My little brother looks up at the stars for Altair, Vega and the Big Dipper.

Before observing, you need to determine the latitude of your observation site. Because the horizon height of Polaris is equal to the geographical latitude of the observer.

After determining the latitude, when night falls on a sunny day, you face the north, look horizontally, look up, and the angle is just the degree of latitude (if you are at 45 degrees north latitude, you have to raise it by 45 degrees, how to measure this angle, hehe, find a protractor if it is simple). At this time, there should be a bright star in the center of your field of vision relative to the stars around it. This star is called Alpha Ursa minor, which China traditionally called "Gouchen II". It is also commonly known as Polaris (the north pole of the sky is the direction pointed by the earth axis). In fact, this star is not in the true position of the North Pole of the sky, but it is the brightest star closest to the North Pole of the sky. Due to precession, Vega will become the North Star after 12000. Polaris never sets. If there is a total solar eclipse during the day, you can see it. Another thing to understand is that in the northern hemisphere, when you observe the starry sky, all the stars revolve around the Polaris (you can think about why? ), which is why the North Pole should be located first when using astronomical telescopes.

Let's talk about the Big Dipper again. The Big Dipper consists of seven stars and belongs to Ursa major in modern astronomy. In fact, these seven stars are relatively easy to identify in the northern sky. The four stars in the hat are near the North Pole, and the three stars in the bucket handle are outside. Most people find the Big Dipper first and then the North Star without tools. As mentioned above, the stars in the northern hemisphere rotate clockwise around the north pole of the celestial sphere, so when you observe the Big Dipper at different times, its position will be different. Do you remember an old saying in China: bucket handle refers to the east, and the world is spring; Bucket handle guide, the world is summer; Bucket handle refers to the west, and the world is autumn; The barrel handle refers to the north, and it is winter all over the world. That is to say, at dusk in spring, you can see that the handle of the bucket points to the east, and so on. At this time, you can find the bucket spoon in the direction of bucket handle. If your latitude is high enough, you can also see it all night (of course, the Big Dipper may be above your head for a while).

As we know, as the date goes on, the Big Dipper turns counterclockwise. In autumn night, the Big Dipper no longer hangs high at the zenith, but has turned to the horizon. At this time, it is more difficult to find the Big Dipper.

The Big Dipper

Beidou consists of Shu Tian, Tian Xuan, Tianji, Tianquan, Yuheng, Kaiyang and Yaoguang. The ancient Han people associated these seven stars together and imagined them as barrels of ancient wine. Shu Tian, Tian Xuan, Tian Ji and Tianquan are composed of Dou Shen and Gu Yue Kui. Yuheng, Kaiyang and Yaoguang are composed of bucket handle, which was called Piao in ancient times. The Big Dipper appears in different directions in the sky at different seasons and different times at night, so the ancients decided the seasons according to the direction pointed by bucket handle at the beginning of fainting: bucket handle points to the east, and the world is spring; Guide to barrel handle, it's summer in the world; Bucket handle refers to the west, and the world is autumn; The barrel handle refers to the north, and it is winter all over the world. The Big Dipper is named α, β, γ, δ, ε, ζ and η respectively from the upper end of the bucket to the end of bucket handle. Astronomers of the ancient Han nationality in China called them Shu Tian, Tian Xuan, Tianji, Tianquan, Yuheng, Kaiyang and Yaoguang respectively. A straight line from Tian Xuan runs through Shu Tian, which is about five times as long as it. You can see a star as bright as the Big Dipper, which is the North Star.

How to find Polaris?

Polaris refers to the star closest to the north celestial pole, so Polaris is not static. At present, it refers to Alpha Star in Ursa minor (official name of China: Dog Chen Yi). About 434 light years away from the earth, it is a star with stable brightness and position that can be seen in the night sky. Ancient astronomers admired Polaris very much, thinking that it was fixed, all the stars revolved around it, and it was the symbol of the emperor (note that the star they worshipped was not today's Polaris Gouchenyi, but the circumjacent Polaris Arctic II, also called Ziweixing or Emperor Star). Because Polaris is closest to true north, people on earth have been navigating by its starlight for thousands of years. Some sailors get lost. They will find the North Star to locate it. Polaris is always in the north. Even without a compass, they can tell the direction.

You can also find today's North Star Gou Chenyi through the Big Dipper, and two stars of the Big Dipper, Shu Tian and Tian Xuan, can find a bright star Gou Chenyi by extending five times in the direction of Shu Tian. Near it is the north celestial pole.

keep a secret

Because the earth revolves around its axis, and Polaris is on the north extension line of the axis, when you look at the sky at night, Polaris is motionless, and it is north overhead, so you can indicate the north. Although the tilt direction of the earth's axis will change because the earth revolves around the sun all year round, the distance between Polaris and the earth is much larger than the radius of the earth's revolution, so the change of the earth's axis caused by the earth's revolution can be ignored. So all the year round, we see that the position of Polaris in the sky seems to be motionless in the north. In fact, we just can't observe the subtle changes with the naked eye, and we feel that the earth axis always points to Polaris.

