 1 magnitude. They are Huang Giant Star and Supergiant star. The spectral type is F type when the brightness is extremely high, G type or K type when the brightness is extremely low, and the absolute magnitude is very large. The spectral type of Cepheid variable I varies between F5 and G2, and the absolute magnitude is -4? 6 and so on. , the luminosity is 5500 times that of the sun, and the distance is 1500 light years.

The discovery of jujube-falling variable stars has played an important role in measuring the distance between celestial bodies. 19 12 years, American female astronomer Loewit studied many Cepheid variables (their light variation period is from 1? From 25 days later to 127 days), it is found that the longer the light variation period of Cepheid variable star, the greater the brightness (i.e. luminosity), that is, the luminosity is proportional to the logarithm of the period, which is called the period-luminosity relationship. Using the period-luminosity relationship, we can know the luminosity of the star, that is, the absolute magnitude m, as long as we measure the light variation period of Cepheid variable star. In addition, the distance r of stars can be calculated from the relationship among apparent magnitude m, absolute magnitude m and star distance r: m = m+5-51gr. For those very distant celestial bodies, such as globular clusters and extragalactic galaxies, as long as Cepheid variables are observed, the distance between clusters and galaxies can be determined by using the period-luminosity relationship. Therefore, Cepheid variable stars are called "celestial ruler". Delta star Cepheus is the best target for variable star lovers to practice observation. Because it is very convenient to compare the brightness of Cepheus delta in the field of view at the same time.

Cepheus is a star with a magnitude of 4. 19 yellow and white FO subgiant, 80 light years away, is a shield deformation star (see "shield"), with light change periods of 59 minutes and 53 minutes. 3 seconds, brightness change range 4? 15 Wait until 4? 2 1 and so on. Cepheus μ, named Cepheid IV in the middle, is a star with an apparent magnitude of 4? Red giant, absolute magnitude -7? 0, etc. The luminosity is 50,000 times that of the sun, and the distance is 5,400 light years. It is the reddest star visible to the naked eye in the northern sky. British astronomer W? Herschel called it pomegranate red star. It is a semi-regular variable star with a dimming period of about 730 days and a dimming range of 3? 43 to 5? 1 etc.

Cepheus VV is a famous eclipsing binary star with a light variation period of 6 19 years and a maximum brightness of 4? 80 and so on. , the minimum hour is 5? 36 and so on. The diameter of the brighter sub-star in the eclipsing binary is 1600 times that of the sun, even larger than the orbital diameter of Jupiter!

Cepheus S and Cepheus T are both long-period variable stars. Cepheus T is 5 when its brightness is extremely high. Second class. , the minimum hour is 1 1? Wait, the dimming period is 388? 14 days; The brightness of Cepheus is at 7? 4 Wait until 12? 9, and so on; The dimming period is 486? 84 days.