What are the characteristics of Andromeda?

South of Cassiopeia, between Perseus and Pegasus is Andromeda. It is also close to Cepheus and is one of the six "royal constellations". The alpha star of Andromeda and the three bright stars of Pegasus constitute the "Pegasus-Fairy Box" which is often hung high in the sky in autumn. This big box is a prominent constellation symbol in the sky in the middle of the night before autumn. The alpha star above the fairy is the main star of Andromeda. There are 1 third star and two second stars in the northeast of this second star. These four stars are arranged in a row, and the interval is almost the same, which constitutes the trunk of Andromeda. Among them, the gamma star is 1, a famous triad star. Its main star is orange, and the other two companion stars are turquoise and orange. Every year around165438+1October 20th, the andromedids appears with this γ star as the radiation point.

There are many nebulae and star clusters in Andromeda, among which Andromeda Nebula M3 1 is the most famous. On a clear night without the moon, we can see its blue-and-white cloud-like figure. In the 1920s, Hubble, a famous American astronomer, confirmed that M3 1 is a huge extragalactic galaxy, about 2 million light years away from us. Although Andromeda nebula is so far away from us, it is still one of the closest extragalactic galaxies.

When we look up at Pegasus in winter night, we can see several bright stars arranged in the northeast. They belong to Andromeda. The bright star in the northeast corner of Pegasus quadrangle is Andromeda α, which covers an area of 7223 square degrees and is located at right ascension: 22: 56 ~ 2: 36 and declination: 2 140 ~ 529. Go to Zhongtian every year1October 27th 165438+20: 00. Andromeda has 106 stars of magnitude 6 or above, including 3 second-class stars (α, β, γ), 1 third-class star (δ),1/fourth-class star.

Andromeda (And), the Latin name of Andromeda, is a girl's name. Legend has it that the king who ruled Ethiopia in ancient times was called Andromeda, and he and his queen Cassiopeia had a daughter named Andromeda. When the princess grows up, she is beautiful and charming. The queen is a vain person. Everyone bragged about how beautiful her daughter was, even more beautiful than the god in the sea. This angered Poseidon, the sea god. He sent sea monsters to the Ethiopian coast to attack the fishermen there, making waves and causing huge waves to drown the kingdom. When the king was at a loss for the country to suffer this ignorant disaster, God revealed to the king that in order to punish the queen's arrogance, he must contribute the princess to Poseidon to calm the disaster. In order to defend his kingdom and save the people, the king had to chain his beloved daughter to the rocks by the sea as a sacrifice for the sea monsters to swallow. Just as this tragedy was about to happen, it happened that the Greek hero Passieux killed the demon Medusa and flew over Ethiopia on a flying horse. He couldn't allow such a tragic thing to happen, so he boarded the coast and saw the sea monster turn into a whale, with his mouth wide open and blowing a terrible whistle, swimming towards Andromeda. Passieux took out Medusa's head and headed for the sea monster. Medusa's head has a kind of magic, and anyone who looks at it will turn to stone. The sea monster didn't know what was at stake, and suddenly turned into a boulder and stood on the coast. The story of the hero saving the United States ended successfully with the marriage of Passieux and Andlau Moda. The protagonist in the story was later placed in the sky and became Cepheus, Cassiopeia, Andromeda, Whale and Perseus.

Andromeda's alpha star is called "Al Praz" in the west, which means "connected heads". On the constellation diagram, this star is right in the head of Andromeda. It is a second-class Bai Zi superstar (B9 Ⅳ) with a distance of 100 light years and an absolute magnitude of -07. , its luminosity is 150 times that of the sun. Mirach is the middle name of Andromeda Beta, and it is called "Mielack" in the west, which means "belt". It is a second-class red giant (Mo ⅲ) with a distance of 84 light years and an absolute magnitude of 0, which is 78 times the luminosity of the sun. Andromeda gamma star is one of the most famous celestial generals, and it is called "Allmacher" in the west, which means "shoes". It is a famous binary star with an angular distance of 9″8. Its neutron star γ 1 is a 22-magnitude red giant (K3Ⅲ) and the other is a 55-magnitude blue dwarf (B8V). γ2 itself is a nearly binary star with an angular distance of only 0″8. Andromeda δ is a red giant star (Sky Ⅲ) with an apparent magnitude of 327, a distance of 160 light years and an absolute magnitude of -02. It has a dark companion with an apparent magnitude of 12, which is a red dwarf with an angular distance of 28″7.

The most famous celestial body in Andromeda is Andromeda galaxy, which used to be called Andromeda Nebula. Ranked 3rd1on the messier cluster nebula list, also called M3 1 galaxy (NGC224). It is located about 1 to the west of Andromeda gamma star (Quezon VII), and it can be seen as a small white cloud with the naked eye on a clear moonless night. M3 1 is the only extragalactic galaxy visible to the naked eye in the northern hemisphere.

