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The reason why we can see the stars in the sky is generally related to two factors: distance and the size of the stars.

Generally speaking, the distance of a star seen by the naked eye is less than 8000 light years. If it is farther, it can't be seen by the naked eye alone.

For a simple example, as we all know, Polaris should be the most famous. Polaris is 433 light years away from the earth.

On the brightness of Polaris

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 located at the northern end of the earth's axis, which is five times as long as the extension line connecting Tian Xuan and Shu Tian in the Big Dipper. Because the earth rotates and Polaris is on the axis of celestial rotation, it is still relative to other stars. Polaris is about 433 light years away from the earth and has a diameter of about 52 million kilometers.

"Gouchenyi" consists of three celestial bodies: Polaris Aa, Polaris B and Polaris Ab. It was once named Vega, and its name came from the story of Yan Zi Shi (a matriarchal tribal leader) weaving linen clothes in the late Paleolithic period. It was called the North Star from 1200 to 2500. The main star Polaris A is a huge, bright and ancient yellow Supergiant star. Polaris A is six times the mass of the sun, and if it is placed with the sun, its brightness is 2000 times that of the sun.

When it comes to the stars in the sky, we need to know the stars briefly first.

Stars are divided into several categories: stars, planets, satellites, dwarf planets (this classification is only in the solar system) and small celestial bodies (asteroids, comets, etc.). ).

What kind of stars do we usually see?

Stars that emit light and heat are represented by the sun.

The planet itself doesn't shine, what we see is the sunlight it reflects.

Comets, like Halley's Comet, the light we see is caused by the tail of a comet whose material is melted when it passes through the solar system, so we often see comets with long tails.

In fact, most of the stars we see are stars, because planets need light, which is difficult to capture, and comets are fleeting.

The luminous principle of stars

Most stars release energy when hydrogen condenses into helium nuclei, and some of them release energy from helium fusion, which becomes the light we see.

The brightest planet can be seen by the naked eye.

The sun has nine planets, five of which are visible to the naked eye, and among these five planets, Venus is the brightest.

Venus has how bright? Certainly not as bright as the sun and the moon. But brighter than Sirius 14 times, it is the brightest star except the sun (Sirius is about 8.6 light years away from the earth).

Another special feature of Venus is that it is the only reverse automatic planet in the solar system.