Why are some stars bright and some stars dim?

There are two reasons for this: first, the problems of the stars themselves, such as the degree of violentness of the star's surface nucleus, the volume of the star itself, etc.; Another reason is the distance. Of course, the closer the star, the brighter it looks.

Because there are two reasons that affect the brightness of stars, there is a term in astronomy called absolute magnitude, which is a unified standard for comparing the brightness of stars assuming that they appear to be light-years away from the observer.

Some are stars, some are planets.

The sun is reflective, and they do not shine on their own, unless they are sun-like stars, and there are also different levels, 1st magnitude stars, 2nd magnitude stars. So there are light and dark.

It's because of the difference in distance and the reflection of the sun.

Because the time of generation of stars is different, the time is darker, and the first generation is brighter, I once saw five star circles, and this is one star.

Because the star is not at the same distance from you, and the reflection of light on its surface is also different

The bright one shows that it is calm on the surface, suitable for people to live in, and wants to attract people to immigrate there. The dark one means that there are already inhabitants there, and they are camouflaging and hiding themselves!

Ancient Greek astronomers divided the stars into six magnitudes, which is what astronomy says"Magnitude"The brightest is a first-magnitude star, and the sixth-magnitude star is barely visible to the naked eye. Later, astronomy stipulated that a star of the first magnitude was a hundred times brighter than a star of the sixth magnitude, that is, the brightness of the star decreased by a factor of two for each increase in magnitude, and the number of magnitudes was extended to negative and decimal numbers. The brightest star we see is the Sun, and the Hubble Space Telescope can see much fainter stars of 26th magnitude or even fainter.

1. Symbolism: The stars themselves have a certain symbolic meaning. For example, the sun and stars usually represent warmth, justice, light, truth, hope, etc.; In classical Chinese poetry, the sun will represent the monarch, the other astrological days are strong, the evening is twilight, the North Star represents the monarch, and the Beidou represents the big names.

2. Romance: Stars are synonymous with romance. At the edge of the Milky Way, 30,000 light-years from Earth, there are two huge galaxies that stage "tango".

These two galaxies are made up of billions of stars and clouds of gas, both in a spiral shape. The stars, gas, and dust of the larger galaxy on the right form an "arm" that surrounds the smaller galaxy on the left, slowly performing graceful dances as they interact.

3. Hope of life: The stars represent the hope of life, like the Big Dipper in the night sky, which can lead the confused people out of the labyrinth, so it has the meaning of hope for life.

There are two main factors that determine whether people observe the stars as light or dark:

One is due to the size of the star's ability to emit light, and the other is the distance between the star and people.

Astronomers usually divide the ability of stars to shine into 25 magnitudes, with the strongest ones being about 10 billion times different from the worst ones.

A star that is close to people has a strong ability to emit light, so people will light up when they see it. However, even if a star is quite capable of emitting light, if it is very far away, it may not be as bright as a star that is tens of thousands of times less capable of emitting light.

The brighter the star, the smaller the magnitude. One of the most common magnitude systems is the U (ultraviolet), b (blue), V (yellow) trichromatic system (see the photometric system "class=link> photometric system"), absolute visual magnitude m=+, etc., chromatic index b-v=, u-b=. The color temperature can be determined by the color index.

For example, there is a star called Antares that is about 100 million times the size of the Sun and has about 50,000 times the ability to emit light, but because it is 410 light-years away from Earth, people can only see it as a bright star with a red light. If Antares were to be moved to the position of the sun, the light and heat it emitted would bake the earth into a large stone ball where everything had disappeared.

01 Stars are generally stars that emit light by themselves, and the brightness and darkness of the stars seen by the naked eye are mostly related to the size and distance of the stars. For example, the stars of Cowherd (Aquila) and Weaver Girl (Lyra) are not as bright as the moon, but they are actually much larger and brighter than the sun, and they appear dark because they are far away from the earth.

The stars in the sky are some bright and some are dark. We know that a 60-watt lamp is brighter than a 20-watt lamp because of its ability to emit light. So, do bright stars shine more than dark stars?

In fact, this is not necessarily the case, in addition to its ability to shine, there is another reason that determines the brightness of the star, which is the distance between the star and us. Generally speaking, the closer the stars are to us, the brighter they look. The above is the apparent brightness of the star, which is the brightness of what it seems.

Apparent brightness is expressed in terms of apparent magnitude. The brightest stars we see are generally classified as 1st magnitude, and the faintest stars that people with normal vision can barely see with the naked eye are classified as 6th magnitude. A bright star in the sky may really be a star that emits a lot of light, but it may also be bright just because it's so close to us.

Conversely, some faint stars are not necessarily dim, and although they can only be seen through telescopes, they may be extremely capable of emitting light, but they appear faint because they are so far away from us.

In order to compare the true luminous power of different stars, they should be compared at the same distance as us. It's like a race, you have to stand on the same starting line and start at the same time. According to international regulations, this "starting line" of the star is set at 10 parsecs, that is, light years.

The brightness of a star at this standard distance is specified as its absolute brightness, which is expressed by absolute magnitude. Athletes can start on the same starting line, and stars can't all move to a distance of 10 seconds, so absolute magnitude is calculated. The apparent brightness of the Sun is the absolute champion, and once it is placed at a distance of 10 parsecs more than 2.06 million times farther than it is now, its absolute magnitude is only +.

The following five celestial bodies in apparent magnitude order should be inverted if they are arranged in absolute magnitude.