Star-seeking method

You can find the Big Dipper first, and then find the North Star through the Big Dipper. The Big Dipper is a part of Ursa major. Graphically, the Big Dipper is located at the back and tail of Ursa Major. Of these seven stars, six are secondary stars and one is tertiary. Through the connection of the two stars in the mouth of the bucket, it extends about 5 times in the direction of the mouth of the bucket and finds the Polaris. Beginners can look for other constellations in turn from the Big Dipper.

Will the pattern of the Big Dipper never change? Will it always be a "tool" to find the North Star? Of course not. Everything in the universe is moving and changing, and stars are no exception. As the stars are also moving, the pattern of the Big Dipper is certainly changing. These seven stars are at different distances from us. At 100 light-years, their respective speeds and directions are different. Astronomers have calculated that the pattern of the Big Dipper seen 654.38 million years ago and the pattern seen 654.38 million years later are very different from today's.

How to find the cowherd and weaver girl in the sky on Tanabata?

On the seventh day of the seventh lunar month, it is a traditional festival in China, and it is also the legendary day when the Cowherd and the Weaver Girl meet at the Yinhe Queqiao once a year. Then, how to find the "Cowherd" and "Weaver Girl" who left an eternal story in the vast sky and feel this eternal romance through time and space?

It is a folk custom to sit and watch cowherd and weaver girl on Tanabata. Shi Zhicheng, a member of the Chinese Astronomical Society and director of the Tianjin Astronomical Society, said that Cowherd and Weaver Girl are folk names. In fact, in astronomy, Cowherd's Chinese name is Hegu II, and Vega is Vega I, the bright stars of Aquila and Lyra respectively.

At night, you can find a safe place that is not affected by town lights, preferably after dark 1 ~ 2 hours. Look up. Near your head, there are three bright stars in the middle and on both sides of the Milky Way, the brightest of which is blue and white. She is in the northwest of the galaxy. This is Vega. There are four dark stars below Vega, forming a small parallelogram. They are beautiful clouds and rainbow shuttles woven by Vega in myths and legends.

Another bright star is in the southeast of Vega, which is the southeast edge of the Milky Way. He is the Altair. Altair is a bright yellowish star, and the two small stars on both sides of it are called shoulder poles. According to legend, they are a pair of children of Altair and Weaver Girl.

Astronomical experts say that the Cowherd and the Weaver Girl will never meet each other, although they will stage a wonderful meeting show on the Queqiao Bridge on Tanabata every year. Because they are about 16 light years apart, that is, about 15 1 trillion kilometers.

Astronomical experts remind that the distance between Altair and Vega is relatively constant, and "Qixi Night" is no exception, and the distance between them will not be minimized on this night. Therefore, in the next three months, if the weather is fine, people can still find their romantic traces in the sky.

Altair

Hegu II is the alpha star of Aquila, commonly known as "Altair". It is a very famous bright star in the sky in summer and autumn, and it is silvery white. It is 0/6.7 light years away from the Earth/kloc-0, its diameter is 0/0.6 times that of the sun, its surface temperature is about 7000℃, its luminous power is 8 times greater than that of the sun, and its visual magnitude is 0.77. It faces Vega across the Milky Way. According to an ancient legend, the Cowherd and the Weaver Girl met at the Magpie Bridge on July 7th. In fact, the Cowherd and the Weaver Girl are 16 light years apart. Even on the most powerful rocket in modern times, they never met after hundreds of years. The two dark stars on both sides of Altair are Altair's two sons-Hegu I and Hegu III. Legend has it that Cowherd and his two sons chased Weaver Girl on a pole.

Low humidity plain

Zhinv 1 is a bright star in Lyra, whose scientific name is Lyra A, and it is one of the most famous bright stars in the summer night sky. Usually, people call it Vega In the west, it is called Vega. Vega's diameter is 3.2 times that of the sun, its volume is 33 times that of the sun, and its surface temperature is 8900 degrees Celsius, showing a bluish white color. It is one of the three brightest stars in the northern hemisphere sky, about 26 light years away from the earth. More than 65438+300,000 years ago, Vega was once the North Star. Due to the precession of the earth's axis, the current Polaris is the A star of Ursa minor. But in 6.5438+0.2 million years, Vega will return to the prominent position of Polaris. Next to Vega, four of them formed a small diamond. Legend has it that this small diamond is a shuttle used by the weaver girl to weave cloth. While knitting, the Weaver Girl looked up at the Cowherd (Hegu II) and her two sons (Hegu I and Hegu III) on the east bank of the Milky Way with deep affection.

Modern astronomical observations show that the entire solar system is moving towards Vega at a speed of 19 km per second.