The Big Dipper looks close, but is actually far away? Their starlight comes from hundreds of years ago

Looking up at the starry sky can bring peace of mind. Far away from the city, if the weather is clear, we can see more than 3,000 stars in the night sky with our naked eyes.

Most of these stars are stars, because outside the solar system, the distance between celestial bodies and us is very far, if they do not emit light, they cannot be directly observed. Even if they are stars that can emit light, if they are too far away, they cannot be directly seen with the naked eye, so all the more than 3,000 stars in the night sky are stars in the Milky Way. At first glance, these stars seem to have no rules, but in fact their relative positions to the earth are almost constant, so we can regard some stars as a whole and name them "constellations".

The stars in the night sky are complex and there are no connecting lines between them. If you don’t stargaze regularly, it may be difficult to see these constellations. But there is one constellation that most people can find, and that is the Ursa Major. The most iconic feature of the Ursa Major is the seven bright stars at its tail, which we call the "Big Dipper."

The position of the Big Dipper in the night sky is not constant. With the change of seasons, the position and direction of these seven stars will change accordingly. In spring, the handle of the Big Dipper points to the east, in summer, the handle points to the south, in autumn, the handle points to the west, and in winter, the handle points to the north.

From the earth, it seems that the seven stars of the Big Dipper are closely connected. No matter how their positions and directions change, their relative positions always remain the same. But in fact, in the universe, there is no connection between these seven stars. Not only are they not connected, they are also far apart.

The Big Dipper can be divided into two parts: the handle and the body. The handle consists of three stars, and the body consists of four stars. The three stars at the handle were called Yaoguang, Kaiyang and Yuheng in ancient times. Yaoguang is the star at the end of the handle, and it has another name, which is "Pojun Star".

Pojun is a very young star, about 10 million years old. Compared with the sun, which is about 5 billion years old, it is indeed a young successor.

The star Pojun in the night sky is located at the end of the handle of the dipper, and in fact it is quite far away from the earth, about 102 light years away. The second star at the handle of the dipper is Kaiyang, also known as the "Wu Qu Star". There are actually six stars here, belonging to two celestial systems, a binary star system and a quadruple star system, but they cannot be identified with the naked eye. The distance between Kaiyang and the earth is about 78.2 light years. The third star at the handle of the dipper is Yuheng, which is about 82 light years away from the earth.

The four stars in the body of the Dipper are Tianshu, Tianxuan, Tianji and Tianquan.

Tianshu, also known as the "Ganlang Star", is the farthest star from the Earth among the Big Dipper, and its distance from the Earth reaches 123 light years. Next is Tianxuan, which has a mass 2.7 times that of the Sun and is about 89 light years away from the Earth. Tianji is a star that looks dim, but its distance from the Earth is not far, about 83 light years away. Finally, there is Tianquan. Ancient literati liked this star very much because it has another name, "Wenquxing". It is about 80 light years away from the Earth.

Looking up at the night sky, we feel that the Big Dipper is not far away from us, but in fact the closest one is 78.2 light-years away from us, and the farthest one is 123 light-years away from us.

123 light years is the distance that light travels in 123 years at the speed of light. That is to say, the starlight we see now actually comes from 123 years ago. In other words, the Big Dipper we see is actually how it looked 100 years ago, and we will never see how it looks now. Of course, if you are still young, you can also watch Kaiyang at night and remember this date. 78 years later, if you are still alive, it will be very interesting to look up at the starry sky again and recall that night 78 years ago.

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