Is Polaris a star?
It is a star. Polaris, also known as Beichen and Zixing, refers to the star closest to the North Celestial Pole. At present, it refers to "Gou Chen Yi". Polaris is a bright star in the northern part of the sky, very close to the north celestial pole, almost facing the earth axis. Seen from the northern hemisphere of the earth, its position is almost unchanged, so it can be used to identify the direction. Because of the rotation of the earth, Polaris is just on the axis of celestial rotation, so it is relative to other stars.
Polaris is known to us because it can guide the way. But the question is, how to find the North Star when you get lost at night and face the stars all over the sky? Polaris is only a second-class star, not very bright. Therefore, in the case of disorientation, we must look for Polaris with the help of other stars. The best way is to find the Big Dipper first.
The Big Dipper is an important star in the northern hemisphere sky. The ancients connected these seven stars and imagined them as the shape of a bucket for scooping wine. We may not have seen ancient utensils for scooping wine, but we can also imagine the connection between them as spoons. The seven stars that make up the Big Dipper are: Shu Tian, Tian Xuan, Celestial Pole, Tianquan, Yuheng, Kaiyang and Ursa Major. In different seasons and nights, the handle of the Big Dipper will point in different directions. But the connection between Shu Tian and Tian Xuan in Doukou always points to another star. This is the North Star we are looking for.
We will extend the connecting line between Shu Tian and Tian Xuan to the Shu Tian side by about five times, and then we will see the Polaris. The brightness of Polaris is similar to that of the Big Dipper. There are no brighter stars around it. Therefore, the North Star can be easily found through the Big Dipper. When we found the North Star, we also found the North. star
Why does the Big Dipper revolve around the North Star?
If we stare at the North Star and the Big Dipper all night, we will find that the Big Dipper revolves around the North Star. What is the reason? The earth moves around the sun. Is this the function of gravity? The distance between Polaris and the Big Dipper is very far. For example, Shu Tian looks closest to Polaris, but the distance between them is 365,438+00 light years. The gravity between them is very weak, and there is no direct connection between Polaris and the Big Dipper.
The Big Dipper seems to revolve around the North Star, but it is actually caused by the rotation of the earth. We are used to taking the earth as a reference object and think that the earth is stationary, so the Big Dipper, which is far away from the earth's rotation axis, will rotate with the earth's rotation. The earth rotates around its axis, and Polaris is very close to the extension line of the axis. So Polaris is a point on the earth's axis. It hardly moves. In this way, we will feel that the Big Dipper revolves around the North Star.
Not only the Big Dipper, but all the stars in the northern sky seem to revolve around Polaris. The stars in the southern sky rise and fall like the sun. This is what we often call "the stars move." In fact, their movement in the sky is the result of the earth's rotation.
The meaning of stars
Stars are giant spheres composed of luminous plasma, mainly composed of hydrogen, helium and trace heavy elements. On a sunny night, there are always countless light spots embedded in the night. Except for a few planets, most of them are stars. The sun is the closest star to the earth, and almost all the stars that can be seen at night are in the Milky Way. Of the 300 billion stars in the Milky Way, humans can only observe a small part. Humans have been observing stars for a long time, and there are various observation methods. Those brighter stars are divided into constellations and clusters, and some stars have their own names. The brightness of a star is called magnitude, and the brighter the star, the lower the magnitude. Astronomers have also compiled a catalogue to facilitate research.
Stars will carry out nuclear fusion at the core to generate energy and transmit it to the outside, and then radiate from the surface to outer space. Once the core nuclear reaction is exhausted, the life of the star will soon end. At the end of life, stars also contain degraded matter. Stars of different sizes and masses will lead to different endings: white dwarfs, neutron stars and black holes.
Two or more stars are bound by gravity and can form binary stars or multiple stars. When such stars are in relatively close orbits, the material exchange between them can have a great influence on their evolution.