It has gone through a tortuous process for humans to confirm that M3 1 is an extragalactic galaxy. Looking back, this large nebula was first discovered by German astronomer Marius in 16 12. 1755, the German philosopher Kant put forward a view that there are infinite worlds in the boundless universe. And galaxies, he compared the universe to the ocean, compared galaxies to "cosmic islands", and thought that some nebulae might be distant "cosmic islands". 178 1 year, the British astronomer William Herschel observed some nebulae and found that some five-star nebulae were often decomposed into a group of dark stars in his telescope, so he asserted that nebulae that could not be decomposed by his telescope would also be decomposed in a larger telescope. He thinks Kant's view on the island of the universe is correct (I later learned that most of the nebulae observed by Herschel are globular clusters and open clusters, not extragalactic galaxies but celestial bodies in the Milky Way. Due to Herschel's prestige in astronomy, people have accepted the idea that there is an island in the universe, that is, an extragalactic galaxy. Soon Herschel discovered 1 celestial body in the process of observing the nebula, with 1 star in the middle and clouds (NGC 15 14) around it, which he called a planetary nebula. Then he found that some diffuse nebulae, such as Orion Nebula, were indecomposable, so he changed his previous view and denied the existence of extragalactic galaxies.

1845, British amateur astronomer william parsons (Earl of Ross) made a reflective telescope with a diameter of 180 cm. Observing with this telescope, he decomposed many nebulae that Herschel could not decompose into stars, and found that M5 1 nebula had a spiral structure. The existence of extragalactic galaxies has once again attracted people's attention, but only visual observation can not solve the physical properties of nebulae.

1864, British astronomer hagens began to observe nebulae through spectral analysis. He said: "I aimed my telescope at the planetary nebula located in Tianlong for the first time on the night of August 29th, 1864. I observed it from the spectroscope, but to my surprise, I didn't see the spectrum! " There is only one bright line. After a while, the real explanation flashed through my mind. Nebulae only emit monochromatic light. "Later, he successively observed that many nebulae showed bright line spectra. Finally, he announced that he had solved the mystery of the nebula: "They are not a group of stars, but a group of glowing gases. "Although he also observed the spectra of some nebulae, such as M3 1, which are similar to the spectra of stars, he ignored these and insisted that all nebulae are gases. So until the end of 19, many astronomers didn't realize the existence of extragalactic galaxies and thought that the Milky Way was the whole universe.

1885, a "new star" appeared in the core of Andromeda Nebula, which provided evidence for the view that the nebula was composed of stars, but at that time, people put forward a view that the new star glowed because it collided with gas, just like a meteor broke into the earth's atmosphere. M3 1 is still considered as a mass of gas.

After photography was used in astronomical observation, many details of the nebula were discovered. 1888, the British astronomer Romanz photographed the Andromeda nebula with a spiral structure, which is called the spiral nebula. 1899 photographed the spectrum of M3 1, and found that there were dark lines in its spectrum similar to the solar spectrum, so people suspected that M3 1 might be a distant star system similar to the Milky Way. But at 19 12, it is found that the reflection nebula also presents an absorption line spectrum similar to that of stars. In a word, it is impossible to determine whether the nebula is on the other side of the river or in Hanoi by telescope analysis or spectral analysis. The nebula that can be decomposed into stars may be a cluster, and the spectrum similar to that of stars is not necessarily an extragalactic galaxy, but a reflection nebula. Only by measuring the size of the Milky Way and the distance of the spiral nebula can we really solve the problem of whether there are galaxies outside the river. If the distance of the spiral nebula is less than the diameter of the Milky Way, it is a Hanoi celestial body, otherwise it is an extragalactic celestial body.

19 18, American astronomer shapley took globular clusters as the boundary of the Milky Way, and measured the distance of globular clusters by using the Zao Fu period-luminosity relationship in globular clusters, thus obtaining that the diameter of the Milky Way is 260,000 light years. This figure is exaggerated because interstellar extinction is not considered. Before him, people measured the distance of some spiral nebulae by inappropriate or inaccurate measurement methods, which generally decreased. Smaller than the diameter of the galaxy he measured. Therefore, shapley opposes the idea of extragalactic galaxies. On the other hand, American astronomer Curtis and others found many new stars in some spiral nebulae. He assumed that the absolute magnitude of these new stars at the maximum brightness is the same as that of the new stars in the Milky Way, and the distance of the spiral nebula can be determined by comparing their apparent magnitudes. The results show that they are far away, far beyond the scope of the Milky Way. So he concluded that these spiral nebulae were extragalactic galaxies. 1920 in April, shapley and Curtis held a scientific debate in Washington. At that time, the arguments of both sides were insufficient, and as a result, they expressed their opinions and did not reach the final correct conclusion.

1923, American astronomer Hubble used the largest telescope in the world at that time to observe the outside of the Andromeda nebula, and decomposed it into a single star, from which several Cepheid variables were determined. So he used the period-luminosity relationship of Cepheid variable to calculate the distance of Andromeda nebula is about 500,000 light years (because the period-luminosity relationship is zero imprecise, the distance data is much smaller than the actual distance data), which is much larger than shapley's estimate of the diameter of the Milky Way. Later, some Cepheid variables were found in other nebulae, and according to them, those nebulae were even farther away. Hubble announced this discovery in 1924, and finally confirmed the extragalactic status of Andromeda nebula.

According to the current measurement, the distance of Andromeda Nebula is 2.2 million light years, and the line diameter is 6.5438+0.7 million light years. 19 14 Pisces measured its rotation. 1949, American astronomer babcock and others determined that its mass was about 4×101/solar mass.