Which constellation is Polaris in? Basic knowledge of astronomy-Polaris.

When people observe the starry sky for a long time, they will feel that the stars in the sky are fixed on the surface of the celestial sphere. But from the earth, as the celestial sphere rotates from east to west, you will see the stars rising and setting in the west. The earth rotates around an imaginary earth axis, and the intersection of the extension line of this earth axis and the celestial sphere is the pole. Polaris is the star closest to the north celestial pole. Because Polaris is located in the north pole of the celestial sphere, it seems that Polaris is motionless, as if it is in the center of the celestial sphere. So the ancients thought that Polaris was "the center of the sky". "Historical Records Tianguan Book": "Zhong Gong, Tianxing. One of them is a wise man, and Taiyi always exists. " "History of Song Dynasty": "The Polaris is in Zi Yuan, arched by the stars of Qiyao, Sanyuan and Erbasu, and is the center of the North Pole and the sky." The ancients paid special attention to Polaris, which was called the "Middle Palace". Based on this, the surrounding stars are combined into a wall, which is called Ziweiyuan. It's for the room of Heaven Emperor, the essence of Taiyi. The official gobbledygook is centered on Taiyi, and there are constellations such as "Sangong", "Princess" and "Hougong" nearby, and even princes serve as guards nearby. However, the Polaris in the center of Ziweiyuan mentioned by Sima Qian is not the Polaris we see today.

The ancient and modern Polaris is not the same star.

We know that the earth moves around the sun, and the sun keeps moving around the center of the galaxy. The sky pointing to the north pole of the earth's rotation axis moves at the speed of 15 arc seconds per year. So Polaris is not a star whose position will never change. In these two weeks, Tianxing is the North Star. Because it is close to the north celestial pole, it seems that all the stars revolve around it, so the ancients thought it was the son of heaven, hence the name Ryuboshi. It is also in the center of Ziwei Garden, so it is also called Ziwei Star. Modern astronomy named the beta star Ursa minor (Chinese name is Arctic II). Before that, Polaris was the alpha star of Draco, and China was called the right pivot in ancient times. From Sui and Tang Dynasties to Song Dynasty, Shu Tian was the North Star (Arctic V). Since the Song Dynasty, Dog Chenyi (Alpha Ursa minor) has been regarded as the North Star (western dog Chenyi). This star is located at the tip of the bear's tail in Ursa minor. In English, Cynosure also means center of attraction, which means that the stars revolve around Hooke Chen.

By about 4000 AD, Cepheus Gamma will become the North Star. Around 14000, Vega, the alpha star of Lyra, will become the North Star. The time for the earth's rotation axis to swing like this is about 25,800 years. Around the year 28000, the north celestial pole will once again point to Ursa Major.

How to identify Polaris

Connect a straight line between Tian Xuan and Shu Tian at the front of the Big Dipper, and then extend the distance to five times that of Shu Tian, and you will meet a bright second-class star-Polaris. (pictured)

The brightness of Polaris (that is, Gou Chenyi) seen today has basically reached the resolution limit of the human eye under the ordinary weather at night in the city, so it is difficult to be directly detected by the naked eye under the northern sky unless the weather is very clear and pollution-free at night.

The role of Polaris

The ancients used Polaris to identify the direction and the distance of navigation, and Beidou to identify the direction and set the season.

"Huainan Ziqi Su Xun": "A boat of confused people knows nothing, but when they see it, they will be embarrassed."

Folk call Polaris a fixed disk star. Star-pulling is a method to determine the position and navigation direction of a ship by using the position of the North Pole star and its angular height with sea level, so it is also called astronomical navigation.

Principle: The tool for drawing stars is called the Star Sketchpad, which is made of high quality ebony. A * * * Twelve square wooden boards, the largest one is about 24 cm long on each side, the lower one is decreasing by 2 cm, and the smallest one is about 2 cm long on each side. The other small square is made of ivory, and there are gaps in four corners. The lengths of the four cut edges are respectively one quarter, one half, three quarters and one eighth of the minimum edge length. For example, observe Polaris with a lead plate, hold the center of one end of the plate with your left hand, and look at the sky with your arms straight. The upper edge of the board is Polaris and the lower edge is horizontal, so you can measure the height of Polaris from the horizontal direction. Twelve wooden boards and four notched ivory blocks can be replaced and adjusted to different heights. After obtaining the height of Polaris, the geographical latitude of the location can be calculated.