The handle of the Big Dipper seven stars points to the northwest, which means the arrival of Li Dong. As the saying goes: the west finger of the bucket handle, the world is autumn; the north finger of the bucket handle, the world is winter. So, what exactly is the Big Dipper? Why can they indicate the seasons on Earth? What does this have to do with each other?
Somewhere in good viewing conditions, there are more than two thousand stars in the night sky that can be seen with the naked eye. There are more than 7,000 stars visible to the naked eye, including the Big Dipper in the northern sky.
Of these stars, water, gold, fire, wood, and earth are planets in the solar system that orbit the sun like Earth. As the only known star in the solar system, the Sun's mass accounts for 99.86% of the total mass of the solar system, and the strong gravitational pull it produces constrains the movement of the major planets.
In addition to the five planets, the stars in the night sky are actually stars, and the Big Dipper is also a star. Since it is a star, it can emit light and heat through nuclear fusion reactions. Not only that, but most stars are like the sun, with planets around them.
While there are thousands of stars in the night sky that are visible to the naked eye, and most of them are actually larger and brighter than our sun, they can't illuminate the night on Earth and bring light and heat to earth like the sun. This is because they are so far away from Earth that most of the light they emit dissipates in the vast space of the universe, and only a small part of them can come to Earth.
So, how far is the Big Dipper from Earth? How big are they?
The seven stars from the handle to the mouth of the bucket are:
(1) YaoGuang
Yaoguang is a very young star, only 10 million years old, and our sun is already 4.6 billion years old. The star is located 103.9 light-years from Earth, has a mass of 6.1 times that of the Sun, and is actually 594 times brighter than the Sun. If the Sun were replaced by Yao light, the Earth would be scorched and the habitable zone would migrate 3.6 billion kilometers away, equivalent to the outer orbit of Uranus.
Due to the large mass of Yaoguang, its own strong gravity makes the temperature and pressure in the core area become very high, making the fusion reaction rate much faster than that of the sun, so it will run out of nuclear fuel faster. It is estimated that yaoguang has a lifespan of less than 110 million years, equivalent to one percent of the sun.
(2) Kaiyang
Located 82.9 light-years away, Kaiyang has a mass equivalent to 2.2 times that of the Sun, is 33.3 times brighter than the Sun, and has an age of 370 million years. If the vision and observation conditions are good enough, you can also see a faint star next to Kaiyang, which is a companion star called "auxiliary".
With the help of modern astronomical telescopes, astronomers have discovered that Kaiyang is not a simple binary star system, but a rare hexagram system. There is also a smaller star near the auxiliary, which forms a binary star system. There are also three stars near Kaiyang, which make up the quadrangle system. These 6 stars, in turn, are bound to each other by gravity, forming a larger star system.
(3) Yuheng
Located 82.6 light-years away, Yuheng has a mass of 2.9 times that of the Sun and 102 times the luminosity of the Sun, making it the brightest of the Big Dipper stars. Astronomers have found that Yuheng's luminosity changes periodically, which is thought to be caused by a substar.
(4) Heavenly rights
Tianquan is also known as Wenqu Star, which is 80.5 light-years away from the Earth, with a mass estimated to be 1.6 times that of the Sun, and its actual brightness is 14 times that of the Sun. There are also two faint companion stars around Tianquan, which form a triad star system.
(5) Tianji
Tianji is 83.2 light-years away from us, and its mass is about 2.9 times that of the Sun, and its luminosity is equivalent to 65 times that of the Sun. Observations have shown that the Celestial Seal oscillates around a point in space because it has a companion star nearby, and the two orbit each other for about 20 years.
(6) Tianxuan
Located 79.7 light-years away, Tianxuan has a mass of 2.7 times that of the Sun and a luminosity of 63 times that of the Sun. According to tianxuan's quality, its life expectancy is estimated at 830 million years. It has been 500 million years since Tianxuan was born, and it is dying.
(7) Tianshu
The hub is 123 light-years away from Earth, has a mass of 3.4 times that of the Sun, and is nearby a companion star with a mass of 1.6 times that of the Sun, which forms a binary star system. The hydrogen fuel in the core of the celestial hub has been depleted and has now expanded into a giant star, nearly 5,000 times the size of the Sun and 165 times the luminosity of the Sun.
The Celestial Hub and Tianxuan are located in the mouth part of the Big Dipper, and they can indicate the direction of the North Star. Extending five times from Tianxuan to the celestial hub, you can see a brighter star, that is, the North Star (actually a triad system). Since the North Star is located just near the North Celestial Pole, no matter how the Earth rotates, the star will not rise and fall, and will always hang in the Northern Sky, so it can be used to distinguish the North.
There is no direct relationship between the Seven Stars of the Big Dipper, and they belong to different star systems. The seven stars of the Big Dipper are far apart, such as Yaoguang and Tianxuan 47 light-years apart. Just from the point of view of the earth, these seven bright stars just arranged in the shape of a spoon. As the Earth rotates and rotates , the Big Dipper rotates around the North Star , and the pointing of the handle is just enough to indicate the seasons.
In the Milky Way, both the Sun and the Big Dipper orbit the center of the Milky Way. Each star has a different orbital velocity, with the Sun orbiting at 220 km/s and a rotation time of 230 million years.
With the relative motion between stars, their relative positions in cosmic space will change, so in the distant future, the arrangement of the Big Dipper will become completely different, no longer the spoon-shaped shape of the present. In the distant past, there was no Big Dipper in the sky. Only in our time, the unique arrangement of the Big Dipper seven stars will appear in the night sky of the earth.