How big is the Big Dipper? How far is it from the earth?

There are countless stars in the night sky, but there are not many that we can name. Among them, apart from the Polaris, the Big Dipper is the most well-known star.

But if someone asks, what stars are the Big Dipper? How big are they? How far is it from the earth? It is estimated that few people can answer clearly, but it doesn't matter, let's make up the knowledge about the Big Dipper.

The Big Dipper is located in the constellation Ursa Major, and under good viewing conditions, we can find them in the northern hemisphere's night sky almost every day. These seven shining stars form a unique spoon shape that is very easy to identify.

In order from the first star at the top of the "spoon" to the tail of the "spoon", their names are: Dubhe, Merak, Phecda, Megrez , Yuheng (Alioth), Kaiyang (Mizat) and Yaoguang (Alkaid).

Tianshu is about 123 light-years away from the earth and is the farthest star in the Big Dipper. Its mass is about 4.25 times that of the sun and its luminosity is 316 times that of the sun.

Since Tianshu has now evolved to a giant star stage, its surface temperature is only 4660K, and its volume cannot be accurately determined, but it is certain that its radius is much larger than that of the sun. In addition, Tianshu also has a companion star whose mass is about 1.6 times that of the sun, the distance between the two is about 23 astronomical units, and the orbital period is about 44.4 years.

The distance between Tianxuan and the earth is about 79.4 light-years. Its radius is about 2.84 times that of the sun, and its mass is about 2.7 times that of the sun. It is a subgiant star that is about to enter the giant star stage. At present, it is in the stage of "hydrogen shell nuclear fusion", its surface temperature is similar to that of the sun, and its luminosity is 63 times that of the sun.

Dimensity is about 83 light-years away from the earth, its mass is about 2.94 times that of the sun, its radius is about 3.04 times that of the sun, its surface temperature is 9355K, and its luminosity is 65 times that of the sun. It is worth mentioning that past observational data show that Dimensity has a companion star whose mass is about 0.79 times that of the sun, but this companion star has not been observed in many recent observations.

Tianquan is the famous "Wenqu Star", which is also the faintest and least massive star in the Big Dipper. The distance between Tianquan and the earth is about 80.5 light-years, the mass is about 1.63 times that of the sun, the radius is about 1.4 times that of the sun, the surface temperature is 8910K, and the luminosity is only 14 times that of the sun. In addition, Tianquan also has companion stars, and there are still two, but these two companion stars are too dim, and astronomers do not know much about them at present.

Yuheng is about 82.6 light-years away from the earth, with a radius of about 4.14 times that of the sun, a mass of about 2.91 times that of the sun, a surface temperature of 9020K, and a luminosity of 102 times that of the sun. Although the luminosity of Yuheng is not as good as that of Tianshu, because it is closer to the earth, in the eyes of us earthlings, Yuheng is the brightest star in the Big Dipper. Astronomers have long suspected that Yuheng also has a companion star, but it has not been found so far.

The distance between Kaiyang and the earth is about 82.9 light-years, the mass is about 2.2 times that of the sun, the radius is about 2.4 times that of the sun, the surface temperature is 9000K, and the luminosity is 33 times that of the sun. If the observation conditions are good, we can tell with the naked eye that there is a faint star in the vicinity of Kaiyang, and in fact, there are 4 stars in this area, which together form a sextuple star system.

Among the Big Dipper stars, except Tianshu and Tianxuan, other stars are in the main sequence stage, and Yaoguang is the "youngest" because its age is only about 10 million years. In addition, Yaoguang also has three "big dipper stars", which are the most massive (6.1 times the mass of the sun), the highest surface temperature (15540K), and the most luminous (594 times the sun's luminosity).

However, since the radius of Yaoguang is only 3.4 times that of the sun, and its distance from the earth is relatively far (about 104 light-years), it can only be regarded as the third brightest star in the Big Dipper in our eyes. (The first and second are Yuheng and Tianshu respectively).

By the way, the Big Dipper is not static. With the movement of the earth, their relative positions in the night sky will also change regularly. It looks like the Big Dipper, the "spoon", is spinning in the sky. Interesting Yes, when the "spoon handle" points to the south, south, north and west respectively, the corresponding seasons on earth are just spring, summer, autumn and winter.