The reason why we can't see the stars on the moon is that all the stars we see on the earth come from distant galaxies. We can see them because we don't have other powerful light shields at night and need a good environment. So when it comes to the moon, like the earth, it is constantly rotating, so there are days and nights. We call it moonlit and moonlit. In principle, the moon is so close to the earth that it should see the same starry sky as us. However, when the moon is dark, the dark side faces the earth, so the earth is equivalent to the moon on the moon at this time. There is almost no atmosphere on the moon, so there are no optical effects such as Rayleigh scattering of the atmosphere. So it reflects strong sunlight, so many photos taken on the moon are based on the earth, but there are no stars. And if it is in the moonlight, it is even more impossible to see the stars. The brightness of sunlight on the moon during the day is enough to make your eyes blind. Such strong sunlight will cover the brilliance of the stars. It's like being directly illuminated by a flashlight. I can only see the light bulb in the flashlight.
The brightness of the stars determines whether people observe the stars bright or dark. There are two main factors: one is the luminous ability of the stars, and the other is the distance between the stars and people. Astronomers usually divide the luminous power of stars into 25 magnitudes, and the difference between the strongest luminous power and the worst luminous power is about 65.438+000 billion times.
Stars close to people have strong luminous ability, so people will light up when they see them. However, even if a star with a fairly strong luminous ability is far away from people, its brightness may not be as good as that of a star with a luminous ability of tens of thousands of times. The brighter the star, the smaller the magnitude. One of the most common magnitude systems is the tricolor system of U (ultraviolet), B (blue) and V (yellow), with absolute visual magnitude M=+4.83, color index B-V=0.63 and U-B=0. 12. The color temperature can be determined by the color index. For example, there is a star called "Antares". Its volume is about 220 million times that of the sun, and its luminous capacity is about 50,000 times that of the sun. But because it is 465,438+00 light years away from the Earth, people can only see that it is a bright star with red light. If Antares moves to the position of the sun, its light and heat will bake the earth into a big stone ball, and everything there will disappear.
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